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• The SPARC SuperCluster

  - by Karoly Vegh

  Oracle has been providing a lead in the Engineered Systems business for quite a while now, in accordance with the motto "Hardware and Software Engineered to Work Together." Indeed it is hard to find a better definition of these systems.  Allow me to summarize the idea. It is:  Build a compute platform optimized to run your technologies Develop application aware, intelligently caching storage components Take an impressively fast network technology interconnecting it with the compute nodes Tune the application to scale with the nodes to yet unseen performance Reduce the amount of data moving via compression Provide this all in a pre-integrated single product with a single-pane management interface All these ideas have been around in IT for quite some time now. The real Oracle advantage is adding the last one to put these all together. Oracle has built quite a portfolio of Engineered Systems, to run its technologies - and run those like they never ran before. In this post I'll focus on one of them that serves as a consolidation demigod, a multi-purpose engineered system.  As you probably have guessed, I am talking about the SPARC SuperCluster. It has many great features inherited from its predecessors, and it adds several new ones. Allow me to pick out and elaborate about some of the most interesting ones from a technological point of view.  I. It is the SPARC SuperCluster T4-4. That is, as compute nodes, it includes SPARC T4-4 servers that we learned to appreciate and respect for their features: The SPARC T4 CPUs: Each CPU has 8 cores, each core runs 8 threads. The SPARC T4-4 servers have 4 sockets. That is, a single compute node can in parallel, simultaneously  execute 256 threads. Now, a full-rack SPARC SuperCluster has 4 of these servers on board. Remember the keyword demigod.  While retaining the forerunner SPARC T3's exceptional throughput, the SPARC T4 CPUs raise the bar with single performance too - a humble 5x better one than their ancestors.  actually, the SPARC T4 CPU cores run in both single-threaded and multi-threaded mode, and switch between these two on-the-fly, fulfilling not only single-threaded OR multi-threaded applications' needs, but even mixed requirements (like in database workloads!). Data security, anyone? Every SPARC T4 CPU core has a built-in encryption engine, that is, encryption algorithms cast into silicon.  A PCI controller right on the chip for customers who need I/O performance.  Built-in, no-cost Virtualization:  Oracle VM for SPARC (the former LDoms or Logical Domains) is not a server-emulation virtualization technology but rather a serverpartitioning one, the hypervisor runs in the server firmware, and all the VMs' HW resources (I/O, CPU, memory) are accessed natively, without performance overhead.  This enables customers to run a number of Solaris 10 and Solaris 11 VMs separated, independent of each other within a physical server II. For Database performance, it includes Exadata Storage Cells - one of the main reasons why the Exadata Database Machine performs at diabolic speed. What makes them important? They provide DB backend storage for your Oracle Databases to run on the SPARC SuperCluster, that is what they are built and tuned for DB performance.  These storage cells are SQL-aware.  That is, if a SPARC T4 database compute node executes a query, it doesn't simply request tons of raw datablocks from the storage, filters the received data, and throws away most of it where the statement doesn't apply, but provides the SQL query to the storage node too. The storage cell software speaks SQL, that is, it is able to prefilter and through that transfer only the relevant data. With this, the traffic between database nodes and storage cells is reduced immensely. Less I/O is a good thing - as they say, all the CPUs of the world do one thing just as fast as any other - and that is waiting for I/O.  They don't only pre-filter, but also provide data preprocessing features - e.g. if a DB-node requests an aggregate of data, they can calculate it, and handover only the results, not the whole set. Again, less data to transfer.  They support the magical HCC, (Hybrid Columnar Compression). That is, data can be stored in a precompressed form on the storage. Less data to transfer.  Of course one can't simply rely on disks for performance, there is Flash Storage included there for caching.  III. The low latency, high-speed backbone network: InfiniBand, that interconnects all the members with: Real High Speed: 40 Gbit/s. Full Duplex, of course. Oh, and a really low latency.  RDMA. Remote Direct Memory Access. This technology allows the DB nodes to do exactly that. Remotely, directly placing SQL commands into the Memory of the storage cells. Dodging all the network-stack bottlenecks, avoiding overhead, placing requests directly into the process queue.  You can also run IP over InfiniBand if you please - that's the way the compute nodes can communicate with each other.  IV. Including a general-purpose storage too: the ZFSSA, which is a unified storage, providing NAS and SAN access too, with the following features:  NFS over RDMA over InfiniBand. Nothing is faster network-filesystem-wise.  All the ZFS features onboard, hybrid storage pools, compression, deduplication, snapshot, replication, NFS and CIFS shares Storageheads in a HA-Cluster configuration providing availability of the data  DTrace Live Analytics in a web-based Administration UI Being a general purpose application data storage for your non-database applications running on the SPARC SuperCluster over whichever protocol they prefer, easily replicating, snapshotting, cloning data for them.  There's a lot of great technology included in Oracle's SPARC SuperCluster, we have talked its interior through. As for external scalability: you can start with a half- of full- rack SPARC SuperCluster, and scale out to several racks - that is, stacking not separate full-rack SPARC SuperClusters, but extending always one large instance of the size of several full-racks. Yes, over InfiniBand network. Add racks as you grow.  What technologies shall run on it? SPARC SuperCluster is a general purpose scaleout consolidation/cloud environment. You can run Oracle Databases with RAC scaling, or Oracle Weblogic (end enjoy the SPARC T4's advantages to run Java). Remember, Oracle technologies have been integrated with the Oracle Engineered Systems - this is the Oracle on Oracle advantage. But you can run other software environments such as SAP if you please too. Run any application that runs on Oracle Solaris 10 or Solaris 11. Separate them in Virtual Machines, or even Oracle Solaris Zones, monitor and manage those from a central UI. Here the key takeaways once again: The SPARC SuperCluster: Is a pre-integrated Engineered System Contains SPARC T4-4 servers with built-in virtualization, cryptography, dynamic threading Contains the Exadata storage cells that intelligently offload the burden of the DB-nodes  Contains a highly available ZFS Storage Appliance, that provides SAN/NAS storage in a unified way Combines all these elements over a high-speed, low-latency backbone network implemented with InfiniBand Can grow from a single half-rack to several full-rack size Supports the consolidation of hundreds of applications To summarize: All these technologies are great by themselves, but the real value is like in every other Oracle Engineered System: Integration. All these technologies are tuned to perform together. Together they are way more than the sum of all - and a careful and actually very time consuming integration process is necessary to orchestrate all these for performance. The SPARC SuperCluster's goal is to enable infrastructure operations and offer a pre-integrated solution that can be architected and delivered in hours instead of months of evaluations and tests. The tedious and most importantly time and resource consuming part of the work - testing and evaluating - has been done.  Now go, provide services.   -- charlie  

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• ASP.NET: Building tree picker dialog using jQuery UI and TreeView control

  - by DigiMortal

  Selecting things from dialogs and data represented as trees are very common things we see in business applications. In this posting I will show you how to use ASP.NET TreeView control and jQuery UI dialog component to build picker dialog that hosts tree data. Source code You can find working example with source code from my examples repository in GitHub. Please feel free to give me feedback about my examples. Source code repository GitHub Building dialog box As I don’t like to invent wheels then I will use jQuery UI to solve the question related to dialogs. If you are not sure how to include jQuery UI to your page then take a look at source code - GitHub also allows you to browse files without downloading them. I add some jQuery based JavaScript to my page head to get dialog and button work. <script type="text/javascript">     $(function () {         $("#dialog-form").dialog({             autoOpen: false,             modal: true         });         $("#pick-node")             .button()             .click(function () {                 $("#dialog-form").dialog("open");                 return false;             });     }); </script> Here is the mark-up of our form’s main content area. <div id="dialog-form" title="Select node">     <asp:TreeView ID="TreeView1" runat="server" ShowLines="True"          ClientIDMode="Static" HoverNodeStyle-CssClass="SelectedNode">         <Nodes>             <asp:TreeNode Text="Root" Value="Root">                 <asp:TreeNode Text="Child1" Value="Child1">                     <asp:TreeNode Text="Child1.1" Value="Child1.1" />                     <asp:TreeNode Text="Child1.2" Value="Child1.2" />                 </asp:TreeNode>                 <asp:TreeNode Text="Child2" Value="Child2">                     <asp:TreeNode Text="Child2.1" Value="Child2.1" />                     <asp:TreeNode Text="Child2.2" Value="Child2.2" />                 </asp:TreeNode>             </asp:TreeNode>         </Nodes>     </asp:TreeView>     &nbsp; </div> <button id="pick-node">Pick user</button> Notice that our mark-up is very compact for what we will achieve. If you are going to use it in some real-world application then this mark-up gets even shorter – I am sure that in most cases the data you display in TreeView comes from database or some domain specific data source. Hacking TreeView TreeView needs some little hacking to make it work as client-side component. Be warned that if you need more than I show you here you need to write a lot of JavaScript code. For more advanced scenarios I suggest you to use some jQuery based tree component. This example works for you if you need something done quickly. Number one problem is getting over the postbacks because in our scenario postbacks only screw up things. Also we need to find a way how to let our client-side code to know that something was selected from TreeView. We solve these to problems at same time: let’s move to JavaScript links. We have to make sure that when user clicks the node then information is sent to some JavaScript function. Also we have to make sure that this function returns something that is not processed by browser. My function is here. <script type="text/javascript">     function         $("#dialog-form").dialog("close");         alert("You selected: " + value + " - " + text);         return undefined;     } </script> Notice that this function returns undefined. You get the better idea why I did so if you look at server-side code that corrects NavigateUrl properties of TreeView nodes. protected override void OnPreRender(EventArgs e) {     base.OnPreRender(e);                 if (IsPostBack)         return;     SetSelectNodeUrls(TreeView1.Nodes); } private void SetSelectNodeUrls(TreeNodeCollection nodes) {     foreach (TreeNode node in nodes)     {         node.NavigateUrl = "javascript:selectNode('" + node.Value +                             "','" + node.Text + "');";         SetSelectNodeUrls(node.ChildNodes);     }        } Now we have TreeView that renders nodes the way that postback doesn’t happen anymore. Instead of postback our callback function is used and provided with selected values. In this function we are free to use node text and value as we like. Result I applied some more bells and whistles and sample data to source code to make my sample more informative. So, here is my final dialog box. Seems very basic but it is not hard to make it look more professional using style sheets. Conclusion jQuery components and ASP.NET controls have both their strong sides and weaknesses. In this posting I showed you how you can quickly produce good results when combining jQuery  and ASP.NET controls without pushing to the limits. We used simple hack to get over the postback issue of TreeView control and we made it work as client-side component that is initialized in server. You can find many other good combinations that make your UI more user-friendly and easier to use.

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• C#/.NET Little Wonders: Constraining Generics with Where Clause

  - by James Michael Hare

  Back when I was primarily a C++ developer, I loved C++ templates.  The power of writing very reusable generic classes brought the art of programming to a brand new level.  Unfortunately, when .NET 1.0 came about, they didn’t have a template equivalent.  With .NET 2.0 however, we finally got generics, which once again let us spread our wings and program more generically in the world of .NET However, C# generics behave in some ways very differently from their C++ template cousins.  There is a handy clause, however, that helps you navigate these waters to make your generics more powerful. The Problem – C# Assumes Lowest Common Denominator In C++, you can create a template and do nearly anything syntactically possible on the template parameter, and C++ will not check if the method/fields/operations invoked are valid until you declare a realization of the type.  Let me illustrate with a C++ example: 1: // compiles fine, C++ makes no assumptions as to T 2: template <typename T> 3: class ReverseComparer 4: { 5: public: 6: int Compare(const T& lhs, const T& rhs) 7: { 8: return rhs.CompareTo(lhs); 9: } 10: }; Notice that we are invoking a method CompareTo() off of template type T.  Because we don’t know at this point what type T is, C++ makes no assumptions and there are no errors. C++ tends to take the path of not checking the template type usage until the method is actually invoked with a specific type, which differs from the behavior of C#: 1: // this will NOT compile! C# assumes lowest common denominator. 2: public class ReverseComparer<T> 3: { 4: public int Compare(T lhs, T rhs) 5: { 6: return lhs.CompareTo(rhs); 7: } 8: } So why does C# give us a compiler error even when we don’t yet know what type T is?  This is because C# took a different path in how they made generics.  Unless you specify otherwise, for the purposes of the code inside the generic method, T is basically treated like an object (notice I didn’t say T is an object). That means that any operations, fields, methods, properties, etc that you attempt to use of type T must be available at the lowest common denominator type: object.  Now, while object has the broadest applicability, it also has the fewest specific.  So how do we allow our generic type placeholder to do things more than just what object can do? Solution: Constraint the Type With Where Clause So how do we get around this in C#?  The answer is to constrain the generic type placeholder with the where clause.  Basically, the where clause allows you to specify additional constraints on what the actual type used to fill the generic type placeholder must support. You might think that narrowing the scope of a generic means a weaker generic.  In reality, though it limits the number of types that can be used with the generic, it also gives the generic more power to deal with those types.  In effect these constraints says that if the type meets the given constraint, you can perform the activities that pertain to that constraint with the generic placeholders. Constraining Generic Type to Interface or Superclass One of the handiest where clause constraints is the ability to specify the type generic type must implement a certain interface or be inherited from a certain base class. For example, you can’t call CompareTo() in our first C# generic without constraints, but if we constrain T to IComparable<T>, we can: 1: public class ReverseComparer<T> 2: where T : IComparable<T> 3: { 4: public int Compare(T lhs, T rhs) 5: { 6: return lhs.CompareTo(rhs); 7: } 8: } Now that we’ve constrained T to an implementation of IComparable<T>, this means that our variables of generic type T may now call any members specified in IComparable<T> as well.  This means that the call to CompareTo() is now legal. If you constrain your type, also, you will get compiler warnings if you attempt to use a type that doesn’t meet the constraint.  This is much better than the syntax error you would get within C++ template code itself when you used a type not supported by a C++ template. Constraining Generic Type to Only Reference Types Sometimes, you want to assign an instance of a generic type to null, but you can’t do this without constraints, because you have no guarantee that the type used to realize the generic is not a value type, where null is meaningless. Well, we can fix this by specifying the class constraint in the where clause.  By declaring that a generic type must be a class, we are saying that it is a reference type, and this allows us to assign null to instances of that type: 1: public static class ObjectExtensions 2: { 3: public static TOut Maybe<TIn, TOut>(this TIn value, Func<TIn, TOut> accessor) 4: where TOut : class 5: where TIn : class 6: { 7: return (value != null) ? accessor(value) : null; 8: } 9: } In the example above, we want to be able to access a property off of a reference, and if that reference is null, pass the null on down the line.  To do this, both the input type and the output type must be reference types (yes, nullable value types could also be considered applicable at a logical level, but there’s not a direct constraint for those). Constraining Generic Type to only Value Types Similarly to constraining a generic type to be a reference type, you can also constrain a generic type to be a value type.  To do this you use the struct constraint which specifies that the generic type must be a value type (primitive, struct, enum, etc). Consider the following method, that will convert anything that is IConvertible (int, double, string, etc) to the value type you specify, or null if the instance is null. 1: public static T? ConvertToNullable<T>(IConvertible value) 2: where T : struct 3: { 4: T? result = null; 5:  6: if (value != null) 7: { 8: result = (T)Convert.ChangeType(value, typeof(T)); 9: } 10:  11: return result; 12: } Because T was constrained to be a value type, we can use T? (System.Nullable<T>) where we could not do this if T was a reference type. Constraining Generic Type to Require Default Constructor You can also constrain a type to require existence of a default constructor.  Because by default C# doesn’t know what constructors a generic type placeholder does or does not have available, it can’t typically allow you to call one.  That said, if you give it the new() constraint, it will mean that the type used to realize the generic type must have a default (no argument) constructor. Let’s assume you have a generic adapter class that, given some mappings, will adapt an item from type TFrom to type TTo.  Because it must create a new instance of type TTo in the process, we need to specify that TTo has a default constructor: 1: // Given a set of Action<TFrom,TTo> mappings will map TFrom to TTo 2: public class Adapter<TFrom, TTo> : IEnumerable<Action<TFrom, TTo>> 3: where TTo : class, new() 4: { 5: // The list of translations from TFrom to TTo 6: public List<Action<TFrom, TTo>> Translations { get; private set; } 7:  8: // Construct with empty translation and reverse translation sets. 9: public Adapter() 10: { 11: // did this instead of auto-properties to allow simple use of initializers 12: Translations = new List<Action<TFrom, TTo>>(); 13: } 14:  15: // Add a translator to the collection, useful for initializer list 16: public void Add(Action<TFrom, TTo> translation) 17: { 18: Translations.Add(translation); 19: } 20:  21: // Add a translator that first checks a predicate to determine if the translation 22: // should be performed, then translates if the predicate returns true 23: public void Add(Predicate<TFrom> conditional, Action<TFrom, TTo> translation) 24: { 25: Translations.Add((from, to) => 26: { 27: if (conditional(from)) 28: { 29: translation(from, to); 30: } 31: }); 32: } 33:  34: // Translates an object forward from TFrom object to TTo object. 35: public TTo Adapt(TFrom sourceObject) 36: { 37: var resultObject = new TTo(); 38:  39: // Process each translation 40: Translations.ForEach(t => t(sourceObject, resultObject)); 41:  42: return resultObject; 43: } 44:  45: // Returns an enumerator that iterates through the collection. 46: public IEnumerator<Action<TFrom, TTo>> GetEnumerator() 47: { 48: return Translations.GetEnumerator(); 49: } 50:  51: // Returns an enumerator that iterates through a collection. 52: IEnumerator IEnumerable.GetEnumerator() 53: { 54: return GetEnumerator(); 55: } 56: } Notice, however, you can’t specify any other constructor, you can only specify that the type has a default (no argument) constructor. Summary The where clause is an excellent tool that gives your .NET generics even more power to perform tasks higher than just the base "object level" behavior.  There are a few things you cannot specify with constraints (currently) though: Cannot specify the generic type must be an enum. Cannot specify the generic type must have a certain property or method without specifying a base class or interface – that is, you can’t say that the generic must have a Start() method. Cannot specify that the generic type allows arithmetic operations. Cannot specify that the generic type requires a specific non-default constructor. In addition, you cannot overload a template definition with different, opposing constraints.  For example you can’t define a Adapter<T> where T : struct and Adapter<T> where T : class.  Hopefully, in the future we will get some of these things to make the where clause even more useful, but until then what we have is extremely valuable in making our generics more user friendly and more powerful!   Technorati Tags: C#,.NET,Little Wonders,BlackRabbitCoder,where,generics

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• How do I get a rt2800usb wireless device working?

  - by Jii

  My brand new desktop running 13.04 has endless problems with wireless. Dozens of others are flooding forums with reports of the same problems. It worked fine for a few days, then there were a few days where it started having problems sometimes and working sometimes. Now it never works at all. I have 5+ devices all able to connect without any trouble at all, including iPhone, Android phone, 3DS, multiple game consoles, a laptop running windows 7, and even a second desktop machine running Ubuntu 12.04 sitting right behind the 13.04 machine. All other devices have full wireless bars displayed (strong signals). At any moment, one of the following is happening, and it changes randomly: Trying to connect forever, but never establishing a connection. Wireless icon constantly animating. Finds no wireless networks at all. (There are 12+ in range according to other devices.) Will not try to connect to the network. If I use the icon to connect, it will display "Disconnected" within a few seconds. Will continuously ask for the network password. Typing it in correctly does not help. Wireless is working fine. This happens sometimes. It can work for days at a time, or only 10 mins at a time. Various things that usually do nothing but sometimes fix the problem: Reboot. This has the best chance of helping, but it usually takes 5+ times. Disable/re-enable Wi-Fi using the wireless icon. Disable/re-enable Networking using the wireless icon. Use the icon to try and connect to a network (if found). Use the icon to open Edit Connections and delete my connection info, causing it to be recreated (once it's actually found again). Various things that seem to make no difference: Changing between using Linux headers in grub at bootup, between 3.10.0, 3.9.0, or 3.8.0. Move the wireless router very close to the desktop. Running sudo rfkill unblock all (I dunno what this is supposed to do.) I've used Ubuntu for 6 years and I've never had a problem with networking. Now I'm spending all my time reading through endless problem reports and trying all the answers. None of them have helped. I am doing this instead of getting work done, which is defeating the whole purpose of using Ubuntu. It's heartbreaking to be honest. In the current state of "no networks are showing up", here are outputs from the random things that other people are usually asked to run: lspic 00:00.0 Host bridge: Intel Corporation Haswell DRAM Controller (rev 06) 00:01.0 PCI bridge: Intel Corporation Haswell PCI Express x16 Controller (rev 06) 00:14.0 USB controller: Intel Corporation Lynx Point USB xHCI Host Controller (rev 04) 00:16.0 Communication controller: Intel Corporation Lynx Point MEI Controller #1 (rev 04) 00:19.0 Ethernet controller: Intel Corporation Ethernet Connection I217-V (rev 04) 00:1a.0 USB controller: Intel Corporation Lynx Point USB Enhanced Host Controller #2 (rev 04) 00:1b.0 Audio device: Intel Corporation Lynx Point High Definition Audio Controller (rev 04) 00:1c.0 PCI bridge: Intel Corporation Lynx Point PCI Express Root Port #1 (rev d4) 00:1c.2 PCI bridge: Intel Corporation 82801 PCI Bridge (rev d4) 00:1d.0 USB controller: Intel Corporation Lynx Point USB Enhanced Host Controller #1 (rev 04) 00:1f.0 ISA bridge: Intel Corporation Lynx Point LPC Controller (rev 04) 00:1f.2 SATA controller: Intel Corporation Lynx Point 6-port SATA Controller 1 [AHCI mode] (rev 04) 00:1f.3 SMBus: Intel Corporation Lynx Point SMBus Controller (rev 04) 01:00.0 VGA compatible controller: NVIDIA Corporation GF119 [GeForce GT 610] (rev a1) 01:00.1 Audio device: NVIDIA Corporation GF119 HDMI Audio Controller (rev a1) 03:00.0 PCI bridge: ASMedia Technology Inc. ASM1083/1085 PCIe to PCI Bridge (rev 03) lsmod Module Size Used by e100 41119 0 nls_iso8859_1 12713 1 parport_pc 28284 0 ppdev 17106 0 bnep 18258 2 rfcomm 47863 12 binfmt_misc 17540 1 arc4 12573 2 rt2800usb 27201 0 rt2x00usb 20857 1 rt2800usb rt2800lib 68029 1 rt2800usb rt2x00lib 55764 3 rt2x00usb,rt2800lib,rt2800usb coretemp 13596 0 mac80211 656164 3 rt2x00lib,rt2x00usb,rt2800lib kvm_intel 138733 0 kvm 452835 1 kvm_intel cfg80211 547224 2 mac80211,rt2x00lib crc_ccitt 12707 1 rt2800lib ghash_clmulni_intel 13259 0 aesni_intel 55449 0 usb_storage 61749 1 aes_x86_64 17131 1 aesni_intel joydev 17613 0 xts 12922 1 aesni_intel nouveau 1001310 3 snd_hda_codec_hdmi 37407 1 lrw 13294 1 aesni_intel gf128mul 14951 2 lrw,xts mxm_wmi 13021 1 nouveau snd_hda_codec_realtek 46511 1 ablk_helper 13597 1 aesni_intel wmi 19256 2 mxm_wmi,nouveau snd_hda_intel 44397 5 ttm 88251 1 nouveau drm_kms_helper 49082 1 nouveau drm 295908 5 ttm,drm_kms_helper,nouveau snd_hda_codec 190010 3 snd_hda_codec_realtek,snd_hda_codec_hdmi,snd_hda_intel cryptd 20501 3 ghash_clmulni_intel,aesni_intel,ablk_helper snd_hwdep 13613 1 snd_hda_codec snd_pcm 102477 3 snd_hda_codec_hdmi,snd_hda_codec,snd_hda_intel btusb 18291 0 snd_page_alloc 18798 2 snd_pcm,snd_hda_intel snd_seq_midi 13324 0 i2c_algo_bit 13564 1 nouveau snd_seq_midi_event 14899 1 snd_seq_midi snd_rawmidi 30417 1 snd_seq_midi snd_seq 61930 2 snd_seq_midi_event,snd_seq_midi bluetooth 251354 22 bnep,btusb,rfcomm snd_seq_device 14497 3 snd_seq,snd_rawmidi,snd_seq_midi lpc_ich 17060 0 snd_timer 29989 2 snd_pcm,snd_seq mei 46588 0 snd 69533 20 snd_hda_codec_realtek,snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_pcm,snd_seq,snd_rawmidi,snd_hda_codec,snd_hda_intel,snd_seq_device psmouse 97838 0 microcode 22923 0 soundcore 12680 1 snd video 19467 1 nouveau mac_hid 13253 0 serio_raw 13215 0 lp 17799 0 parport 46562 3 lp,ppdev,parport_pc hid_generic 12548 0 usbhid 47346 0 hid 101248 2 hid_generic,usbhid ahci 30063 3 libahci 32088 1 ahci e1000e 207005 0 ptp 18668 1 e1000e pps_core 14080 1 ptp sudo lshw -c network 00:00.0 Host bridge: Intel Corporation Haswell DRAM Controller (rev 06) 00:01.0 PCI bridge: Intel Corporation Haswell PCI Express x16 Controller (rev 06) 00:14.0 USB controller: Intel Corporation Lynx Point USB xHCI Host Controller (rev 04) 00:16.0 Communication controller: Intel Corporation Lynx Point MEI Controller #1 (rev 04) 00:19.0 Ethernet controller: Intel Corporation Ethernet Connection I217-V (rev 04) 00:1a.0 USB controller: Intel Corporation Lynx Point USB Enhanced Host Controller #2 (rev 04) 00:1b.0 Audio device: Intel Corporation Lynx Point High Definition Audio Controller (rev 04) 00:1c.0 PCI bridge: Intel Corporation Lynx Point PCI Express Root Port #1 (rev d4) 00:1c.2 PCI bridge: Intel Corporation 82801 PCI Bridge (rev d4) 00:1d.0 USB controller: Intel Corporation Lynx Point USB Enhanced Host Controller #1 (rev 04) 00:1f.0 ISA bridge: Intel Corporation Lynx Point LPC Controller (rev 04) 00:1f.2 SATA controller: Intel Corporation Lynx Point 6-port SATA Controller 1 [AHCI mode] (rev 04) 00:1f.3 SMBus: Intel Corporation Lynx Point SMBus Controller (rev 04) 01:00.0 VGA compatible controller: NVIDIA Corporation GF119 [GeForce GT 610] (rev a1) 01:00.1 Audio device: NVIDIA Corporation GF119 HDMI Audio Controller (rev a1) 03:00.0 PCI bridge: ASMedia Technology Inc. ASM1083/1085 PCIe to PCI Bridge (rev 03) sudo iwconfig eth0 no wireless extensions. lo no wireless extensions. wlan0 IEEE 802.11bgn ESSID:off/any Mode:Managed Access Point: Not-Associated Tx-Power=20 dBm Retry long limit:7 RTS thr:off Fragment thr:off Encryption key:off Power Management:on sudo iwlist scan eth0 Interface doesn't support scanning. lo Interface doesn't support scanning. wlan0 No scan results NOTE: This dmesg was done after a reboot where the network manager was continuously displaying the "disconnected" message over and over. So it must have been trying to connect at this time. My network was displayed in the list of options, as the only option despite other devices picking up 12+ access points. The router channel is set to auto. dmesg | tail -30 [ 187.418446] wlan0: associated [ 190.405601] wlan0: disassociated from 00:14:d1:a8:c3:44 (Reason: 15) [ 190.443312] cfg80211: Calling CRDA to update world regulatory domain [ 190.443431] wlan0: deauthenticating from 00:14:d1:a8:c3:44 by local choice (reason=3) [ 190.451635] cfg80211: World regulatory domain updated: [ 190.451643] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) [ 190.451648] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 190.451652] cfg80211: (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) [ 190.451656] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) [ 190.451659] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 190.451662] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 191.824451] wlan0: authenticate with 00:14:d1:a8:c3:44 [ 191.850608] wlan0: send auth to 00:14:d1:a8:c3:44 (try 1/3) [ 191.884604] wlan0: send auth to 00:14:d1:a8:c3:44 (try 2/3) [ 191.886309] wlan0: authenticated [ 191.886579] rt2800usb 3-5.3:1.0 wlan0: disabling HT as WMM/QoS is not supported by the AP [ 191.886588] rt2800usb 3-5.3:1.0 wlan0: disabling VHT as WMM/QoS is not supported by the AP [ 191.889556] wlan0: associate with 00:14:d1:a8:c3:44 (try 1/3) [ 192.001493] wlan0: associate with 00:14:d1:a8:c3:44 (try 2/3) [ 192.040274] wlan0: RX AssocResp from 00:14:d1:a8:c3:44 (capab=0x431 status=0 aid=3) [ 192.044235] wlan0: associated [ 193.948188] wlan0: deauthenticating from 00:14:d1:a8:c3:44 by local choice (reason=3) [ 193.981501] cfg80211: Calling CRDA to update world regulatory domain [ 193.984080] cfg80211: World regulatory domain updated: [ 193.984082] cfg80211: (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp) [ 193.984084] cfg80211: (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 193.984085] cfg80211: (2457000 KHz - 2482000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) [ 193.984085] cfg80211: (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm) [ 193.984086] cfg80211: (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) [ 193.984087] cfg80211: (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm) The router uses MAC filtering, and security is WPA PSK with cipher as auto. So, any ideas? Or is the solution just to not use 13.04 unless you have a wired connection? (I don't have this option.) If so, please just tell me straight. I survived 9.04 Jaunty, and I can survive 13.04 Raring. Update #1 Results from trying Wild Man's first answer: jii@conan:~$ echo "options rt2800usb nohwcrypt=y" | sudo tee /etc/modprobe.d/rt2800usb.conf options rt2800usb nohwcrypt=y jii@conan:~$ sudo modprobe -rfv rt2800usb rmmod rt2800usb rmmod rt2800lib rmmod crc_ccitt rmmod rt2x00usb rmmod rt2x00lib rmmod mac80211 rmmod cfg80211 jii@conan:~$ sudo modprobe -v rt2800usb insmod /lib/modules/3.10.0-031000-generic/kernel/lib/crc-ccitt.ko insmod /lib/modules/3.10.0-031000-generic/kernel/net/wireless/cfg80211.ko insmod /lib/modules/3.10.0-031000-generic/kernel/net/mac80211/mac80211.ko insmod /lib/modules/3.10.0-031000-generic/kernel/drivers/net/wireless/rt2x00/rt2x00lib.ko insmod /lib/modules/3.10.0-031000-generic/kernel/drivers/net/wireless/rt2x00/rt2800lib.ko insmod /lib/modules/3.10.0-031000-generic/kernel/drivers/net/wireless/rt2x00/rt2x00usb.ko insmod /lib/modules/3.10.0-031000-generic/kernel/drivers/net/wireless/rt2x00/rt2800usb.ko nohwcrypt=y I tried: gksudo gedit /etc/pm/power.d/wireless but I didn't have the package. It said to install gksu. I tried that, but of course, not having Internet, I didn't get the package. So instead I did: sudo gedit /etc/pm/power.d/wireless Which created the file. Here is the body: #!/bin/sh /sbin/iwconfig wlan0 power off I then rebooted. No change. I tried adding exit 0 to the bottom of the wireless file, and rebooted. No change. Please note that this is a desktop machine. I'm assuming power management is primarily for laptops, but the iwconfig does state that power management is on, so who knows. The recommended router changes I did not do, since the current router settings are (I think) required for some of the older devices I have, and because the current settings work on all my modern devices including Ubuntu 12.04 and Windows 7. I do appreciate the advice though, and I'll look into it when I have time. Anything else to try? Update #2 I booted into Ubuntu 12.04.3 from a dvd, and the same problems exist. I have a separate old desktop machine with 12.04 installed that has no wireless problems at all. So obviously the problem is wireless hardware compatibility in both 12.04.03 LTS and 13.04. Update #3 The same problems exist even when using a wired connection. I plugged an ethernet cable directly to the router and the network manager added an "Auto Ethernet" entry, but it cannot establish a connection to it. So the problem is not specific to wireless. Meanwhile, I purchased a Trendnet N300 wireless USB adapter, TEW-664UB. I plugged it in, but I have no idea how to get Ubuntu to try and use it. Can anyone tell me how? Can I download a package on another computer and copy the .deb over to do an install, etc? I'm installing windows 7 to double check that the internet connection works there and it's not just some magically faulty hardware. Thanks for your help.

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• How to invalidate nginx reverse proxy cache in front of other nginx servers?

  - by Olivier Lance

  I'm running a Proxmox server on a single IP address, that will dispatch HTTP requests to containers depending on the requested host. I am using nginx on the Proxmox side to listen to HTTP requests and I am using the proxy_pass directive in my different server blocks to dispatch requests according to the server_name. My containers run on Ubuntu and are also running a nginx instance. I'm having troubles with caching on a particular website that is fully static: nginx keeps on serving me stale content after files updates, until I: Clear /var/cache/nginx/ and restart nginx or set proxy_cache off for this server and reload the config Here's the detail of my configuration: On the server (proxmox): /etc/nginx/nginx.conf: user www-data; worker_processes 8; pid /var/run/nginx.pid; events { worker_connections 768; # multi_accept on; use epoll; } http { ## # Basic Settings ## sendfile on; #tcp_nopush on; tcp_nodelay on; #keepalive_timeout 65; types_hash_max_size 2048; server_tokens off; # server_names_hash_bucket_size 64; # server_name_in_redirect off; include /etc/nginx/mime.types; default_type application/octet-stream; client_body_buffer_size 1k; client_max_body_size 8m; large_client_header_buffers 1 1K; ignore_invalid_headers on; client_body_timeout 5; client_header_timeout 5; keepalive_timeout 5 5; send_timeout 5; server_name_in_redirect off; ## # Logging Settings ## access_log /var/log/nginx/access.log; error_log /var/log/nginx/error.log; ## # Gzip Settings ## gzip on; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; gzip_vary on; gzip_proxied any; gzip_comp_level 6; # gzip_buffers 16 8k; gzip_http_version 1.1; gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript; limit_conn_zone $binary_remote_addr zone=gulag:1m; limit_conn gulag 50; ## # Virtual Host Configs ## include /etc/nginx/conf.d/*.conf; include /etc/nginx/sites-enabled/*; } /etc/nginx/conf.d/proxy.conf: proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_hide_header X-Powered-By; proxy_intercept_errors on; proxy_buffering on; proxy_cache_key "$scheme://$host$request_uri"; proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=cache:10m inactive=7d max_size=700m; /etc/nginx/sites-available/my-domain.conf: server { listen 80; server_name .my-domain.com; access_log off; location / { proxy_pass http://my-domain.local:80/; proxy_cache cache; proxy_cache_valid 12h; expires 30d; proxy_cache_use_stale error timeout invalid_header updating; } } On the container (my-domain.local): nginx.conf: (everything is inside the main config file -- it's been done quickly...) user www-data; worker_processes 1; error_log logs/error.log; events { worker_connections 1024; } http { include mime.types; default_type application/octet-stream; sendfile on; #tcp_nopush on; keepalive_timeout 65; gzip off; server { listen 80; server_name .my-domain.com; root /var/www; access_log logs/host.access.log; } } I've read many blog posts and answers before resolving to posting my own questions... most answers I can see suggest setting sendfile off; but that didn't work for me. I have tried many other things, double checked my settings and all seems fine. So I'm wondering whether I am not expecting nginx's cache to do something it's not meant to...? Basically, I thought that if one of my static files in my container was updated, the cache in my reverse proxy would be invalidated and my browser would get the new version of the file when it requests it... But I now have the sentiment I misunderstood many things. Of all things, I now wonder how nginx on the server can know about a file in the container has changed? I have seen a directive proxy_header_pass (or something alike), should I use this to let the nginx instance from the container somehow inform the one in Proxmox about updated files? Is this expectation just a dream, or can I do it with nginx on my current architecture?

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• Contract Work - Lessons Learned

  - by samerpaul

  I thought I would write a post of a different nature today, but still relevant to the tech world. I do a lot of contract jobs myself and really enjoy it. It's nice to keep jumping from project to project, and not having to go to an office or keep regular hours, etc. I really enjoy it. I have learned a lot in the past few years of doing it (both from experience and from help given to me from others, and the internet) so I thought I'd share some of that knowledge/experience today.So here's my own personal "lesson's learned" that hopefully will help you if you find yourself doing contract work:Should I take the job?Ok, so this is the first step. Assuming you were given sufficient information about what they want, then you should really think about what you're capable of doing and whether or not you should take this job. Personally, my rule is, if I know it's possible, I'll say yes, even if I don't yet know how to do it. That's because the internet is such a great help, it would be rare to run into an issue that you can't figure out with some help. So if your clients are asking for something that you don't yet know how to program, but you know you can do it on the platform then go for it. How else are you going to learn?Use this rule with some limitation, however. If you're really lacking the expertise or foundation in something, then unless you have tons of time to complete the project, then I wouldn't say yes. For example, I haven't personally done any 3d/openGL programming yet so I wouldn't say yes to a project that extensively uses it. OK, so I want the job, but how much do I charge?This part can be tricky. There is no set formula really, but I have some tips for pricing that will hopefully give you a better idea on how to confidently ask your price and have them accept. Here are some personal guidelinesHow much time do you have to complete the project? If it's shorter than average, then charge more. You can even make a subtle note about this (or not so subtle if they still don't get it.) If it seems too short of a time (i.e. near impossible to complete), be sure to say that. It looks bad to promise a time that you can't keep--and it makes it less likely for them to return to you for work.Your Hourly rate: How long have you been working in that language? Do you have existing projects to back you up? Or previous contacts that can vouch for your work? Are there very few people with your particular skill set? All of these things will lend themselves to setting an hourly rate. I'd also try out a quick google search of what your line of work is, to see what the industry standard is at that point in time.I wouldn't price too low, because you want to make your time worth it. You also want them to feel like they're paying for quality work (assuming you can deliver it :) ). Finally, think about your client. If it's a small business, then don't price it too high if you want the job. If it's an enterprise (like a Fortune company), then don't be afraid to price higher. They have the budget for it.Fixed price: If they want a fixed price project, then you need to think about how many hours it will take you to complete it and multiply it by the hourly rate you set for yourself. Then, honestly, I would add 10-20% on top of that. Why? Because nothing ever works exactly how you want it to. There are lots of times that something "trivial" is way harder than it should be, or something that "should work" doesn't for hours and it eats away at your hourly rate. I can't count the number of times I encountered a logical bug that took away an entire's day work because debuggers don't help in those cases. By adding that padding in, it's still OK to have those days where you don't get as much done as you want. And another useful tip: Depending on your client, and the scope, you most likely want to set that you both sign off on a specification sheet before doing any work, and that any changes will result in a re-evaulation of the price. This is to help protect you from being handed a huge new addition to the project half-way in, without any extra payment.Scope of project: Finally, is it a huge project? Is it really small/fast? This affects how much your client will be willing to pay. If it sounds big, they will be willing to pay more for it. If it seems really small, then you won't be able to get away with a large asking price (as easily).Ok, I priced it, now what?So now that you have the price, you want to make sure it feels justified to your client. I never set a price before I can really think about everything. For example, if you're still in your introduction phase, and they want a price, don't give one! Just comment that you will send them a proposal sheet with all the features outlined, and a price for everything. You don't want to shout out a low number and then deliver something that is way higher. You also don't want to shock them with a big number before they feel like they are getting a great product.Make up a proposal document in a word editor. Personally, I leave the price till the very end. Why? Because by the time they reach the end, you've already discussed all the great features you plan to implement, and how it's the best product they'll ever use, etc etc...so your price comes off as a steal! If you hit them up front with a price, they will read through the document with a negative bias. Think about those commercials on TV. They always go on about their product, then at the end, ask "What would you pay for something like this? $100? $50? How about $20!!". This is not by accident.Scenario: I finished the job way earlier than expectedYou have two options then. You can either polish the hell out of the application, and even throw in a few bonus features (assuming they are in-line with the customer's needs) or you can sit and wait on it until you near your deadline. Why don't you want to turn it in too early? Because you should treat that extra time as a surplus. If you said it is going to take you 3 weeks, and it took you only 1, you have a surplus of 2 weeks. I personally don't want to let them know that I can do a 3 week project in 1 week. Why not? Because that may not always be the case! I may later have a 3 week project that takes all 3 weeks, but if I set a precedent of delivering super early, then the pressure is on for that longer project. It also makes it harder to quote longer times if you keep delivering too early.Feel free to deliver early, but again, don't do it too early. They may also wonder why they paid you for 3 weeks of work if you're done in 1. They may further wonder if the product sucks, or what is wrong with it, if it's done so early, etc.I would just polish the application. Everyone loves polish in their applications. The smallest details are what make an application go from "functional" to "fantastic". And since you are still delivering on time, then they are still going to be very happy with you.Scenario: It's taking way too long to finish this, and the deadline is nearing/here!So this is not a fun scenario to be in, but it'll happen. Sometimes the scope of the project gets out of hand. The best policy here is OPENNESS/HONESTY. Tell them that the project is taking longer than expected, and give a reasonable time for when you think you'll have it done. I typically explain it in a way that makes it sound like it isn't something that I did wrong, but it's just something about the nature of the project. This really goes for any scenario, to be honest. Just continue to stay open and communicative about your progress. This doesn't mean that you should email them every five minutes (unless they want you to), but it does mean that maybe every few days or once a week, give them an update on where you're at, and what's next. They'll be happy to know they are paying for progress, and it'll make it easier to ask for an extension when something goes wrong, because they know that you've been working on it all along.Final tips and thoughts:In general, contract work is really fun and rewarding. It's nice to learn new things all the time, as mandated by the project ,and to challenge yourself to do things you may not have done before. The key is to build a great relationship with your clients for future work, and for recommendations. I am always very honest with them and I never promise something I can't deliver. Again, under promise, over deliver!I hope this has proved helpful!Cheers,samerpaul

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• Web browsing is fast, but downloads are slow

  - by Ricket

  I work for a company on my university's campus, helping with general IT problems and some web development. But lately there has been a problem that has me and my boss completely stumped. We, plus one contractor, make up the entire IT department, so I'm reaching out to you for help. All around the office, we have wall jacks. These collect in a closet down the hall and all plug into a switch. This switch, along with our individual server jacks, plugs into another switch, and that switch plugs into our firewall hardware. Then the firewall is connected out to our campus network. Our campus internet is, well, very fast. I don't know exactly the terms, tiers, etc., but we have thousands of students and downloads can run as fast as 10 MB/s at night; uploads are sometimes even faster. I think we're practically ISP level. In short, I have a lot of faith that it is not the campus side of things that is causing a problem, combined with other evidence I'll mention in a moment. So our symptoms: web browsing is fast. Web pages, images, etc. load instantly. No problems there. But then when I go to download something, the download starts fast but very quickly (a matter of seconds) drops to nearly 0. Often it will actually drop to 0 and time out. This happens with even very small files, 1 MB or less. It smells to me like a QoS sort of thing. I'm not entirely sure, and I wanted to get your opinions first. My boss is hesitant to touch our firewall, much less let me touch it, and it was set up and is managed by a consultant remotely. These problems don't seem tied to a time of the day. I've tried downloads after 5:00 and still the same thing happens. From my desk, I can turn on my wireless adapter and pick up the campus wireless access point. If I unplug ethernet and connect to it, downloads are fast. This adds to my suspicion that it's limited to our company network. Also, a number of weeks ago the consultant upgraded our firewall firmware. Suddenly everything was very fast. I tested with downloads from Sun and speedtest.net and things were blazing fast, as they should be with our campus internet! It was wonderful, and I figured the slow speeds were an old firmware bug. In a matter of days, things steadily declined until they were back to the old symptoms. Oh, and we have antivirus installed on every computer, and we keep it up to date. Though I suppose the possibility is still there that someone could have spyware which is bogging down our internet, in which case what is the easiest/best way to find this out? (maybe this should go in a separate question) Thank you for your patience in reading all of this. Do you have any ideas as to what I can try? Is this something that you've experienced before? What sort of tools or methods can I use to try and diagnose the problem? P.S. everything here is Windows. Windows Server 2003 and 2008 on our servers, and Windows XP on employees' machines. Update: We are submitting a ticket to the university to just take a look and see if they see anything unusual and/or can suggestion methods for us to try and pinpoint our problem. Hopefully they'll be helpful! I'll update this to let you know what goes on. Update again: We found a hub (yes, a HUB) right between our campus connection and our firewall. It had only those two ethernet cables plugged into it, nothing else. After removing the hub, our speeds have jumped up to several mbps. However in talking with the campus, we got them to run a gigabit line to our firewall in place of the 100mbps line. As of friday, we are at about 65 mbps up and down (according to speedtest.net at 8am)!! Go NC State!!

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• Building Enterprise Smartphone App &ndash; Part 4: Application Development Considerations

  - by Tim Murphy

  This is the final part in a series of posts based on a talk I gave recently at the Chicago Information Technology Architects Group.  Feel free to leave feedback. Application Development Considerations Now we get to the actual building of your solutions.  What are the skills and resources that will be needed in order to develop a smartphone application in the enterprise? Language Knowledge One of the first things you need to consider when you are deciding which platform language do you either have the most in house skill base or can you easily acquire.  If you already have developers who know Java or C# you may want to use either Android or Windows Phone.  You should also take into consideration the market availability of developers.  If your key developer leaves how easy is it to find a knowledgeable replacement? A second consideration when it comes to programming languages is the qualities exposed by the languages of a particular platform.  How well does that development language and its associated frameworks support things like security and access to the features of the smartphone hardware?  This will play into your overall cost of ownership if you have to create this infrastructure on your own. Manage Limited Resources Everything is limited on a smartphone: battery, memory, processing power, network bandwidth.  When developing your applications you will have to keep your footprint as small as possible in every way.  This means not running unnecessary processes in the background that will drain the battery or pulling more data over the airwaves than you have to.  You also want to keep your on device in as compact a format as possible. Mobile Design Patterns There are a number of design patterns that have either come to life because of smartphone development or have been adapted for this use.  The main pattern in the Windows Phone environment is the MVVM (Model-View-View-Model).  This is great for overall application structure and separation of concerns.  The fun part is trying to keep that separation as pure as possible.  Many of the other patterns may or may not have strict definitions, but some that you need to be concerned with are push notification, asynchronous communication and offline data storage. Real estate is limited on smartphones and even tablets. You are also limited in the type of controls that can be represented in the UI. This means rethinking how you modularize your application. Typing is also much harder to do so you want to reduce this as much as possible.  This leads to UI patterns.  While not what we would traditionally think of as design patterns the guidance each platform has for UI design is critical to the success of your application.  If user find the application difficult navigate they will not use it. Development Process Because of the differences in development tools required, test devices and certification and deployment processes your teams will need to learn new way of working together.  This will include the need to integrate service contracts of back-end systems with mobile applications.  You will also want to make sure that you present consistency across different access points to corporate data.  Your web site may have more functionality than your smartphone application, but it should have a consistent core set of functionality.  This all requires greater communication between sub-teams of your developers. Testing Process Testing of smartphone apps has a lot more to do with what happens when you lose connectivity or if the user navigates away from your application. There are a lot more opportunities for the user or the device to perform disruptive acts.  This should be your main testing concentration aside from the main business requirements.  You will need to do things like setting the phone to airplane mode and seeing what the application does in order to weed out any gaps in your handling communication interruptions. Need For Outside Experts Since this is a development area that is new to most companies the need for experts is a lot greater. Whether these are consultants, vendor representatives or just development community forums you will need to establish expert contacts. Nothing is more dangerous for your project timelines than a lack of knowledge.  Make sure you know who to call to avoid lengthy delays in your project because of knowledge gaps. Security Security has to be a major concern for enterprise applications. You aren't dealing with just someone's game standings. You are dealing with a companies intellectual property and competitive advantage. As such you need to start by limiting access to the application itself.  Once the user is in the app you need to ensure that the data is secure at all times.  This includes both local storage and across the wire.  This means if a platform doesn’t natively support encryption for these functions you will need to find alternatives to secure your data.  You also need to keep secret (encryption) keys obfuscated or locked away outside of the application. People can disassemble the code otherwise and break your encryption. Offline Capabilities As we discussed earlier one your biggest concerns is not having connectivity.  Because of this a good portion of your code may be dedicated to handling loss of connection and reconnection situations.  What do you do if you lose the network?  Back up all your transactions and store of any supporting data so that operations can continue off line. In order to support this you will need to determine the available flat file or local data base capabilities of the platform.  Any failed transactions will need to support a retry mechanism whether it is automatic or user initiated.  This also includes your services since they will need to be able to roll back partially completed transactions.  What ever you do, don’t ignore this area when you are designing your system. Deployment Each platform has different deployment capabilities. Some are more suited to enterprise situations than others. Apple's approach is probably the most mature at the moment. Prior to the current generation of smartphone platforms it would have been Windows CE. Windows Phone 7 has the limitation that the app has to be distributed through the same network as public facing applications. You mark them as private which means that they are only accessible by a direct URL. Unfortunately this does not make them undiscoverable (although it is very difficult). This will change with Windows Phone 8 where companies will be able to certify their own applications and distribute them.  Given this Windows Phone applications need to be more diligent with application access in order to keep them restricted to the company's employees. My understanding of the Android deployment schemes is that it is much less standardized then either iOS or Windows Phone. Someone would have to confirm or deny that for me though since I have not yet put the time into researching this platform further. Given my limited exposure to the iOS and Android platforms I have not been able to confirm this, but there are varying degrees of user involvement to install and keep applications updated. At one extreme the user just goes to a website to do the install and in other case they may need to download files and perform steps to install them. Future Bluetooth Today we use Bluetooth for keyboards, mice and headsets.  In the future it could be used to interrogate car computers or manufacturing systems or possibly retail machines by service techs.  This would open smartphones to greater use as a almost a Star Trek Tricorder.  You would get you all your data as well as being able to use it as a universal remote for just about any device or machine. Better corporation controlled deployment At least in the Windows Phone world the upcoming release of Windows Phone 8 will include a private certification and deployment option that is currently not available with Windows Phone 7 (Mango). We currently have to run the apps through the Marketplace certification process and use a targeted distribution method. Platform independent approaches HTML5 and JavaScript with Web Service has become a popular topic lately for not only creating flexible web site, but also creating cross platform mobile applications.  I’m not yet convinced that this lowest common denominator approach is viable in most cases, but it does have it’s place and seems to be growing.  Be sure to keep an eye on it. Summary From my perspective enterprise smartphone applications can offer a great competitive advantage to many companies.  They are not cheap to build and should be approached cautiously.  Understand the factors I have outlined in this series, do you due diligence and see if there is a portion of your business that can benefit from the mobile experience. del.icio.us Tags: Architecture,Smartphones,Windows Phone,iOS,Android

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• Stumbling Through: Visual Studio 2010 (Part IV)

  So finally we get to the fun part the fruits of all of our middle-tier/back end labors of generating classes to interface with an XML data source that the previous posts were about can now be presented quickly and easily to an end user.  I think.  Well see.  Well be using a WPF window to display all of our various MFL information that weve collected in the two XML files, and well provide a means of adding, updating and deleting each of these entities using as little code as possible.  Additionally, I would like to dig into the performance of this solution as well as the flexibility of it if were were to modify the underlying XML schema.  So first things first, lets create a WPF project and include our xml data in a data folder within.  On the main window, well drag out the following controls: A combo box to contain all of the teams A list box to show the players of the selected team, along with add/delete player buttons A text box tied to the selected players name, with a save button to save any changes made to the player name A combo box of all the available positions, tied to the currently selected players position A data grid tied to the statistics of the currently selected player, with add/delete statistic buttons This monstrosity of a form and its associated project will look like this (dont forget to reference the DataFoundation project from the Presentation project): To get to the visual data binding, as we learned in a previous post, you have to first make sure the project containing your bindable classes is compiled.  Do so, and then open the Data Sources pane to add a reference to the Teams and Positions classes in the DataFoundation project: Why only Team and Position?  Well, we will get to Players from Teams, and Statistics from Players so no need to make an interface for them as well see in a second.  As for Positions, well need a way to bind the dropdown to ALL positions they dont appear underneath any of the other classes so we need to reference it directly.  After adding these guys, expand every node in your Data Sources pane and see how the Team node allows you to drill into Players and then Statistics.  This is why there was no need to bring in a reference to those classes for the UI we are designing: Now for the seriously hard work of binding all of our controls to the correct data sources.  Drag the following items from the Data Sources pane to the specified control on the window design canvas: Team.Name > Teams combo box Team.Players.Name > Players list box Team.Players.Name > Player name text box Team.Players.Statistics > Statistics data grid Position.Name > Positions combo box That is it!  Really?  Well, no, not really there is one caveat here in that the Positions combo box is not bound the selected players position.  To do so, we will apply a binding to the position combo boxs SelectedValue to point to the current players PositionId value: That should do the trick now, all we need to worry about is loading the actual data.  Sadly, it appears as if we will need to drop to code in order to invoke our IO methods to load all teams and positions.  At least Visual Studio kindly created the stubs for us to do so, ultimately the code should look like this: Note the weirdness with the InitializeDataFiles call that is my current means of telling an IO where to load the data for each of the entities.  I havent thought of a more intuitive way than that yet, but do note that all data is loaded from Teams.xml besides for positions, which is loaded from Lookups.xml.   I think that may be all we need to do to at least load all of the data, lets run it and see: Yay!  All of our glorious data is being displayed!  Er, wait, whats up with the position dropdown?  Why is it red?  Lets select the RB and see if everything updates: Crap, the position didnt update to reflect the selected player, but everything else did.  Where did we go wrong in binding the position to the selected player?  Thinking about it a bit and comparing it to how traditional data binding works, I realize that we never set the value member (or some similar property) to tell the control to join the Id of the source (positions) to the position Id of the player.  I dont see a similar property to that on the combo box control, but I do see a property named SelectedValuePath that might be it, so I set it to Id and run the app again: Hey, all right!  No red box around the positions combo box.  Unfortunately, selecting the RB does not update the dropdown to point to Runningback.  Hmmm.  Now what could it be?  Maybe the problem is that we are loading teams before we are loading positions, so when it binds position Id, all of the positions arent loaded yet.  I went to the code behind and switched things so position loads first and no dice.  Same result when I run.  Why?  WHY?  Ok, ok, calm down, take a deep breath.  Get something with caffeine or sugar (preferably both) and think rationally. Ok, gigantic chocolate chip cookie and a mountain dew chaser have never let me down in the past, so dont fail me now!  Ah ha!  of course!  I didnt even have to finish the mountain dew and I think Ive got it:  Data Context.  By default, when setting on the selected value binding for the dropdown, the data context was list_team.  I dont even know what the heck list_team is, we want it to be bound to our team players view source resource instead, like this: Running it now and selecting the various players: Done and done.  Everything read and bound, thank you caffeine and sugar!  Oh, and thank you Visual Studio 2010.  Lets wire up some of those buttons now There has got to be a better way to do this, but it works for now.  What the add player button does is add a new player object to the currently selected team.  Unfortunately, I couldnt get the new object to automatically show up in the players list (something about not using an observable collection gotta look into this) so I just save the change immediately and reload the screen.  Terrible, but it works: Lets go after something easier:  The save button.  By default, as we type in new text for the players name, it is showing up in the list box as updated.  Cool!  Why couldnt my add new player logic do that?  Anyway, the save button should be as simple as invoking MFL.IO.Save for the selected player, like this: MFL.IO.Save((MFL.Player)lbTeamPlayers.SelectedItem, true); Surprisingly, that worked on the first try.  Lets see if we get as lucky with the Delete player button: MFL.IO.Delete((MFL.Player)lbTeamPlayers.SelectedItem); Refresh(); Note the use of the Refresh method again I cant seem to figure out why updates to the underlying data source are immediately reflected, but adds and deletes are not.  That is a problem for another day, and again my hunch is that I should be binding to something more complex than IEnumerable (like observable collection). Now that an example of the basic CRUD methods are wired up, I want to quickly investigate the performance of this beast.  Im going to make a special button to add 30 teams, each with 50 players and 10 seasons worth of stats.  If my math is right, that will end up with 15000 rows of data, a pretty hefty amount for an XML file.  The save of all this new data took a little over a minute, but that is acceptable because we wouldnt typically be saving batches of 15k records, and the resulting XML file size is a little over a megabyte.  Not huge, but big enough to see some read performance numbers or so I thought.  It reads this file and renders the first team in under a second.  That is unbelievable, but we are lazy loading and the file really wasnt that big.  I will increase it to 50 teams with 100 players and 20 seasons each - 100,000 rows.  It took a year and a half to save all of that data, and resulted in an 8 megabyte file.  Seriously, if you are loading XML files this large, get a freaking database!  Despite this, it STILL takes under a second to load and render the first team, which is interesting mostly because I thought that it was loading that entire 8 MB XML file behind the scenes.  I have to say that I am quite impressed with the performance of the LINQ to XML approach, particularly since I took no efforts to optimize any of this code and was fairly new to the concept from the start.  There might be some merit to this little project after all Look out SQL Server and Oracle, use XML files instead!  Next up, I am going to completely pull the rug out from under the UI and change a number of entities in our model.  How well will the code be regenerated?  How much effort will be required to tie things back together in the UI?Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Understanding Node.js and concept of non-blocking I/O

  - by Saif Bechan

  Recently I became interested in using Node.js to tackle some of the parts of my web-application. I love the part that its full JavaScript and its very light weight so no use anymore to call an JavaScript-PHP call but a lighter JavaScript-JavaScript call. I however do not understand all the concepts explained. Basic concepts Now in the presentation for Node.js Ryan Dahl talks about non-blocking IO and why this is the way we need to create our programs. I can understand the theoretical concept. You just don't wait for a response, you go ahead and do other things. You make a callback for the response, and when the response arrives millions of clock-cycles later, you can fire that. If you have not already I recommend to watch this presentation. It is very easy to follow and pretty detailed. There are some nice concepts explained on how to write your code in a good manner. There are also some examples given and I am going to work with the basic example given. Examples The way we do thing now: puts("Enter your name: "); var name = gets(); puts("Name: " + name); Now the problem with this is that the code is halted at line 1. It blocks your code. The way we need to do things according to node puts("Enter your name: "); gets(function (name) { puts("Name: " + name); }); Now with this your program does not halt, because the input is a function within the output. So the programs continues to work without halting. Questions Now the basic question I have is how does this work in real-life situations. I am talking here for the use in web-applications. The application I am writing does I/O, bit is still does it in am blocking matter. I think that most of the time, if not all, you need to block, because you have to wait on what the response is you have to work with. When you need to get some information from the database, most of the time this data needs to be verified before you can further with the code. Example 1 If you take a login for example. You have to wait for the database to response to return, because you can not do anything else. I can't see a way around this without blocking. Example 2 Going back to the basic example. The use just request something from a database which does not need any verification. You still have to block because you don't have anything to do more. I can not come up with a single example where you want to do other things while you wait for the response to return. Possible answers I have read that this frees up recourses. When you program like this it takes less CPU or memory usage. So this non-blocking IO is ONLY meant to free up recourses and does not have any other practical use. Not that this is not a huge plus, freeing up recourses is always good. Yet I fail to see this as a good solution. because in both of the above examples, the program has to wait for the response of the user. Whether this is inside a function, or just inline, in my opinion there is a program that wait for input. Resources I looked at I have looked at some recourses before I posted this question. They talk a lot about the theoretical concept, which is quite clear. Yet i fail to see some real-life examples where this is makes a huge difference. Stackoverflow: What is in simple words blocking IO and non-blocking IO? Blocking IO vs non-blocking IO; looking for good articles tidy code for asynchronous IO Other recources: Wikipedia: Asynchronous I/O Introduction to non-blocking I/O The C10K problem

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• "Invalid Handle Object" when plotting 2 figures Matlab

  - by pinnacler

  I'm having a difficult time understanding the paradigm of Matlab classes vs compared to c++. I wrote code the other day, and I thought it should work. It did not... until I added <handle after the classdef. So I have two classes, landmarks and robot, both are called from within the simulation class. This is the main loop of obj.simulation.animate() and it works, until I try to plot two things at once. DATA.path is a record of all the places a robot has been on the map, and it's updated every time the position is updated. When I try to plot it, by uncommenting the two marked lines below, I get this error: ??? Error using == set Invalid handle object. Error in == simulationsimulation.animate at 45 set(l.lm,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); %INITIALIZE GLOBALS global DATA XX XX = [obj.robot.x ; obj.robot.y]; DATA.i=1; DATA.path = XX; %Setup Plots fig=figure; xlabel('meters'), ylabel('meters') set(fig, 'name', 'Phil''s AWESOME 80''s Robot Simulator') xymax = obj.landmarks.mapSize*3; xymin = -(obj.landmarks.mapSize*3); l.lm=scatter([0],[0],'b+'); %"UNCOMMENT ME"l.pth= plot(0,0,'k.','markersize',2,'erasemode','background'); % vehicle path axis([xymin xymax xymin xymax]); %Simulation Loop for n = 1:720, %Calculate and Set Heading/Location XX = [obj.robot.x;obj.robot.y]; store_data(XX); if n == 120, DATA.path end %Update Position headingChange = navigate(n); obj.robot.updatePosition(headingChange); obj.landmarks.updatePerspective(obj.robot.heading, obj.robot.x, obj.robot.y); %Animate %"UNCOMMENT ME" set(l.pth, 'xdata', DATA.path(1,1:DATA.i), 'ydata', DATA.path(2,1:DATA.i)); set(l.lm,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); rectangle('Position',[-2,-2,4,4]); drawnow This is the classdef for landmarks classdef landmarks <handle properties fixedPositions; %# positions in a fixed coordinate system. [ x, y ] mapSize; %Map Size. Value is side of square x; y; heading; headingChange; end properties (Dependent) apparentPositions end methods function obj = landmarks(mapSize, numberOfTrees) obj.mapSize = mapSize; obj.fixedPositions = obj.mapSize * rand([numberOfTrees, 2]) .* sign(rand([numberOfTrees, 2]) - 0.5); end function apparent = get.apparentPositions(obj) currentPosition = [obj.x ; obj.y]; apparent = bsxfun(@minus,(obj.fixedPositions)',currentPosition)'; apparent = ([cosd(obj.heading) -sind(obj.heading) ; sind(obj.heading) cosd(obj.heading)] * (apparent)')'; end function updatePerspective(obj,tempHeading,tempX,tempY) obj.heading = tempHeading; obj.x = tempX; obj.y = tempY; end end end To me, this is how I understand things. I created a figure l.lm that has about 100 xy points. I can rotate this figure by using set(l.lm,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2)); When I do that, things work. When I try to plot a second group of XY points, stored in DATA.path, it craps out and I can't figure out why.

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• How do I evaluate my skillset against the current market to see what needs improvement and where my

  - by baijajusav

  First of all, this question may be out of bounds for this site. If so, remove it. I say this because this site seems to be a place for more concrete questions that are not so relative in nature. And before I begin, for those of you whom just prefer a question and not this sort of dialog, here is my question: How can I assess my current skills as a programmer and decide where and what areas to improve upon? That said, here's what I'm asking/talking about, in essence. The market is always in constant flux. As programmers we're always having to learn new things, update our skills, push ourselves into that next project. There's not a very good litmus test that I know of for us to get an idea of where we stand as programmers. I came across this blog post by Jeff Atwood talking about why can't programmers code. Instinctively (and as the post goes on to state) I rushed through the program in about 4 minutes (most of that time was b/c I was hand writing it out. Still, this doesn't really answer the question of where do my skills need to be to succeed in today's world. I real blogs, listen to podcasts, try to keep up on the latest things coming out. It has only been in the past couple of months that I made a decision to pick a focus area for my learning as I can't learn everything and trying to do so is to spread myself too thin. I chose ASP.NET MVC & C#. I plan to stick with Microsoft technologies, not out of some sense of loyalty or stubbornness, but rather because they seem to stream together and have a unifying connection between them. With Windows Phone 7 coming out, it seems that now is the obvious time to pick up WPF and Silverlight as well. Still, if you asked me to code something apart from intellisense and the internet, I probably couldn't get the syntax right. I don't have libraries memorized or know precisely where the classes I use exist within the .Net framework, namely because I haven't had to pull that knowledge out of the air. In a way, I suppose Visual Studio has insulated me, which isn't a good thing, but, at the same time, I've still been able to be productive. I'm working on my own side project to try and help my learning. In doing so, I'm trying to make use of best practices and 3rd party frameworks where I can. I'm using automapper and EF 1.0. I know everyone in the .net community seems to cry foul at the sound of EF 1.0, but I can't say why because I've never used it. There's no lazy loading and that has proven rather annoying; however, aside from that, I haven't had that much of an issue. Granted this is probably because I'm not writing tests as I go (which I'm not doing because I don't know how to test EF in tests and don't really have a clue how to write tests for ASP.NET MVC 1.0). I'm also using a custom membership provider; granted, it's a barebone implementation, but I'm using it still. My thinking in all of this is, while I am neglecting a great many important technologies that are in the mainstream, I'll have a working project in the end. I can come back and add those things after I finish. Doing it all now and at once seems like too much. I know how I work and I don't think I'd ever get it done that way. I've elected to make this a community wiki as I think this question might fight better there. If a moderator disagrees with that choice or the decision to post this here, the just delete the question. I'm not trying to make undue work for anyone. I'm just a programmer trying to assess my where his skills are now and where I should be improving.

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• Where do I start ?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be learning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• Please recommend me intermediate-to-advanced Python books to buy.

  - by anonnoir

  I'm in the final year, final semester of my law degree, and will be graduating very soon. (April, to be specific.) But before I begin practice, I plan to take 2 two months off, purely for serious programming study. So I'm currently looking for some Python-related books, gauged intermediate to advanced, which are interesting (because of the subject matter itself) and possibly useful to my future line of work. I've identified 2 possible purchases at the moment: Natural Language Processing with Python. The law deals mostly with words, and I've quite a number of ideas as to where I might go with NLP. Data extraction, summaries, client management systems linked with document templates, etc. Programming Collective Intelligence. This book fascinates me, because I've always liked the idea of machine learning (and I'm currently studying it by the side too, for fun). I'd like to build/play around with Web 2.0 applications; and who knows if I can apply some of the things I learn to my legal work. (E.g. Playground experiments to determine how and under what circumstances judges might be biased, by forcing algorithms to pore through judgments and calculate similarities, etc.) Please feel free to criticize my current choices, but do at least offer or recommend other books that I should read in their place. My budget can deal with 4 books, max. These books will be used heavily throughout the 2 months; I will be reading them back to back, absorbing the explanations given, and hacking away at their code. Also, the books themselves should satisfy 2 main criteria: Application. The book must teach how to solve problems. I like reading theory, but I want to build things and solve problems first. Even playful applications are fine, because games and experiments always have real-world applications sooner or later. Readability. I like reading technical books, no matter how difficult they are. I enjoy the effort and the feeling that you're learning something. But the book shouldn't contain code or explanations that are too cryptic or erratic. Even if it's difficult, the book's content should be accessible with focused reading. Note: I realize that I am somewhat of a beginner to the whole programming thing, so please don't put me down. But from experience, I think it's better to aim up and leave my comfort zone when learning new things, rather than to just remain stagnant the way I am. (At least the difficulty gives me focus: i.e. if a programmer can be that good, perhaps if I sustain my own efforts I too can be as good as him someday.) If anything, I'm also a very determined person, so two months of day-to-night intensive programming study with nothing else on my mind should, I think, give me a bit of a fighting chance to push my programming skills to a much higher level.

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• How do I learn algorithms?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be lear ning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• Faulty to use memcache together with a php web-browser-game in this way?

  - by Crowye

  Background We are currently working on a strategy web-browser game based on php, html and javascript. The plan is to have 10,000+ users playing within the same world. Currently we are using memcached to: store json static data, language files store changeable serialized php class objects (such as armies, inventorys, unit-containers, buildings, etc) In the back we have a mysql server running and holding all the game data aswell. When a object is loaded through our ObjectLoader it loads in this order: checks a static hashmap in the script for the object checks memcache if it has already been loaded into it otherwise loads from database, and saves it into memcache and the static temp hashmap We have built the whole game using a class-object-oriented approach where functionality is always made between objects. Beause of this we think we have managed to get a nice structure, and with the help of memcached we have received good request times from client-server when interacting with the game. I'm aware that memcache is not synchronized, and also is not commonly used for holding a full game in memory. In the beginning after a server's startup the load times when loading objects into memcache for the first time will be high, but after the server's been online for a while and most loads are from memcache, the loads will be well reduced. Currently we are saving changed objects into memcache and database at the same time. Earlier we had an idea to save objects into db only after a certain time or at intervals, but due to risk inconsistency if the memcache/server went down, we skipped it for now. Client requests to server often return object's status simple json-format without changing the object, which in turn is represented in the browser visually with images and javascript. But from time to time depending on when an object was last updated, it updates them with new information (e.g. a build-queue holding planned buildings time-progress is increased, and/or planned-queue-items-array has changed). Questions: Do you see how this could work or are we walking in blindness here? Do you expect us to have a lot of inconsistency issues if someone loads and updates the a memcache objects while someone else does the same? Is it even doable to do it in the way he have done it? Seems to be working fine atm, but so far we have only been 4 people online at the same time.. Is some other cache program more fit for this class-object approach than memcached? Is there any other tips you have for this situation? UPDATE Since it is simply a "normal webpage" (no applet, flash, etc), we are implementing the game so that the server is the only one holding a "real game-state".. the state of the different javascript-objects on the client is more like a approximative version of the server's game state. From time to time and before you do certain things important things, the client's visual state is updated to the server's state (e.g. the client things he can afford a barracks, asks the server to build a barracks, server updates current resources according to income-data on server and then tries to build a barracks or casts an error-message, and then sends the current server-state on resources, buildings back to the client).. It is not a fast-paced game lika real strategy game. More like a quite slow 3-4 months playtime game, where buildings can take +1 minute up to several days to complete.

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• Java - Layering issues with Lists and Graphics2D

  - by Mirrorcrazy

  So I have a DisplayPanel class that extends JPanel and that also paints my numerous images for my program using Graphics2D. In order to be able to easily customly use this I set it up so that every time the panel is repainted it uses a List, that I can add to or remove from as the program processes. My problem is with layering. I've run into an issue where the List must have reached its resizing point (or something whacky like that) and so the images i want to display end up beneath all of the other images already on the screen. I've come to the community for an answer because I have faith you will provide a good one. DisplayPanel: package earthworm; import java.awt.Graphics; import java.awt.Graphics2D; import java.util.ArrayList; import java.util.List; import javax.swing.JPanel; public class DisplayPanel extends JPanel { private List<ImageMap> images = new ArrayList(); public DisplayPanel() { setSize(800, 640); refresh(); } public void refresh() { revalidate(); repaint(); } @Override public void paintComponent(Graphics g) { super.paintComponent(g); Graphics2D g2d = (Graphics2D) g; g2d.clearRect(0, 0, 800, 640); for(int i = 0; i < images.size(); i++) g2d.drawImage( images.get(i).getImage(), images.get(i).getX(), images.get(i).getY(), null); } public void paintImage(ImageMap[] images, ImageMap[] clearImages, boolean clear) { if(clear) this.images.clear(); else if(clearImages!=null) for(int i = 0; i < clearImages.length; i++) this.images.remove(clearImages[i]); if(images!=null) for(int i = 0; i<images.length; i++) this.images.add(images[i]); refresh(); } }

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• How to define template directives (from an API perspective)?

  - by Ralph

  Preface I'm writing a template language (don't bother trying to talk me out of it), and in it, there are two kinds of user-extensible nodes. TemplateTags and TemplateDirectives. A TemplateTag closely relates to an HTML tag -- it might look something like div(class="green") { "content" } And it'll be rendered as <div class="green">content</div> i.e., it takes a bunch of attributes, plus some content, and spits out some HTML. TemplateDirectives are a little more complicated. They can be things like for loops, ifs, includes, and other such things. They look a lot like a TemplateTag, but they need to be processed differently. For example, @for($i in $items) { div(class="green") { $i } } Would loop over $items and output the content with the variable $i substituted in each time. So.... I'm trying to decide on a way to define these directives now. Template Tags The TemplateTags are pretty easy to write. They look something like this: [TemplateTag] static string div(string content = null, object attrs = null) { return HtmlTag("div", content, attrs); } Where content gets the stuff between the curly braces (pre-rendered if there are variables in it and such), and attrs is either a Dictionary<string,object> of attributes, or an anonymous type used like a dictionary. It just returns the HTML which gets plunked into its place. Simple! You can write tags in basically 1 line. Template Directives The way I've defined them now looks like this: [TemplateDirective] static string @for(string @params, string content) { var tokens = Regex.Split(@params, @"\sin\s").Select(s => s.Trim()).ToArray(); string itemName = tokens[0].Substring(1); string enumName = tokens[1].Substring(1); var enumerable = data[enumName] as IEnumerable; var sb = new StringBuilder(); var template = new Template(content); foreach (var item in enumerable) { var templateVars = new Dictionary<string, object>(data) { { itemName, item } }; sb.Append(template.Render(templateVars)); } return sb.ToString(); } (Working example). Basically, the stuff between the ( and ) is not split into arguments automatically (like the template tags do), and the content isn't pre-rendered either. The reason it isn't pre-rendered is because you might want to add or remove some template variables or something first. In this case, we add the $i variable to the template variables, var templateVars = new Dictionary<string, object>(data) { { itemName, item } }; And then render the content manually, sb.Append(template.Render(templateVars)); Question I'm wondering if this is the best approach to defining custom Template Directives. I want to make it as easy as possible. What if the user doesn't know how to render templates, or doesn't know that he's supposed to? Maybe I should pass in a Template instance pre-filled with the content instead? Or maybe only let him tamper w/ the template variables, and then automatically render the content at the end? OTOH, for things like "if" if the condition fails, then the template wouldn't need to be rendered at all. So there's a lot of flexibility I need to allow in here. Thoughts?

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• Using a large list of terms, search through page text and replace words with links

  - by dunc

  A while ago I posted this question asking if it's possible to convert text to HTML links if they match a list of terms from my database. I have a fairly huge list of terms - around 6000. The accepted answer on that question was superb, but having never used XPath, I was at a loss when problems started occurring. At one point, after fiddling with code, I somehow managed to add over 40,000 random characters to our database - the majority of which required manual removal. Since then I've lost faith in that idea and the more simple PHP solutions simply weren't efficient enough to deal with the amount of data and the quantity of terms. My next attempt at a solution is to write a JS script which, once the page has loaded, retrieves the terms and matches them against the text on a page. This answer has an idea which I'd like to attempt. I would use AJAX to retrieve the terms from the database, to build an object such as this: var words = [ { word: 'Something', link: 'http://www.something.com' }, { word: 'Something Else', link: 'http://www.something.com/else' } ]; When the object has been built, I'd use this kind of code: //for each array element $.each(words, function() { //store it ("this" is gonna become the dom element in the next function) var search = this; $('.message').each( function() { //if it's exactly the same if ($(this).text() === search.word) { //do your magic tricks $(this).html('<a href="' + search.link + '">' + search.link + '</a>'); } } ); } ); Now, at first sight, there is a major issue here: with 6,000 terms, will this code be in any way efficient enough to do what I'm trying to do?. One option would possibly be to perform some of the overhead within the PHP script that the AJAX communicates with. For instance, I could send the ID of the post and then the PHP script could use SQL statements to retrieve all of the information from the post and match it against all 6,000 terms.. then the return call to the JavaScript could simply be the matching terms, which would significantly reduce the number of matches the above jQuery would make (around 50 at most). I have no problem with the script taking a few seconds to "load" on the user's browser, as long as it isn't impacting their CPU usage or anything like that. So, two questions in one: Can I make this work? What steps can I take to make it as efficient as possible? Thanks in advance,

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• Monitor randomly shutting down, computer accepting no input, need to restart to get working

  - by Sebastian Lamerichs

  First off, spec list: OS: Windows 7 Ultimate 64-bit SP1 CPU: i7-4820k @ 3.7GHz (stock) GPU: Two 3GB Radeon HD 7970s @ 1.05GHz Mobo: AsRock X79 Extreme6 HDD: 2TB Seagate Barracuda 7200rpm RAM: 16GB quad-channel Kingston 1600MHz PSU: Antec HCG 900W Monitors: Acer S220HQL 1920x1080 + ViewSonic VA2251 1920x1080. Plugged into different GPUs. My problem is that, on a daily-ish basis, my monitors will turn off and not turn back on. My computer will still be running, GPU/CPU/case fans all still going, but the monitors will not turn back on. Additionally, it seems to cease all network activity. It doesn't seem to log any errors at all. I've verified that this is not a monitor issue, as when I press the num/caps/scroll lock buttons on my keyboard, the lights don't change, so the computer is clearly not accepting input. I have noticed a few other people on the internet with this problem, and some have claimed that it was solved by disabling PCI-Express Link State Power Management, but the issue still occurs for me after this. Whilst my CPU and GPUs both run at 100% 24/7, the temperatures are certainly not at dangerous levels, with the CPU averaging 65°C and the GPUs at 70°C and 78°C average. All components are brand new. I have tried forcing MSI Afterburner to start when Windows starts and to force a constant voltage, as this fixed the issue for a few days for another user, but he reported back saying that it had stopped working properly again, so I'm not putting too much faith in this working. Many people have said to adjust display sleep mode settings, but this will clearly not work, as the keyboard lights would still work if the monitors were the issue. The closest I can get to a log file for this issue is the following Folding@Home logs: 14:45:21:WU01:FS00:0x17:Completed 1120000 out of 2000000 steps (56%) 14:46:43:WU00:FS01:0x17:Completed 480000 out of 2000000 steps (24%) 14:46:49:WU01:FS00:0x17:Completed 1140000 out of 2000000 steps (57%) 14:48:30:WU01:FS00:0x17:Completed 1160000 out of 2000000 steps (58%) 14:49:55:WU01:FS00:0x17:Completed 1180000 out of 2000000 steps (59%) As you can see, the second GPU (FS01) stops computation approximately three and a half minutes before the issue occurs (it should be completing 1% every 80-120 seconds), and the first GPU (FS00) continues for a few minutes more before the logs just end. As far as I can tell, the computer has a network failure at the time the first GPU stops working, the latest IRC message I received from this time was at 14:47:58. That being said, there could have just not been any messages between then and 14:50:00, so I'm going to be connecting a laptop to the same bouncer to double-check if it happens again. The GPUs functioned perfectly well in another computer for a significant period of time, so I'm fairly confident that they aren't the issue, which means that this is being caused by either software or the motherboard, or possibly RAM. I really hope it's software. I heard from a forum board that there was a patch from Microsoft that fixed this problem, but "I've forgot which KB it was or the google search terms I used to find the patch, LOL.", so that's not much help. Haven't seen it mentioned by anyone else on about a dozen threads about this issue either. The computer is plugged in via a surge-protected power board, and I've run several other computers and pieces of hardware through it with no issues, so that is not the cause. I have just set the hard disk to never turn off, although I don't believe that that will solve the issue. Strangely, this has only happened when I'm not at the computer (which is actually a minority of the time). Until today it had only happened when I had not been actively using the computer for 6 hours, but today it happened within 10-30 minutes of me last using the computer actively. I have enabled file logging from MSI Afterburner, so hopefully this will shed some light on the issue, but I'm not too optimistic. I've heard that it could be a motherboard problem, but I figured I should ask around before RMAing it. Any help?

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• WPF: Draw a grid on a Canvas?

  - by stefan.at.wpf

  Hello community, I'm currently trying to add gridlines to a canvas. I need an exact free space between them, where I'd like to place something for hit detection per cell, maybe simply a transparent border or such a thing. While I thought this would be an easy thing, I'm facing problems like antialiasing and that lines in WPF aren't very "calculate" / exact drawing friendly - e.g. if I draw a line on x=20 with a thickness of 10, the line's width goes from x=15 to x=25 (maybe not exactly, just some kind like that), so it takes the given position as middle point - if it would draw from 20 to 30 it would be easier in my case. Besides that making things more complex, how does WPF handle e.g. a thickness of 5? Draw thickness 3 left from the given point and the remaining 2 right from it? Or maybe just the opposite way? Well, just wanted to show you which problems I have, though this all maybe just seems simple to be done. Just wondering if anyone has ever done this before. Currently I find a Border without content and just 2 sites set to a thickness greater than 0 as line seems to work the best in my tests, seems like it's clear where they are drawn and they somehow don't seem to make any antialiasing problems. Just wondering if there's a more intuitive / better way of doing this? I don't want to lay a Canvas over a Grid, I think this maybe makes some things more complex in the end (by the way: how would I place a Canvas on top of a Grid?). Thanks for any hint!

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• Programmatically creating scrollview(s) from custom component in android

  - by jaapbeetstra

  I'm trying to build a compound control in Android, containing (among other things) a ScrollView. Things go wrong when I try to view the control in Eclipse, crashing with a NullPointerException after the error message: "Parser is not a BridgeXmlBlockParser". Stacktrace: java.lang.NullPointerException at android.view.View.<init>(View.java:1720) at android.view.ViewGroup.<init>(ViewGroup.java:277) at android.widget.FrameLayout.<init>(FrameLayout.java:83) at android.widget.ScrollView.<init>(ScrollView.java:128) at android.widget.ScrollView.<init>(ScrollView.java:124) at android.widget.ScrollView.<init>(ScrollView.java:120) at my.compound.control.StringPicker.onMeasure(StringPicker.java:46) ... I've traced the error to the following conditions: The NPE is thrown because a Context.obtainStyledAttributes() call returns null when the attrs argument passed is null. This only applies to the BridgeContext implementation used in Eclipse, which expects attrs to be an instance of the BridgeXmlBlockParser. The attrs argument is null because I create the ScrollView using the (Context) constructor. There is a workaround of course, which is passing the attrs I receive when Eclipse constructs the compound control, but I don't want all the attributes set on the compound control to apply to my inner control. Am I doing something wrong, is this a bug in Android Eclipse, ...?

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• Gomoku array-based AI-algorithm?

  - by Lasse V. Karlsen

  Way way back (think 20+ years) I encountered a Gomoku game source code in a magazine that I typed in for my computer and had a lot of fun with. The game was difficult to win against, but the core algorithm for the computer AI was really simply and didn't account for a lot of code. I wonder if anyone knows this algorithm and has some links to some source or theory about it. The things I remember was that it basically allocated an array that covered the entire board. Then, whenever I, or it, placed a piece, it would add a number of weights to all locations on the board that the piece would possibly impact. For instance (note that the weights are definitely wrong as I don't remember those): 1 1 1 2 2 2 3 3 3 444 1234X4321 3 3 3 2 2 2 1 1 1 Then it simply scanned the array for an open location with the lowest or highest value. Things I'm fuzzy on: Perhaps it had two arrays, one for me and one for itself and there was a min/max weighting? There might've been more to the algorithm, but at its core it was basically an array and weighted numbers Does this ring a bell with anyone at all? Anyone got anything that would help?

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• iPhone: Software Development And Distribution

  - by xsl

  I have a few quick questions about the iPhone software development. I did some research about the topic, but there are a few specific things I would like to ask here, because I will have to estimate the cost of the required hardware and software, before I am allowed to buy anything. I never did any Mac development nor have I ever owned an iPhone, so needless to say this is quite hard for me. I will buy an iMac mini with 2 GB RAM for iPhone development. I will have to use it at the same time as my regular PC, but the majority of the time I won't use the Mac at all. Do I have to buy an additional monitor, a mouse and a keyboard or is there a better solution? I will have to port a C library to the iPhone platform and develop an iPhone application that uses the ported library. Do I need anything else than the iPhone SDK to do this? If I use an external library (see above), can I test the application with the integrated emulator, or is it recommend to buy the device? In a later phase of the project I will have to buy an iPhone, but I will have to wait until the iPhone 4 is released here in Europe, because the application requires a camera. In addition to this I will have to send data to a remote webservice. Aside from these two things I don't require any other features. Can I just buy the iPhone online from another country (the iPhones here are sim locked), or should I buy one with a contract? When the application is ready, it will be installed on a few iPhones owned by our customer. Because of security reasons it is crucial that there is no third party involved in this process (i.e. the application should not be distributed on the app store). Is this possible?

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• Blend "Window is not supported in a WPF Project"

  - by Andy Dent

  I am having a frustrating time with Blend reporting "Window is not supported in a Windows Presentation Foundation (WPF) project." due to unbuildable configurations but can't quite work out how to mangle my way out of it. I've worked out it is probably due to my trying to have a single solution with x86 and x64 configurations. There is no way to tell Blend 2 which is the active Solution Configuration and active Solution Platform. I think it's a bit of a weakness in the configuration system, or maybe the way I've set things up, but I have Debug64 and Debug solution configurations one of each is used with the platform x86 and x64. I also think it's a simple sorting problem - x64 comes before x86 and Debug comes before Debug64 so Blend ends up with an unbuildable config of Debug with x64. When I choose the combination of Debug and x64 in VS, its XAML editor can't load either. The solution is a moderately complex one - there's a pure Win32 DLL, C++/CLI Model project and two other WPF assemblies used by the main WPF project. UPDATE I have ripped all the x64 config out of my solution and rebuilt everything with no effect. I then uninstalled Blend 2 and installed Blend 3 - it doesn't like things either. The Visual Studio XAML editor is still very happy as is the program building and running. (echoes of strangled scream of frustration from oz)

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