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  • Is it evil to model JSON responses to classes when they are mostly smilar?

    - by Aybe
    Here's the problem : While implementing a C# wrapper for an online API (Discogs) I've been faced to a dilemma : quite often the responses returned have mostly similar members and while modeling these responses to classes, some questions surfaces on which way to go would be the best. Example : Querying for a 'release' or a 'master' will return an object that contains an array of 'artist', however these 'artists' do not exactly have the same members. Currently I decided to represent these 'artists' as a single 'Artist' class, against having respective 'ReleaseArtist' and 'MasterArtist' classes which soon becomes very confusing even though another problem arises : when a category (master or release) does not return these members, they will be null. Though it might sound confusing as well I find it less confusing than the former situation as I've tackled the problem by simply not showing null members when visualizing these objects. Is this the right approach to follow ? An example of these differences : public class Artist { public List<Alias> Aliases { get; set; } public string DataQuality { get; set; } public List<Image> Images { get; set; } public string Name { get; set; } public List<string> NameVariations { get; set; } public string Profile { get; set; } public string Realname { get; set; } public string ReleasesUrl { get; set; } public string ResourceUrl { get; set; } public string Uri { get; set; } public List<string> Urls { get; set; } } public class ReleaseArtist { public string Join { get; set; } public string Name { get; set; } public string Anv { get; set; } public string Tracks { get; set; } public string Role { get; set; } public string ResourceUrl { get; set; } public int Id { get; set; } }

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  • ZFS for Database Log Files

    - by user12620111
    I've been troubled by drop outs in CPU usage in my application server, characterized by the CPUs suddenly going from close to 90% CPU busy to almost completely CPU idle for a few seconds. Here is an example of a drop out as shown by a snippet of vmstat data taken while the application server is under a heavy workload. # vmstat 1  kthr      memory            page            disk          faults      cpu  r b w   swap  free  re  mf pi po fr de sr s3 s4 s5 s6   in   sy   cs us sy id  1 0 0 130160176 116381952 0 16 0 0 0 0  0  0  0  0  0 207377 117715 203884 70 21 9  12 0 0 130160160 116381936 0 25 0 0 0 0 0  0  0  0  0 200413 117162 197250 70 20 9  11 0 0 130160176 116381920 0 16 0 0 0 0 0  0  1  0  0 203150 119365 200249 72 21 7  8 0 0 130160176 116377808 0 19 0 0 0 0  0  0  0  0  0 169826 96144 165194 56 17 27  0 0 0 130160176 116377800 0 16 0 0 0 0  0  0  0  0  1 10245 9376 9164 2  1 97  0 0 0 130160176 116377792 0 16 0 0 0 0  0  0  0  0  2 15742 12401 14784 4 1 95  0 0 0 130160176 116377776 2 16 0 0 0 0  0  0  1  0  0 19972 17703 19612 6 2 92  14 0 0 130160176 116377696 0 16 0 0 0 0 0  0  0  0  0 202794 116793 199807 71 21 8  9 0 0 130160160 116373584 0 30 0 0 0 0  0  0 18  0  0 203123 117857 198825 69 20 11 This behavior occurred consistently while the application server was processing synthetic transactions: HTTP requests from JMeter running on an external machine. I explored many theories trying to explain the drop outs, including: Unexpected JMeter behavior Network contention Java Garbage Collection Application Server thread pool problems Connection pool problems Database transaction processing Database I/O contention Graphing the CPU %idle led to a breakthrough: Several of the drop outs were 30 seconds apart. With that insight, I went digging through the data again and looking for other outliers that were 30 seconds apart. In the database server statistics, I found spikes in the iostat "asvc_t" (average response time of disk transactions, in milliseconds) for the disk drive that was being used for the database log files. Here is an example:                     extended device statistics     r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 2053.6    0.0 8234.3  0.0  0.2    0.0    0.1   0  24 c3t60080E5...F4F6d0s0     0.0 2162.2    0.0 8652.8  0.0  0.3    0.0    0.1   0  28 c3t60080E5...F4F6d0s0     0.0 1102.5    0.0 10012.8  0.0  4.5    0.0    4.1   0  69 c3t60080E5...F4F6d0s0     0.0   74.0    0.0 7920.6  0.0 10.0    0.0  135.1   0 100 c3t60080E5...F4F6d0s0     0.0  568.7    0.0 6674.0  0.0  6.4    0.0   11.2   0  90 c3t60080E5...F4F6d0s0     0.0 1358.0    0.0 5456.0  0.0  0.6    0.0    0.4   0  55 c3t60080E5...F4F6d0s0     0.0 1314.3    0.0 5285.2  0.0  0.7    0.0    0.5   0  70 c3t60080E5...F4F6d0s0 Here is a little more information about my database configuration: The database and application server were running on two different SPARC servers. Storage for the database was on a storage array connected via 8 gigabit Fibre Channel Data storage and log file were on different physical disk drives Reliable low latency I/O is provided by battery backed NVRAM Highly available: Two Fibre Channel links accessed via MPxIO Two Mirrored cache controllers The log file physical disks were mirrored in the storage device Database log files on a ZFS Filesystem with cutting-edge technologies, such as copy-on-write and end-to-end checksumming Why would I be getting service time spikes in my high-end storage? First, I wanted to verify that the database log disk service time spikes aligned with the application server CPU drop outs, and they did: At first, I guessed that the disk service time spikes might be related to flushing the write through cache on the storage device, but I was unable to validate that theory. After searching the WWW for a while, I decided to try using a separate log device: # zpool add ZFS-db-41 log c3t60080E500017D55C000015C150A9F8A7d0 The ZFS log device is configured in a similar manner as described above: two physical disks mirrored in the storage array. This change to the database storage configuration eliminated the application server CPU drop outs: Here is the zpool configuration: # zpool status ZFS-db-41   pool: ZFS-db-41  state: ONLINE  scan: none requested config:         NAME                                     STATE         ZFS-db-41                                ONLINE           c3t60080E5...F4F6d0  ONLINE         logs           c3t60080E5...F8A7d0  ONLINE Now, the I/O spikes look like this:                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1053.5    0.0 4234.1  0.0  0.8    0.0    0.7   0  75 c3t60080E5...F8A7d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1131.8    0.0 4555.3  0.0  0.8    0.0    0.7   0  76 c3t60080E5...F8A7d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1167.6    0.0 4682.2  0.0  0.7    0.0    0.6   0  74 c3t60080E5...F8A7d0s0     0.0  162.2    0.0 19153.9  0.0  0.7    0.0    4.2   0  12 c3t60080E5...F4F6d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1247.2    0.0 4992.6  0.0  0.7    0.0    0.6   0  71 c3t60080E5...F8A7d0s0     0.0   41.0    0.0   70.0  0.0  0.1    0.0    1.6   0   2 c3t60080E5...F4F6d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1241.3    0.0 4989.3  0.0  0.8    0.0    0.6   0  75 c3t60080E5...F8A7d0s0                     extended device statistics                  r/s    w/s   kr/s   kw/s wait actv wsvc_t asvc_t  %w  %b device     0.0 1193.2    0.0 4772.9  0.0  0.7    0.0    0.6   0  71 c3t60080E5...F8A7d0s0 We can see the steady flow of 4k writes to the ZIL device from O_SYNC database log file writes. The spikes are from flushing the transaction group. Like almost all problems that I run into, once I thoroughly understand the problem, I find that other people have documented similar experiences. Thanks to all of you who have documented alternative approaches. Saved for another day: now that the problem is obvious, I should try "zfs:zfs_immediate_write_sz" as recommended in the ZFS Evil Tuning Guide. References: The ZFS Intent Log Solaris ZFS, Synchronous Writes and the ZIL Explained ZFS Evil Tuning Guide: Cache Flushes ZFS Evil Tuning Guide: Tuning ZFS for Database Performance

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  • Incorrect results for frustum cull

    - by DeadMG
    Previously, I had a problem with my frustum culling producing too optimistic results- that is, including many objects that were not in the view volume. Now I have refactored that code and produced a cull that should be accurate to the actual frustum, instead of an axis-aligned box approximation. The problem is that now it never returns anything to be in the view volume. As the mathematical support library I'm using does not provide plane support functions, I had to code much of this functionality myself, and I'm not really the mathematical type, so it's likely that I've made some silly error somewhere. As follows is the relevant code: class Plane { public: Plane() { r0 = Math::Vector(0,0,0); normal = Math::Vector(0,1,0); } Plane(Math::Vector p1, Math::Vector p2, Math::Vector p3) { r0 = p1; normal = Math::Cross((p2 - p1), (p3 - p1)); } Math::Vector r0; Math::Vector normal; }; This class represents one plane as a point and a normal vector. class Frustum { public: Frustum( const std::array<Math::Vector, 8>& points ) { planes[0] = Plane(points[0], points[1], points[2]); planes[1] = Plane(points[4], points[5], points[6]); planes[2] = Plane(points[0], points[1], points[4]); planes[3] = Plane(points[2], points[3], points[6]); planes[4] = Plane(points[0], points[2], points[4]); planes[5] = Plane(points[1], points[3], points[5]); } Plane planes[6]; }; The points are passed in order where (the inverse of) each bit of the index of each point indicates whether it's the left, top, and back of the frustum, respectively. As such, I just picked any three points where they all shared one bit in common to define the planes. My intersection test is as follows (based on this): bool Intersects(Math::AABB lhs, const Frustum& rhs) const { for(int i = 0; i < 6; i++) { Math::Vector pvertex = lhs.TopRightFurthest; Math::Vector nvertex = lhs.BottomLeftClosest; if (rhs.planes[i].normal.x <= -0.0f) { std::swap(pvertex.x, nvertex.x); } if (rhs.planes[i].normal.y <= -0.0f) { std::swap(pvertex.y, nvertex.y); } if (rhs.planes[i].normal.z <= -0.0f) { std::swap(pvertex.z, nvertex.z); } if (Math::Dot(rhs.planes[i].r0, nvertex) < 0.0f) { return false; } } return true; } Also of note is that because I'm using a left-handed co-ordinate system, I wrote my Cross function to return the negative of the formula given on Wikipedia. Any suggestions as to where I've made a mistake?

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  • SFML 2.0 Too Many Variables in Class Preventing Draw To Screen

    - by Josh
    This is a very strange phenomenon to me. I have a class definition for a game, but when I add another variable to the class, the draw method does not print everything to the screen. It will be easier understood showing the code and output. Code for good draw output: class board { protected: RectangleShape rect; int top, left; int i, j; int rowSelect, columnSelect; CircleShape circleArr[4][10]; CircleShape codeArr[4]; CircleShape keyArr[4][10]; //int pegPresent[4]; public: board(void); void draw(RenderWindow& Window); int mouseOver(RenderWindow& Window); void placePeg(RenderWindow& Window, int pegSelect); }; Screen: Code for missing draw: class board { protected: RectangleShape rect; int top, left; int i, j; int rowSelect, columnSelect; CircleShape circleArr[4][10]; CircleShape codeArr[4]; CircleShape keyArr[4][10]; int pegPresent[4]; public: board(void); void draw(RenderWindow& Window); int mouseOver(RenderWindow& Window); void placePeg(RenderWindow& Window, int pegSelect); }; Screen: As you can see, all I do is un-comment the protected array and most of the pegs are gone from the right hand side. I have checked and made sure that I didn't accidentally created a variable with that name already. I haven't used it anywhere. Why does it not draw the remaining pegs as it should? My only thought is that maybe I am declaring too many variables for the class, but that doesn't really make sense to me. Any thoughts and help is greatly appreciated.

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  • WiX, MSDeploy and an appealing configuration/deployment paradigm

    - by alexhildyard
    I do a lot of application and server configuration; I've done this for many years and have tended to view the complexity of this strictly in terms of the complexity of the ultimate configuration to be deployed. For example, specific APIs aside, I would tend to regard installing a server certificate as a more complex activity than, say, copying a file or adding a Registry entry.My prejudice revolved around the idea of a sequential deployment script that not only had the explicit prescription to apply a specific server configuration, but also made the implicit presumption that the server in question was in a good known state. Scripts like this fail for hundreds of reasons -- the Default Website didn't exist; the application had already been deployed; the application had already been partially deployed and failed to rollback fully, and so on. And so the problem is that the more complex the configuration activity, the more scope for error in any individual part of that activity, and therefore the greater the chance the server in question will not end up at exactly the desired configuration level.Recently I was introduced to a completely different mindset, which, for want of a better turn of phrase, I will call the "make it so" mindset. It's extremely simple both to explain and to implement. In place of the head-down, imperative script you used to use, you substitute a set of checks -- much like exception handlers -- around each configuration activity, starting with a check of the current system state. Thus the configuration logic becomes: "IF these services aren't started then start them, and IF XYZ website doesn't exist then create it, and IF these shares don't exist then create them, and IF these shares aren't permissioned in some particular way, then permission them so." This works. Really well, in my experience. Scenario 1: You want to get a system into a good known state; it's already in a good known state; you quickly realise there is nothing to do.Scenario 2: You want to get the system into a good known state; your script is flawed or the system is bust; it cannot be put into that state. You know exactly where (at least part of) the problem is and why.Scenario 3: You want to get the system into a good known state; people are fiddling around with the system just now. That's fine. You do what you can, and later you come back and try it againScenario 4: No one wants to deploy anything; they want you to prove that the previous deployment was successful. So you re-run the deployment script with the "-WhatIf" flag. It reports that there was nothing to change. There's your proof.I mentioned two technologies in the title -- MSI and MSDeploy. I am thinking specifically of the conversation that took place here. Having worked with both technologies, I think Rob Mensching's response is appropriately nuanced, and in essence the difference is this: sometimes your target is either to achieve a specific new server state, or to rollback to a known good one. Then again, your target may be to configure what you can, and to understand what you can't. Implicitly MSDeploy's "rollback" is simply to redeploy the previous version, whereas a well-crafted MSI will actively put your system into that state without further intervention. Either way, if all goes well it will leave you with a system in one of two states, whereas MSDeploy could leave your system in one of many states. The key is that MSDeploy and MSI are complementary technologies; which suits you best depends as much on Operational guidance as your Configuration remit.What I wanted to say was that I have always been for atomic, transactional-based configuration, but having worked with the "make it so" paradigm, I have been favourably impressed by the actual results. I'm tempted to put a more technical post up on this in due course.

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  • Too much delay while sending object over UDP to server

    - by RomZes
    I'm getting 4 sec delay when sending objects over UDP. Working on small game and trying to implement multiplayer. For now just trying to synchronize movements of 2 balls on the screen. StartingPoint.java is my server(first player), that receiving serialized objects (coordinates). SecondPlayer.java is client that sending serialized objects to server. When I'm moving my first object it appears 4 seconds later on different screen. StartingPoint.java @Override public void run() { byte[] receiveData = new byte[256]; byte[] sendData = new byte[256]; // DatagramSocket socketS; try { socket = new DatagramSocket(5000); System.out.println("Socket created on "+ port + " port"); } catch (SocketException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true){ b1.update(this); b3.update(); System.out.println("Starting server..."); //// Receiving and deserializing object try { //socket.setSoTimeout(1000); DatagramPacket packet = new DatagramPacket(buf, buf.length); socket.receive(packet); byte[] data = packet.getData(); ByteArrayInputStream in = new ByteArrayInputStream(data); ObjectInputStream is = new ObjectInputStream(in); // socket.setSoTimeout(300); b1 = (Ball) is.readObject(); } catch (IOException | ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } SecondPlayer.java @Override public void run() { while(true){ b.update(); networkSend(); repaint(); try { Thread.sleep(17); } catch (InterruptedException e) { e.printStackTrace(); } } public void networkSend(){ // Serialize to a byte array try { ByteArrayOutputStream bStream = new ByteArrayOutputStream(); ObjectOutputStream oo; oo = new ObjectOutputStream(bStream); oo.writeObject(b); oo.flush(); oo.close(); byte[] bufCar = bStream.toByteArray(); //socket = new DatagramSocket(); //socket.setSoTimeout(1000); InetAddress address = InetAddress.getByName("localhost"); DatagramPacket packet = new DatagramPacket(bufCar, bufCar.length, address, port); socket.send(packet); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }

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  • Comparing Apples and Pairs

    - by Tony Davis
    A recent study, High Costs and Negative Value of Pair Programming, by Capers Jones, pulls no punches in its assessment of the costs-to- benefits ratio of pair programming, two programmers working together, at a single computer, rather than separately. He implies that pair programming is a method rushed into production on a wave of enthusiasm for Agile or Extreme Programming, without any real regard for its effectiveness. Despite admitting that his data represented a far from complete study of the economics of pair programming, his conclusions were stark: it was 2.5 times more expensive, resulted in a 15% drop in productivity, and offered no significant quality benefits. The author provides a more scientific analysis than Jon Evans’ Pair Programming Considered Harmful, but the theme is the same. In terms of upfront-coding costs, pair programming is surely more expensive. The claim of productivity loss is dubious and contested by other studies. The third claim, though, did surprise me. The author’s data suggests that if both the pair and the individual programmers employ static code analysis and testing, then there is no measurable difference in the resulting code quality, in terms of defects per function point. In other words, pair programming incurs a massive extra cost for no tangible return in investment. There were, inevitably, many criticisms of his data and his conclusions, a few of which are persuasive. Firstly, that the driver/observer model of pair programming, on which the study bases its findings, is far from the most effective. For example, many find Ping-Pong pairing, based on use of test-driven development, far more productive. Secondly, that it doesn’t distinguish between “expert” and “novice” pair programmers– that is, independently of other programming skills, how skilled was an individual at pair programming. Thirdly, that his measure of quality is too narrow. This point rings true, certainly at Red Gate, where developers don’t pair program all the time, but use the method in short bursts, while tackling a tricky problem and needing a fresh perspective on the best approach, or more in-depth knowledge in a particular domain. All of them argue that pair programming, and collective code ownership, offers significant rewards, if not in terms of immediate “bug reduction”, then in removing the likelihood of single points of failure, and improving the overall quality and longer-term adaptability/maintainability of the design. There is also a massive learning benefit for both participants. One developer told me how he once worked in the same team over consecutive summers, the first time with no pair programming and the second time pair-programming two-thirds of the time, and described the increased rate of learning the second time as “phenomenal”. There are a great many theories on how we should develop software (Scrum, XP, Lean, etc.), but woefully little scientific research in their effectiveness. For a group that spends so much time crunching other people’s data, I wonder if developers spend enough time crunching data about themselves. Capers Jones’ data may be incomplete, but should cause a pause for thought, especially for any large IT departments, supporting commerce and industry, who are considering pair programming. It certainly shouldn’t discourage teams from exploring new ways of developing software, as long as they also think about how to gather hard data to gauge their effectiveness.

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  • Syncing client and server CRUD operations using json and php

    - by Justin
    I'm working on some code to sync the state of models between client (being a javascript application) and server. Often I end up writing redundant code to track the client and server objects so I can map the client supplied data to the server models. Below is some code I am thinking about implementing to help. What I don't like about the below code is that this method won't handle nested relationships very well, I would have to create multiple object trackers. One work around is for each server model after creating or loading, simply do $model->clientId = $clientId; IMO this is a nasty hack and I want to avoid it. Adding a setCientId method to all my model object would be another way to make it less hacky, but this seems like overkill to me. Really clientIds are only good for inserting/updating data in some scenarios. I could go with a decorator pattern but auto generating a proxy class seems a bit involved. I could use a generic proxy class that uses a __call function to allow for original object data to be accessed, but this seems wrong too. Any thoughts or comments? $clientData = '[{name: "Bob", action: "update", id: 1, clientId: 200}, {name:"Susan", action:"create", clientId: 131} ]'; $jsonObjs = json_decode($clientData); $objectTracker = new ObjectTracker(); $objectTracker->trackClientObjs($jsonObjs); $query = $this->em->createQuery("SELECT x FROM Application_Model_User x WHERE x.id IN (:ids)"); $query->setParameters("ids",$objectTracker->getClientSpecifiedServerIds()); $models = $query->getResults(); //Apply client data to server model foreach ($models as $model) { $clientModel = $objectTracker->getClientJsonObj($model->getId()); ... } //Create new models and persist foreach($objectTracker->getNewClientObjs() as $newClientObj) { $model = new Application_Model_User(); .... $em->persist($model); $objectTracker->trackServerObj($model); } $em->flush(); $resourceResponse = $objectTracker->createResourceResponse(); //Id mappings will be an associtave array representing server id resources with client side // id. //This method Dosen't seem to flexible if we want to return additional data with each resource... //Would have to modify the returned data structure, seems like tight coupling... //Ex return value: //[{clientId: 200, id:1} , {clientId: 131, id: 33}];

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  • It's Here! Visual Studio 2010 and ASP.NET 4.0 Ship

    Today Microsoft released Visual Studio 2010 and ASP.NET 4.0. I've been using the RC version of Visual Studio 2010 quite a bit for the past couple of months and have really grown to like it. It has a host of features and enhancements that improve developer productivity, from improved IntelliSense to better multiple monitor support. Plus there's something about the user experience that, to me, makes it feel better than Visual Studio 2008. I don't know if it's the new blue color motif or what, but the IDE seems more modern looking and more responsive to my mouse movements and other input. Anyway, if you've not yet downloaded Visual Studio 2010 and ASP.NET 4.0, why not? As with previous versions of Visual Studio there's a free Express Edition and VS2010 and ASP.NET 4.0 runs side-by-side with earlier versions of Visual Studio and ASP.NET. And with Visual Studio 2010's multi-targeting you can even use VS2010 as your development editor for ASP.NET 2.0 and ASP.NET 3.5 web applications. (Although be forewarned if you have multiple developers working on the application that the project files in VS2010 and earlier versions of Visual Studio differ.) This week's article on 4Guys explores my favorite new features of Visual Studio 2010. Here's an excerpt: The Visual Studio 2010 user experience is noticeably different than with previous versions. Some of the changes are cosmetic - gone is the decades-old red and orange color scheme, having been replaced with blues and purples - while others are more substantial. For instance, the Visual Studio 2010 shell was rewritten from the ground up to use Microsoft's Windows Presentation Foundation (WPF). In addition to an updated user experience, Visual Studio introduces an array of new features designed to improve developer productivity. There are new tools for searching for files, types, and class members; it's now easier than ever to use IntelliSense; the Toolbox can be searched using the keyboard; and you can use a single editor - Visual Studio 2010 - to work on. This article explores some of the new features in Visual Studio 2010. It is not meant to be an exhaustive list, but rather highlights those features that I, as an ASP.NET developer, find most useful in my line of work. Read on to learn more! And, in closing, here are some helpful VS2010 and ASP.NET 4.0 links: One click installation for ASP.NET 4.0, Visual Web Developer 2010, .NET Framework 4.0, and ASP.NET MVC 2 Eight Quick Hit videos showing some of the cool new VS2010 features VS2010 and ASP.NET 4.0 Release Announcement with some great info/links from none other than Scott Guthrie Happy Programming!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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  • Zooming in isometric engine using XNA

    - by Yheeky
    I´m currently working on an isometric game engine and right now I´m looking for help concerning my zoom function. On my tilemap there are several objects, some of them are selectable. When a house (texture size 128 x 256) is placed on the map I create an array containing all pixels (= 32768 pixels). Therefore each pixel has an alpha value I check if the value is bigger than 200 so it seems to be a pixel which belongs to the building. So if the mouse cursor is on this pixel the building will be selected - PixelCollision. Now I´ve already implemented my zooming function which works quite well. I use a scale variable which will change my calculation on drawing all map items. What I´m looking for right now is a precise way to find out if a zoomed out/in house is selected. My formula works for values like 0,5 (zoomed out) or 2 (zoomed in) but not for in between. Here is the code I use for the pixel index: var pixelIndex = (int)(((yPos / (Scale * Scale)) * width) + (xPos / Scale) + 1); Example: Let´s assume my mouse is over pixel coordinate 38/222 on the original house texture. Using the code above we get the following pixel index. var pixelIndex = ((222 / (1 * 1)) * 128) + (38 / 1) + 1; = (222 * 128) + 39 = 28416 + 39 = 28455 If we now zoom out to scale 0,5, the texture size will change to 64 x 128 and the amount of pixels will decrease from 32768 to 8192. Of course also our mouse point changes by the scale to 19/111. The formula makes it easy to calculate the original pixelIndex using our new coordinates: var pixelIndex = ((111 / (0.5 * 0.5)) * 64) + (19 / 0.5) + 1; = (444 * 64) + 39 = 28416 + 39 = 28455 But now comes the problem. If I zoom out just to scale 0.75 it does not work any more. The pixel amount changes from 32768 to 18432 pixels since texture size is 96 x 192. Mouse point is transformed to point 28/166. The formula gives me a wrong pixelIndex. var pixelIndex = ((166 / (0.75 * 0.75)) * 96) + (28 / 0.75) + 1; = (295.11 * 96) + 38.33 = 28330.66 + 38.33 = 28369 Does anyone have a clue what´s wrong in my code? Must be the first part (28330.66) which causes the calculation problem. Thanks! Yheeky

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  • Proper Usage of Arrays and Functions [closed]

    - by Ssegawa Victor
    Can some one help me write a C code that solves the following problem. PROBLEM Consider the faculty registrar who has to process results for 1st year 1st semester students. Students offer five courses CSC 1100, CSK 1101, CSC 1104, CSC 1105 and CSC 1106. The courses have credit units 4,4,4,3 and 3 respectively. Lecturers provide course work and exam marks. For each course, course work constitutes 40% of the final mark while the exam constitutes 60% of the final mark. The role of the registrar is to Compute the final mark for each student for each course. The final mark must be a whole number Compute the grade and grade point of the students for each course they offered. According to senate regulations, grades and grade points are awarded to final marks according to the following criteria Range Grade Grade Point 90 – 100 A+ 5.0 80 – 89 A 5.0 75 – 79 B+ 4.5 70 – 74 B 4.0 65 – 69 C+ 3.5 60 – 64 C 3.0 55 – 59 D+ 2.5 50 – 54 D 2.0 45 – 49 E 1.5 40 – 44 E- 1.0 0 – 39 F 0.0 Put a comment ‘Retake’ to a student for every course where the Grade Point is less than 2.0 Compute the cumulative grade point average CGPA for each student. The senate formula for CGPA is GGPA =(?_(i=1)^(i=N)¦?CU _i×GP _i ?)/(?_(i=1)^(i=N)¦CU i) Put a comment “Progress” for any student whose GGPA is greater than 2 and “Stay Put” on a student whose CGPA is less than 2 You are required to create a c program that considers a class of 25 students and: 1.Initializes an array ‘student’ which stores student names 2.Initializes arrays for course work and exam for each course. ‘cw_csc_1100’ and ‘ex_csc_1100’ store course work and exam marks (respectively) for CSC 1100. The same approach is considered for all other courses 3.Initializes the coursework and exam marks arrays with marks between 0 and 99 4.Write appropriate functions that will generate the final marks, generate grades, generate grade points, generate cumulative grade points, generate comments for students and comments for courses per student 5.Create appropriate arrays for final marks and insert the data there using the appropriate functions 6.Without having to create any extra arrays, use the functions created to generate a report per student that looks like the one bellow. Student Name: Ngubiri Course Unit Final mark Grade Grade Point Course Comment CSC 1100 43 E- 1.0 Retake CSK 1101 50 D 2.0 CSC 1104 59 D+ 2.5 CSC 1105 70 B 4.0 CSC 1106 65 C+ 3.5 CGPA 2.47 Overall Comment Progress NB It is advisable that the indices are used to identify the owners. Eg if student[x] is John, then cs_csc_100[x] should be a mark for John since the index is the same

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  • Observing flow control idle time in TCP

    - by user12820842
    Previously I described how to observe congestion control strategies during transmission, and here I talked about TCP's sliding window approach for handling flow control on the receive side. A neat trick would now be to put the pieces together and ask the following question - how often is TCP transmission blocked by congestion control (send-side flow control) versus a zero-sized send window (which is the receiver saying it cannot process any more data)? So in effect we are asking whether the size of the receive window of the peer or the congestion control strategy may be sub-optimal. The result of such a problem would be that we have TCP data that we could be transmitting but we are not, potentially effecting throughput. So flow control is in effect: when the congestion window is less than or equal to the amount of bytes outstanding on the connection. We can derive this from args[3]-tcps_snxt - args[3]-tcps_suna, i.e. the difference between the next sequence number to send and the lowest unacknowledged sequence number; and when the window in the TCP segment received is advertised as 0 We time from these events until we send new data (i.e. args[4]-tcp_seq = snxt value when window closes. Here's the script: #!/usr/sbin/dtrace -s #pragma D option quiet tcp:::send / (args[3]-tcps_snxt - args[3]-tcps_suna) = args[3]-tcps_cwnd / { cwndclosed[args[1]-cs_cid] = timestamp; cwndsnxt[args[1]-cs_cid] = args[3]-tcps_snxt; @numclosed["cwnd", args[2]-ip_daddr, args[4]-tcp_dport] = count(); } tcp:::send / cwndclosed[args[1]-cs_cid] && args[4]-tcp_seq = cwndsnxt[args[1]-cs_cid] / { @meantimeclosed["cwnd", args[2]-ip_daddr, args[4]-tcp_dport] = avg(timestamp - cwndclosed[args[1]-cs_cid]); @stddevtimeclosed["cwnd", args[2]-ip_daddr, args[4]-tcp_dport] = stddev(timestamp - cwndclosed[args[1]-cs_cid]); @numclosed["cwnd", args[2]-ip_daddr, args[4]-tcp_dport] = count(); cwndclosed[args[1]-cs_cid] = 0; cwndsnxt[args[1]-cs_cid] = 0; } tcp:::receive / args[4]-tcp_window == 0 && (args[4]-tcp_flags & (TH_SYN|TH_RST|TH_FIN)) == 0 / { swndclosed[args[1]-cs_cid] = timestamp; swndsnxt[args[1]-cs_cid] = args[3]-tcps_snxt; @numclosed["swnd", args[2]-ip_saddr, args[4]-tcp_dport] = count(); } tcp:::send / swndclosed[args[1]-cs_cid] && args[4]-tcp_seq = swndsnxt[args[1]-cs_cid] / { @meantimeclosed["swnd", args[2]-ip_daddr, args[4]-tcp_sport] = avg(timestamp - swndclosed[args[1]-cs_cid]); @stddevtimeclosed["swnd", args[2]-ip_daddr, args[4]-tcp_sport] = stddev(timestamp - swndclosed[args[1]-cs_cid]); swndclosed[args[1]-cs_cid] = 0; swndsnxt[args[1]-cs_cid] = 0; } END { printf("%-6s %-20s %-8s %-25s %-8s %-8s\n", "Window", "Remote host", "Port", "TCP Avg WndClosed(ns)", "StdDev", "Num"); printa("%-6s %-20s %-8d %@-25d %@-8d %@-8d\n", @meantimeclosed, @stddevtimeclosed, @numclosed); } So this script will show us whether the peer's receive window size is preventing flow ("swnd" events) or whether congestion control is limiting flow ("cwnd" events). As an example I traced on a server with a large file transfer in progress via a webserver and with an active ssh connection running "find / -depth -print". Here is the output: ^C Window Remote host Port TCP Avg WndClosed(ns) StdDev Num cwnd 10.175.96.92 80 86064329 77311705 125 cwnd 10.175.96.92 22 122068522 151039669 81 So we see in this case, the congestion window closes 125 times for port 80 connections and 81 times for ssh. The average time the window is closed is 0.086sec for port 80 and 0.12sec for port 22. So if you wish to change congestion control algorithm in Oracle Solaris 11, a useful step may be to see if congestion really is an issue on your network. Scripts like the one posted above can help assess this, but it's worth reiterating that if congestion control is occuring, that's not necessarily a problem that needs fixing. Recall that congestion control is about controlling flow to prevent large-scale drops, so looking at congestion events in isolation doesn't tell us the whole story. For example, are we seeing more congestion events with one control algorithm, but more drops/retransmission with another? As always, it's best to start with measures of throughput and latency before arriving at a specific hypothesis such as "my congestion control algorithm is sub-optimal".

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  • Essbase BSO Data Fragmentation

    - by Ann Donahue
    Essbase BSO Data Fragmentation Data fragmentation naturally occurs in Essbase Block Storage (BSO) databases where there are a lot of end user data updates, incremental data loads, many lock and send, and/or many calculations executed.  If an Essbase database starts to experience performance slow-downs, this is an indication that there may be too much fragmentation.  See Chapter 54 Improving Essbase Performance in the Essbase DBA Guide for more details on measuring and eliminating fragmentation: http://docs.oracle.com/cd/E17236_01/epm.1112/esb_dbag/daprcset.html Fragmentation is likely to occur in the following situations: Read/write databases that users are constantly updating data Databases that execute calculations around the clock Databases that frequently update and recalculate dense members Data loads that are poorly designed Databases that contain a significant number of Dynamic Calc and Store members Databases that use an isolation level of uncommitted access with commit block set to zero There are two types of data block fragmentation Free space tracking, which is measured using the Average Fragmentation Quotient statistic. Block order on disk, which is measured using the Average Cluster Ratio statistic. Average Fragmentation Quotient The Average Fragmentation Quotient ratio measures free space in a given database.  As you update and calculate data, empty spaces occur when a block can no longer fit in its original space and will either append at the end of the file or fit in another empty space that is large enough.  These empty spaces take up space in the .PAG files.  The higher the number the more empty spaces you have, therefore, the bigger the .PAG file and the longer it takes to traverse through the .PAG file to get to a particular record.  An Average Fragmentation Quotient value of 3.174765 means the database is 3% fragmented with free space. Average Cluster Ratio Average Cluster Ratio describes the order the blocks actually exist in the database. An Average Cluster Ratio number of 1 means all the blocks are ordered in the correct sequence in the order of the Outline.  As you load data and calculate data blocks, the sequence can start to be out of order.  This is because when you write to a block it may not be able to place back in the exact same spot in the database that it existed before.  The lower this number the more out of order it becomes and the more it affects performance.  An Average Cluster Ratio value of 1 means no fragmentation.  Any value lower than 1 i.e. 0.01032828 means the data blocks are getting further out of order from the outline order. Eliminating Data Block Fragmentation Both types of data block fragmentation can be removed by doing a dense restructure or export/clear/import of the data.  There are two types of dense restructure: 1. Implicit Restructures Implicit dense restructure happens when outline changes are done using EAS Outline Editor or Dimension Build. Essbase restructures create new .PAG files restructuring the data blocks in the .PAG files. When Essbase restructures the data blocks, it regenerates the index automatically so that index entries point to the new data blocks. Empty blocks are NOT removed with implicit restructures. 2. Explicit Restructures Explicit dense restructure happens when a manual initiation of the database restructure is executed. An explicit dense restructure is a full restructure which comprises of a dense restructure as outlined above plus the removal of empty blocks Empty Blocks vs. Fragmentation The existence of empty blocks is not considered fragmentation.  Empty blocks can be created through calc scripts or formulas.  An empty block will add to an existing database block count and will be included in the block counts of the database properties.  There are no statistics for empty blocks.  The only way to determine if empty blocks exist in an Essbase database is to record your current block count, export the entire database, clear the database then import the exported data.  If the block count decreased, the difference is the number of empty blocks that had existed in the database.

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  • SharePoint: Numeric/Integer Site Column (Field) Types

    - by CharlesLee
    What field type should you use when creating number based site columns as part of a SharePoint feature? Windows SharePoint Services 3.0 provides you with an extensible and flexible method of developing and deploying Site Columns and Content Types (both of which are required for most SharePoint projects requiring list or library based data storage) via the feature framework (more on this in my next full article.) However there is an interesting behaviour when working with a column or field which is required to hold a number, which I thought I would blog about today. When creating Site Columns in the browser you get a nice rich UI in order to choose the properties of this field: However when you are recreating this as a feature defined in CAML (Collaborative Application Mark-up Language), which is a type of XML (more on this in my article) then you do not get such a rich experience.  You would need to add something like this to the element manifest defined in your feature: <Field SourceID="http://schemas.microsoft.com/sharepoint/3.0"        ID="{C272E927-3748-48db-8FC0-6C7B72A6D220}"        Group="My Site Columns"        Name="MyNumber"        DisplayName="My Number"        Type="Numeric"        Commas="FALSE"        Decimals="0"        Required="FALSE"        ReadOnly="FALSE"        Sealed="FALSE"        Hidden="FALSE" /> OK, its not as nice as the browser UI but I can deal with this. Hang on. Commas="FALSE" and yet for my number 1234 I get 1,234.  That is not what I wanted or expected.  What gives? The answer lies in the difference between a type of "Numeric" which is an implementation of the SPFieldNumber class and "Integer" which does not correspond to a given SPField class but rather represents a positive or negative integer.  The numeric type does not respect the settings of Commas or NegativeFormat (which defines how to display negative numbers.)  So we can set the Type to Integer and we are good to go.  Yes? Sadly no! You will notice at this point that if you deploy your site column into SharePoint something has gone wrong.  Your site column is not listed in the Site Column Gallery.  The deployment must have failed then?  But no, a quick look at the site columns via the API reveals that the column is there.  What new evil is this?  Unfortunately the base type for integer fields has this lovely attribute set on it: UserCreatable = FALSE So WSS 3.0 accordingly hides your field in the gallery as you cannot create fields of this type. However! You can use them in content types just like any other field (except not in the browser UI), and if you add them to the content type as part of your feature then they will show up in the UI as a field on that content type.  Most of the time you are not going to be too concerned that your site columns are not listed in the gallery as you will know that they are there and that they are still useable. So not as bad as you thought after all.  Just a little quirky.  But that is SharePoint for you.

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  • Intermittent internet connectivity

    - by Rob Oplawar
    UPDATED: I recently built a new computer and set it up to dual-boot Windows 7 and Ubuntu 11.10. In Windows, using the same hardware, my LAN connectivity is solid. In Ubuntu, however, my network interface periodically dies and resets itself; I'll have a solid connection for 30 seconds, and then it will go out for 30 seconds. When I tail the log: tail -f /var/log/kern.log I see "eth0 link up" messages appear periodically, corresponding with the return of connectivity. I posted the original question months ago, and misinterpreted what was going on. With a working Internet connection in Windows, I ignored the problem for some months. See my answer below for the solution (drivers). ORIGINAL POST In Ubuntu, although I maintain a solid connection to my LAN (pinging the router IP address consistently returns a good result), my internet connectivity drops in and out. When I continuously ping 74.125.227.18 (a google.com server), I get responses for a while, then I start getting "Destination Host Unreachable" for a while, then I get responses again. This happens consistently, dropping the connection for about 30 seconds out of every minute or two. Whether I configure my network via the network manager or via /etc/network/interfaces seems to make no difference. I configure with the following settings: address 192.168.1.101 network 192.168.1.0 gateway 192.168.1.99 (my router's IP address) netmask 255.255.255.0 (confirmed as the right netmask for the router) broadcast 192.168.1.255 (also confirmed with the router). ifconfig confirms that these settings are working: eth0 Link encap:Ethernet HWaddr 50:e5:49:40:da:a6 inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::52e5:49ff:fe40:daa6/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:11557 errors:0 dropped:11557 overruns:0 frame:11557 TX packets:13117 errors:0 dropped:211 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:9551488 (9.5 MB) TX bytes:1930952 (1.9 MB) Interrupt:41 Base address:0xa000 I get the same issue when I use automatic DHCP address settings, although I did confirm that there is no other machine on the network with the static IP address I want to use. As I said, the connection to the local network stays solid - I never have any trouble pinging 192.168.1.* - it's internet addresses that I intermittently cannot reach. It's not a DNS issue because pinging known IP addresses directly shows the same behavior. Also, I don't think it's a hardware issue, as I never have any internet connectivity problems on the same machine in Windows. The network hardware is built into the motherboard: Gigabyte Z68XP-UD3P. I managed to bring the OS fully up to date, according to the update manager, but it didn't fix the issue, and with my limited understanding of network architecture I'm at my wit's end. The only clue I can see is that ifconfig is reporting a lot of dropped packets, but I'm not sure what to do about it. UPDATE: It seems my problem is a little more generic than I described; now when I try pinging my router and google simultaneously, they both go unreachable at the same time. Running ifdown eth0 and then ifup eth0 brings it back temporarily; if I just wait it comes back after a couple of minutes. I'll broaden my search through intermittent network connectivity problems.

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  • SQL 2014 does data the way developers want

    - by Rob Farley
    A post I’ve been meaning to write for a while, good that it fits with this month’s T-SQL Tuesday, hosted by Joey D’Antoni (@jdanton) Ever since I got into databases, I’ve been a fan. I studied Pure Maths at university (as well as Computer Science), and am very comfortable with Set Theory, which undergirds relational database concepts. But I’ve also spent a long time as a developer, and appreciate that that databases don’t exactly fit within the stuff I learned in my first year of uni, particularly the “Algorithms and Data Structures” subject, in which we studied concepts like linked lists. Writing in languages like C, we used pointers to quickly move around data, without a database in sight. Of course, if we had a power failure all this data was lost, as it was only persisted in RAM. Perhaps it’s why I’m a fan of database internals, of indexes, latches, execution plans, and so on – the developer in me wants to be reassured that we’re getting to the data as efficiently as possible. Back when SQL Server 2005 was approaching, one of the big stories was around CLR. Many were saying that T-SQL stored procedures would be a thing of the past because we now had CLR, and that obviously going to be much faster than using the abstracted T-SQL. Around the same time, we were seeing technologies like Linq-to-SQL produce poor T-SQL equivalents, and developers had had a gutful. They wanted to move away from T-SQL, having lost trust in it. I was never one of those developers, because I’d looked under the covers and knew that despite being abstracted, T-SQL was still a good way of getting to data. It worked for me, appealing to both my Set Theory side and my Developer side. CLR hasn’t exactly become the default option for stored procedures, although there are plenty of situations where it can be useful for getting faster performance. SQL Server 2014 is different though, through Hekaton – its In-Memory OLTP environment. When you create a table using Hekaton (that is, a memory-optimized one), the table you create is the kind of thing you’d’ve made as a developer. It creates code in C leveraging structs and pointers and arrays, which it compiles into fast code. When you insert data into it, it creates a new instance of a struct in memory, and adds it to an array. When the insert is committed, a small write is made to the transaction to make sure it’s durable, but none of the locking and latching behaviour that typifies transactional systems is needed. Indexes are done using hashes and using bw-trees (which avoid locking through the use of pointers) and by handling each updates as a delete-and-insert. This is data the way that developers do it when they’re coding for performance – the way I was taught at university before I learned about databases. Being done in C, it compiles to very quick code, and although these tables don’t support every feature that regular SQL tables do, this is still an excellent direction that has been taken. @rob_farley

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  • Questions to ask to ensure someone understands programming? (and iOS)

    - by Stephen J
    So, I've been tutoring my friend for 2 years. Most people learn programming on their own in 3-6 months, (sans algorithms). It's confusing 'cause he'll run anywhere I tell him to, understands how to read C and C++ honestly better than the average college student, and he'll modify and repeat anything I do... but for the love of god he doesn't move on to new things and he still has test anxiety. I've recently realized he's copied and toyed with existing, but not once gained an understanding of why. I was under the impression he was learning fast because he could write it, but when you say "Make a function that takes an NSString" and he says "How?" and I say "The same way you make ANY function that takes any parameter, NSString is just a type like int" and all I hear is "No, it's an NSString, it's a special thing." and we get into an arguing match 'cause I'm like "It's just a class like any other class, you've used them for months now" and blah... I've subconsciously avoided comprehension questions because of this. Anyway, if you have him copy a program and say "Just initialize it" "Where?" "I don't care, didLoad or initWithCoder or Awake from nib, anywhere it gets initialized" and "No, it has to be exactly where you had it!" "No it doesn't!" I'm sick of this, but he won't give up. So I'm done avoiding these yelling matches and becoming a sadist from now on. I would like some help in finding questions to ask him that force him to understand what he's doing. I'd like some help and any resources I can find. CQuestions looked like a good site, but now I need some iPhone stuff. For example: *What do properties do? How are they changed? How do you change the name of the getter? *Why are Booleans inefficent? What advantage does int have over a boolean and how does the bit-shift operator help? *What does Copy do to a string? *What's the difference between a view controller and a uiview? *Write a program from memory that displays blah on screen, and flashes each view one by one. From beginner up to intermediate, hobbyist with some algebra at most. I'm just looking for resources to work with. I left in backstory so you know to "twist" the questions so he doesn't know he's supposed to init a variable here or there, but has to figure it out, and learn why it goes "here" or that "anywhere is fine as long as it's". Sample programs, anything. I'm relatively open about this because, being a programmer, I seriously doubt he's the only one who has this issue. I'd like to know how others have overcome similar. What made things "click"? for you? Did you have a hard time finding answers on Google, and how did you learn a better way to find what you were looking for? (He's so exact, he'll search for how to write a checkers program with color X and Y inside a uiview, as his search string, instead of breaking it up into components, I need help with that too, and believe it is related). This type of problem has to remind one of us of someone they know. So, Exercises to force them to think? Ways we overcame this thing in the past? I greatly appreciate any help.

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  • Test your internet connection - Emtel Fixed Broadband

    Already at the begin of April, I had a phone conversation with my representative at Emtel Ltd. about some upcoming issues due to the ongoing construction work in my neighbourhood. Unfortunately, they finally raised the house two levels above ours, and of course this has to have a negative impact on the visibility between the WiMAX outdoor unit on the roof and the aimed access point at Medine. So, today I had a technical team here to do a site survey and to come up with potential solutions. Short version: It doesn't look good after all. The site survey Well, the two technicians did their work properly, even re-arranged the antenna to check the connection with another end point down at La Preneuse. But no improvements. Looks like we are out of luck since the construction next door hasn't finished yet and at the moment, it even looks like they are planning to put at least one more level on top. I really wonder about the sanity of the responsible bodies at the local district council. But that's another story. Anyway, the outdoor unit was once again pointed towards Medine and properly fixed with new cable guides (air from the sea and rust...). Both of them did a good job and fine-tuned the reception signal to a mere 3 over 9; compared to the original 7 over 9 I had before the daily terror started. The site survey has been done, and now it's up to Emtel to come up with (better) solutions. Well, I wouldn't mind to have an unlimited, symmetric 3G/UMTS or even LTE connection. Let's see what they can do... Testing the connection There are several online sites available which offer you to check certain aspects of your internet connection. Personally, I'm used to speedtest.net and it works very well. I think it is good and necessary to check your connection from time to time, and only a couple of days ago, I posted the following on Emtel's wall at Facebook (21.05.2013 - 14:06 hrs): Dear Emtel, could you eventually provide an answer on the miserable results of SpeedTest? I chose Rose Hill (Hosted by Emtel Ltd.) as testing endpoint... Sadly, no response to this. Seems that the marketing department is not willing to deal with customers on Facebook. Okay, over at speedtest.net you can use their Flash-based test suite to check your connection to quite a number of servers of different providers world-wide. It's actually very interesting to see the results for different end points and to compare them to each other. The results Following are the results of Rose Hill (hosted by Emtel) and respectively Frankfurt, Germany (hosted by Vodafone DE): Speedtest.net result of 30.05.2013 between Flic en Flac and Rose Hill, Mauritius (Emtel - Fixed Broadband) Speedtest.net result of 30.05.2013 between Flic en Flac and Frankfurt, Germany (Emtel - Fixed Broadband) Luckily, the results are quite similar in terms of connection speed; which is good. I'm currently on a WiMAX tariff called 'Classic Browsing 2', or Fixed Broadband as they call it now, which provides a symmetric line of 768 Kbps (or roughly 0.75 Mbps). In terms of downloads or uploads this means that I would be able to transfer files in either direction with approximately 96 KB/s. Frankly speaking, thanks to compression, my choice of browser and operating system I usually exceed this value and I have download rates up to 120 KB/s - not too bad after all. Only the ping times are a little bit of concern. Due to the difference in distance, or better said based on the number of hubs between the endpoints, they indicate the amount of time that it takes to send a package from your machine to the remote server and get a response back. A lower value is better, and usually the ping is less than 300 ms between Mauritius and Europe. The alternatives in Mauritius Not sure whether I should note this done because for my requirements there are no alternatives to Emtel WiMAX at the moment. It would be great to have your opinion on the situation of internet connectivity in Mauritius. Are there really alternatives? And if so, what are the conditions?

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  • jQuery - discrepency between classname and selectors

    - by Ciel
    I have the following code that I wrote, which I personally found to be pretty nice. It takes a <ul> and it drops down the contents when clicked. But I am having a disconnect here in comprehension, and one I had to do what I feel is a 'dirty hack' to solve. The problem is that I do not want the class `'sidebar-dropdown-open' to be so 'hardwired' in the plugin. However I discovered that there is a very stark difference between... $('.sidebar-dropdown-open') and 'sidebar-dropdown-open and even '.sidebar-dropdown-open. I 'solved' this problem by including two different 'parameters' in my plugin, but I was wondering if someone might give me some insight as to how I could perform this better, and why this was behaving this way. wiring (document load) $(document).ready(function () { $('[data-role="sidebar-dropdown"]').drawer({ open: 'sidebar-dropdown-open', css: '.sidebar-dropdown-open' }); }); html <ul> <li class=" dropdown" data-role="sidebar-dropdown"> <a href="pages/.." class="remote">Link Text</a> <ul class="sub-menu light sidebar-dropdown-menu"> <li><a class="remote" href="pages/...">Link Text</a></li> <li><a class="remote" href="pages/...">Link Text</a></li> <li><a class="remote" href="pages/...">Link Text</a></li> </ul> </li> </ul> javascript (function ($) { $.fn.drawer = function (options) { // Create some defaults, extending them with any options that were provided var settings = $.extend({ open: 'open', css: '.open' }, options); return this.each(function () { $(this).on('click', function (e) { // slide up all open dropdown menus $(settings.css).not($(this)).each(function () { $(this).removeClass(settings.open); // retrieve the appropriate menu item var $menu = $(this).children(".dropdown-menu, .sidebar-dropdown-menu"); // slide down the one clicked on. $menu.slideUp('fast'); $menu.removeClass('active'); }); // mark this menu as open $(this).addClass(settings.open); // retrieve the appropriate menu item var $menu = $(this).children(".dropdown-menu, .sidebar-dropdown-menu"); // slide down the one clicked on. $menu.slideDown(100); $menu.addClass('active'); e.preventDefault(); e.stopPropagation(); }).on("mouseleave", function () { $(this).children(".dropdown-menu").hide().delay(300); }); }) }; })(jQuery); I have tried using settings.open and demanding that it just be a className (.open), etc. - but that does not seem to work. It seems to get ignored by the removeClass function.

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  • Internet of Things Becoming Reality

    - by kristin.jellison
    The Internet of Things is not just on the radar—it’s becoming a reality. A globally connected continuum of devices and objects will unleash untold possibilities for businesses and the people they touch. But the “things” are only a small part of a much larger, integrated architecture. A great example of this comes from the healthcare industry. Imagine an expectant mother who needs to watch her blood pressure. She lives in a mountain village 100 miles away from medical attention. Luckily, she can use a small “wearable” device to monitor her status and wirelessly transmit the information to a healthcare hub in her village. Now, say the healthcare hub identifies that the expectant mother’s blood pressure is dangerously high. It sends a real-time alert to the patient’s wearable device, advising her to contact her doctor. It also pushes an alert with the patient’s historical data to the doctor’s tablet PC. He inserts a smart security card into the tablet to verify his identity. This ensures that only the right people have access to the patient’s data. Then, comparing the new data with the patient’s medical history, the doctor decides she needs urgent medical attention. GPS tracking devices on ambulances in the field identify and dispatch the closest one available. An alert also goes to the closest hospital with the necessary facilities. It sends real-time information on her condition directly from the ambulance. So when she arrives, they already have a treatment plan in place to ensure she gets the right care. The Internet of Things makes a huge difference for the patient. She receives personalized and responsive healthcare. But this technology also helps the businesses involved. The healthcare provider achieves a competitive advantage in its services. The hospital benefits from cost savings through more accurate treatment and better application of services. All of this, in turn, translates into savings on insurance claims. This is an ideal scenario for the Internet of Things—when all the devices integrate easily and when the relevant organizations have all the right systems in place. But in reality, that can be difficult to achieve. Core design principles are required to make the whole system work. Open standards allow these systems to talk to each other. Integrated security protects personal, financial, commercial and regulatory information. A reliable and highly available systems infrastructure is necessary to keep these systems running 24/7. If this system were just made up of separate components, it would be prohibitively complex and expensive for almost any organization. The solution is integration, and Oracle is leading the way. We’re developing converged solutions, not just from device to datacenter, but across devices, utilizing the Java platform, and through data acquisition and management, integration, analytics, security and decision-making. The Internet of Things (IoT) requires the predictable action and interaction of a potentially endless number of components. It’s in that convergence that the true value of the Internet of Things emerges. Partners who take the comprehensive view and choose to engage with the Internet of Things as a fully integrated platform stand to gain the most from the Internet of Things’ many opportunities. To discover what else Oracle is doing to connect the world, read about Oracle’s Internet of Things Platform. Learn how you can get involved as a partner by checking out the Oracle Java Knowledge Zone. Best regards, David Hicks

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  • A* algorithm very slow

    - by Amaranth
    I have an programming a RTS game (I use XNA with C#). The pathfinding is working fine, except that when it has a lot of node to search in, there is a lag period of one or two seconds, it happens mainly when there is no path to the target destination, since it that situation there is more nodes to explore. I have the same problem when the path is shorter but selected more than 3 units (can't take the same path since the selected units can be in different part of the map). private List<NodeInfo> FindPath(Unit u, NodeInfo start, NodeInfo end) { Map map = GameInfo.GetInstance().GameMap; _nearestToTarget = start; start.MoveCost = 0; Vector2 endPosition = map.getTileByPos(end.X, end.Y).Position; //getTileByPos simply gets the tile in a 2D array with the X and Y indexes start.EstimatedRemainingCost = (int)(endPosition - map.getTileByPos(start.X, start.Y).Position).Length(); start.Parent = null; List<NodeInfo> openedNodes = new List<NodeInfo>(); ; List<NodeInfo> closedNodes = new List<NodeInfo>(); Point[] movements = GetMovements(u.UnitType); openedNodes.Add(start); while (!closedNodes.Contains(end) && openedNodes.Count > 0) { //Loop in nodes to find lowest cost NodeInfo currentNode = FindLowestCostOpenedNode(openedNodes); openedNodes.Remove(currentNode); closedNodes.Add(currentNode); Vector2 previousMouvement; if (currentNode.Parent == null) { previousMouvement = ConvertRotationToDirectionVector(u.Rotation); } else { previousMouvement = map.getTileByPos(currentNode.X, currentNode.Y).Position - map.getTileByPos(currentNode.Parent.X, currentNode.Parent.Y).Position; previousMouvement.Normalize(); } //For each neighbor foreach (Point movement in movements) { Point exploredGridPos = new Point(currentNode.X + movement.X, currentNode.Y + movement.Y); //Checks if valid move and checks if not if closed nodes list if (ValidNavigableNode(u.UnitType, new Point(currentNode.X, currentNode.Y), exploredGridPos) && !closedNodes.Contains(_gridMap[exploredGridPos.Y, exploredGridPos.X])) { NodeInfo exploredNode = _gridMap[exploredGridPos.Y, exploredGridPos.X]; Tile.TileType exploredTerrain = map.getTileByPos(exploredGridPos.X, exploredGridPos.Y).TerrainType; if(openedNodes.Contains(exploredNode)) { int newCost = currentNode.MoveCost + GetMoveCost(previousMouvement, movement, exploredTerrain); if (newCost < exploredNode.MoveCost) { exploredNode.Parent = currentNode; exploredNode.MoveCost = newCost; //Find nearest tile to the target (in case doesn't find path to target) //Only compares the node to the current nearest FindNearest(exploredNode); } } else { exploredNode.Parent = currentNode; exploredNode.MoveCost = currentNode.MoveCost + GetMoveCost(previousMouvement, movement, exploredTerrain); Vector2 exploredNodeWorldPos = map.getTileByPos(exploredGridPos.X, exploredGridPos.Y).Position; exploredNode.EstimatedRemainingCost = (int)(endPosition - exploredNodeWorldPos).Length(); //Find nearest tile to the target (in case doesn't find path to target) //Only compares the node to the current nearest FindNearest(exploredNode); openedNodes.Add(exploredNode); } } } } return closedNodes; } After that, I simply check if the end node is contained in the returned nodes. If so, I add the end node and each parent until I reach the start. If not, I add the nearestToTarget and each parent until I reach the start. I added a condition before calling FindPath so that only one unit can call a find path each frame (60 frame per second), but it makes no difference. I thought maybe I could solve this by allowing the find path to run in background while the game continues to run correctly, even if it takes a few frame (it is currently sequential sonce it is called in the update() of the unit if there's a target location but no path), but I don't really know how... I also though about sorting my opened nodes list by cost so I don't have to loop them, but I don't know if that would have an effect on the performance... Would there be other solutions? P.S. In the code, when I get the Move Cost, I check if the unit has to turn to perform the move, and the terrain type, nothing hard to do.

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  • An observation on .NET loops – foreach, for, while, do-while

    It’s very common that .NET programmers use “foreach” loop for iterating through collections. Following is my observation whilst I was testing simple scenario on loops. “for” loop is 30% faster than “foreach” and “while” loop is 50% faster than “foreach”. “do-while” is bit faster than “while”. Someone may feel that how does it make difference if I’m iterating only 1000 times in a loop. This test case is only for simple iteration. According to the "Data structure" concepts, best and worst cases are completely based on the data we provide to the algorithm. so we can not conclude that a "foreach" algorithm is not good. All I want to tell that we need to be little cautious even choosing the loops. Example:- You might want to chose quick sort when you want to sort more numbers. At the same time bubble sort may be effective than quick sort when you want to sort less numbers. Take a simple scenario, a request of a simple web application fetches the data of 10000 (10K) rows and iterating them for some business logic. Think, this application is being accessed by 1000 (1K) people simultaneously. In this simple scenario you are ending up with 10000000 (10Million or 1 Crore) iterations. below is the test scenario with simple console application to test 100 Million records. using System;using System.Collections.Generic;using System.Diagnostics;namespace ConsoleApplication1{ class Program { static void Main(string[] args) { var sw = new Stopwatch(); var numbers = GetSomeNumbers(); sw.Start(); foreach (var item in numbers) { } sw.Stop(); Console.WriteLine( String.Format("\"foreach\" took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); for (int i = 0; i < numbers.Count; i++) { } sw.Stop(); Console.WriteLine( String.Format("\"for\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it = 0; while (it++ < numbers.Count) { } sw.Stop(); Console.WriteLine( String.Format("\"while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); sw.Reset(); sw.Start(); var it2 = 0; do { } while (it2++ < numbers.Count); sw.Stop(); Console.WriteLine( String.Format("\"do-while\" loop took {0} milliseconds", sw.ElapsedMilliseconds)); } #region Get me 10Crore (100 Million) numbers private static List<int> GetSomeNumbers() { var lstNumbers = new List<int>(); var count = 100000000; for (var i = 1; i <= count; i++) { lstNumbers.Add(i); } return lstNumbers; } #endregion Get me some numbers }} In above example, I was just iterating through 100 Million numbers. You can see the time to execute various  loops provided in .NET Output "foreach" took 1108 milliseconds "for" loop took 727 milliseconds "while" loop took 596 milliseconds "do-while" loop took 594 milliseconds   Press any key to continue . . . So I feel we need to be careful while choosing the looping strategy. Please comment your thoughts. span.fullpost {display:none;}

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  • PHP - Internal APIs/Libraries - What makes sense?

    - by Mark Locker
    I've been having a discussion lately with some colleagues about the best way to approach a new project, and thought it'd be interesting to get some external thoughts thrown into the mix. Basically, we're redeveloping a fairly large site (written in PHP) and have differing opinions on how the platform should be setup. Requirements: The platform will need to support multiple internal websites, as well as external (non-PHP) projects which at the moment consist of a mobile app and a toolbar. We have no plans/need in the foreseeable future to open up an API externally (for use in products other than our own). My opinion: We should have a library of well documented native model classes which can be shared between projects. These models will represent everything in our database and can take advantage of object orientated features such as inheritance, traits, magic methods, etc. etc. As well as employing ORM. We can then add an API layer on top of these models which can basically accept requests and route them to the appropriate methods, translating the response so that it can be used platform independently. This routing for each method can be setup as and when it's required. Their opinion: We should have a single HTTP API which is used by all projects (internal PHP ones or otherwise). My thoughts: To me, there are a number of issues with using the sole HTTP API approach: It will be very expensive performance wise. One page request will result in several additional http requests (which although local, are still ones that Apache will need to handle). You'll lose all of the best features PHP has for OO development. From simple inheritance, to employing the likes of ORM which can save you writing a lot of code. For internal projects, the actual process makes me cringe. To get a users name, for example, a request would go out of our box, over the LAN, back in, then run through a script which calls a method, JSON encodes the output and feeds that back. That would then need to be JSON decoded, and be presented as an array ready to use. Working with arrays, as appose to objects, makes me sad in a modern PHP framework. Their thoughts (and my responses): Having one method of doing thing keeps things simple. - You'd only do things differently if you were using a different language anyway. It will become robust. - Seeing as the API will run off the library of models, I think my option would be just as robust. What do you think? I'd be really interested to hear the thoughts of others on this, especially as opinions on both sides are not founded on any past experience.

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  • What Counts for a DBA: Skill

    - by drsql
    “Practice makes perfect:” right? Well, not exactly. The reality of it all is that this saying is an untrustworthy aphorism. I discovered this in my “younger” days when I was a passionate tennis player, practicing and playing 20+ hours a week. No matter what my passion level was, without some serious coaching (and perhaps a change in dietary habits), my skill level was never going to rise to a level where I could make any money at the sport that involved something other than selling tennis balls at a sporting goods store. My game may have improved with all that practice but I had too many bad practices to overcome. Practice by itself merely reinforces what we know and what we can figure out naturally. The truth is actually closer to the expression used by Vince Lombardi: “Perfect practice makes perfect.” So how do you get to become skilled as a DBA if practice alone isn’t sufficient? Hit the Internet and start searching for SQL training and you can find 100 different sites. There are also hundreds of blogs, magazines, books, conferences both onsite and virtual. But then how do you know who is good? Unfortunately often the worst guide can be to find out the experience level of the writer. Some of the best DBAs are frighteningly young, and some got their start back when databases were stored on stacks of paper with little holes in it. As a programmer, is it really so hard to understand normalization? Set based theory? Query optimization? Indexing and performance tuning? The biggest barrier often is previous knowledge, particularly programming skills cultivated before you get started with SQL. In the world of technology, it is pretty rare that a fresh programmer will gravitate to database programming. Database programming is very unsexy work, because without a UI all you have are a bunch of text strings that you could never impress anyone with. Newbies spend most of their time building UIs or apps with procedural code in C# or VB scoring obvious interesting wins. Making matters worse is that SQL programming requires mastery of a much different toolset than most any mainstream programming skill. Instead of controlling everything yourself, most of the really difficult work is done by the internals of the engine (written by other non-relational programmers…we just can’t get away from them.) So is there a golden road to achieving a high skill level? Sadly, with tennis, I am pretty sure I’ll never discover it. However, with programming it seems to boil down to practice in applying the appropriate techniques for whatever type of programming you are doing. Can a C# programmer build a great database? As long as they don’t treat SQL like C#, absolutely. Same goes for a DBA writing C# code. None of this stuff is rocket science, as long as you learn to understand that different types of programming require different skill sets and you as a programmer must recognize the difference between one of the procedural languages and SQL and treat them differently. Skill comes from practicing doing things the right way and making “right” a habit.

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  • Dual monitor not working completely in 12.10 after upgrade

    - by Mark Baldridge
    At 12.04, dual monitors worked perfectly. After upgrading to 12.10, the primary monitor works, the second monitor only partly works. I am sure there is some difference between the releases that I have missed setting properly. System settings - Displays show both correctly as Acer 22" monitors at 1680x1050 (16:10). An icon on monitor 2 is present, but elongated; almost an artifact, since other icons on the primary screen are absent, but this one icon is there on th second monitor. Selecting the icons on both screens exist. Painting is weird on monitor 2. Launcher exists and works on both screens, but even with sticky edges off, the cursor stops at the left edge of monitor 2. Clicking on text editor on screen 2 launcer will launch gedit there. If I drag it, it leaves a trail of after images like repaint is failing. If I drive the cursor on the launcher, the help tags like "LibreOffice Writer" appear, but stay on screen unless I drag the active gedit window over them. Then part of the help bubbles are overwritten, leaving behind after images of the gedit window on screen. What is really fascinating is that the System settings - Displays is now ignoring monitor selection, after allowing it earlier. Just before this, the help popup which said "Select a monitor to change its properties; drag to rearrange its placement" actually let me do that. Maybe a trick of where I grab the edge of the monitor in the Displays setting. I just found a working handle. When I drag monitor 1 to the right of monitor 2, "Apply" and confirm, both monitors work normally (although the right monitor lets the cursor slide off the right edge onto the left edge of monitor 1 - which sounds correct). Painting of windows does not leave an after image. However, success is only temporary. The setting survives the reboot, but painting on the left monitor, now monitor 2, now replicates the issues from before. The after image of the gedit window and the small window for "Are you sure you want to close all programs and restart the computer?" are still on monitor 2 (on the left now), even though they are not real windows, nor do they have processes behind them. Curiously, in Displays, the "green" monitor on the left in the display window is matched by the right monitor color in the monitor upper left corner. Probably makes sense as the one on the right is now monitor 1. If I repeat the "drag the left monitor to the right of the right monitor on the "Displays" window, things are oriented properly, with no display artifacts as I drag windows around either screen. Also the description bubbles that pop up are overwritten on both screens, so none of those artifacts either. This goodness does not survive a reboot, however. Have not tried logging out and back in. All of this after positing that the motherboard VGA and HDMI ports could have been the issue. So, I installed an e-GeForce 7600 GT Dual DVI (I know the web thinks it is not DVI, but VGA, but the connectors are DVI). No change to the weird behavior. The good parts continue to work, the weirdness also works, and swapping monitor positions seems to cure the issue. So, is there a setting I have missed? Given "swapping" monitor 1 and 2 on the System Settings... - Displays makes it work, just not across boot, I suspect so.

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