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• Why Apple’s New SDK Limitation is So Offensive

  - by TStewartDev

  I am not an Apple fanboy, nor have I ever been. However, I have owned a Mac, an iPod, and an iPhone in my lifetime, and for more than a decade, I have defended Apple against the untruths that the haters so enjoy spewing. I encouraged my wife to buy a MacBook when she needed a new laptop two years ago, and I often recommend them to my friends and relatives. I have proudly and happily used my first generation iPhone for nearly three years. Now, for the first time in well over ten years, I find myself ready to swear off Apple and encourage everyone I know to do the same. I was disappointed when Apple wouldn't allow native apps, but I still bought the iPhone. I've stomached their ambiguous app approval process even though it's apparent that Steve may just reject your app because he doesn't like you or feels threatened by you (I'm still lamenting the rejection of the Google Voice app). But, as a developer, I can no longer tolerate Apple's terms and the kind of totalitarian control they indicate Apple wants. In case you are not already familiar, Apple has dictated in their OS 4.0 SDK license agreement (the now infamous Section 3.3.1) that all apps developed for the iPhone must be coded in C, C++, or Objective C, and moreover, that using any cross-compiling platforms is a violation of the agreement. For those of you who aren't developers, let me try to illustrate why this angers those of us who are. Imagine you're a professional writer. You've had articles published in some journals and magazines, and you've got a couple popular books out there, too. You've got an idea for a new book, and so you take it to your publisher. Your publisher agrees that it's a good idea. "But," says the publisher, "we want to hold our books to a tighter standard so that our readers get the experience we want them to have. Therefore, from now on, all our writers may only use words from this list of the 10,000 most common English words. Furthermore, if you cite any other works or quote anyone, they must comply with that same list, or you'll have to rewrite the entire work as well in case our readers want to look up your citation." What do you do? If your work is a children's book, this probably isn't a big deal to you. If it's an autobiography, textbook, or even a novel, though, you're going to have a lot of trouble describing your content with only common words. It's going to take you longer to complete your book, too, since you'll be looking up less common words frequently to see if you can use them. You could always go to another publisher, but this one has the best ability to distribute your book. The next largest distributor can only do a quarter as much. You could abandon the project altogether, but then everyone loses. Isn't this a silly scenario? Who would put such a limitation on writers? Yet this is very much what Apple is doing. They are using their dominant position in the market to coerce developers to write their apps exclusively for the iPhone OS by making it too expensive to write for multiple platforms. It is at least a threefold attack, striking at Adobe who is set to release a compiler that lets Flash source be compiled to iPhone binaries; striking at Google whose Android platform stands the best chance at the moment of providing serious competition to the iPhone; and reinforcing their own strong position by keeping popular apps exclusively to iPhone. And while developers are already very upset about this, the sad fact is that most of us will cave and give in to Apple because consumers don't know any better. They will continue to buy Apple's toy forcing developers to play Apple's maniacal game in order to make any money, at least until Steve Jobs decides he doesn't like them or he intends to release a competing application (bye-bye OpenFeint). Apple has been kept in check on the desktop front by a very dominant Microsoft, but I'm afraid that their success with iPods, iTunes, and iPhones has created a monster that we may have to bear until it is slain by an anti-trust suit or dies with the retirement of Steve Jobs.

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• Monitoring Windows Azure Service Bus Endpoint with BizTalk 360?

  - by Michael Stephenson

  I'm currently working with a customer who is undergoing an initiative to expose some of their line of business applications to external partners and SAAS applications and as part of this we have been looking at using the Windows Azure Service Bus. For the first part of the project we were focused on some synchronous request response scenarios where an external application would use the Service Bus relay functionality to get data from some internal applications. When we were looking at the operational monitoring side of the solution it was obvious that although most of the normal server monitoring capabilities would be required for the on premise components we would have to look at new approaches to validate that the operation of the service from outside of the organization was working as expected. A number of months ago one of my colleagues Elton Stoneman wrote about an approach I have introduced with a number of clients in the past where we implement a diagnostics service in each service component we build. This service would allow us to make a call which would flex some of the working parts of the system to prove it was working within any SLA. This approach is discussed on the following article: http://geekswithblogs.net/EltonStoneman/archive/2011/12/12/the-value-of-a-diagnostics-service.aspx In our solution we wanted to take the same approach but we had to consider that the service clients were external to the service. We also had to consider that by going through Windows Azure Service Bus it's not that easy to make most of your standard monitoring solutions just give you an easy way to do this. In a previous article I have described how you can use BizTalk 360 to monitor things using a custom extension to the Web Endpoint Manager and I felt that we could use this approach to provide an excellent way to monitor our service bus endpoint. The previous article is available on the following link: http://geekswithblogs.net/michaelstephenson/archive/2012/09/12/150696.aspx   The Monitoring Solution BizTalk 360 currently has an easy way to hook up the endpoint manager to a url which it will then call and if a successful response is returned it then considers the endpoint to be in a healthy state. We would take advantage of this by creating an ASP.net web page which would be called by BizTalk 360 and behind this page we would implement the functionality to call the diagnostics service on our Service Bus endpoint. The ASP.net page could include logic to work out how to handle the response from the diagnostics service. For example if the overall result of the diagnostics service was successful but the call to the diagnostics service was longer than a certain amount of time then we could return an error and indicate the service is taking too long. The following diagram illustrates the monitoring pattern.   The diagnostics service which is hosted in the line of business application allows us to ping a simple message through the Azure Service Bus relay to the WCF services in the LOB application and we they get a response back indicating that the service is working fine. To implement this I used the exact same approach I described in my previous post to create a custom web page which calls the diagnostics service and then it would return an HTTP response code which would depend on the error condition returned or a 200 if it was successful. One of the limitations of this approach is that the competing consumer pattern for listening to messages from service bus means that you cannot guarantee which server would process your diagnostics check message but with BizTalk 360 you could simply add multiple endpoint checks so that it could access the individual on-premise web servers directly to ensure that each server is working fine and then check that messages can also be processed through the cloud. Conclusion It took me about 15 minutes to get a proof of concept of this up and running which was able to monitor our web services which had been exposed via Windows Azure Service Bus. I was then able to inherit all of the monitoring benefits of BizTalk 360 to provide an enterprise class monitoring solution for our cloud enabled API.

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• Get More From Your Service Request

  - by Get Proactive Customer Adoption Team

  Leveraging Service Request Best Practices Use best practices to get there faster. In the daily conversations I have with customers, they sometimes express frustration over their Service Requests. They often feel powerless to make needed changes, so their sense of frustration grows. To help you avoid some of the frustration you might feel in dealing with your Service Requests (SR), here are a few pointers that come from our best practice discussions. Be proactive. If you can anticipate some of the questions that Support will ask, or the information they may need, try to provide this up front, when you log the SR. This could be output from the Remote Diagnostic Agent (RDA), if this is a database issue, or the output from another diagnostic tool, if you’re an EBS customer. Any information you can supply that helps us understand the situation better, helps us resolve the issue sooner. As you use some of these tools proactively, you might even find the solution to the problem before you log an SR! Be right. Make sure you have the correct severity level. Since you select the initial severity level, it’s easy to accept the default without considering how significant this may be. Business impact is the driving factor, so make sure you take a moment to select the severity level that is appropriate to the situation. Also, make sure you ask us to change the severity level, should the situation dictate. Be responsive! If this is an important issue to you, quickly follow up on any action plan submitted to you by Oracle Support. The support engineer assigned to your Service Request will be able to move the issue forward more aggressively when they have the needed information. This is crucial in resolving your issues in a timely manner. Be thorough. If there are five questions in the action plan, make sure you provide an answer for all five questions in one response, rather than trickling them in one at a time. This will allow the engineer to look at all of the information as a whole and to avoid multiple trips to your SR, saving valuable time and getting you a resolution sooner. Be your own advocate! You know your situation best; make sure Oracle Support understands both how and why this issue is important to you and your company. Use the escalation process if you're concerned that your SR isn't going the right direction, the right pace, or through the right person. Don't wait until you're frustrated and angry. An escalation is as simple as a quick conversation on the phone and can be amazingly effective in getting your issues back on track. The support manager you speak with is empowered to make any needed changes. Be our partner. You can make your support experience better. When your SR has been resolved, you may receive a survey request. This is intended to get your feedback about how your SR went and what we can do to improve your overall support experience. Oracle Support is here to help you. Our goal with any Service Request is to provide the best possible solution as quickly as possible. With your help, we’ll be able to do this with your Service Request too.  

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• Representing Mauritius in the 2013 Bench Games

  Only by chance I came across an interesting option for professionals and enthusiasts in IT, and quite honestly I can't even remember where I caught attention of Brainbench and their 2013 Bench Games event. But having access to 600+ free exams in a friendly international intellectual competition doesn't happen to be available every day. So, it was actually a no-brainer to sign up and browse through the various categories. Most interestingly, Brainbench is not only IT-related. They offer a vast variety of fields in their Test Center, like Languages and Communication, Office Skills, Management, Aptitude, etc., and it can be a little bit messy about how things are organised. Anyway, while browsing through their test offers I added a couple of exams to 'My Plan' which I would give a shot afterwards. Self-assessments Actually, I took the tests based on two major aspects: 'Fun Factor' and 'How good would I be in general'... Usually, you have to pay for any kind of exams and given this unique chance by Brainbench to simply train this kind of tests was already worth the time. Frankly speaking, the tests are very close to the ones you would be asked to do at Prometric or Pearson Vue, ie. Microsoft exams, etc. Go through a set of multiple choice questions in a given time frame. Most of the tests I did during the Bench Games were based on 40 questions, each with a maximum of 3 minutes to answer. Ergo, one test in maximum 2 hours - that sounds feasible, doesn't it? The Measure of Achievement While the 2013 Bench Games are considered a worldwide friendly competition of knowledge I was really eager to get other Mauritians attracted. Using various social media networks and community activities it all looked quite well at the beginning. Mauritius was listed on rank #19 of Most Certified Citizens and rank #10 of Most Master Level Certified Nation - not bad, not bad... Until... the next update of the Bench Games Leaderboard. The downwards trend seemed to be unstoppable and I couldn't understand why my results didn't show up on the Individual Leader Board. First of all, I passed exams that were not even listed and second, I had better results on some exams listed. After some further information from the organiser it turned out that my test transcript wasn't available to the public. Only then results are considered and counted in the competition. During that time, I actually managed to hold 3 test results on the Individuals... Other participants were merciless, eh, more successful than me, produced better test results than I did. But still I managed to stay on the final score board: An 'exotic' combination of exam, test result, country and person itself Representing Mauritius and the Visual FoxPro community in that fun event. And although I mainly develop in Visual FoxPro 9.0 SP2 and C# using .NET Framework from 2.0 to 4.5 since a couple of years I still managed to pass on Master Level. Hm, actually my Microsoft Certified Programmer (MCP) exams are dated back in June 2004 - more than 9 years ago... Look who got lucky... As described above I did a couple of exams as time allowed and without any preparations, but still I received the following mail notification: "Thank you for recently participating in our Bench Games event.  We wanted to inform you that you obtained a top score on our test(s) during this event, and as a result, will receive a free annual Brainbench subscription.  Your annual subscription will give you access to all our tests just like Bench Games, but for an entire year plus additional benefits!" -- Leader Board Notification from Brainbench Even fun activities get rewarded sometimes. Thanks to @Brainbench_com for the free annual subscription based on my passed 2013 Bench Games Master Level exam. It would be interesting to know about the total figures, especially to see how many citizens of Mauritius took part in this year's Bench Games. Anyway, I'm looking forward to be able to participate in other challenges like this in the future.

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• Hyper-V for Developers Part 1 Internal Networks

  Over the last year, weve been working with Microsoft to build training and demo content for the next version of Office Communications Server code-named Microsoft Communications Server 14.  This involved building multi-server demo environments in Hyper-V, getting them running on demo servers which we took to TechEd, PDC, and other training events, and sometimes connecting the demo servers to the show networks at those events.  ITPro stuff that should scare the hell out of a developer! It can get ugly when I occasionally have to venture into ITPro land.  Lets leave it at that. Having gone through this process about 10 to 15 times in the last year, I finally have it down.  This blog series is my attempt to put all that knowledge in one place if anything, so I can find it somewhere when I need it again.  Ill start with the most simple scenario and then build on top of it in future blog posts. If youre an ITPro, please resist the urge to laugh at how trivial this is. Internal Hyper-V Networks Lets start simple.  An internal network is one that intended only for the virtual machines that are going to be on that network it enables them to communicate with each other. Create an Internal Network On your host machine, fire up the Hyper-V Manager and click the Virtual Network Manager in the Actions panel. Select Internal and leave all the other default values. Give the virtual network a name, and leave all the other default values. After the virtual network is created, open the Network and Sharing Center and click Change Adapter Settings to see the list of network connections. The only thing I recommend that you do is to give this connection a friendly label, e.g. Hyper-V Internal.  When you have multiple networks and virtual networks on the host machines, this helps group the networks so you can easily differentiate them from each other.  Otherwise, dont touch it, only bad things can happen. Connect the Virtual Machines to the Internal Network Im assuming that you have more than 1 virtual machine already configured in Hyper-V, for example a Domain Controller, and Exchange Server, and a SharePoint Server. What you need to do is basically plug in the network to the virtual machine.  In order to do this, the machine needs to have a virtual network adapter.  If the VM doesnt have a network adapter, open the VMs Settings and click Add Hardware in the left pane.  Choose the virtual network to which to bind the adapter to. If you already have a virtual network adapter on the VM, simply connect it to the virtual network. Assign IP Addresses to the Virtual Machines on the Internal Network Open the Network and Sharing Center on your VM, there should only be 1 network at this time.  Open the Properties of the connection, select Internet Protocol Version 4 (TCP/IPv4) and hit Properties. In this environment, Im assigning IP addresses as 192.168.0.xxx.  This particular VM has an IP address of 192.168.0.40 with a subnet mask of 255.255.255.0, and a DNS Server of 192.168.0.18.  DNS is running on the Domain Controller VM which has an IP address of 192.168.0.18. Repeat this process on every VM in your environment, obviously assigning a unique IP address to each.  In an environment with a domain controller, you should now be able to ping the machines from each other. What Next? After completing this process, heres what you still cannot do: Access the internet from any of the VMs Remote desktop to a VM from the host Remote desktop to a VM over the network In the next post, well take a look configuring an External network adapter on the virtual machines.  Well then build on top of that so that you can RDP into the VMs from the host machine and over the network.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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• Access Control Lists for Roles

  - by Kyle Hatlestad

  Back in an earlier post, I wrote about how to enable entity security (access control lists, aka ACLs) for UCM 11g PS3.  Well, there was actually an additional security option that was included in that release but not fully supported yet (only for Fusion Applications).  It's the ability to define Roles as ACLs to entities (documents and folders).  But now in PS5, this security option is now fully supported.   The benefit of defining Roles for ACLs is that those user roles come from the enterprise security directory (e.g. OID, Active Directory, etc) and thus the WebCenter Content administrator does not need to define them like they do with ACL Groups (Aliases).  So it's a bit of best of both worlds.  Users are managed through the LDAP repository and are automatically granted/denied access through their group membership which are mapped to Roles in WCC.  A different way to think about it is being able to add multiple Accounts to content items...which I often get asked about.  Because LDAP groups can map to Accounts, there has always been this association between the LDAP groups and access to the entity in WCC.  But that mapping had to define the specific level of access (RWDA) and you could only apply one Account per content item or folder.  With Roles for ACLs, it basically takes away both of those restrictions by allowing users to define more then one Role and define the level of access on-the-fly. To turn on ACLs for Roles, there is a component to enable.  On the Component Manager page, click the 'advanced component manager' link in the description paragraph at the top.   In the list of Disabled Components, enable the RoleEntityACL component. Then restart.  This is assuming the other configuration settings have been made for the other ACLs in the earlier post.   Once enabled, a new metadata field called xClbraRoleList will be created.  If you are using OracleTextSearch as the search indexer, be sure to run a Fast Rebuild on the collection. For Users and Groups, these values are automatically picked up from the corresponding database tables.  In the case of Roles, there is an explicitly defined list of choices that are made available.  These values must match the roles that are coming from the enterprise security repository. To add these values, go to Administration -> Admin Applets -> Configuration Manager.  On the Views tab, edit the values for the ExternalRolesView.  By default, 'guest' and 'authenticated' are added.  Once added, you can assign the roles to your content or folder. If you are a user that can both access the Security Group for that item and you belong to that particular Role, you now have access to that item.  If you don't belong to that Role, you won't! [Extra] Because the selection mechanism for the list is using a type-ahead field, users may not even know the possible choices to start typing to.  To help them, one thing you can add to the form is a placeholder field which offers the entire list of roles as an option list they can scroll through (assuming its a manageable size)  and view to know what to type to.  By being a placeholder field, it won't need to be added to the custom metadata database table or search engine.  

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• A .NET Developers day with the iPad.

  - by mbcrump

  The Apple iPad is currently getting a lot of buzz because of the app store, the book store and of course iTunes. I had the chance to play with one and this is what I have learned about the device. Let’s get this out of the way first, the iPad is awesome. It is the device for media consumption and casual web browsing. But how does it measure up to those of us with .NET on our brains all days. Let’s find out… Main Screen – you can customize everything on this page. I guess I should replace that image with a C# or VS logo. Its pretty standard stuff if you have an iPhone.   Programming Books If you have a subscription to Safari Books Online, then you are in luck, its very easy to read the books on the iPad. Just fire up Safari web browser and goto the Safari Books Online. The biggest benefit that I can see with the iPad is the ability to read books wherever and not have to worry about purchasing books that I already have the .PDF for. Below is a sample from Code Complete 2nd Edition. Below is a PDF of the ECMA-334 C# Language Specification. As you can see its very readable and you should have no problem reading actual code.   Example of Code shown below: It is however easier to read the PDF and store them with a 3rd party PDF reader. I have seen several for .99 cents or less. You can however switch the screen to vertical to get more viewing space as shown below: I was disappointed with the iBooks application. I could not find a single .NET programming book anywhere. I was able to download the excellent sci-fi book “A memory of Wind” for free though. If I just overlooked them, then please email me with the names and titles. I couldn’t even find a technology category in the categories list. Web Surfing – Technical Sites Below is an example of my site in Safari. The code is very readable and the experience was identical to viewing it in Firefox. I tried multiple programming site and the pages looked great except those that used flash and of course it did not display on those pages.   News Apps - Technical Content The standard NY Times and USA Today looked great, but the Technical Content was lacking. It would probably be better to use Google Reader for online technical news.     YouTube Videos – Technical Content  Since its YouTube, we already know that a lot of technical content exist and it plays great on the iPad. I watched several programming videos and could clearly see the code being written. Taking Technical Notes The iPad comes with a great notepad for taking notes. I found that it was easy to take notes regarding projects that I am currently working on.   Calendar The calendar that ships with the iPad is great for organizing. You can setup exchange server or manually enter the information. Pretty standard stuff.    Random Applications that I like: TweetDeck.   and Adobe Ideas. Adobe Ideas is kinda like SketchFlow except you use your finger to mock up the sketches.  Don’t forget that the iPad is great for any type of podcasting. That pretty much sums it up, I would definitely recommend this device as it will only get better. I believe the iOS4 comes out on the 24th and the iPad will only get more and more apps. You could save a few bucks by waiting for the 2nd generation, but that’s a call that only you can make.

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• Using WKA in Large Coherence Clusters (Disabling Multicast)

  - by jpurdy

  Disabling hardware multicast (by configuring well-known addresses aka WKA) will place significant stress on the network. For messages that must be sent to multiple servers, rather than having a server send a single packet to the switch and having the switch broadcast that packet to the rest of the cluster, the server must send a packet to each of the other servers. While hardware varies significantly, consider that a server with a single gigabit connection can send at most ~70,000 packets per second. To continue with some concrete numbers, in a cluster with 500 members, that means that each server can send at most 140 cluster-wide messages per second. And if there are 10 cluster members on each physical machine, that number shrinks to 14 cluster-wide messages per second (or with only mild hyperbole, roughly zero). It is also important to keep in mind that network I/O is not only expensive in terms of the network itself, but also the consumption of CPU required to send (or receive) a message (due to things like copying the packet bytes, processing a interrupt, etc). Fortunately, Coherence is designed to rely primarily on point-to-point messages, but there are some features that are inherently one-to-many: Announcing the arrival or departure of a member Updating partition assignment maps across the cluster Creating or destroying a NamedCache Invalidating a cache entry from a large number of client-side near caches Distributing a filter-based request across the full set of cache servers (e.g. queries, aggregators and entry processors) Invoking clear() on a NamedCache The first few of these are operations that are primarily routed through a single senior member, and also occur infrequently, so they usually are not a primary consideration. There are cases, however, where the load from introducing new members can be substantial (to the point of destabilizing the cluster). Consider the case where cluster in the first paragraph grows from 500 members to 1000 members (holding the number of physical machines constant). During this period, there will be 500 new member introductions, each of which may consist of several cluster-wide operations (for the cluster membership itself as well as the partitioned cache services, replicated cache services, invocation services, management services, etc). Note that all of these introductions will route through that one senior member, which is sharing its network bandwidth with several other members (which will be communicating to a lesser degree with other members throughout this process). While each service may have a distinct senior member, there's a good chance during initial startup that a single member will be the senior for all services (if those services start on the senior before the second member joins the cluster). It's obvious that this could cause CPU and/or network starvation. In the current release of Coherence (3.7.1.3 as of this writing), the pure unicast code path also has less sophisticated flow-control for cluster-wide messages (compared to the multicast-enabled code path), which may also result in significant heap consumption on the senior member's JVM (from the message backlog). This is almost never a problem in practice, but with sufficient CPU or network starvation, it could become critical. For the non-operational concerns (near caches, queries, etc), the application itself will determine how much load is placed on the cluster. Applications intended for deployment in a pure unicast environment should be careful to avoid excessive dependence on these features. Even in an environment with multicast support, these operations may scale poorly since even with a constant request rate, the underlying workload will increase at roughly the same rate as the underlying resources are added. Unless there is an infrastructural requirement to the contrary, multicast should be enabled. If it can't be enabled, care should be taken to ensure the added overhead doesn't lead to performance or stability issues. This is particularly crucial in large clusters.

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• Why is this beat detection code failing to register some beats properly?

  - by Quincy

  I made this SoundAnalyzer class to detect beats in songs: class SoundAnalyzer { public SoundBuffer soundData; public Sound sound; public List<double> beatMarkers = new List<double>(); public SoundAnalyzer(string path) { soundData = new SoundBuffer(path); sound = new Sound(soundData); } // C = threshold, N = size of history buffer / 1024 B = bands public void PlaceBeatMarkers(float C, int N, int B) { List<double>[] instantEnergyList = new List<double>[B]; GetEnergyList(B, ref instantEnergyList); for (int i = 0; i < B; i++) { PlaceMarkers(instantEnergyList[i], N, C); } beatMarkers.Sort(); } private short[] getRange(int begin, int end, short[] array) { short[] result = new short[end - begin]; for (int i = 0; i < end - begin; i++) { result[i] = array[begin + i]; } return result; } // get a array of with a list of energy for each band private void GetEnergyList(int B, ref List<double>[] instantEnergyList) { for (int i = 0; i < B; i++) { instantEnergyList[i] = new List<double>(); } short[] samples = soundData.Samples; float timePerSample = 1 / (float)soundData.SampleRate; int sampleIndex = 0; int nextSamples = 1024; int samplesPerBand = nextSamples / B; // for the whole song while (sampleIndex + nextSamples < samples.Length) { complex[] FFT = FastFourier.Calculate(getRange(sampleIndex, nextSamples + sampleIndex, samples)); // foreach band for (int i = 0; i < B; i++) { double energy = 0; for (int j = 0; j < samplesPerBand; j++) energy += FFT[i * samplesPerBand + j].GetMagnitude(); energy /= samplesPerBand; instantEnergyList[i].Add(energy); } if (sampleIndex + nextSamples >= samples.Length) nextSamples = samples.Length - sampleIndex - 1; sampleIndex += nextSamples; samplesPerBand = nextSamples / B; } } // place the actual markers private void PlaceMarkers(List<double> instantEnergyList, int N, float C) { double timePerSample = 1 / (double)soundData.SampleRate; int index = N; int numInBuffer = index; double historyBuffer = 0; //Fill the history buffer with n * instant energy for (int i = 0; i < index; i++) { historyBuffer += instantEnergyList[i]; } // If instantEnergy / samples in buffer < instantEnergy for the next sample then add beatmarker. while (index + 1 < instantEnergyList.Count) { if(instantEnergyList[index + 1] > (historyBuffer / numInBuffer) * C) beatMarkers.Add((index + 1) * 1024 * timePerSample); historyBuffer -= instantEnergyList[index - numInBuffer]; historyBuffer += instantEnergyList[index + 1]; index++; } } } For some reason it's only detecting beats from 637 sec to around 641 sec, and I have no idea why. I know the beats are being inserted from multiple bands since I am finding duplicates, and it seems that it's assigning a beat to each instant energy value in between those values. It's modeled after this: http://www.flipcode.com/misc/BeatDetectionAlgorithms.pdf So why won't the beats register properly?

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• Faster Memory Allocation Using vmtasks

  - by Steve Sistare

  You may have noticed a new system process called "vmtasks" on Solaris 11 systems: % pgrep vmtasks 8 % prstat -p 8 PID USERNAME SIZE RSS STATE PRI NICE TIME CPU PROCESS/NLWP 8 root 0K 0K sleep 99 -20 9:10:59 0.0% vmtasks/32 What is vmtasks, and why should you care? In a nutshell, vmtasks accelerates creation, locking, and destruction of pages in shared memory segments. This is particularly helpful for locked memory, as creating a page of physical memory is much more expensive than creating a page of virtual memory. For example, an ISM segment (shmflag & SHM_SHARE_MMU) is locked in memory on the first shmat() call, and a DISM segment (shmflg & SHM_PAGEABLE) is locked using mlock() or memcntl(). Segment operations such as creation and locking are typically single threaded, performed by the thread making the system call. In many applications, the size of a shared memory segment is a large fraction of total physical memory, and the single-threaded initialization is a scalability bottleneck which increases application startup time. To break the bottleneck, we apply parallel processing, harnessing the power of the additional CPUs that are always present on modern platforms. For sufficiently large segments, as many of 16 threads of vmtasks are employed to assist an application thread during creation, locking, and destruction operations. The segment is implicitly divided at page boundaries, and each thread is given a chunk of pages to process. The per-page processing time can vary, so for dynamic load balancing, the number of chunks is greater than the number of threads, and threads grab chunks dynamically as they finish their work. Because the threads modify a single application address space in compressed time interval, contention on locks protecting VM data structures locks was a problem, and we had to re-scale a number of VM locks to get good parallel efficiency. The vmtasks process has 1 thread per CPU and may accelerate multiple segment operations simultaneously, but each operation gets at most 16 helper threads to avoid monopolizing CPU resources. We may reconsider this limit in the future. Acceleration using vmtasks is enabled out of the box, with no tuning required, and works for all Solaris platform architectures (SPARC sun4u, SPARC sun4v, x86). The following tables show the time to create + lock + destroy a large segment, normalized as milliseconds per gigabyte, before and after the introduction of vmtasks: ISM system ncpu before after speedup ------ ---- ------ ----- ------- x4600 32 1386 245 6X X7560 64 1016 153 7X M9000 512 1196 206 6X T5240 128 2506 234 11X T4-2 128 1197 107 11x DISM system ncpu before after speedup ------ ---- ------ ----- ------- x4600 32 1582 265 6X X7560 64 1116 158 7X M9000 512 1165 152 8X T5240 128 2796 198 14X (I am missing the data for T4 DISM, for no good reason; it works fine). The following table separates the creation and destruction times: ISM, T4-2 before after ------ ----- create 702 64 destroy 495 43 To put this in perspective, consider creating a 512 GB ISM segment on T4-2. Creating the segment would take 6 minutes with the old code, and only 33 seconds with the new. If this is your Oracle SGA, you save over 5 minutes when starting the database, and you also save when shutting it down prior to a restart. Those minutes go directly to your bottom line for service availability.

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• Is Your Company Social on the Inside?

  - by Mike Stiles

  As we talk about the extension of social from an outbound-facing marketing tool to a platform that will reach across the entire enterprise, servicing multiple functions of that enterprise, it might be time to take a look at how social can be effectively employed for internal communications. Remember the printed company newsletter? Yeah, nobody reads it. Remember the emailed company newsletter? Yeah, nobody reads it. Why not? Shouldn’t your employees care about the company more than anything else in life and be voraciously hungry for any information related to it? The more realistic prospect is that a company’s employees don’t behave much differently at work where information is concerned than they do in their personal lives. They “tune in” to information that’s immediately relevant to them, that peaks their interest, and/or that’s presented in a visually engaging way. That currently makes an internal social platform the most ideal way to communicate within the organization. It not only facilitates more immediate, more targeted (and thus more relevant) messaging from the company out to employees, it sets a stage for employees to communicate with each other and efficiently get answers to questions from peers. It’s a collaboration tool on steroids. If you build such an internal social portal and you do it right, will employees use it? Considering social media has officially been declared more addictive than cigarettes, booze and sex…probably. But what does it mean to do an internal social platform “right”? The bar has been set pretty high. Your employees are used to Twitter and Facebook, and would roll their eyes at anything less simple or harder to navigate than those. All the Facebook best practices would apply to your internal social as well, including the importance of managing posting frequency, using photos and video, moderation & response, etc. And don’t worry, you won’t be the first to jump in. WPP's global digital agency Possible has its own social network called Colab. Nestle has “The Nest.” Red Robin’s got one. I myself got an in-depth look at McGraw-Hill’s internal social platform at Blogwell NYC. Some of these companies are building their own platforms, others are buying them off the shelf or customizing readymade solutions. But you won’t be the last either. Prescient Digital Media and the IABC learned 39% of companies don’t offer employees any social tools. Not a social network, not discussion forums, not even IM. And a great many continue to ban the use of Facebook and Twitter on the premises. That’s pretty astonishing since social has become as essential a modern day communications tool as the telephone. But such holdouts will pay a big price for being mired in fear while competitors exploit social connections unchallenged. Fish where the fish are. If social has become the way people communicate and take in information, let that be the way communication is trafficked in the organization.

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• College Ratings via the Federal Government

  - by user9147039

  A few weeks back you might remember news about a higher education rating system proposal from the Obama administration. As I've discussed previously, political and stakeholder pressures to improve outcomes and increase transparency are stronger than ever before. The executive branch proposal is intended to make progress in this area. Quoting from the proposal itself, "The ratings will be based upon such measures as: Access, such as percentage of students receiving Pell grants; Affordability, such as average tuition, scholarships, and loan debt; and Outcomes, such as graduation and transfer rates, graduate earnings, and advanced degrees of college graduates.” This is going to be quite complex, to say the least. Most notably, higher ed is not monolithic. From community and other 2-year colleges, to small private 4-year, to professional schools, to large public research institutions…the many walks of higher ed life are, well, many. Designing a ratings system that doesn't wind up with lots of unintended consequences and collateral damage will be difficult. At best you would end up potentially tarnishing the reputation of certain institutions that were actually performing well against the metrics and outcome measures that make sense in their "context" of education. At worst you could spend a lot of time and resources designing a system that would lose credibility with its "customers". A lot of institutions I work with already have in place systems like the one described above. They are tracking completion rates, completion timeframes, transfers to other institutions, job placement, and salary information. As I talk to these institutions there are several constants worth noting: • Deciding on which metrics to measure is complicated. While employment and salary data are relatively easy to track, qualitative measures are more difficult. How do you quantify the benefit to someone who studies in one field that may not compensate him or her as well as another field but that provides huge personal fulfillment and reward is a difficult measure to quantify? • The data is available but the systems to transform the data into actual information that can be used in meaningful ways are not. Too often in higher ed information is siloed. As such, much of the data that need to be a part of a comprehensive system sit in multiple organizations, oftentimes outside the reach of core IT. • Politics and culture are big barriers. One of the areas that my team and I spend a lot of time talking about with higher ed institutions all over the world is the imperative to optimize for student success. This, like the tracking of the students’ achievement after graduation, requires a level or organizational capacity that does not currently exist. The primary barrier is the culture of "data islands" in higher ed, and the need for leadership to drive out the divisions between departments, schools, colleges, etc. and institute academy-wide analytics and data stewardship initiatives that will enable student success. • Data quality is a very big issue. So many disparate systems exist (some on premise, some "in the cloud") that keep data about "persons" using different means to identify them. Establishing a single source of truth about an individual and his or her data is difficult without some type of data quality policy and tools. Good tools actually exist but are seldom leveraged. Don't misunderstand - I think it's a great idea to drive additional transparency and accountability into the system of higher education. And not just at home, but globally. Students and parents need access to key data to make informed, responsible choices. The tools exist to not only enable this kind of information to be shared but to capture the very metrics stakeholders care most about and in a way that makes sense in the context of a given institution's "place" in the overall higher ed panoply.

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• SSMS Tools Pack 2.7 is released. New website, improved licensing and features.

  - by Mladen Prajdic

  New website Nice, isn't it? Cleaner, simpler, better looking and more modern. If you have any suggestions for further improvements I'd be glad to hear them. Simpler licensing With SSMS tools Pack 2.7 the licensing is finally where it should be. It is now based on the activate/deactivate model. This way you can move a license from machine to machine with simple deactivation on one and reactivation on another machine. Much better, no? Because of very good feedback I have added an option for 6 machines and lowered the 4 machines option to 3 machines. This should make it much simpler for you to choose the right option for yourself. Improved features Version 2.5.3 was already extremely stable and 2.7 continues with that tradition. Because of that I could fully focus on features and why 3.0 will rock even more that 2.7! ;) In version 2.7 I have addressed quite a few improvements you were requesting for a while now. SQL History This is probably the biggest time saver out there, therefore it's only fair it gets a few important updates. If you have an existing .sql file opened, the Window Content History now saves your code to that existing file and also makes a backup in the SQL History log default location. Search is still done through the SQL History log but the Tab Sessions Restore opens your existing .sql file. This way you don't have to remember to save your existing files by yourself anymore. A bug when you couldn't search properly if you copied the log files to a new location was fixed. Unfortunately this removed the option to filter a search with the time component. The smallest search interval is now one day. The SSMS Tools Pack now remembers the visibility of the Current Window History window when you exit SSMS. SQL Snippets You can now set the position of the cursor in your snippets by placing {C} somewhere in your snippet. It's a small improvement but can be a huge time saver since you don't have to move through the snippet to the desired location anymore. Run script on multiple databases Database choices can now be saved with a name and then loaded again next time. You can also choose to run the script in a new window for each chosen database. Search through grid results You can now go previous/next search result with the Prev/Next control inside the search window. This is extremely useful if you have a large resultset. IT saves you the scrolling. CRUD generator Four new variables have been added: |CurrentDate| writes current date in format yyyy-MM-dd to your script |CurrentTime| writes current time in 24h format HH:mm:ss to your script |CurrentWinUser| writes current Windows logged on user to your script |CurrentSqlUser| writes current SQL logged on login to your script This was actually quite a requested feature so if you have any other ideas for extra variables, do let me know. That's about it. I hope you're going to enjoy this version as much as the previous ones. Have fun!

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• Appropriate design / technologies to handle dynamic string formatting?

  - by Mark W

  recently I was tasked with implementing a way of adding support for versioning of hardware packet specifications to one of our libraries. First a bit of information about the project. We have a hardware library which has classes for each of the various commands we support sending to our hardware. These hardware modules are essentially just lights with a few buttons, and a 2 or 4 digit display. The packets typically follow the format {SOH}AADD{ETX}, where AA is our sentinel action code, and DD is the device ID. These packet specs are different from one command to the next obviously, and the different firmware versions we have support different specifications. For example, on version 1 an action code of 14 may have a spec of {SOH}AADDTEXT{ETX} which would be AA = 14 literal, DD = device ID, TEXT = literal text to display on the device. Then we come out with a revision with adds an extended byte(s) onto the end of the packet like this {SOH}AADDTEXTE{ETX}. Assume the TEXT field is fixed width for this example. We have now added a new field onto the end which could be used to say specify the color or flash rate of the text/buttons. Currently this java library only supports one version of the commands, the latest. In our hardware library we would have a class for this command, say a DisplayTextArgs.java. That class would have fields for the device ID, the text, and the extended byte. The command class would expose a method which generates the string ("{SOH}AADDTEXTE{ETX}") using the value from the class. In practice we would create the Args class as needed, populate the fields, call the method to get our packet string, then ship that down across the CAN. Some of our other commands specification can vary for the same command, on the same version, depending on some runtime state. For example, another command for version 1 may be {SOH}AA{ETX}, where this action code clears all of the modules behind a specific controller device of their text. We may overload this packet to have option fields with multiple meanings like {SOH}AAOC{ETX} where OC is literal text, which tells the controller to only clear text on a specific module type, and to leave the others alone, or the spec could also have an option format of {SOH}AADD{ETX} to clear the text off a a specific device. Currently, in the method which generates the packet string, we would evaluate fields on the args class to determine which spec we will be using when formatting the packet. For this example, it would be along the lines of: if m_DeviceID != null then use {SOH}AADD{ETX} else if m_ClearOCs == true then use {SOH}AAOC{EXT} else use {SOH}AA{ETX} I had considered using XML, or a database to store String.format format strings, which were linked to firmware version numbers in some table. We would load them up at startup, and pass in the version number of the hardwares firmware we are currently using (I can query the devices for their firmware version, but the version is not included in all packets as part of the spec). This breaks down pretty quickly because of the dynamic nature of how we select which version of the command to use. I then considered using a rule engine to possibly build out expressions which could be interpreted at runtume, to evaluate the args class's state, and from that select the appropriate format string to use, but my brief look at rule engines for java scared me away with its complexity. While it seems like it might be a viable solution, it seems overly complex. So this is why I am here. I wouldn't say design is my strongest skill, and im having trouble figuring out the best way to approach this problem. I probably wont be able to radically change the args classes, but if the trade off was good enough, I may be able to convince my boss that the change is appropriate. What I would like from the community is some feedback on some best practices / design methodologies / API or other resources which I could use to accomplish: Logic to determine which set of commands to use for a given firmware version Of those command, which version of each command to use (based on the args classes state) Keep the rules logic decoupled from the application so as to avoid needing releases for every firmware version Be simple enough so I don't need weeks of study and trial and error to implement effectively.

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• Webcast On-Demand: Building Java EE Apps That Scale

  - by jeckels

  With some awesome work by one of our architects, Randy Stafford, we recently completed a webcast on scaling Java EE apps efficiently. Did you miss it? No problem. We have a replay available on-demand for you. Just hit the '+' sign drop-down for access.Topics include: Domain object caching Service response caching Session state caching JSR-107 HotCache and more! Further, we had several interesting questions asked by our audience, and we thought we'd share a sampling of those here for you - just in case you had the same queries yourself. Enjoy! What is the largest Coherence deployment out there? We have seen deployments with over 500 JVMs in the Coherence cluster, and deployments with over 1000 JVMs using the Coherence jar file, in one system. On the management side there is an ecosystem of monitoring tools from Oracle and third parties with dashboards graphing values from Coherence's JMX instrumentation. For lifecycle management we have seen a lot of custom scripting over the years, but we've also integrated closely with WebLogic to leverage its management ecosystem for deploying Coherence-based applications and managing process life cycles. That integration introduces a new Java EE archive type, the Grid Archive or GAR, which embeds in an EAR and can be seen by a WAR in WebLogic. That integration also doesn't require any extra WebLogic licensing if Coherence is licensed. How is Coherence different from a NoSQL Database like MongoDB? Coherence can be considered a NoSQL technology. It pre-dates the NoSQL movement, having been first released in 2001 whereas the term "NoSQL" was coined in 2009. Coherence has a key-value data model primarily but can also be used for document data models. Coherence manages data in memory currently, though disk persistence is in a future release currently in beta testing. Where the data is managed yields a few differences from the most well-known NoSQL products: access latency is faster with Coherence, though well-known NoSQL databases can manage more data. Coherence also has features that well-known NoSQL database lack, such as grid computing, eventing, and data source integration. Finally Coherence has had 15 years of maturation and hardening from usage in mission-critical systems across a variety of industries, particularly financial services. Can I use Coherence for local caching? Yes, you get additional features beyond just a java.util.Map: you get expiration capabilities, size-limitation capabilities, eventing capabilites, etc. Are there APIs available for GoldenGate HotCache? It's mostly a black box. You configure it, and it just puts objects into your caches. However you can treat it as a glass box, and use Coherence event interceptors to enhance its behavior - and there are use cases for that. Are Coherence caches updated transactionally? Coherence provides several mechanisms for concurrency control. If a project insists on full-blown JTA / XA distributed transactions, Coherence caches can participate as resources. But nobody does that because it's a performance and scalability anti-pattern. At finer granularity, Coherence guarantees strict ordering of all operations (reads and writes) against a single cache key if the operations are done using Coherence's "EntryProcessor" feature. And Coherence has a unique feature called "partition-level transactions" which guarantees atomic writes of multiple cache entries (even in different caches) without requiring JTA / XA distributed transaction semantics.

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• Making user input/math on data fast, unlike excel type programs

  - by proGrammar

  I'm creating a research platform solely for myself to do some research on data. Programs like excel are terribly slow for me so I'm trying to come up with another solution. Originally I used excel. A1 was the cell that contained the data and all other cells in use calculated something on A1, or on other cells, that all could be in the end traced to A1. A1 was like an element of an array, I then I incremented it to go through all my data. This was way too slow. So the only other option I found originally was to hand code in c# the calculations inside a loop. Then I simply recompiled each time I changed my math. This was terribly slow to do and I had to order everything correctly so things would update correctly (dependencies). I could have also used events, but hand coding events for each cell like calculation would also be very slow. Next I created an application to read Excel and to perfectly imitate it. Which is what I now use. Basically I write formulas onto a fraction of my data to get live results inside excel. Then my program reads excel, writes another c# program, compiles it, and runs that program which runs my excel created formulas through a lot more data a whole lot faster. The advantage being my application dependency sorts everything (or I could use events) so I don't have to (like excel does) And of course the speed. But now its not a single application anymore. Instead its 2 applications, one which only reads my formulas and writes another program. The other one being the result which only lives for a short while before I do other runs through my data with different formulas / settings. So I can't see multiple results at one time without introducing even more programs like a database or at least having the 2 applications talking to each other. My idea was to have a dll that would be written, compiled, loaded, and unloaded again and again. So a self-updating program, sort of. But apparently that's not possible without another appdomain which means data has to be marshaled to be moved between the appdomains. Which would slow things down, not for summaries, but for other stuff I need to do with all my data. I'm also forgetting to mention a huge problem with restarting an application again and again which is having to reload ALL my data into memory again and again. But its still a whole lot faster than excel. I'm really super puzzled as to what people do when they want to research data fast. I'm completely unable to have a program accept user input and having it fast. My understanding is that it would have to do things like excel which is to evaluate strings again and again. So my only option is to repeatedly compile applications. Do I have a correct understanding on computer science? I've only just began programming, and didn't think I would have to learn much to do some simple math on data. My understanding is its either compiling my user defined stuff to a program or evaluating them from a string or something stupid again and again. And my only option is to probably switch operating systems or something to be able to have a program compile and run itself without stopping (writing/compiling dll, loading dll to program, unloading, and repeating). Can someone give me some idea on how computers work? Is anything better possible? Like a running program, that can accept user input and compile it and then unload it later? I mean heck operating systems dont need to be RESTARTED with every change to user input. What is this the cave man days? Sorry, it's just so super frustrating not knowing what one can do, and can't do. If only I could understand and learn this stuff fast enough.

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• Is there any kind of established architecture for browser based games?

  - by black_puppydog

  I am beginning the development of a broser based game in which players take certain actions at any point in time. Big parts of gameplay will be happening in real life and just have to be entered into the system. I believe a good kind of comparison might be a platform for managing fantasy football, although I have virtually no experience playing that, so please correct me if I am mistaken here. The point is that some events happen in the program (i.e. on the server, out of reach for the players) like pulling new results from some datasource, starting of a new round by a game master and such. Other events happen in real life (two players closing a deal on the transfer of some team member or whatnot - again: have never played fantasy football) and have to be entered into the system. The first part is pretty easy since the game masters will be "staff" and thus can be trusted to a certain degree to not mess with the system. But the second part bothers me quite a lot, especially since the actions may involve multiple steps and interactions with different players, like registering a deal with the system that then has to be approved by the other party or denied and passed on to a game master to decide. I would of course like to separate the game logic as far as possible from the presentation and basic form validation but am unsure how to do this in a clean fashion. Of course I could (and will) put some effort into making my own architectural decisions and prototype different ideas. But I am bound to make some stupid mistakes at some point, so I would like to avoid some of that by getting a little "book smart" beforehand. So the question is: Is there any kind of architectural works that I can read up on? Papers, blogs, maybe design documents or even source code? Writing this down this seems more like a business application with business rules, workflows and such... Any good entry points for that? EDIT: After reading the first answers I am under the impression of having made a mistake when including the "MMO" part into the title. The game will not be all fancy (i.e. 3D or such) on the client side and the logic will completely exist on the server. That is, apart from basic form validation for the user which will also be mirrored on the server side. So the target toolset will be HTML5, JavaScript, probably JQuery(UI). My question is more related to the software architecture/design of a system that enforces certain rules. Separation of ruleset and presentation One problem I am having is that I want to separate the game rules from the presentation. The first step would be to make an own module for the game "engine" that only exposes an interface that allows all actions to be taken in a clean way. If an action fails with regard to some pre/post condition, the engine throws an exception which is then presented to the user like "you cannot sell something you do not own" or "after that you would end up in a situation which is not a valid game state." The problem here is that I would like to be able to not even present invalid action in the first place or grey out the corresponding UI elements. Changing and tweaking the ruleset Another big thing is the ruleset. It will probably evolve over time and most definitely must be tweaked. What's more, it should be possible (to a certain extent) to build a ruleset that fits a specific game round, i.e. choosing different kinds of behaviours in different aspects of the game. This would do something like "we play it with extension A today but we throw out extension B." For me, this screams "Architectural/Design pattern" but I have no idea on who might have published on something like this, not even what to google for.

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• How to be Agile when new work keeps affecting completed work?

  - by jdln

  The project I'm working on is to re-skin an existing website. The functionally will stay the same, its just the styles that are changing. The HTML is not changing, I'm only modifying the CSS files. The site is pretty complex. There are dozens of pages. Users can be logged in and have a number of different roles. Depending on their role the content of the page and what pages they are allowed to see varys. We're using GIT and Github. I'm trying to write CSS that works as components. So when the same form elements, headings, etc appear on multiple pages they are already styled and are consistent. Most of time this is working well. Sadly the format and class names in the HTML are at times messy and unpredictable. When I fix something on one page it can break another. The job is also harder as no one knows exactly all the variations that are possible due to the user roles. As such I'm continuously finding new variations as I go along. I'm making headway by putting a lot of comments in my CSS. If I need to remove a CSS rule Ill comment it out so I can still see it with the chrome dev tools, and ill put a comment in the CSS saying why I removed it and for what page this was done. This means that if on another page I'm about to add add the rule to fix a different problem, there is more of a chance I will see how this would break the first page. This allows me to either find a different solution that will work for both pages, or I can make the override page specific. This has been working quite well for me. If I had complete free reign and the only deadline was to finish the project by the end then this method would be fine. However my manager is trying to mitigate risk by breaking the work into areas to be completed per sprint. This is counter to how I have been approaching things as something like my typography styles will affect all other pages on the site. The other issue is that the different stakeholders want to sign off each section as I go along. However once I've finished a section it may change if I change CSS that affects it and also affects a new section I'm working on. I've asked that the stakeholders have a quick unofficial sign off in stages (eg per sprint), and have the final official sign off at the end of the project, but this is being met with resistance. I do understand why it would be higher risk to do this, but the only way to guarantee that a signed off section will not change is to make ALL future changes page specific. In addition to this I'm being told that all work that I push to the Git repo should be ready to go live, and as such should not contain any code comments. This is risky for me as I wont know until I've finished the site if I will ever benefit from these comments or not. Has anyone else been in a similar situation and managed to find a compromise that worked for my development approach and also the desires of management and stakeholders to have a more Agile approach? A more Agile workflow works great when you can break the work into components and know that once something is done it wont be affected by future work. However the nature of this project makes this hard to achieve.

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• I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

  - by Register Sole

  Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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• Reading graph inputs for a programming puzzle and then solving it

  - by Vrashabh

  I just took a programming competition question and I absolutely bombed it. I had trouble right at the beginning itself from reading the input set. The question was basically a variant of this puzzle http://codercharts.com/puzzle/evacuation-plan but also had an hour component in the first line(say 3 hours after start of evacuation). It reads like this This puzzle is a tribute to all the people who suffered from the earthquake in Japan. The goal of this puzzle is, given a network of road and locations, to determine the maximum number of people that can be evacuated. The people must be evacuated from evacuation points to rescue points. The list of road and the number of people they can carry per hour is provided. Input Specifications Your program must accept one and only one command line argument: the input file. The input file is formatted as follows: the first line contains 4 integers n r s t n is the number of locations (each location is given by a number from 0 to n-1) r is the number of roads s is the number of locations to be evacuated from (evacuation points) t is the number of locations where people must be evacuated to (rescue points) the second line contains s integers giving the locations of the evacuation points the third line contains t integers giving the locations of the rescue points the r following lines contain to the road definitions. Each road is defined by 3 integers l1 l2 width where l1 and l2 are the locations connected by the road (roads are one-way) and width is the number of people per hour that can fit on the road Now look at the sample input set 5 5 1 2 3 0 3 4 0 1 10 0 2 5 1 2 4 1 3 5 2 4 10 The 3 in the first line is the additional component and is defined as the number of hours since the resuce has started which is 3 in this case. Now my solution was to use Dijisktras algorithm to find the shortest path between each of the rescue and evac nodes. Now my problem started with how to read the input set. I read the first line in python and stored the values in variables. But then I did not know how to store the values of the distance between the nodes and what DS to use and how to input it to say a standard implementation of dijikstras algorithm. So my question is two fold 1.) How do I take the input of such problems? - I have faced this problem in quite a few competitions recently and I hope I can get a simple code snippet or an explanation in java or python to read the data input set in such a way that I can input it as a graph to graph algorithms like dijikstra and floyd/warshall. Also a solution to the above problem would also help. 2.) How to solve this puzzle? My algorithm was: Find shortest path between evac points (in the above example it is 14 from 0 to 3) Multiply it by number of hours to get maximal number of saves Also the answer given for the variant for the input set was 24 which I dont understand. Can someone explain that also. UPDATE: I get how the answer is 14 in the given problem link - it seems to be just the shortest path between node 0 and 3. But with the 3 hour component how is the answer 24 UPDATE I get how it is 24 - its a complete graph traversal at every hour and this is how I solve it Hour 1 Node 0 to Node 1 - 10 people Node 0 to Node 2- 5 people TotalRescueCount=0 Node 1=10 Node 2= 5 Hour 2 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5(Rescued) Node 0 to Node 1 = 10 Node 0 to Node 2 = 5 Node 1 to Node 2 = 4 TotalRescueCount = 10 Node 1 = 10 Node 2= 5+4 = 9 Hour 3 Node 1 to Node 3 = 5(Rescued) Node 2 to Node 4 = 5+4 = 9(Rescued) TotalRescueCount = 9+5+10 = 24 It hard enough for this case , for multiple evac and rescue points how in the world would I write a pgm for this ?

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• I thought the new AUTO_SAMPLE_SIZE in Oracle Database 11g looked at all the rows in a table so why do I see a very small sample size on some tables?

  - by Maria Colgan

  I recently got asked this question and thought it was worth a quick blog post to explain in a little more detail what is going on with the new AUTO_SAMPLE_SIZE in Oracle Database 11g and what you should expect to see in the dictionary views. Let’s take the SH.CUSTOMERS table as an example.  There are 55,500 rows in the SH.CUSTOMERS tables. If we gather statistics on the SH.CUSTOMERS using the new AUTO_SAMPLE_SIZE but without collecting histogram we can check what sample size was used by looking in the USER_TABLES and USER_TAB_COL_STATISTICS dictionary views. The sample sized shown in the USER_TABLES is 55,500 rows or the entire table as expected. In USER_TAB_COL_STATISTICS most columns show 55,500 rows as the sample size except for four columns (CUST_SRC_ID, CUST_EFF_TO, CUST_MARTIAL_STATUS, CUST_INCOME_LEVEL ). The CUST_SRC_ID and CUST_EFF_TO columns have no sample size listed because there are only NULL values in these columns and the statistics gathering procedure skips NULL values. The CUST_MARTIAL_STATUS (38,072) and the CUST_INCOME_LEVEL (55,459) columns show less than 55,500 rows as their sample size because of the presence of NULL values in these columns. In the SH.CUSTOMERS table 17,428 rows have a NULL as the value for CUST_MARTIAL_STATUS column (17428+38072 = 55500), while 41 rows have a NULL values for the CUST_INCOME_LEVEL column (41+55459 = 55500). So we can confirm that the new AUTO_SAMPLE_SIZE algorithm will use all non-NULL values when gathering basic table and column level statistics. Now we have clear understanding of what sample size to expect lets include histogram creation as part of the statistics gathering. Again we can look in the USER_TABLES and USER_TAB_COL_STATISTICS dictionary views to find the sample size used. The sample size seen in USER_TABLES is 55,500 rows but if we look at the column statistics we see that it is same as in previous case except  for columns  CUST_POSTAL_CODE and  CUST_CITY_ID. You will also notice that these columns now have histograms created on them. The sample size shown for these columns is not the sample size used to gather the basic column statistics. AUTO_SAMPLE_SIZE still uses all the rows in the table - the NULL rows to gather the basic column statistics (55,500 rows in this case). The size shown is the sample size used to create the histogram on the column. When we create a histogram we try to build it on a sample that has approximately 5,500 non-null values for the column.  Typically all of the histograms required for a table are built from the same sample. In our example the histograms created on CUST_POSTAL_CODE and the CUST_CITY_ID were built on a single sample of ~5,500 (5,450 rows) as these columns contained only non-null values. However, if one or more of the columns that requires a histogram has null values then the sample size maybe increased in order to achieve a sample of 5,500 non-null values for those columns. n addition, if the difference between the number of nulls in the columns varies greatly, we may create multiple samples, one for the columns that have a low number of null values and one for the columns with a high number of null values.  This scheme enables us to get close to 5,500 non-null values for each column. +Maria Colgan

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• tightvnc authentication failure

  - by broiyan

  When I run a tightvnc client to establish a VNC session I sometimes receive an error message that suggests there are repeated failed VNC login attempts or a brute force attack. The message dialog title is "unsupported security type" and the text content is "too many authentication failures, try another connection? yes/no". This problem goes away if I reboot the Ubuntu server and reload the VNC server program and try again. From that point, it will work for multiple VNC sessions. My VNC sessions are typically about 20 minutes. At some time in the future, the problem may recur so it seems correlated to the time the server has been up or the time tightvnc has been loaded. Typically it takes only a day or so before the problem comes back. I am using tightvnc 1.3 on an server running Ubuntu 12.04. The version of vncserver is rather dated because that seems to be all that is available from tightvnc for linux servers. On the client side I use the newest Java-based VNC client (version 2.5) for both Windows access and Ubuntu access. All my VNC sessions are via SSH. I am the only user and I will typically use only the same client computer. How can I stop this problem from recurring? Edit I found the log file. This is a small excerpt of what I am seeing. Essentially, various IPs, not my own, are attempting to connect. What is the practical solution for this? 05/06/12 20:07:32 Got connection from client 69.194.204.90 05/06/12 20:07:32 Non-standard protocol version 3.4, using 3.3 instead 05/06/12 20:07:32 Too many authentication failures - client rejected 05/06/12 20:07:32 Client 69.194.204.90 gone 05/06/12 20:07:32 Statistics: 05/06/12 20:07:32 framebuffer updates 0, rectangles 0, bytes 0 05/06/12 20:24:56 Got connection from client 79.161.16.40 05/06/12 20:24:56 Non-standard protocol version 3.4, using 3.3 instead 05/06/12 20:24:56 Too many authentication failures - client rejected 05/06/12 20:24:56 Client 79.161.16.40 gone 05/06/12 20:24:56 Statistics: 05/06/12 20:24:56 framebuffer updates 0, rectangles 0, bytes 0 05/06/12 20:29:27 Got connection from client 109.230.246.54 05/06/12 20:29:27 Non-standard protocol version 3.4, using 3.3 instead 05/06/12 20:29:28 rfbVncAuthProcessResponse: authentication failed from 109.230.246.54 05/06/12 20:29:28 Client 109.230.246.54 gone 05/06/12 20:29:28 Statistics: 05/06/12 20:29:28 framebuffer updates 0, rectangles 0, bytes 0

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• SQL Server Licensing in a VMware vSphere Cluster

  - by Helvick

  If I have SQL Server 2008 instances running in virtual machines on a VMware vSphere cluster with vMotion\DRS enabled so that the VM's can (potentially) run on any one of the physical servers in the cluster what precisely are the license requirements? For example assume that I have 4 physical ESX Hosts with dual physical CPU's and 3 separate single vCPU Virtual Machines running SQL Server 2008 running in that cluster. How many SQL Standard Processor licenses would I need? Is it 3 (one per VM) or 12 (one per VM on each physical host) or something else? How many SQL Enterprise Processor licenses would I need? Is it 3 (one per VM) or 8 (one for each physical CPU in the cluster) or, again, something else? The range in the list prices for these options goes from $17k to $200k so getting it right is quite important. Bonus question: If I choose the Server+CAL licensing model do I need to buy multiple Server instance licenses for each of the ESX hosts (so 12 copies of the SQL Server Standard server license so that there are enough licenses on each host to run all VM's) or again can I just license the VM and what difference would using Enterprise per server licensing make? Edited to Add Having spent some time reading the SQL 2008 Licensing Guide (63 Pages! Includes Maps!*) I've come across this: • Under the Server/CAL model, you may run unlimited instances of SQL Server 2008 Enterprise within the server farm, and move those instances freely, as long as those instances are not running on more servers than the number of licenses assigned to the server farm. • Under the Per Processor model, you effectively count the greatest number of physical processors that may support running instances of SQL Server 2008 Enterprise at any one time across the server farm and assign that number of Processor licenses And earlier: ..For SQL Server, these rule changes apply to SQL Server 2008 Enterprise only. By my reading this means that for my 3 VM's I only need 3 SQL 2008 Enterprise Processor Licenses or one copy of Server Enterprise + CALs for the cluster. By implication it means that I have to license all processors if I choose SQL 2008 Standard Processor licensing or that I have to buy a copy of SQL Server 2008 Standard for each ESX host if I choose to use CALs. *There is a map to demonstrate that a Server Farm cannot extend across an area broader than 3 timezones unless it's in the European Free Trade Area, I wasn't expecting that when I started reading it.

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• Replace dual-XP installs with single-XP install and repartition drive?

  - by caeious

  Hello, The Current Situation I have a hard drive that currently is split up like so: Primary Partition C: 9.77 GB NTFS Healthy (System) with XP Pro (in Polish) installed Extended Partition D: 39.82 GB NTFS Healthy (Boot) with XP Pro (in English) installed 6.30 GB Free space When I start my comuter I get a black and white Windows Boot Manager dual boot screen with 2 choices both being Microsoft Windows XP. The first choice is the English version of XP and the second choice is the Polish version of XP. Images of my Computer Management window and Dual Boot screen The Mission What I need to do is get rid of the entire extended partition (D: 39.82 GB & 6.30 free space) and just have the one primary C: drive which I assume will be somewheres around 55 GB big. So in the end I just want XP Pro in English running on my C: drive and no black and white boot screen to show up when starting up my laptop. The Question How do I go about successfully completing The Mission with out making my computer a useless pile of silicon, plastic and metal? UPDATE: So I went ahead and tried to follow Neal's suggestion but hit a wall. I got to a Windows XP Pro install screen that had the 3 following options as well as my drive data: To set up Windows XP on the selected item, press Enter To create a partition in the unpartitioned space, press C To delete the selected partition, press D 57232 MB Disk 0 at Id 0 on bus 0 on atapi [MBR] C: Partition1 [NTFS] 10001 MB ( 4642 MB free ) Unpartitioned space 6448 MB D: Partition2 [NTFS] 40774 MB ( 26225 MB free ) Unpartitioned space 8 MB I figured I would go with the first choice ((To set up Windows XP on the selected item, press Enter)) because I just wanted to set up Windows XP on C: Partition1 (which was preselected) so I pressed Enter which brought me to a screen displaying this message: You chose to install Windows XP on a partition that contains another operating system. Installing Windows XP on this partition might cause the other operating system to function improperly. CAUTION: Installing multiple operating systems on a single partition is not recommended. So this leads me to 2 new questions: How do I get rid of the Windows XP (Polish language) install on C: Partition 1 so that I can cleanly and safely install Windows XP (English language) on it? Neal, is this what you meant by me possibly having to delete the partition that the Windows XP (Polish language) install was located on? Since I have the option to delete partitions with the 3rd choice ((To delete the selected partition, press D)), should I do that on this screen or wait until I have Windows XP (English language) safely installed on C: Partition 1? I have to ask these questions because I have read that it is possibly dangerous to delete hard drive partitions. Just being cautious.

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• LVM mirror attempt results in "Insufficient free space"

  - by MattK

  Attempting to add a disk to mirror an LVM volume on CentOS 7 always fails with "Insufficient free space: 1 extents needed, but only 0 available". Having searched for a solution, I have tried specifying disks, multiple logging options, adding 3rd log partition, but have not found a solution Not sure if I am making a rookie mistake, or there is something more subtle wrong (I am more familiar with ZFS, new to using LVM): # lvconvert -m1 centos_bi/home Insufficient free space: 1 extents needed, but only 0 available # lvconvert -m1 --corelog centos_bi/home Insufficient free space: 1 extents needed, but only 0 available # lvconvert -m1 --corelog --alloc anywhere centos_bi/home Insufficient free space: 1 extents needed, but only 0 available # lvconvert -m1 --mirrorlog mirrored --alloc anywhere centos_bi/home /dev/sda2 Insufficient free space: 1 extents needed, but only 0 available # lvconvert -m1 --corelog --alloc anywhere centos_bi/home /dev/sdi2 /dev/sda2 Insufficient free space: 1 extents needed, but only 0 available The two disks are of the same size, and have identical partition layouts via "sfdisk -d /dev/sdi part_table; sfdisk /dev/sda < part_table". The current configuration is detailed below. # pvs PV VG Fmt Attr PSize PFree /dev/sda1 centos_bi lvm2 a-- 496.00m 496.00m /dev/sda2 centos_bi lvm2 a-- 465.27g 465.27g /dev/sdi2 centos_bi lvm2 a-- 465.27g 0 # vgs VG #PV #LV #SN Attr VSize VFree centos_bi 3 3 0 wz--n- 931.02g 465.75g # lvs -a -o +devices LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert Devices home centos_bi -wi-ao---- 391.64g /dev/sdi2(6050) root centos_bi -wi-ao---- 50.00g /dev/sdi2(106309) swap centos_bi -wi-ao---- 23.63g /dev/sdi2(0) # pvdisplay --- Physical volume --- PV Name /dev/sdi2 VG Name centos_bi PV Size 465.27 GiB / not usable 3.00 MiB Allocatable yes (but full) PE Size 4.00 MiB Total PE 119109 Free PE 0 Allocated PE 119109 --- Physical volume --- PV Name /dev/sda2 VG Name centos_bi PV Size 465.27 GiB / not usable 3.00 MiB Allocatable yes PE Size 4.00 MiB Total PE 119109 Free PE 119109 Allocated PE 0 --- Physical volume --- PV Name /dev/sda1 VG Name centos_bi PV Size 500.00 MiB / not usable 4.00 MiB Allocatable yes PE Size 4.00 MiB Total PE 124 Free PE 124 Allocated PE 0 # vgdisplay --- Volume group --- VG Name centos_bi System ID Format lvm2 Metadata Areas 3 Metadata Sequence No 10 VG Access read/write VG Status resizable MAX LV 0 Cur LV 3 Open LV 3 Max PV 0 Cur PV 3 Act PV 3 VG Size 931.02 GiB PE Size 4.00 MiB Total PE 238342 Alloc PE / Size 119109 / 465.27 GiB Free PE / Size 119233 / 465.75 GiB # lvdisplay --- Logical volume --- LV Path /dev/centos_bi/swap LV Name swap VG Name centos_bi LV Write Access read/write LV Creation host, time localhost, 2014-08-07 16:34:34 -0400 LV Status available # open 2 LV Size 23.63 GiB Current LE 6050 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:1 --- Logical volume --- LV Path /dev/centos_bi/home LV Name home VG Name centos_bi LV Write Access read/write LV Creation host, time localhost, 2014-08-07 16:34:35 -0400 LV Status available # open 1 LV Size 391.64 GiB Current LE 100259 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:2 --- Logical volume --- LV Path /dev/centos_bi/root LV Name root VG Name centos_bi LV Write Access read/write LV Creation host, time localhost, 2014-08-07 16:34:37 -0400 LV Status available # open 1 LV Size 50.00 GiB Current LE 12800 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0

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