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• Analysing and measuring the performance of a .NET application (survey results)

  - by Laila

  Back in December last year, I asked myself: could it be that .NET developers think that you need three days and a PhD to do performance profiling on their code? What if developers are shunning profilers because they perceive them as too complex to use? If so, then what method do they use to measure and analyse the performance of their .NET applications? Do they even care about performance? So, a few weeks ago, I decided to get a 1-minute survey up and running in the hopes that some good, hard data would clear the matter up once and for all. I posted the survey on Simple Talk and got help from a few people to promote it. The survey consisted of 3 simple questions: Amazingly, 533 developers took the time to respond - which means I had enough data to get representative results! So before I go any further, I would like to thank all of you who contributed, because I now have some pretty good answers to the troubling questions I was asking myself. To thank you properly, I thought I would share some of the results with you. First of all, application performance is indeed important to most of you. In fact, performance is an intrinsic part of the development cycle for a good 40% of you, which is much higher than I had anticipated, I have to admit. (I know, "Have a little faith Laila!") When asked what tool you use to measure and analyse application performance, I found that nearly half of the respondents use logging statements, a third use performance counters, and 70% of respondents use a profiler of some sort (a 3rd party performance profilers, the CLR profiler or the Visual Studio profiler). The importance attributed to logging statements did surprise me a little. I am still not sure why somebody would go to the trouble of manually instrumenting code in order to measure its performance, instead of just using a profiler. I personally find the process of annotating code, calculating times from log files, and relating it all back to your source terrifyingly laborious. Not to mention that you then need to remember to turn it all off later! Even when you have logging in place throughout all your code anyway, you still have a fair amount of potentially error-prone calculation to sift through the results; in addition, you'll only get method-level rather than line-level timings, and you won't get timings from any framework or library methods you don't have source for. To top it all, we all know that bottlenecks are rarely where you would expect them to be, so you could be wasting time looking for a performance problem in the wrong place. On the other hand, profilers do all the work for you: they automatically collect the CPU and wall-clock timings, and present the results from method timing all the way down to individual lines of code. Maybe I'm missing a trick. I would love to know about the types of scenarios where you actively prefer to use logging statements. Finally, while a third of the respondents didn't have a strong opinion about code performance profilers, those who had an opinion thought that they were mainly complex to use and time consuming. Three respondents in particular summarised this perfectly: "sometimes, they are rather complex to use, adding an additional time-sink to the process of trying to resolve the existing problem". "they are simple to use, but the results are hard to understand" "Complex to find the more advanced things, easy to find some low hanging fruit". These results confirmed my suspicions: Profilers are seen to be designed for more advanced users who can use them effectively and make sense of the results. I found yet more interesting information when I started comparing samples of "developers for whom performance is an important part of the dev cycle", with those "to whom performance is only looked at in times of crisis", and "developers to whom performance is not important, as long as the app works". See the three graphs below. Sample of developers to whom performance is an important part of the dev cycle: Sample of developers to whom performance is important only in times of crisis: Sample of developers to whom performance is not important, as long as the app works: As you can see, there is a strong correlation between the usage of a profiler and the importance attributed to performance: indeed, the more important performance is to a development team, the more likely they are to use a profiler. In addition, developers to whom performance is an important part of the dev cycle have a higher tendency to use a much wider range of methods for performance measurement and analysis. And, unsurprisingly, the less important performance is, the less varied the methods of measurement are. So all in all, to come back to my random questions: .NET developers do care about performance. Those who care the most use a wider range of performance measurement methods than those who care less. But overall, logging statements, performance counters and third party performance profilers are the performance measurement methods of choice for most developers. Finally, although most of you find code profilers complex to use, those of you who care the most about performance tend to use profilers more than those of you to whom performance is not so important.

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• Demystified - BI in SharePoint 2010

  - by Sahil Malik

  Ad:: SharePoint 2007 Training in .NET 3.5 technologies (more information). Frequently, my clients ask me if there is a good guide on deciphering the seemingly daunting choice of products from Microsoft when it comes to business intelligence offerings in a SharePoint 2010 world. These are all described in detail in my book, but here is a one (well maybe two) page executive overview. Microsoft Excel: Yes, Microsoft Excel! Your favorite and most commonly used in the world database. No it isn’t a database in technical pure definitions, but this is the most commonly used ‘database’ in the world. You will find many business users craft up very compelling excel sheets with tonnes of logic inside them. Good for: Quick Ad-Hoc reports. Excel 64 bit allows the possibility of very large datasheets (Also see 32 bit vs 64 bit Office, and PowerPivot Add-In below). Audience: End business user can build such solutions. Related technologies: PowerPivot, Excel Services Microsoft Excel with PowerPivot Add-In: The powerpivot add-in is an extension to Excel that adds support for large-scale data. Think of this as Excel with the ability to deal with very large amounts of data. It has an in-memory data store as an option for Analysis services. Good for: Ad-hoc reporting and logic with very large amounts of data. Audience: End business user can build such solutions. Related technologies: Excel, and Excel Services Excel Services: Excel Services is a Microsoft SharePoint Server 2010 shared service that brings the power of Excel to SharePoint Server by providing server-side calculation and browser-based rendering of Excel workbooks. Thus, excel sheets can be created by end users, and published to SharePoint server – which are then rendered right through the browser in read-only or parameterized-read-only modes. They can also be accessed by other software via SOAP or REST based APIs. Good for: Sharing excel sheets with a larger number of people, while maintaining control/version control etc. Sharing logic embedded in excel sheets with other software across the organization via REST/SOAP interfaces Audience: End business users can build such solutions once your tech staff has setup excel services on a SharePoint server instance. Programmers can write software consuming functionality/complex formulae contained in your sheets. Related technologies: PerformancePoint Services, Excel, and PowerPivot. Visio Services: Visio Services is a shared service on the Microsoft SharePoint Server 2010 platform that allows users to share and view Visio diagrams that may or may not have data connected to them. Connected data can update these diagrams allowing a visual/graphical view into the data. The diagrams are viewable through the browser. They are rendered in silverlight, but will automatically down-convert to .png formats. Good for: Showing data as diagrams, live updating. Comes with a developer story. Audience: End business users can build such solutions once your tech staff has setup visio services on a SharePoint server instance. Developers can enhance the visualizations Related Technologies: Visio Services can be used to render workflow visualizations in SP2010 Reporting Services: SQL Server reporting services can integrate with SharePoint, allowing you to store reports and data sources in SharePoint document libraries, and render these reports and associated functionality such as subscriptions through a SharePoint site. In SharePoint 2010, you can also write reports against SharePoint lists (access services uses this technique). Good for: Showing complex reports running in a industry standard data store, such as SQL server. Audience: This is definitely developer land. Don’t expect end users to craft up reports, unless a report model has previously been published. Related Technologies: PerformancePoint Services PerformancePoint Services: PerformancePoint Services in SharePoint 2010 is now fully integrated with SharePoint, and comes with features that can either be used in the BI center site definition, or on their own as activated features in existing site collections. PerformancePoint services allows you to build reports and dashboards that target a variety of back-end datasources including: SQL Server reporting services, SQL Server analysis services, SharePoint lists, excel services, simple tables, etc. Using these you have the ability to create dashboards, scorecards/kpis, and simple reports. You can also create reports targeting hierarchical multidimensional data sources. The visual decomposition tree is a new report type that lets you quickly breakdown multi-dimensional data. Good for: Mostly everything :), except your wallet – it’s not free! But this is the most comprehensive offering. If you have SharePoint server, forget everything and go with performance point. Audience: Developers need to setup the back-end sources, manageability story. DBAs need to setup datawarehouses with cubes. Moderately sophisticated business users, or developers can craft up reports using dashboard designer which is a click-once App that deploys with PerformancePoint Related Technologies: Excel services, reporting services, etc.   Other relevant technologies to know about: Business Connectivity Services: Allows for consumption of external data in SharePoint as columns or external lists. This can be paired with one or more of the above BI offerings allowing insight into such data. Access Services: Allows the representation/publishing of an access database as a SharePoint 2010 site, leveraging many SharePoint features. Reporting services is used by Access services. Secure Store Service: The SP2010 Secure store service is a replacement for the SP2007 single sign on feature. This acts as a credential policeman providing credentials to various applications running with SharePoint. BCS, PerformancePoint Services, Excel Services, and many other apps use the SSS (Secure Store Service) for credential control. Comment on the article ....

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• NDepend 4 – First Steps

  - by Ricardo Peres

  Introduction Thanks to Patrick Smacchia I had the chance to test NDepend 4. I can only say: awesome! This will be the first of a series of posts on NDepend, where I will talk about my discoveries. Keep in mind that I am just starting to use it, so more experienced users may find these too basic, I just hope I don’t say anything foolish! I must say that I am in no way affiliated with NDepend and I never actually met Patrick. Installation No installation program – a curious decision, I’m not against it -, just unzip the files to a folder and run the executable. It will optionally register itself with Visual Studio 2008, 2010 and 11 as well as RedGate’s Reflector; also, it automatically looks for updates. NDepend can either be used as a stand-alone program (with or without a GUI) or from within Visual Studio or Reflector. Getting Started One thing that really pleases me is the Getting Started section of the stand-alone, with links to pages on NDepend’s web site, featuring detailed explanations, which usually include screenshots and small videos (<5 minutes). There’s also an How do I with hierarchical navigation that guides us to through the major features so that we can easily find what we want. Usage There are two basic ways to use NDepend: Analyze .NET solutions, projects or assemblies; Compare two versions of the same assembly. I have so far not used NDepend to compare assemblies, so I will first talk about the first option. After selecting a solution and some of its projects, it generates a single HTML page with an highly detailed report of the analysis it produced. This includes some metrics such as number of lines of code, IL instructions, comments, types, methods and properties, the calculation of the cyclomatic complexity, coupling and lots of others indicators, typically grouped by type, namespace and assembly. The HTML also includes some nice diagrams depicting assembly dependencies, type and method relative proportions (according to the number of IL instructions, I guess) and assembly analysis relating to abstractness and stability. Useful, I would say. Then there’s the rules; NDepend tests the target assemblies against a set of more than 120 rules, grouped in categories Code Quality, Object Oriented Design, Design, Architecture and Layering, Dead Code, Visibility, Naming Conventions, Source Files Organization and .NET Framework Usage. The full list can be configured on the application, and an explanation of each rule can be found on the web site. Rules can be validated, violated and violated in a critical manner, and the HTML will contain the violated rules, their queries – more on this later - and results. The HTML uses some nice JavaScript effects, which allow paging and sorting of tables, so its nice to use. Similar to the rules, there are some queries that display results for a number (about 200) questions grouped as Object Oriented Design, API Breaking Changes (for assembly version comparison), Code Diff Summary (also for version comparison) and Dead Code. The difference between queries and rules is that queries are not classified as passes, violated or critically violated, just present results. The queries and rules are expressed through CQLinq, which is a very powerful LINQ derivative specific to code analysis. All of the included rules and queries can be enabled or disabled and new ones can be added, with intellisense to help. Besides the HTML report file, the NDepend application can be used to explore all analysis results, compare different versions of analysis reports and to run custom queries. Comparison to Other Analysis Tools Unlike StyleCop, NDepend only works with assemblies, not source code, so you can’t expect it to be able to enforce brackets placement, for example. It is more similar to FxCop, but you don’t have the option to analyze at the IL level, that is, other that the number of IL instructions and the complexity. What’s Next In the next days I’ll continue my exploration with a real-life test case. References The NDepend web site is http://www.ndepend.com/. Patrick keeps an updated blog on http://codebetter.com/patricksmacchia/ and he regularly monitors StackOverflow for questions tagged NDepend, which you can find on http://stackoverflow.com/questions/tagged/ndepend. The default list of CQLinq rules, queries and statistics can be found at http://www.ndepend.com/DefaultRules/webframe.html. The syntax itself is described at http://www.ndepend.com/Doc_CQLinq_Syntax.aspx and its features at http://www.ndepend.com/Doc_CQLinq_Features.aspx.

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• Shadow mapping with deffered shading for directional lights - shadow map projection problem

  - by Harry

  I'm trying to implement shadow mapping to my engine. I started with directional lights because they seemed to be the easiest one, but I was wrong :) I have implemented deferred shading and I retrieve position from depth. I think that there is the biggest problem but code looks ok for me. Now more about problem: Shadow map projected onto meshes looks bad scaled and translated and also some informations from shadow map texture aren't visible. You can see it on this screen: http://img5.imageshack.us/img5/2254/93dn.png Yelow frustum is light frustum and I have mixed shadow map preview and actual scene. As you can see shadows are in wrong place and shadow of cone and sphere aren't visible. Could you look at my codes and tell me where I have a mistake? // create shadow map if(!_shd)glGenTextures(1, &_shd); glBindTexture(GL_TEXTURE_2D, _shd); glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, 1024, 1024, 0, GL_DEPTH_COMPONENT, GL_FLOAT,NULL); // shadow map size glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, _shd, 0); glDrawBuffer(GL_NONE); // setting camera Vector dire=Vector(0,0,1); ACamera.setLookAt(dire,Vector(0)); ACamera.setPerspectiveView(60.0f,1,0.1f,10.0f); // currently needed for proper frustum corners calculation Vector min(ACamera._point[0]),max(ACamera._point[0]); for(int i=0;i<8;i++){ max=Max(max,ACamera._point[i]); min=Min(min,ACamera._point[i]); } ACamera.setOrthogonalView(min.x,max.x,min.y,max.y,-max.z,-min.z); glBindFramebuffer(GL_DRAW_FRAMEBUFFER, _s_buffer); // framebuffer for shadow map // rendering to depth buffer glBindFramebuffer(GL_DRAW_FRAMEBUFFER, _g_buffer); Shaders["DirLight"].set(true); Matrix4 bias; bias.x.set(0.5,0.0,0.0,0.0); bias.y.set(0.0,0.5,0.0,0.0); bias.z.set(0.0,0.0,0.5,0.0); bias.w.set(0.5,0.5,0.5,1.0); Shaders["DirLight"].set("textureMatrix",ACamera.matrix*Projection3D*bias); // order of multiplications are 100% correct, everything gives mi the same result as using glm glActiveTexture(GL_TEXTURE5); glBindTexture(GL_TEXTURE_2D,_shd); lightDir(dir); // light calculations Vertex Shader makes nothing related to shadow calculatons Pixel shader function which calculates if pixel is in shadow or not: float readShadowMap(vec3 eyeDir) { // retrieve depth of pixel float z = texture2D(depth, gl_FragCoord.xy/screen).z; vec3 pos = vec3(gl_FragCoord.xy/screen, z); // transform by the projection and view inverse vec4 worldSpace = inverse(View)*inverse(ProjectionMatrix)*vec4(pos*2-1,1); worldSpace /= worldSpace.w; vec4 coord=textureMatrix*worldSpace; float vis=1.0f; if(texture2D(shadow, coord.xy).z < coord.z-0.001)vis=0.2f; return vis; } I also have question about shadows specifically for directional light. Currently I always look at 0,0,0 position and in further implementation I have to move light frustum along to camera frustum. I've found how to do this here: http://www.gamedev.net/topic/505893-orthographic-projection-for-shadow-mapping/ but it doesn't give me what I want. Maybe because of problems mentioned above, but I want know your opinion. EDIT: vec4 worldSpace is position read from depht of the scene (not shadow map). Maybe I wasn't precise so I'll try quick explain what is what: View is camera view matrix, ProjectionMatrix is camera projection,. First I try to get world space position from depth map and then multiply it by textureMatrix which is light view *light projection*bias. Rest of code is the same as in many tutorials. I can't use vertex shader to make something like gl_Position=textureMatrix*gl_Vertex and get it interpolated in fragment shader because of deffered rendering use so I want get it from depht buffer. EDIT2: I also tried make it as in Coding Labs tutorial about Shadow Mapping with Deferred Rendering but unfortunately this either works wrong.

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• Using Hadooop (HDInsight) with Microsoft - Two (OK, Three) Options

  - by BuckWoody

  Microsoft has many tools for “Big Data”. In fact, you need many tools – there’s no product called “Big Data Solution” in a shrink-wrapped box – if you find one, you probably shouldn’t buy it. It’s tempting to want a single tool that handles everything in a problem domain, but with large, complex data, that isn’t a reality. You’ll mix and match several systems, open and closed source, to solve a given problem. But there are tools that help with handling data at large, complex scales. Normally the best way to do this is to break up the data into parts, and then put the calculation engines for that chunk of data right on the node where the data is stored. These systems are in a family called “Distributed File and Compute”. Microsoft has a couple of these, including the High Performance Computing edition of Windows Server. Recently we partnered with Hortonworks to bring the Apache Foundation’s release of Hadoop to Windows. And as it turns out, there are actually two (technically three) ways you can use it. (There’s a more detailed set of information here: http://www.microsoft.com/sqlserver/en/us/solutions-technologies/business-intelligence/big-data.aspx, I’ll cover the options at a general level below)  First Option: Windows Azure HDInsight Service  Your first option is that you can simply log on to a Hadoop control node and begin to run Pig or Hive statements against data that you have stored in Windows Azure. There’s nothing to set up (although you can configure things where needed), and you can send the commands, get the output of the job(s), and stop using the service when you are done – and repeat the process later if you wish. (There are also connectors to run jobs from Microsoft Excel, but that’s another post)   This option is useful when you have a periodic burst of work for a Hadoop workload, or the data collection has been happening into Windows Azure storage anyway. That might be from a web application, the logs from a web application, telemetrics (remote sensor input), and other modes of constant collection.   You can read more about this option here:  http://blogs.msdn.com/b/windowsazure/archive/2012/10/24/getting-started-with-windows-azure-hdinsight-service.aspx Second Option: Microsoft HDInsight Server Your second option is to use the Hadoop Distribution for on-premises Windows called Microsoft HDInsight Server. You set up the Name Node(s), Job Tracker(s), and Data Node(s), among other components, and you have control over the entire ecostructure.   This option is useful if you want to  have complete control over the system, leave it running all the time, or you have a huge quantity of data that you have to bulk-load constantly – something that isn’t going to be practical with a network transfer or disk-mailing scheme. You can read more about this option here: http://www.microsoft.com/sqlserver/en/us/solutions-technologies/business-intelligence/big-data.aspx Third Option (unsupported): Installation on Windows Azure Virtual Machines  Although unsupported, you could simply use a Windows Azure Virtual Machine (we support both Windows and Linux servers) and install Hadoop yourself – it’s open-source, so there’s nothing preventing you from doing that.   Aside from being unsupported, there are other issues you’ll run into with this approach – primarily involving performance and the amount of configuration you’ll need to do to access the data nodes properly. But for a single-node installation (where all components run on one system) such as learning, demos, training and the like, this isn’t a bad option. Did I mention that’s unsupported? :) You can learn more about Windows Azure Virtual Machines here: http://www.windowsazure.com/en-us/home/scenarios/virtual-machines/ And more about Hadoop and the installation/configuration (on Linux) here: http://en.wikipedia.org/wiki/Apache_Hadoop And more about the HDInsight installation here: http://www.microsoft.com/web/gallery/install.aspx?appid=HDINSIGHT-PREVIEW Choosing the right option Since you have two or three routes you can go, the best thing to do is evaluate the need you have, and place the workload where it makes the most sense.  My suggestion is to install the HDInsight Server locally on a test system, and play around with it. Read up on the best ways to use Hadoop for a given workload, understand the parts, write a little Pig and Hive, and get your feet wet. Then sign up for a test account on HDInsight Service, and see how that leverages what you know. If you're a true tinkerer, go ahead and try the VM route as well. Oh - there’s another great reference on the Windows Azure HDInsight that just came out, here: http://blogs.msdn.com/b/brunoterkaly/archive/2012/11/16/hadoop-on-azure-introduction.aspx  

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• Extreme Optimization – Numerical Algorithm Support

  - by JoshReuben

  Function Delegates Many calculations involve the repeated evaluation of one or more user-supplied functions eg Numerical integration. The EO MathLib provides delegate types for common function signatures and the FunctionFactory class can generate new delegates from existing ones. RealFunction delegate - takes one Double parameter – can encapsulate most of the static methods of the System.Math class, as well as the classes in the Extreme.Mathematics.SpecialFunctions namespace: var sin = new RealFunction(Math.Sin); var result = sin(1); BivariateRealFunction delegate - takes two Double parameters: var atan2 = new BivariateRealFunction (Math.Atan2); var result = atan2(1, 2); TrivariateRealFunction delegate – represents a function takes three Double arguments ParameterizedRealFunction delegate - represents a function taking one Integer and one Double argument that returns a real number. The Pow method implements such a function, but the arguments need order re-arrangement: static double Power(int exponent, double x) { return ElementaryFunctions.Pow(x, exponent); } ... var power = new ParameterizedRealFunction(Power); var result = power(6, 3.2); A ComplexFunction delegate - represents a function that takes an Extreme.Mathematics.DoubleComplex argument and also returns a complex number. MultivariateRealFunction delegate - represents a function that takes an Extreme.Mathematics.LinearAlgebra.Vector argument and returns a real number. MultivariateVectorFunction delegate - represents a function that takes a Vector argument and returns a Vector. FastMultivariateVectorFunction delegate - represents a function that takes an input Vector argument and an output Matrix argument – avoiding object construction  The FunctionFactory class RealFromBivariateRealFunction and RealFromParameterizedRealFunction helper methods - transform BivariateRealFunction or a ParameterizedRealFunction into a RealFunction delegate by fixing one of the arguments, and treating this as a new function of a single argument. var tenthPower = FunctionFactory.RealFromParameterizedRealFunction(power, 10); var result = tenthPower(x); Note: There is no direct way to do this programmatically in C# - in F# you have partial value functions where you supply a subset of the arguments (as a travelling closure) that the function expects. When you omit arguments, F# generates a new function that holds onto/remembers the arguments you passed in and "waits" for the other parameters to be supplied. let sumVals x y = x + y     let sumX = sumVals 10     // Note: no 2nd param supplied.     // sumX is a new function generated from partially applied sumVals.     // ie "sumX is a partial application of sumVals." let sum = sumX 20     // Invokes sumX, passing in expected int (parameter y from original)  val sumVals : int -> int -> int val sumX : (int -> int) val sum : int = 30 RealFunctionsToVectorFunction and RealFunctionsToFastVectorFunction helper methods - combines an array of delegates returning a real number or a vector into vector or matrix functions. The resulting vector function returns a vector whose components are the function values of the delegates in the array. var funcVector = FunctionFactory.RealFunctionsToVectorFunction(     new MultivariateRealFunction(myFunc1),     new MultivariateRealFunction(myFunc2));  The IterativeAlgorithm<T> abstract base class Iterative algorithms are common in numerical computing - a method is executed repeatedly until a certain condition is reached, approximating the result of a calculation with increasing accuracy until a certain threshold is reached. If the desired accuracy is achieved, the algorithm is said to converge. This base class is derived by many classes in the Extreme.Mathematics.EquationSolvers and Extreme.Mathematics.Optimization namespaces, as well as the ManagedIterativeAlgorithm class which contains a driver method that manages the iteration process.  The ConvergenceTest abstract base class This class is used to specify algorithm Termination , convergence and results - calculates an estimate for the error, and signals termination of the algorithm when the error is below a specified tolerance. Termination Criteria - specify the success condition as the difference between some quantity and its actual value is within a certain tolerance – 2 ways: absolute error - difference between the result and the actual value. relative error is the difference between the result and the actual value relative to the size of the result. Tolerance property - specify trade-off between accuracy and execution time. The lower the tolerance, the longer it will take for the algorithm to obtain a result within that tolerance. Most algorithms in the EO NumLib have a default value of MachineConstants.SqrtEpsilon - gives slightly less than 8 digits of accuracy. ConvergenceCriterion property - specify under what condition the algorithm is assumed to converge. Using the ConvergenceCriterion enum: WithinAbsoluteTolerance / WithinRelativeTolerance / WithinAnyTolerance / NumberOfIterations Active property - selectively ignore certain convergence tests Error property - returns the estimated error after a run MaxIterations / MaxEvaluations properties - Other Termination Criteria - If the algorithm cannot achieve the desired accuracy, the algorithm still has to end – according to an absolute boundary. Status property - indicates how the algorithm terminated - the AlgorithmStatus enum values:NoResult / Busy / Converged (ended normally - The desired accuracy has been achieved) / IterationLimitExceeded / EvaluationLimitExceeded / RoundOffError / BadFunction / Divergent / ConvergedToFalseSolution. After the iteration terminates, the Status should be inspected to verify that the algorithm terminated normally. Alternatively, you can set the ThrowExceptionOnFailure to true. Result property - returns the result of the algorithm. This property contains the best available estimate, even if the desired accuracy was not obtained. IterationsNeeded / EvaluationsNeeded properties - returns the number of iterations required to obtain the result, number of function evaluations.  Concrete Types of Convergence Test classes SimpleConvergenceTest class - test if a value is close to zero or very small compared to another value. VectorConvergenceTest class - test convergence of vectors. This class has two additional properties. The Norm property specifies which norm is to be used when calculating the size of the vector - the VectorConvergenceNorm enum values: EuclidianNorm / Maximum / SumOfAbsoluteValues. The ErrorMeasure property specifies how the error is to be measured – VectorConvergenceErrorMeasure enum values: Norm / Componentwise ConvergenceTestCollection class - represent a combination of tests. The Quantifier property is a ConvergenceTestQuantifier enum that specifies how the tests in the collection are to be combined: Any / All  The AlgorithmHelper Class inherits from IterativeAlgorithm<T> and exposes two methods for convergence testing. IsValueWithinTolerance<T> method - determines whether a value is close to another value to within an algorithm's requested tolerance. IsIntervalWithinTolerance<T> method - determines whether an interval is within an algorithm's requested tolerance.

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• Limiting Audit Exposure and Managing Risk – Q&A and Follow-Up Conversation

  - by Tanu Sood

  Thanks to all who attended the live ISACA webcast on Limiting Audit Exposure and Managing Risk with Metrics-Driven Identity Analytics. We were really fortunate to have Don Sparks from ISACA moderate the webcast featuring Stuart Lincoln, Vice President, IT P&L Client Services, BNP Paribas, North America and Neil Gandhi, Principal Product Manager, Oracle Identity Analytics. Stuart’s insights given the team’s role in providing IT for P&L Client Services and his tremendous experience in identity management and establishing sustainable compliance programs were true value-add at yesterday’s webcast. And if you are a healthcare organization looking to solve your compliance and security challenges, we recommend you join us for a live webcast on Tuesday, November 29 at 10 am PT. The webcast will feature experts from Kaiser Permanente, PricewaterhouseCoopers and Oracle and the focus of the discussion will be around the compliance challenges a healthcare organization faces and best practices for tackling those. Here are the details: Healthcare IT News Webcast: Managing Risk and Enforcing Compliance in Healthcare with Identity Analytics Tuesday, November 29, 201110:00 a.m. PT / 1:00 p.m. ET Register Today The ISACA webcast replay is now available on-demand and the slides are also available for download. Since we didn’t have time to address all the questions we received during the live Q&A portion of the webcast, we have captured responses to the remaining questions here. Please continue to provide us your feedback and insights from your experience in deploying identity compliance solutions. Q. Can you please clarify the mechanism utilized to populate the Identity Warehouse from each individual application's access management function / files? A. Oracle Identity Analytics (OIA) supports direct imports from applications. Data collection is based on Extract, Transform and Load (ETL) that eliminates the need to write connectors to different applications. Oracle Identity Analytics’ import engine supports complex entitlement feeds saved as either text files or XML. The imports can be scheduled on a periodic basis or triggered as needed. If the applications are synchronized with a user provisioning solution like Oracle Identity Manager, Oracle Identity Analytics has a seamless integration to pull in data from Oracle Identity Manager. Q.  Can you provide a short summary of the new features in your latest release of Oracle Identity Analytics? A. Oracle recently announced availability of enhanced Oracle Identity Analytics. This release focused on easing the certification process by offering risk analytics driven certification, advanced certification screens, business centric views and significant improvement in performance including 3X faster data imports, 3X faster certification campaign generation and advanced auto-certification features, that  will allow organizations to improve user productivity by up to 80%. Closed-loop risk feedback and IT policy monitoring with Oracle Identity Manager, a leading user provisioning solution, allows for more accurate certification reviews. And, OIA's improved performance enables customers to scale compliance initiatives supporting millions of user entitlements across thousands of applications, whether on premise or in the cloud, without compromising speed or integrity. Q. Will ISACA grant a CPE credit for attending this ISACA-sponsored webinar today? A. From ISACA: Hello and thank you for your interest in the 2011 ISACA Webinar Program!  Unfortunately, there are no CPEs offered for this program, archived or live.  We will be looking into the feasibility of offering them in the future.  Q. Would you be able to use this to help manage licenses for software? That is to say - could it track software that is not used by a user, thus eliminating the software license? A. OIA’s integration with Oracle Identity Manager, a leading user provisioning solution, allows organizations to detect ghost accounts or unused accounts via account reconciliation. Based on company’s policies, this could trigger an automated workflow for account deletion or asking for further investigation. Closed-loop feedback between the two solutions would then allow visibility into the complete audit trail of when the account was detected, the action taken, by whom, when and the current status. Q. We have quarterly attestations and .xls mechanisms are not working. Once the identity data is correlated in Identity Analytics, do you then automate access certification? A. OIA’s identity warehouse analyzes and correlates identity data across various resources that allows OIA to determine a user’s risk profile, who the access review request should go to, along with all the relevant access details of the user. The access certification manager gets notification on what to review, when and the relevant data is presented in a business friendly screen. Based on the result of the access certification process, actions are triggered and results recorded and archived. Access review managers have visual risk indicators that also allow them to prioritize access certification tasks and efforts. Q. How does Oracle Identity Analytics work with Cloud Security? A. For enterprises looking to build their own cloud(s), Oracle offers a set of security services that cloud developers can leverage including Oracle Identity Analytics.  For enterprises looking to manage their compliance requirements but without hosting those in-house and instead having a hosting provider offer managed Identity Management services to the organizations, Oracle Identity Analytics can be leveraged much the same way as you’d in an on-premise (within the enterprise) environment. In fact, organizations today are leveraging Oracle Identity Analytics to manage identity compliance in both these ways. Q. Would you recommend this as a cost effective solution for a smaller organization with @ 2,500 users? A. The key return-on-investment (ROI) on Oracle Identity Analytics is derived from automating compliance processes thereby eliminating administrative overhead, minimizing errors, maintaining cost- and time-effective sustainable compliance processes and minimizing audit exposures and penalties.  Of course, there are other tangible benefits that are derived from an Oracle Identity Analytics implementation as outlined in the webcast. For a quantitative analysis of your requirements and potential ROI calculation, we recommend you refer to the Forrester Study on Total Economic Impact of Oracle Identity Analytics. For an in-person discussion, please email Richard Caldwell.

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• Organization &amp; Architecture UNISA Studies &ndash; Chap 5

  - by MarkPearl

  Learning Outcomes Describe the operation of a memory cell Explain the difference between DRAM and SRAM Discuss the different types of ROM Explain the concepts of a hard failure and a soft error respectively Describe SDRAM organization Semiconductor Main Memory The two traditional forms of RAM used in computers are DRAM and SRAM DRAM (Dynamic RAM) Divided into two technologies… Dynamic Static Dynamic RAM is made with cells that store data as charge on capacitors. The presence or absence of charge in a capacitor is interpreted as a binary 1 or 0. Because capacitors have natural tendency to discharge, dynamic RAM requires periodic charge refreshing to maintain data storage. The term dynamic refers to the tendency of the stored charge to leak away, even with power continuously applied. Although the DRAM cell is used to store a single bit (0 or 1), it is essentially an analogue device. The capacitor can store any charge value within a range, a threshold value determines whether the charge is interpreted as a 1 or 0. SRAM (Static RAM) SRAM is a digital device that uses the same logic elements used in the processor. In SRAM, binary values are stored using traditional flip flop logic configurations. SRAM will hold its data as along as power is supplied to it. Unlike DRAM, no refresh is required to retain data. SRAM vs. DRAM DRAM is simpler and smaller than SRAM. Thus it is more dense and less expensive than SRAM. The cost of the refreshing circuitry for DRAM needs to be considered, but if the machine requires a large amount of memory, DRAM turns out to be cheaper than SRAM. SRAMS are somewhat faster than DRAM, thus SRAM is generally used for cache memory and DRAM is used for main memory. Types of ROM Read Only Memory (ROM) contains a permanent pattern of data that cannot be changed. ROM is non volatile meaning no power source is required to maintain the bit values in memory. While it is possible to read a ROM, it is not possible to write new data into it. An important application of ROM is microprogramming, other applications include library subroutines for frequently wanted functions, System programs, Function tables. A ROM is created like any other integrated circuit chip, with the data actually wired into the chip as part of the fabrication process. To reduce costs of fabrication, we have PROMS. PROMS are… Written only once Non-volatile Written after fabrication Another variation of ROM is the read-mostly memory, which is useful for applications in which read operations are far more frequent than write operations, but for which non volatile storage is required. There are three common forms of read-mostly memory, namely… EPROM EEPROM Flash memory Error Correction Semiconductor memory is subject to errors, which can be classed into two categories… Hard failure – Permanent physical defect so that the memory cell or cells cannot reliably store data Soft failure – Random error that alters the contents of one or more memory cells without damaging the memory (common cause includes power supply issues, etc.) Most modern main memory systems include logic for both detecting and correcting errors. Error detection works as follows… When data is to be read into memory, a calculation is performed on the data to produce a code Both the code and the data are stored When the previously stored word is read out, the code is used to detect and possibly correct errors The error checking provides one of 3 possible results… No errors are detected – the fetched data bits are sent out An error is detected, and it is possible to correct the error. The data bits plus error correction bits are fed into a corrector, which produces a corrected set of bits to be sent out An error is detected, but it is not possible to correct it. This condition is reported Hamming Code See wiki for detailed explanation. We will probably need to know how to do a hemming code – refer to the textbook (pg. 188 – 189) Advanced DRAM organization One of the most critical system bottlenecks when using high-performance processors is the interface to main memory. This interface is the most important pathway in the entire computer system. The basic building block of main memory remains the DRAM chip. In recent years a number of enhancements to the basic DRAM architecture have been explored, and some of these are now on the market including… SDRAM (Synchronous DRAM) DDR-DRAM RDRAM SDRAM (Synchronous DRAM) SDRAM exchanges data with the processor synchronized to an external clock signal and running at the full speed of the processor/memory bus without imposing wait states. SDRAM employs a burst mode to eliminate the address setup time and row and column line precharge time after the first access In burst mode a series of data bits can be clocked out rapidly after the first bit has been accessed SDRAM has a multiple bank internal architecture that improves opportunities for on chip parallelism SDRAM performs best when it is transferring large blocks of data serially There is now an enhanced version of SDRAM known as double data rate SDRAM or DDR-SDRAM that overcomes the once-per-cycle limitation of SDRAM

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• Is this how dynamic language copes with dynamic requirement?

  - by Amumu

  The question is in the title. I want to have my thinking verified by experienced people. You can add more or disregard my opinion, but give me a reason. Here is an example requirement: Suppose you are required to implement a fighting game. Initially, the game only includes fighters, who can attack each other. Each fighter can punch, kick or block incoming attacks. Fighters can have various fighting styles: Karate, Judo, Kung Fu... That's it for the simple universe of the game. In an OO like Java, it can be implemented similar to this way: abstract class Fighter { int hp, attack; void punch(Fighter otherFighter); void kick(Fighter otherFighter); void block(Figther otherFighter); }; class KarateFighter extends Fighter { //...implementation...}; class JudoFighter extends Fighter { //...implementation... }; class KungFuFighter extends Fighter { //...implementation ... }; This is fine if the game stays like this forever. But, somehow the game designers decide to change the theme of the game: instead of a simple fighting game, the game evolves to become a RPG, in which characters can not only fight but perform other activities, i.e. the character can be a priest, an accountant, a scientist etc... At this point, to make it more generic, we have to change the structure of our original design: Fighter is not used to refer to a person anymore; it refers to a profession. The specialized classes of Fighter (KaraterFighter, JudoFighter, KungFuFighter) . Now we have to create a generic class named Person. However, to adapt this change, I have to change the method signatures of the original operations: class Person { int hp, attack; List<Profession> skillSet; }; abstract class Profession {}; class Fighter extends Profession { void punch(Person otherFighter); void kick(Person otherFighter); void block(Person otherFighter); }; class KarateFighter extends Fighter { //...implementation...}; class JudoFighter extends Fighter { //...implementation... }; class KungFuFighter extends Fighter { //...implementation ... }; class Accountant extends Profession { void calculateTax(Person p) { //...implementation...}; void calculateTax(Company c) { //...implementation...}; }; //... more professions... Here are the problems: To adapt to the method changes, I have to fix the places where the changed methods are called (refactoring). Every time a new requirement is introduced, the current structural design has to be broken to adapt the changes. This leads to the first problem. Rigid structure makes it hard for code reuse. A function can only accept the predefined types, but it cannot accept future unknown types. A written function is bound to its current universe and has no way to accommodate to the new types, without modifications or rewrite from scratch. I see Java has a lot of deprecated methods. OO is an extreme case because it has inheritance to add up the complexity, but in general for statically typed language, types are very strict. In contrast, a dynamic language can handle the above case as follow: ;;fighter1 punch fighter2 (defun perform-punch (fighter1 fighter2) ...implementation... ) ;;fighter1 kick fighter2 (defun perform-kick (fighter1 fighter2) ...implementation... ) ;;fighter1 blocks attacks from fighter2 (defun perform-block (fighter1 fighter2) ...implementation... ) fighter1 and fighter2 can be anything as long as it has the required data for calculation; or methods (duck typing). You don't have to change from the type Fighter to Person. In the case of Lisp, because Lisp only has a single data structure: list, it's even easier to adapt to changes. However, other dynamic languages can have similar behaviors as well. I work primarily with static languages (mainly C and Java, but working with Java was a long time ago). I started learning Lisp and some other dynamic languages this year. I can see how it helps improving my productivity.

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• Using Transaction Logging to Recover Post-Archived Essbase data

  - by Keith Rosenthal

  Data recovery is typically performed by restoring data from an archive.  Data added or removed since the last archive took place can also be recovered by enabling transaction logging in Essbase.  Transaction logging works by writing transactions to a log store.  The information in the log store can then be recovered by replaying the log store entries in sequence since the last archive took place.  The following information is recorded within a transaction log entry: Sequence ID Username Start Time End Time Request Type A request type can be one of the following categories: Calculations, including the default calculation as well as both server and client side calculations Data loads, including data imports as well as data loaded using a load rule Data clears as well as outline resets Locking and sending data from SmartView and the Spreadsheet Add-In.  Changes from Planning web forms are also tracked since a lock and send operation occurs during this process. You can use the Display Transactions command in the EAS console or the query database MAXL command to view the transaction log entries. Enabling Transaction Logging Transaction logging can be enabled at the Essbase server, application or database level by adding the TRANSACTIONLOGLOCATION essbase.cfg setting.  The following is the TRANSACTIONLOGLOCATION syntax: TRANSACTIONLOGLOCATION [appname [dbname]] LOGLOCATION NATIVE ENABLE | DISABLE Note that you can have multiple TRANSACTIONLOGLOCATION entries in the essbase.cfg file.  For example: TRANSACTIONLOGLOCATION Hyperion/trlog NATIVE ENABLE TRANSACTIONLOGLOCATION Sample Hyperion/trlog NATIVE DISABLE The first statement will enable transaction logging for all Essbase applications, and the second statement will disable transaction logging for the Sample application.  As a result, transaction logging will be enabled for all applications except the Sample application. A location on a physical disk other than the disk where ARBORPATH or the disk files reside is recommended to optimize overall Essbase performance. Configuring Transaction Log Replay Although transaction log entries are stored based on the LOGLOCATION parameter of the TRANSACTIONLOGLOCATION essbase.cfg setting, copies of data load and rules files are stored in the ARBORPATH/app/appname/dbname/Replay directory to optimize the performance of replaying logged transactions.  The default is to archive client data loads, but this configuration setting can be used to archive server data loads (including SQL server data loads) or both client and server data loads. To change the type of data to be archived, add the TRANSACTIONLOGDATALOADARCHIVE configuration setting to the essbase.cfg file.  Note that you can have multiple TRANSACTIONLOGDATALOADARCHIVE entries in the essbase.cfg file to adjust settings for individual applications and databases. Replaying the Transaction Log and Transaction Log Security Considerations To replay the transactions, use either the Replay Transactions command in the EAS console or the alter database MAXL command using the replay transactions grammar.  Transactions can be replayed either after a specified log time or using a range of transaction sequence IDs. The default when replaying transactions is to use the security settings of the user who originally performed the transaction.  However, if that user no longer exists or that user's username was changed, the replay operation will fail. Instead of using the default security setting, add the REPLAYSECURITYOPTION essbase.cfg setting to use the security settings of the administrator who performs the replay operation.  REPLAYSECURITYOPTION 2 will explicitly use the security settings of the administrator performing the replay operation.  REPLAYSECURITYOPTION 3 will use the administrator security settings if the original user’s security settings cannot be used. Removing Transaction Logs and Archived Replay Data Load and Rules Files Transaction logs and archived replay data load and rules files are not automatically removed and are only removed manually.  Since these files can consume a considerable amount of space, the files should be removed on a periodic basis. The transaction logs should be removed one database at a time instead of all databases simultaneously.  The data load and rules files associated with the replayed transactions should be removed in chronological order from earliest to latest.  In addition, do not remove any data load and rules files with a timestamp later than the timestamp of the most recent archive file. Partitioned Database Considerations For partitioned databases, partition commands such as synchronization commands cannot be replayed.  When recovering data, the partition changes must be replayed manually and logged transactions must be replayed in the correct chronological order. If the partitioned database includes any @XREF commands in the calc script, the logged transactions must be selectively replayed in the correct chronological order between the source and target databases. References For additional information, please see the Oracle EPM System Backup and Recovery Guide.  For EPM 11.1.2.2, the link is http://docs.oracle.com/cd/E17236_01/epm.1112/epm_backup_recovery_1112200.pdf

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• SPARC T4-4 Delivers World Record Performance on Oracle OLAP Perf Version 2 Benchmark

  - by Brian

  Oracle's SPARC T4-4 server delivered world record performance with subsecond response time on the Oracle OLAP Perf Version 2 benchmark using Oracle Database 11g Release 2 running on Oracle Solaris 11. The SPARC T4-4 server achieved throughput of 430,000 cube-queries/hour with an average response time of 0.85 seconds and the median response time of 0.43 seconds. This was achieved by using only 60% of the available CPU resources leaving plenty of headroom for future growth. The SPARC T4-4 server operated on an Oracle OLAP cube with a 4 billion row fact table of sales data containing 4 dimensions. This represents as many as 90 quintillion aggregate rows (90 followed by 18 zeros). Performance Landscape Oracle OLAP Perf Version 2 Benchmark 4 Billion Fact Table Rows System Queries/hour Users* Response Time (sec) Average Median SPARC T4-4 430,000 7,300 0.85 0.43 * Users - the supported number of users with a given think time of 60 seconds Configuration Summary and Results Hardware Configuration: SPARC T4-4 server with 4 x SPARC T4 processors, 3.0 GHz 1 TB memory Data Storage 1 x Sun Fire X4275 (using COMSTAR) 2 x Sun Storage F5100 Flash Array (each with 80 FMODs) Redo Storage 1 x Sun Fire X4275 (using COMSTAR with 8 HDD) Software Configuration: Oracle Solaris 11 11/11 Oracle Database 11g Release 2 (11.2.0.3) with Oracle OLAP option Benchmark Description The Oracle OLAP Perf Version 2 benchmark is a workload designed to demonstrate and stress the Oracle OLAP product's core features of fast query, fast update, and rich calculations on a multi-dimensional model to support enhanced Data Warehousing. The bulk of the benchmark entails running a number of concurrent users, each issuing typical multidimensional queries against an Oracle OLAP cube consisting of a number of years of sales data with fully pre-computed aggregations. The cube has four dimensions: time, product, customer, and channel. Each query user issues approximately 150 different queries. One query chain may ask for total sales in a particular region (e.g South America) for a particular time period (e.g. Q4 of 2010) followed by additional queries which drill down into sales for individual countries (e.g. Chile, Peru, etc.) with further queries drilling down into individual stores, etc. Another query chain may ask for yearly comparisons of total sales for some product category (e.g. major household appliances) and then issue further queries drilling down into particular products (e.g. refrigerators, stoves. etc.), particular regions, particular customers, etc. Results from version 2 of the benchmark are not comparable with version 1. The primary difference is the type of queries along with the query mix. Key Points and Best Practices Since typical BI users are often likely to issue similar queries, with different constants in the where clauses, setting the init.ora prameter "cursor_sharing" to "force" will provide for additional query throughput and a larger number of potential users. Except for this setting, together with making full use of available memory, out of the box performance for the OLAP Perf workload should provide results similar to what is reported here. For a given number of query users with zero think time, the main measured metrics are the average query response time, the median query response time, and the query throughput. A derived metric is the maximum number of users the system can support achieving the measured response time assuming some non-zero think time. The calculation of the maximum number of users follows from the well-known response-time law N = (rt + tt) * tp where rt is the average response time, tt is the think time and tp is the measured throughput. Setting tt to 60 seconds, rt to 0.85 seconds and tp to 119.44 queries/sec (430,000 queries/hour), the above formula shows that the T4-4 server will support 7,300 concurrent users with a think time of 60 seconds and an average response time of 0.85 seconds. For more information see chapter 3 from the book "Quantitative System Performance" cited below. -- See Also Quantitative System Performance Computer System Analysis Using Queueing Network Models Edward D. Lazowska, John Zahorjan, G. Scott Graham, Kenneth C. Sevcik external local Oracle Database 11g – Oracle OLAP oracle.com OTN SPARC T4-4 Server oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 oracle.com OTN Disclosure Statement Copyright 2012, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners. Results as of 11/2/2012.

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• Trying to detect collision between two polygons using Separating Axis Theorem

  - by Holly

  The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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• Error in my Separating Axis Theorem collision code

  - by Holly

  The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; int x; int y; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } public void update(int xPos, int yPos){ x = xPos; y = yPos; } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(new Vect(vertices[0].x+x, vertices[0].y+y)); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(new Vect(vertices[i].x+x, vertices[i].y+y)); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if(y > other.x && other.y > x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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• k-d tree implementation [closed]

  - by user466441

  when i run my code and debugged,i got this error - this 0x00093584 {_Myproxy=0x00000000 _Mynextiter=0x00000000 } std::_Iterator_base12 * const - _Myproxy 0x00000000 {_Mycont=??? _Myfirstiter=??? } std::_Container_proxy * _Mycont CXX0017: Error: symbol "" not found _Myfirstiter CXX0030: Error: expression cannot be evaluated + _Mynextiter 0x00000000 {_Myproxy=??? _Mynextiter=??? } std::_Iterator_base12 * but i dont know what does it means,code is this #include<iostream> #include<vector> #include<algorithm> using namespace std; struct point { float x,y; }; vector<point>pointleft(4); vector<point>pointright(4); //we are going to implement two comparison function for x and y coordinates,we need it in calculation of median (we should sort vector //by x or y according to depth informaton,is depth even or odd. bool sortby_X(point &a,point &b) { return a.x<b.x; } bool sortby_Y(point &a,point &b) { return a.y<b.y; } //so i am going to implement to median finding algorithm,one for finding median by x and another find median by y point medianx(vector<point>points) { point temp; sort(points.begin(),points.end(),sortby_X); temp=points[(points.size()/2)]; return temp; } point mediany(vector<point>points) { point temp; sort(points.begin(),points.end(),sortby_Y); temp=points[(points.size()/2)]; return temp; } //now construct basic tree structure struct Tree { float x,y; Tree(point a) { x=a.x; y=a.y; } Tree *left; Tree *right; }; Tree * build_kd( Tree *root,vector<point>points,int depth) { point temp; if(points.size()==1)// that point is as a leaf { if(root==NULL) root=new Tree(points[0]); return root; } if(depth%2==0) { temp=medianx(points); root=new Tree(temp); for(int i=0;i<points.size();i++) { if (points[i].x<temp.x) pointleft[i]=points[i]; else pointright[i]=points[i]; } } else { temp=mediany(points); root=new Tree(temp); for(int i=0;i<points.size();i++) { if(points[i].y<temp.y) pointleft[i]=points[i]; else pointright[i]=points[i]; } } return build_kd(root->left,pointleft,depth+1); return build_kd(root->right,pointright,depth+1); } void print(Tree *root) { while(root!=NULL) { cout<<root->x<<" " <<root->y; print(root->left); print(root->right); } } int main() { int depth=0; Tree *root=NULL; vector<point>points(4); float x,y; int n=4; for(int i=0;i<n;i++) { cin>>x>>y; points[i].x=x; points[i].y=y; } root=build_kd(root,points,depth); print(root); return 0; } i am trying ti implement in c++ this pseudo code tuple function build_kd_tree(int depth, set points): if points contains only one point: return that point as a leaf. if depth is even: Calculate the median x-value. Create a set of points (pointsLeft) that have x-values less than the median. Create a set of points (pointsRight) that have x-values greater than or equal to the median. else: Calculate the median y-value. Create a set of points (pointsLeft) that have y-values less than the median. Create a set of points (pointsRight) that have y-values greater than or equal to the median. treeLeft = build_kd_tree(depth + 1, pointsLeft) treeRight = build_kd_tree(depth + 1, pointsRight) return(median, treeLeft, treeRight) please help me what this error means?

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• Increasing efficiency of N-Body gravity simulation

  - by Postman

  I'm making a space exploration type game, it will have many planets and other objects that will all have realistic gravity. I currently have a system in place that works, but if the number of planets goes above 70, the FPS decreases an practically exponential rates. I'm making it in C# and XNA. My guess is that I should be able to do gravity calculations between 100 objects without this kind of strain, so clearly my method is not as efficient as it should be. I have two files, Gravity.cs and EntityEngine.cs. Gravity manages JUST the gravity calculations, EntityEngine creates an instance of Gravity and runs it, along with other entity related methods. EntityEngine.cs public void Update() { foreach (KeyValuePair<string, Entity> e in Entities) { e.Value.Update(); } gravity.Update(); } (Only relevant piece of code from EntityEngine, self explanatory. When an instance of Gravity is made in entityEngine, it passes itself (this) into it, so that gravity can have access to entityEngine.Entities (a dictionary of all planet objects)) Gravity.cs namespace ExplorationEngine { public class Gravity { private EntityEngine entityEngine; private Vector2 Force; private Vector2 VecForce; private float distance; private float mult; public Gravity(EntityEngine e) { entityEngine = e; } public void Update() { //First loop foreach (KeyValuePair<string, Entity> e in entityEngine.Entities) { //Reset the force vector Force = new Vector2(); //Second loop foreach (KeyValuePair<string, Entity> e2 in entityEngine.Entities) { //Make sure the second value is not the current value from the first loop if (e2.Value != e.Value ) { //Find the distance between the two objects. Because Fg = G * ((M1 * M2) / r^2), using Vector2.Distance() and then squaring it //is pointless and inefficient because distance uses a sqrt, squaring the result simple cancels that sqrt. distance = Vector2.DistanceSquared(e2.Value.Position, e.Value.Position); //This makes sure that two planets do not attract eachother if they are touching, completely unnecessary when I add collision, //For now it just makes it so that the planets are not glitchy, performance is not significantly improved by removing this IF if (Math.Sqrt(distance) > (e.Value.Texture.Width / 2 + e2.Value.Texture.Width / 2)) { //Calculate the magnitude of Fg (I'm using my own gravitational constant (G) for the sake of time (I know it's 1 at the moment, but I've been changing it) mult = 1.0f * ((e.Value.Mass * e2.Value.Mass) / distance); //Calculate the direction of the force, simply subtracting the positions and normalizing works, this fixes diagonal vectors //from having a larger value, and basically makes VecForce a direction. VecForce = e2.Value.Position - e.Value.Position; VecForce.Normalize(); //Add the vector for each planet in the second loop to a force var. Force = Vector2.Add(Force, VecForce * mult); //I have tried Force += VecForce * mult, and have not noticed much of an increase in speed. } } } //Add that force to the first loop's planet's position (later on I'll instead add to acceleration, to account for inertia) e.Value.Position += Force; } } } } I have used various tips (about gravity optimizing, not threading) from THIS question (that I made yesterday). I've made this gravity method (Gravity.Update) as efficient as I know how to make it. This O(N^2) algorithm still seems to be eating up all of my CPU power though. Here is a LINK (google drive, go to File download, keep .Exe with the content folder, you will need XNA Framework 4.0 Redist. if you don't already have it) to the current version of my game. Left click makes a planet, right click removes the last planet. Mouse moves the camera, scroll wheel zooms in and out. Watch the FPS and Planet Count to see what I mean about performance issues past 70 planets. (ALL 70 planets must be moving, I've had 100 stationary planets and only 5 or so moving ones while still having 300 fps, the issue arises when 70+ are moving around) After 70 planets are made, performance tanks exponentially. With < 70 planets, I get 330 fps (I have it capped at 300). At 90 planets, the FPS is about 2, more than that and it sticks around at 0 FPS. Strangely enough, when all planets are stationary, the FPS climbs back up to around 300, but as soon as something moves, it goes right back down to what it was, I have no systems in place to make this happen, it just does. I considered multithreading, but that previous question I asked taught me a thing or two, and I see now that that's not a viable option. I've also thought maybe I could do the calculations on my GPU instead, though I don't think it should be necessary. I also do not know how to do this, it is not a simple concept and I want to avoid it unless someone knows a really noob friendly simple way to do it that will work for an n-body gravity calculation. (I have an NVidia gtx 660) Lastly I've considered using a quadtree type system. (Barnes Hut simulation) I've been told (in the previous question) that this is a good method that is commonly used, and it seems logical and straightforward, however the implementation is way over my head and I haven't found a good tutorial for C# yet that explains it in a way I can understand, or uses code I can eventually figure out. So my question is this: How can I make my gravity method more efficient, allowing me to use more than 100 objects (I can render 1000 planets with constant 300+ FPS without gravity calculations), and if I can't do much to improve performance (including some kind of quadtree system), could I use my GPU to do the calculations?

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• Answers to Conference Revenue Tweet Questions

  - by D'Arcy Lussier

  Originally posted on: http://geekswithblogs.net/dlussier/archive/2014/05/27/156612.aspxI tweeted this the other day… …and I had some people tweet back questioning/asking about the profit number. So here’s how I came to that figure. Total Revenue Let’s talk total revenue first. This conference has a huge list of companies/organizations paying some amount for sponsorship. Platinum ($1500) x 5 = $7500 Gold ($1000) x 3 = $3000 Silver ($500) x 9 = $4500 Bronze ($250) x 13 = $3250 There’s also a title sponsor level but there’s no mention of how much that is…more than $1500 though, so let’s just say $2500. Total Sponsorship Revenue: $20750.00 For registrations, this conference is claiming over 300 attendees. We’ll just calculate at 300 and the discounted “member rate” – $249. Total Registration Revenue: $74700.00 Booth space is also sold for a vendor area, but let’s just leave that out of the calculation. Total Event Revenue: $95450.00 Now that we know how much money we’re playing with, let’s knock out the costs for the event. Total Costs Hard Costs Audio/Visual Services $2000 Conference Rooms (4 Breakouts + Plenary) $2500 Insurance $700 Printing/Signage $1500 Travel/Hotel Rooms $2000 Keynotes $2000 So let’s talk about these hard costs first. First you may be asking about the Audio Visual. Yes those services can be that high, actually higher. But since there’s an A/V company touted as the official A/V provider, I gotta think there’s some discount for being branded as such. Conference rooms are actually an inflated amount of $500 per. Venues make money on the food they sell at events, not on room rentals. The more food, the cheaper the rooms tend to be offered at. Still, for the sake of argument, let’s set the rooms at $500 each knowing that they could be lower. For travel and hotel rooms…it appears that most of the speakers at this conference are local, meaning there’s no travel or hotel cost. But a few of them I wasn’t too sure…so let’s factor in enough to cover two outside speakers (airfare and hotel). There are two keynotes for this event and depending on the event those may be paid gigs. I’m not sure if they are or not, but considering the closing one is a comedian I’m going to add some funds here for that just in case. Total Hard Costs: $10700 Now that the hard costs are out of the way, let’s talk about the food costs. Food Costs The conference is providing a continental breakfast (YEEEESH!), some level of luncheon, and I have to assume coffee breaks in between. Let’s look at those costs. Continental Breakfast $12 per person Lunch Buffet $18 per person Coffee Breaks (2) $6 per person (or $3 a cup) Snacks (2) $10 per person (or $5 each) Note that the lunch buffet assumes a *good* lunch buffet – two entrees, starch, vegetable, salads, and bread. Not sure if there’ll be snacks during coffee breaks but let’s assume so. Total Food Cost Per Person: $46 Food Cost: $14950 Gratuity: $2691 Total Food Cost: $17641 Total food cost is based on the $46 per person cost x 325. 300 for attendance, 12 for speakers, extra 13 for volunteers/organizers. Gratuity is 18%. Grand Totals So let’s sum things up here. Total Costs Hard Costs: $10700.00 Food Costs: $17641.00 Total:          $28341.00 Taxes:         $3685.00 Grand Total  $32026.00 Total Revenue Sponsorship  $20750 Registration   $74700 Grand Total   $95450.00 Total Profit $63424.00 Now what if the registration numbers were lower and they only got 100 people to show up. In that scenario there’d still be a profit of just under $26000. Closing Comments A couple of things to note: - I haven’t factored in anything for prizes. Not sure if any will be given out - We didn’t add in the booth space revenue - We’re assuming speakers aren’t getting paid, but even if they were at the high end its $12000 ($1000 per session), which is probably an inflated number for local speakers. - Note that all registrations were set to the “member” discounted price. The non-member registration price is higher. There is also an option for those that just want to show up for the opening keynote. There you have it! Let me know if you have any questions. D

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• Copies of GameScene created when called additional times

  - by Orin MacGregor

  I have a game with a level select managed by a SceneManager, which basically just uses ReplaceScene. The first time I load a level everything works fine. On subsequent calls, for example: completing the level and continuing to the next, things blow up. The level loads fine, but when I try to pan the map or try to move the player the game crashes. Debugging through I found that there are multiple occurrences of self and related children like player and mapLayer. As a test, I put this code in my ccTouchesBegan: NSLog(@"test %i", [self retainCount]); The first time a level is loaded, it gives: test 2 The second time I load a level it gives: test 2 test 1 as in it spits out both values by looping through twice, not just appending an output to the last. It continues with this pattern for each subsequent load. So the third time will give 2 1 1. Particular code that causes the game to crash involve calling _tileMap.tileSize because there is a second GameScene with a tileMap that was supposedly destroyed, so it has tileSize and mapSize of 0. I noticed dealloc doesn't really ever get called, so I tried to manage some things with -(void) onExit -(void) onExit { [self unscheduleAllSelectors]; [_player stopAllActions]; //stop any animations just in case. normally handled in ccTouchesEnded [self removeAllChildrenWithCleanup:YES]; } I never replace the GameScene while I'm in a GameScene; if the level is completed it goes to a GameOver scene, or I use a back button that goes to the LevelSelect scene. This is [the relevant parts of] my init, in case something like the adding of children matters: -(id) init { _mapLayer = [CCLayer node]; //load data for level GameData *gameData = [GameDataParser loadData]; int selectedChapter = gameData.selectedChapter; int selectedLevel = gameData.selectedLevel; Levels *chapterLevels = [LevelParser loadLevelsForChapter:selectedChapter]; //loop until we get selected level, then do stuff for (Level *level in chapterLevels.levels) { if (level.number == selectedLevel) { //load the level map _tileMap = [CCTMXTiledMap tiledMapWithTMXFile:level.file]; } } _background = [_tileMap layerNamed:@"Background"]; _foreground = [_tileMap layerNamed:@"Foreground"]; _meta = [_tileMap layerNamed:@"Meta"]; _meta.visible = NO; //initialize Spawn Point object and place player there CCTMXObjectGroup *objects = [_tileMap objectGroupNamed:@"Objects"]; NSAssert(objects != nil, @"'Objects' object group not found"); NSMutableDictionary *spawnPoint = [objects objectNamed:@"SpawnPoint"]; NSAssert(spawnPoint != nil, @"SpawnPoint object not found"); int x = [[spawnPoint valueForKey:@"x"] intValue] / retinaScaling; int y = [[spawnPoint valueForKey:@"y"] intValue] / retinaScaling; //setup animations [[CCSpriteFrameCache sharedSpriteFrameCache] addSpriteFramesWithFile:@"MouseRightAnim_24x21.plist"]; CCSpriteBatchNode *spriteSheet = [CCSpriteBatchNode batchNodeWithFile:@"MouseRightAnim_24x21.png"]; [_mapLayer addChild:spriteSheet z:1]; NSMutableArray *rightAnimFrames = [NSMutableArray array]; for(int i = 1; i <= 3; ++i) { [rightAnimFrames addObject: [[CCSpriteFrameCache sharedSpriteFrameCache] spriteFrameByName: [NSString stringWithFormat:@"MouseRight%d_24x21.png", i]]]; } CCAnimation *rightAnim = [CCAnimation animationWithSpriteFrames:rightAnimFrames delay:0.1f]; self.player = [CCSprite spriteWithSpriteFrameName:@"MouseRight2_24x21.png"]; _player.position = ccp(x, y); self.rightAction = [CCRepeatForever actionWithAction:[CCAnimate actionWithAnimation:rightAnim]]; rightAnim.restoreOriginalFrame = NO; [spriteSheet addChild:_player]; //get map size in pixels mapHeight = _tileMap.contentSize.height; mapWidth = _tileMap.contentSize.width; //setup defaults //this value works well for the calculation later, trial and error really distance = 150; lastGoodDistance = 150; mapScale = 1; [self setViewpointCenter:_player.position]; [_mapLayer addChild:_tileMap]; [self addChild:_mapLayer z:-1]; self.isTouchEnabled = YES; } return self; } And here's the SceneManager code for replacing scenes: +(void) goGameScene { CCLayer *gameLayer = [GameScene node]; [SceneManager go:gameLayer:[GameHUD node]]; } //this is what every call looks like besides the GameScene one above +(void) goLevelSelect { [SceneManager go:[LevelSelect node]:nil]; } +(void) go:(CCLayer *)layer: (CCLayer *)hudLayer { CCDirector *director = [CCDirector sharedDirector]; CCScene *newScene = [SceneManager wrap:layer:hudLayer]; if ([director runningScene]) { [director replaceScene:newScene]; } else { [director runWithScene:newScene]; } } +(CCScene *) wrap:(CCLayer *)layer: (CCLayer *)hudLayer { CCScene *newScene = [CCScene node]; [newScene addChild: layer]; if (hudLayer != nil) { [newScene addChild: hudLayer z:1]; } return newScene; } Any ideas why I'm getting these fatal artifacts? I'm hoping this isn't considered too localized since it basically combines 3 tutorials that anyone could end up following. (Ray Wenderlich Animations, Tim Roadley Scene Manager, Pan and Zoom with Tiled Maps.

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• Question About Example In Robert C Martin's _Clean Code_

  - by Jonah

  This is a question about the concept of a function doing only one thing. It won't make sense without some relevant passages for context, so I'll quote them here. They appear on pgs 37-38: To say this differently, we want to be able to read the program as though it were a set of TO paragraphs, each of which is describing the current level of abstraction and referencing subsequent TO paragraphs at the next level down. To include the setups and teardowns, we include setups, then we include the test page content, and then we include the teardowns. To include the setups, we include the suite setup if this is a suite, then we include the regular setup. It turns out to be very dif?cult for programmers to learn to follow this rule and write functions that stay at a single level of abstraction. But learning this trick is also very important. It is the key to keeping functions short and making sure they do “one thing.” Making the code read like a top-down set of TO paragraphs is an effective technique for keeping the abstraction level consistent. He then gives the following example of poor code: public Money calculatePay(Employee e) throws InvalidEmployeeType { switch (e.type) { case COMMISSIONED: return calculateCommissionedPay(e); case HOURLY: return calculateHourlyPay(e); case SALARIED: return calculateSalariedPay(e); default: throw new InvalidEmployeeType(e.type); } } and explains the problems with it as follows: There are several problems with this function. First, it’s large, and when new employee types are added, it will grow. Second, it very clearly does more than one thing. Third, it violates the Single Responsibility Principle7 (SRP) because there is more than one reason for it to change. Fourth, it violates the Open Closed Principle8 (OCP) because it must change whenever new types are added. Now my questions. To begin, it's clear to me how it violates the OCP, and it's clear to me that this alone makes it poor design. However, I am trying to understand each principle, and it's not clear to me how SRP applies. Specifically, the only reason I can imagine for this method to change is the addition of new employee types. There is only one "axis of change." If details of the calculation needed to change, this would only affect the submethods like "calculateHourlyPay()" Also, while in one sense it is obviously doing 3 things, those three things are all at the same level of abstraction, and can all be put into a TO paragraph no different from the example one: TO calculate pay for an employee, we calculate commissioned pay if the employee is commissioned, hourly pay if he is hourly, etc. So aside from its violation of the OCP, this code seems to conform to Martin's other requirements of clean code, even though he's arguing it does not. Can someone please explain what I am missing? Thanks.

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• OpenGL FrameBuffer Objects weird behavior

  - by Ben Jones

  My algorithm is this: Render the scene to a FBO with shadow mapping from multiple locations Render the scene to the screen with shadow mapping ...black magic that I still have to imlement... Combine the samples from step 1 with the image from step 2 I'm trying to debug steps 1 and 2 and am coming across STRANGE behavior. My algorithm for each shadow mapped pass is: render the scene to a FBO connected to a depth array texture from the POV of each light render the scene from the viewpoint and use vertex/frag shaders to compare the depths When I run my algorithm this way: render from point to FBO render from point to screen glutSwapBuffers() The normal vectors in the screen pass appear to be incorrect (inverted possibly). I'm pretty sure that's the issue because my diffuse lighting calculation is incorrect, but the material colors are correct, and the shadows appear in the correct places. So, it seems like the only thing that could be the culprit is the normals. However if I do render from point to FBO render from point to Screen glutSwapBuffers() //wrong here render from point to Screen glutSwapBuffers() the second pass is correct. I assume there's a problem with my framebuffer calls. Can anyone see what the problem is from the log below? Its from a bugle trace grepped for 'buffer' with a few edits to make it a little more clear. Thanks! [INFO] trace.call: glGenFramebuffersEXT(1, 0xdfeb90 - { 1 }) [INFO] trace.call: glGenFramebuffersEXT(1, 0xdfebac - { 2 }) [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 1) [INFO] trace.call: glDrawBuffer(GL_NONE) [INFO] trace.call: glReadBuffer(GL_NONE) [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 0) //start render to FBO [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 2) [INFO] trace.call: glReadBuffer(GL_NONE) [INFO] trace.call: glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, 2, 0) [INFO] trace.call: glFramebufferTexture2DEXT(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, 3, 0) [INFO] trace.call: glDrawBuffer(GL_COLOR_ATTACHMENT0) //bind to the FBO attached to a depth tex array for shadows [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 1) [INFO] trace.call: glFramebufferTextureLayerARB(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, 1, 0, 0) [INFO] trace.call: glClear(GL_DEPTH_BUFFER_BIT) //draw geometry //bind to the FBO I want the shadow mapped image rendered to [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 2) [INFO] trace.call: glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) //draw geometry //draw to screen pass //again shadow mapping FBO [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 1) [INFO] trace.call: glFramebufferTextureLayerARB(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, 1, 0, 0) [INFO] trace.call: glClear(GL_DEPTH_BUFFER_BIT) //draw geometry //bind to the screen [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 0) [INFO] trace.call: glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) //finished, swap buffers [INFO] trace.call: glXSwapBuffers(0xd5fc10, 0x05800002) //INCORRECT OUTPUT //second try at render to screen: [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 1) [INFO] trace.call: glFramebufferTextureLayerARB(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, 1, 0, 0) [INFO] trace.call: glClear(GL_DEPTH_BUFFER_BIT) //draw geometry [INFO] trace.call: glBindFramebufferEXT(GL_FRAMEBUFFER, 0) [INFO] trace.call: glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) draw geometry [INFO] trace.call: glXSwapBuffers(0xd5fc10, 0x05800002) //correct output

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• point light illumination using Phong model

  - by Myx

  Hello: I wish to render a scene that contains one box and a point light source using the Phong illumination scheme. The following are the relevant code snippets for my calculation: R3Rgb Phong(R3Scene *scene, R3Ray *ray, R3Intersection *intersection) { R3Rgb radiance; if(intersection->hit == 0) { radiance = scene->background; return radiance; } ... // obtain ambient term ... // this is zero for my test // obtain emissive term ... // this is also zero for my test // for each light in the scene, obtain calculate the diffuse and specular terms R3Rgb intensity_diffuse(0,0,0,1); R3Rgb intensity_specular(0,0,0,1); for(unsigned int i = 0; i < scene->lights.size(); i++) { R3Light *light = scene->Light(i); R3Rgb light_color = LightIntensity(scene->Light(i), intersection->position); R3Vector light_vector = -LightDirection(scene->Light(i), intersection->position); // check if the light is "behind" the surface normal if(normal.Dot(light_vector)<=0) continue; // calculate diffuse reflection if(!Kd.IsBlack()) intensity_diffuse += Kd*normal.Dot(light_vector)*light_color; if(Ks.IsBlack()) continue; // calculate specular reflection ... // this I believe to be irrelevant for the particular test I'm doing } radiance = intensity_diffuse; return radiance; } R3Rgb LightIntensity(R3Light *light, R3Point position) { R3Rgb light_intensity; double distance; double denominator; if(light->type != R3_DIRECTIONAL_LIGHT) { distance = (position-light->position).Length(); denominator = light->constant_attenuation + (light->linear_attenuation*distance) + (light->quadratic_attenuation*distance*distance); } switch(light->type) { ... case R3_POINT_LIGHT: light_intensity = light->color/denominator; break; ... } return light_intensity; } R3Vector LightDirection(R3Light *light, R3Point position) { R3Vector light_direction; switch(light->type) { ... case R3_POINT_LIGHT: light_direction = position - light->position; break; ... } light_direction.Normalize(); return light_direction; } I believe that the error must be somewhere in either LightDirection(...) or LightIntensity(...) functions because when I run my code using a directional light source, I obtain the desired rendered image (thus this leads me to believe that the Phong illumination equation is correct). Also, in Phong(...), when I computed the intensity_diffuse and while debugging, I divided light_color by 10, I was obtaining a resulting image that looked more like what I need. Am I calculating the light_color correctly? Thanks.

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• What do you expect from a package manager for Emacs

  - by tarsius

  Although several hundred Emacs Lisp libraries exist GNU Emacs does not have an (internal) package manager. I guess that most users would agree that it is currently rather inconvenient to find, install and especially keep up-to-date Emacs Lisp libraries. These pages make life a bit easier Emacs Lisp List - Problem: I see dead people (links). Emacswiki - Problem: May contain traces of nuts (malicious code). These are some package managers XEmacs package manager package.el - ELPA pases install.el install-elisp.el plugin.el use-package.el jem-pkg.el epkg/elm - the one I am working. And this are some packages that provide functionality that might be useful in a package manager ell.el - Browse the Emacs Lisp List genauto.el - helps generate autoloads for your elisp packages date-calc.el - date calculation and parsing routines strptime.el - partial implementation of POSIX date and time parsing wikirel.el - Visit relevant pages on the Emacs Wiki loadhist.el, lib-requires.el, elisp-depend.el - Commands to list Emacs Lisp library dependencies. project-root.el - Define a project root and take actions based upon it So I would like to know from you what you consider important/unimportant/supplementary... in a package manager for Emacs. Some ideas Many packages (incorporate the Emacs Lisp List and other lists of libraries). Only packages that have been tested. Support for more than one package archive (so people can choose between many/tested packages). Dependency calculated based on required features only. Dependencies take particular versions into account. Only use versions that have been released upstream. Use versions from version control systems if available. Packages are categorized. Packages can be uninstalled and updated not only installed. Support creating fork of upstream version of packages. Support publishing these forks. Support choosing a fork. After installation packages are activated. Generate autoloads. Integration with Emacswiki (see wikirel.el). Users can tag, comment ... packages and share that information. Only FSF-assigned/GPL/FOSS software or don't care about license. Package manager should be integrated in Emacs. Support contacting author. Lots of metadata. Suggest alternatives before installing a particular package. Some discussions about the subject at hand emacs-devel 20080801 comp.emacs 20021121 RationalElispPackaging I am hoping for these kinds of answers Pointers to more implementations, discussions etc. Lengthy descriptions of a set of features that make up your ideal package manager. Descriptions of one particular disired/undisired feature. This has the advantage that the regular voting mechanism allows us to see what features are most welcomed. Feel free to elaborate on my ideas from above. Surprise me.

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• Calculating multiple column average in SQLite3

  - by Benjamin Oakes

  I need to average some values in a row-wise fashion, rather than a column-wise fashion. (If I were doing a column-wise average, I could just use avg()). My specific application of this requires me ignore NULLs in averaging. It's pretty straightforward logic, but seems awfully difficult to do in SQL. Is there an elegant way of doing my calculation? I'm using SQLite3, for what it's worth. Details If you need more details, here's an illustration: I have a a table with a survey: | q1 | q2 | q3 | ... | q144 | |----|-------|-------|-----|------| | 1 | 3 | 7 | ... | 2 | | 4 | 2 | NULL | ... | 1 | | 5 | NULL | 2 | ... | 3 | (Those are just some example values and simple column names. The valid values are 1 through 7 and NULL.) I need to calculate some averages like so: q7 + q33 + q38 + q40 + ... + q119 / 11 as domain_score_1 q10 + q11 + q34 + q35 + ... + q140 / 13 as domain_score_2 ... q2 + q5 + q13 + q25 + ... + q122 / 12 as domain_score_14 ...but i need to pull out the nulls and average based on the non-nulls. So, for domain_score_1 (which has 11 items), I would need to do: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 (3 + 5 + 7 + 2 + 3 + 1 + 5 + 1) / (11 - 3) 27 / 8 3.375 A simple algorithm I'm considering is: Input: 3, 5, NULL, 7, 2, NULL, 3, 1, 5, NULL, 1 Coalesce each value to 0 if NULL: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 Sum: 27 Get the number of non-zeros by converting values 0 to 1 and sum: 3, 5, 0, 7, 2, 0, 3, 1, 5, 0, 1 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1 8 Divide those two numbers 27 / 8 3.375 But that seems like a lot more programming than this should take. Is there an elegant way of doing this that I'm not aware of? Update: Unless I'm misunderstanding something, avg() won't work for this. Example of what I would want to do: select avg(q7, q33, q38, ..., q119) from survey; Output: SQL error near line 3: wrong number of arguments to function avg()

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• How to interpolate hue values in HSV colour space?

  - by nick

  Hi, I'm trying to interpolate between two colours in HSV colour space to produce a smooth colour gradient. I'm using a linear interpolation, eg: h = (1 - p) * h1 + p * h2 s = (1 - p) * s1 + p * s2 v = (1 - p) * v1 + p * v2 (where p is the percentage, and h1, h2, s1, s2, v1, v2 are the hue, saturation and value components of the two colours) This produces a good result for s and v but not for h. As the hue component is an angle, the calculation needs to work out the shortest distance between h1 and h2 and then do the interpolation in the right direction (either clockwise or anti-clockwise). What formula or algorithm should I use? EDIT: By following Jack's suggestions I modified my JavaScript gradient function and it works well. For anyone interested, here's what I ended up with: // create gradient from yellow to red to black with 100 steps var gradient = hsbGradient(100, [{h:0.14, s:0.5, b:1}, {h:0, s:1, b:1}, {h:0, s:1, b:0}]); function hsbGradient(steps, colours) { var parts = colours.length - 1; var gradient = new Array(steps); var gradientIndex = 0; var partSteps = Math.floor(steps / parts); var remainder = steps - (partSteps * parts); for (var col = 0; col < parts; col++) { // get colours var c1 = colours[col], c2 = colours[col + 1]; // determine clockwise and counter-clockwise distance between hues var distCCW = (c1.h >= c2.h) ? c1.h - c2.h : 1 + c1.h - c2.h; distCW = (c1.h >= c2.h) ? 1 + c2.h - c1.h : c2.h - c1.h; // ensure we get the right number of steps by adding remainder to final part if (col == parts - 1) partSteps += remainder; // make gradient for this part for (var step = 0; step < partSteps; step ++) { var p = step / partSteps; // interpolate h var h = (distCW <= distCCW) ? c1.h + (distCW * p) : c1.h - (distCCW * p); if (h < 0) h = 1 + h; if (h > 1) h = h - 1; // interpolate s, b var s = (1 - p) * c1.s + p * c2.s; var b = (1 - p) * c1.b + p * c2.b; // add to gradient array gradient[gradientIndex] = {h:h, s:s, b:b}; gradientIndex ++; } } return gradient; }

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• Android - How to scan Access Points and select strongest signal?

  - by Donal Rafferty

  I am currently trying to write a class in Android that will Scan for access points, calculate which access point has the best signal and then connect to that access point. So the application will be able to scan on the move and attach to new access points on the go. I have the scanning and calculation of the best signal working. But when it comes to attaching to the best access point I am having trouble. It appears that enableNetwork(netid, othersTrueFalse) is the only method for attaching to an Access point but this causes problems as from my Scan Results I am not able to get the id of the access point with the strongest signal. This is my code: public void doWifiScan(){ scanTask = new TimerTask() { public void run() { handler.post(new Runnable() { public void run() { sResults = wifiManager.scan(getBaseContext()); if(sResults!=null) Log.d("TIMER", "sResults count" + sResults.size()); ScanResult scan = wifiManager.calculateBestAP(sResults); wifiManager.addNewAccessPoint(scan); } }); }}; t.schedule(scanTask, 3000, 30000); } public ScanResult calculateBestAP(List<ScanResult> sResults){ ScanResult bestSignal = null; for (ScanResult result : sResults) { if (bestSignal == null || WifiManager.compareSignalLevel(bestSignal.level, result.level) < 0) bestSignal = result; } String message = String.format("%s networks found. %s is the strongest. %s is the bsid", sResults.size(), bestSignal.SSID, bestSignal.BSSID); Log.d("sResult", message); return bestSignal; } public void addNewAccessPoint(ScanResult scanResult){ WifiConfiguration wc = new WifiConfiguration(); wc.SSID = '\"' + scanResult.SSID + '\"'; //wc.preSharedKey = "\"password\""; wc.hiddenSSID = true; wc.status = WifiConfiguration.Status.ENABLED; wc.allowedGroupCiphers.set(WifiConfiguration.GroupCipher.TKIP); wc.allowedGroupCiphers.set(WifiConfiguration.GroupCipher.CCMP); wc.allowedKeyManagement.set(WifiConfiguration.KeyMgmt.WPA_PSK); wc.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.TKIP); wc.allowedPairwiseCiphers.set(WifiConfiguration.PairwiseCipher.CCMP); wc.allowedProtocols.set(WifiConfiguration.Protocol.RSN); int res = mainWifi.addNetwork(wc); Log.d("WifiPreference", "add Network returned " + res ); boolean b = mainWifi.enableNetwork(res, false); Log.d("WifiPreference", "enableNetwork returned " + b ); } When I try to use addNewAccessPoint(ScanResult scanResult) it just adds another AP to the list in the settings application with the same name as the one with the best signal, so I end up with loads of duplicates and not actually attaching to them. Can anyone point me in the direction of a better solution?

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• Load on page inside another onClick

  - by Robin I Knight

  Hello, I need to include the content, scripts, forms and dynamic abilities of one page in another onClick. Take a look at http://www.divethegap.com/scuba-diving-programmes-dive-the-gap/dahab-master-scuba-diver.html Then follow one of the links that says 'Beginner' 'Open Water Diver' etc.... You will find a PHP page with a series of options. It is an adaption of the wordpress blog system to produce only specific options for specific programmes by considering each type of each diving programme a category and then displaying only results from that category. You will see that each option is also a collapsible panel and there are also several javascripts that calculate durations, quantities and prices. There is also a validating webform at the end. Now go back to the first page. What I would like to do is include all the content from the second page after the main header inside tabbed panels on the first page so that the customers can immidietly see everything that is included. Essentially the options on the first page would become a series of tabs. The only way I can see to do this is with an iFrame as each option would need a unique URL ending (that is .php?cat=26 or .php?cat=27). THe problem is that the collapsible panels will not work with an iFrame as the iFrame will not resize when the panels open. There were also some calculation problems, but I think that was more down to me staring at the screen for the last 3 hours not remembering to include everything. I have tried it with resizing iframe SSI scripts and have got nowhere. I tried actually embedding it in the page better with a ajax script, but that left behind all the scripts that make it work. I checked with full URL's on everything and it would not take work with any scripts. I know that you could just make the whole page reload but then the user would be at the top of the page again, and even if another script was applied to slowly bring them down again it would not be anything near as easy to use as if it was like tabbed panels. Any ideas. Kind Regards,

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