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• VBoxHeadless - Running Virtual Machines With VirtualBox 3.1.x On A Headless Fedora 12 Server

  <b>Howtoforge:</b> "This guide explains how you can run virtual machines with Sun VirtualBox 3.1.x on a headless Fedora 12 server. Normally you use the VirtualBox GUI to manage your virtual machines, but a server does not have a desktop environment. Fortunately, VirtualBox comes with a tool called VBoxHeadless that allows you to connect to the virtual machines over a remote desktop connection, so there's no need for the VirtualBox GUI."

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• How to solve exception_priv _instruction exception while running destop project? [on hold]

  - by Haritha

  While running desktop project im getting exception_priv _instruction how to solve this??? while running this page is coming # # A fatal error has been detected by the Java Runtime Environment: # # EXCEPTION_PRIV_INSTRUCTION (0xc0000096) at pc=0x02f5a92b, pid=3012, tid=3104 # # JRE version: 7.0-b147 # Java VM: Java HotSpot(TM) Client VM (21.0-b17 mixed mode, sharing windows-x86 ) # Problematic frame: # C 0x02f5a92b # # Failed to write core dump. Minidumps are not enabled by default on client versions of Windows # # If you would like to submit a bug report, please visit: # http://bugreport.sun.com/bugreport/crash.jsp # The crash happened outside the Java Virtual Machine in native code. # See problematic frame for where to report the bug. # --------------- T H R E A D --------------- Current thread (0x02f5a800): JavaThread "LWJGL Application" [_thread_in_native, id=3104, stack(0x076f0000,0x07740000)] siginfo: ExceptionCode=0xc0000096 Registers: EAX=0x000df4f0, EBX=0x32afc180, ECX=0x000df4f0, EDX=0x00000020 ESP=0x0773f768, EBP=0x0773f790, ESI=0x32afc180, EDI=0x02f5a800 EIP=0x02f5a92b, EFLAGS=0x00010206 Top of Stack: (sp=0x0773f768) 0x0773f768: 02bd429c 02bd429c 0773f770 32afc180 0x0773f778: 0773f7b8 32b022c8 00000000 32afc180 0x0773f788: 00000000 0773f7a0 0773f7dc 00943187 0x0773f798: 229ec1c0 00948839 69081736 00000000 0x0773f7a8: 089b0048 00000000 00000014 00001406 0x0773f7b8: 00000002 0773f7bc 32afbeb0 0773f7f8 0x0773f7c8: 32b022c8 00000000 32afbf00 0773f7a0 0x0773f7d8: 0773f7f0 0773f81c 00943187 69081736 Instructions: (pc=0x02f5a92b) 0x02f5a90b: 00 43 00 00 00 00 f0 bc 02 e8 00 e9 22 40 f7 73 0x02f5a91b: 07 85 a5 94 00 90 f7 73 07 50 cc a0 6d d8 49 c0 0x02f5a92b: 6d 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x02f5a93b: 00 00 00 00 00 00 00 00 00 08 80 3d 37 00 00 00 Register to memory mapping: EAX=0x000df4f0 is an unknown value EBX=0x32afc180 is an oop {method} - klass: {other class} ECX=0x000df4f0 is an unknown value EDX=0x00000020 is an unknown value ESP=0x0773f768 is pointing into the stack for thread: 0x02f5a800 EBP=0x0773f790 is pointing into the stack for thread: 0x02f5a800 ESI=0x32afc180 is an oop {method} - klass: {other class} EDI=0x02f5a800 is a thread Stack: [0x076f0000,0x07740000], sp=0x0773f768, free space=317k Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code) C 0x02f5a92b j org.lwjgl.opengl.GL11.glVertexPointer(IILjava/nio/FloatBuffer;)V+48 j com.badlogic.gdx.backends.lwjgl.LwjglGL10.glVertexPointer(IIILjava/nio/Buffer;)V+53 j com.badlogic.gdx.graphics.glutils.VertexArray.bind()V+149 j com.badlogic.gdx.graphics.Mesh.bind()V+25 j com.badlogic.gdx.graphics.Mesh.render(IIIZ)V+32 j com.badlogic.gdx.graphics.Mesh.render(III)V+8 j com.badlogic.gdx.graphics.g2d.SpriteBatch.flush()V+197 j com.badlogic.gdx.graphics.g2d.SpriteBatch.switchTexture(Lcom/badlogic/gdx/graphics/Texture;)V+1 j com.badlogic.gdx.graphics.g2d.SpriteBatch.draw(Lcom/badlogic/gdx/graphics/Texture;FFFF)V+33 j sevenseas.game.WorldRenderer.drawBob()V+54 j sevenseas.game.WorldRenderer.render()V+12 j sevenseas.game.GameClass.render(F)V+38 j com.badlogic.gdx.Game.render()V+19 j com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop()V+642 j com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run()V+27 v ~StubRoutines::call_stub V [jvm.dll+0x122c7e] V [jvm.dll+0x1c9c0e] V [jvm.dll+0x122e73] V [jvm.dll+0x122ed7] V [jvm.dll+0xccd1f] V [jvm.dll+0x14433f] V [jvm.dll+0x171549] C [msvcr100.dll+0x5c6de] endthreadex+0x3a C [msvcr100.dll+0x5c788] endthreadex+0xe4 C [kernel32.dll+0xb713] GetModuleFileNameA+0x1b4 Java frames: (J=compiled Java code, j=interpreted, Vv=VM code) j org.lwjgl.opengl.GL11.nglVertexPointer(IIIJJ)V+0 j org.lwjgl.opengl.GL11.glVertexPointer(IILjava/nio/FloatBuffer;)V+48 j com.badlogic.gdx.backends.lwjgl.LwjglGL10.glVertexPointer(IIILjava/nio/Buffer;)V+53 j com.badlogic.gdx.graphics.glutils.VertexArray.bind()V+149 j com.badlogic.gdx.graphics.Mesh.bind()V+25 j com.badlogic.gdx.graphics.Mesh.render(IIIZ)V+32 j com.badlogic.gdx.graphics.Mesh.render(III)V+8 j com.badlogic.gdx.graphics.g2d.SpriteBatch.flush()V+197 j com.badlogic.gdx.graphics.g2d.SpriteBatch.switchTexture(Lcom/badlogic/gdx/graphics/Texture;)V+1 j com.badlogic.gdx.graphics.g2d.SpriteBatch.draw(Lcom/badlogic/gdx/graphics/Texture;FFFF)V+33 j sevenseas.game.WorldRenderer.drawBob()V+54 j sevenseas.game.WorldRenderer.render()V+12 j sevenseas.game.GameClass.render(F)V+38 j com.badlogic.gdx.Game.render()V+19 j com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop()V+642 j com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run()V+27 v ~StubRoutines::call_stub --------------- P R O C E S S --------------- Java Threads: ( => current thread ) 0x003d6c00 JavaThread "DestroyJavaVM" [_thread_blocked, id=3240, stack(0x008c0000,0x00910000)] =>0x02f5a800 JavaThread "LWJGL Application" [_thread_in_native, id=3104, stack(0x076f0000,0x07740000)] 0x02bcf000 JavaThread "Service Thread" daemon [_thread_blocked, id=2612, stack(0x02e00000,0x02e50000)] 0x02bc1000 JavaThread "C1 CompilerThread0" daemon [_thread_blocked, id=2776, stack(0x02db0000,0x02e00000)] 0x02bbf400 JavaThread "Attach Listener" daemon [_thread_blocked, id=2448, stack(0x02d60000,0x02db0000)] 0x02bbe000 JavaThread "Signal Dispatcher" daemon [_thread_blocked, id=1764, stack(0x02d10000,0x02d60000)] 0x02bb8000 JavaThread "Finalizer" daemon [_thread_blocked, id=3864, stack(0x02cc0000,0x02d10000)] 0x02bb3400 JavaThread "Reference Handler" daemon [_thread_blocked, id=2424, stack(0x02c70000,0x02cc0000)] Other Threads: 0x02bb1800 VMThread [stack: 0x02c20000,0x02c70000] [id=3076] 0x02bd1000 WatcherThread [stack: 0x02e50000,0x02ea0000] [id=3276] VM state:not at safepoint (normal execution) VM Mutex/Monitor currently owned by a thread: None Heap def new generation total 4928K, used 2571K [0x229c0000, 0x22f10000, 0x27f10000) eden space 4416K, 46% used [0x229c0000, 0x22bc2e38, 0x22e10000) from space 512K, 100% used [0x22e90000, 0x22f10000, 0x22f10000) to space 512K, 0% used [0x22e10000, 0x22e10000, 0x22e90000) tenured generation total 10944K, used 634K [0x27f10000, 0x289c0000, 0x329c0000) the space 10944K, 5% used [0x27f10000, 0x27faea60, 0x27faec00, 0x289c0000) compacting perm gen total 12288K, used 1655K [0x329c0000, 0x335c0000, 0x369c0000) the space 12288K, 13% used [0x329c0000, 0x32b5dc58, 0x32b5de00, 0x335c0000) ro space 10240K, 42% used [0x369c0000, 0x36dfc660, 0x36dfc800, 0x373c0000) rw space 12288K, 53% used [0x373c0000, 0x37a38180, 0x37a38200, 0x37fc0000) Code Cache [0x00940000, 0x009d8000, 0x02940000) total_blobs=305 nmethods=80 adapters=158 free_code_cache=32183Kb largest_free_block=32955904 Dynamic libraries: 0x00400000 - 0x0042f000 C:\Program Files\Java\jre7\bin\javaw.exe 0x7c900000 - 0x7c9af000 C:\WINDOWS\system32\ntdll.dll 0x7c800000 - 0x7c8f6000 C:\WINDOWS\system32\kernel32.dll 0x77dd0000 - 0x77e6b000 C:\WINDOWS\system32\ADVAPI32.dll 0x77e70000 - 0x77f02000 C:\WINDOWS\system32\RPCRT4.dll 0x77fe0000 - 0x77ff1000 C:\WINDOWS\system32\Secur32.dll 0x7e410000 - 0x7e4a1000 C:\WINDOWS\system32\USER32.dll 0x77f10000 - 0x77f59000 C:\WINDOWS\system32\GDI32.dll 0x773d0000 - 0x774d3000 C:\WINDOWS\WinSxS\x86_Microsoft.Windows.Common-Controls_6595b64144ccf1df_6.0.2600.5512_x-ww_35d4ce83\COMCTL32.dll 0x77c10000 - 0x77c68000 C:\WINDOWS\system32\msvcrt.dll 0x77f60000 - 0x77fd6000 C:\WINDOWS\system32\SHLWAPI.dll 0x76390000 - 0x763ad000 C:\WINDOWS\system32\IMM32.DLL 0x629c0000 - 0x629c9000 C:\WINDOWS\system32\LPK.DLL 0x74d90000 - 0x74dfb000 C:\WINDOWS\system32\USP10.dll 0x78aa0000 - 0x78b5e000 C:\Program Files\Java\jre7\bin\msvcr100.dll 0x6d940000 - 0x6dc61000 C:\Program Files\Java\jre7\bin\client\jvm.dll 0x71ad0000 - 0x71ad9000 C:\WINDOWS\system32\WSOCK32.dll 0x71ab0000 - 0x71ac7000 C:\WINDOWS\system32\WS2_32.dll 0x71aa0000 - 0x71aa8000 C:\WINDOWS\system32\WS2HELP.dll 0x76b40000 - 0x76b6d000 C:\WINDOWS\system32\WINMM.dll 0x76bf0000 - 0x76bfb000 C:\WINDOWS\system32\PSAPI.DLL 0x6d8d0000 - 0x6d8dc000 C:\Program Files\Java\jre7\bin\verify.dll 0x6d370000 - 0x6d390000 C:\Program Files\Java\jre7\bin\java.dll 0x6d920000 - 0x6d933000 C:\Program Files\Java\jre7\bin\zip.dll 0x6cec0000 - 0x6cf42000 C:\Documents and Settings\7stl0225\Local Settings\Temp\libgdx7stl0225\37fe1abc\gdx.dll 0x10000000 - 0x1004c000 C:\Documents and Settings\7stl0225\Local Settings\Temp\libgdx7stl0225\52d76f2b\lwjgl.dll 0x5ed00000 - 0x5edcc000 C:\WINDOWS\system32\OPENGL32.dll 0x68b20000 - 0x68b40000 C:\WINDOWS\system32\GLU32.dll 0x73760000 - 0x737ab000 C:\WINDOWS\system32\DDRAW.dll 0x73bc0000 - 0x73bc6000 C:\WINDOWS\system32\DCIMAN32.dll 0x77c00000 - 0x77c08000 C:\WINDOWS\system32\VERSION.dll 0x070b0000 - 0x07115000 C:\DOCUME~1\7stl0225\LOCALS~1\Temp\libgdx7stl0225\52d76f2b\OpenAL32.dll 0x7c9c0000 - 0x7d1d7000 C:\WINDOWS\system32\SHELL32.dll 0x774e0000 - 0x7761d000 C:\WINDOWS\system32\ole32.dll 0x5ad70000 - 0x5ada8000 C:\WINDOWS\system32\uxtheme.dll 0x76fd0000 - 0x7704f000 C:\WINDOWS\system32\CLBCATQ.DLL 0x77050000 - 0x77115000 C:\WINDOWS\system32\COMRes.dll 0x77120000 - 0x771ab000 C:\WINDOWS\system32\OLEAUT32.dll 0x73f10000 - 0x73f6c000 C:\WINDOWS\system32\dsound.dll 0x76c30000 - 0x76c5e000 C:\WINDOWS\system32\WINTRUST.dll 0x77a80000 - 0x77b15000 C:\WINDOWS\system32\CRYPT32.dll 0x77b20000 - 0x77b32000 C:\WINDOWS\system32\MSASN1.dll 0x76c90000 - 0x76cb8000 C:\WINDOWS\system32\IMAGEHLP.dll 0x72d20000 - 0x72d29000 C:\WINDOWS\system32\wdmaud.drv 0x72d10000 - 0x72d18000 C:\WINDOWS\system32\msacm32.drv 0x77be0000 - 0x77bf5000 C:\WINDOWS\system32\MSACM32.dll 0x77bd0000 - 0x77bd7000 C:\WINDOWS\system32\midimap.dll 0x73ee0000 - 0x73ee4000 C:\WINDOWS\system32\KsUser.dll 0x755c0000 - 0x755ee000 C:\WINDOWS\system32\msctfime.ime 0x69000000 - 0x691a9000 C:\WINDOWS\system32\sisgl.dll 0x73b30000 - 0x73b45000 C:\WINDOWS\system32\mscms.dll 0x73000000 - 0x73026000 C:\WINDOWS\system32\WINSPOOL.DRV 0x66e90000 - 0x66ed1000 C:\WINDOWS\system32\icm32.dll 0x07760000 - 0x0778d000 C:\Program Files\WordWeb\WHook.dll 0x74c80000 - 0x74cac000 C:\WINDOWS\system32\OLEACC.dll 0x76080000 - 0x760e5000 C:\WINDOWS\system32\MSVCP60.dll VM Arguments: jvm_args: -Dfile.encoding=Cp1252 java_command: sevenseas.game.MainDesktop Launcher Type: SUN_STANDARD Environment Variables: PATH=C:/Program Files/Java/jre7/bin/client;C:/Program Files/Java/jre7/bin;C:/Program Files/Java/jre7/lib/i386;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program Files\Java\jdk1.7.0\bin;C:\eclipse; USERNAME=7stl0225 OS=Windows_NT PROCESSOR_IDENTIFIER=x86 Family 15 Model 4 Stepping 1, GenuineIntel --------------- S Y S T E M --------------- OS: Windows XP Build 2600 Service Pack 3 CPU:total 1 (1 cores per cpu, 1 threads per core) family 15 model 4 stepping 1, cmov, cx8, fxsr, mmx, sse, sse2, sse3 Memory: 4k page, physical 2031088k(939252k free), swap 3969920k(3011396k free) vm_info: Java HotSpot(TM) Client VM (21.0-b17) for windows-x86 JRE (1.7.0-b147), built on Jun 27 2011 02:25:52 by "java_re" with unknown MS VC++:1600 time: Sat Oct 26 12:35:14 2013 elapsed time: 0 seconds

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• Postgres 8.4 stackbuilder not run in Ubuntu12.04

  - by vikas

  I have installed Postgres 8.4 in my Ubuntu 12.04 , but after installation it does not run stackbuilder.It also not running from menu bar . How can i run stackbuilder ? edit:I install this from postgres-8.4.run package.It uses a GUI interface.After installing postgres it should run stackbuilder but it not run stackbuilder GUI. This prob is related to ubuntu 12.04 because in 11.04, I have used this application.This question also asked on other forms but there is no solution. Thank you.

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• Why you need to learn async in .NET

  - by PSteele

  I had an opportunity to teach a quick class yesterday about what’s new in .NET 4.0.  One of the topics was the TPL (Task Parallel Library) and how it can make async programming easier.  I also stressed that this is the direction Microsoft is going with for C# 5.0 and learning the TPL will greatly benefit their understanding of the new async stuff.  We had a little time left over and I was able to show some code that uses the Async CTP to accomplish some stuff, but it wasn’t a simple demo that you could jump in to and understand so I thought I’d thrown one together and put it in a blog post. The entire solution file with all of the sample projects is located here. A Simple Example Let’s start with a super-simple example (WindowsApplication01 in the solution). I’ve got a form that displays a label and a button.  When the user clicks the button, I want to start displaying the current time for 15 seconds and then stop. What I’d like to write is this: lblTime.ForeColor = Color.Red; for (var x = 0; x < 15; x++) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); Thread.Sleep(1000); } lblTime.ForeColor = SystemColors.ControlText; (Note that I also changed the label’s color while counting – not quite an ILM-level effect, but it adds something to the demo!) As I’m sure most of my readers are aware, you can’t write WinForms code this way.  WinForms apps, by default, only have one thread running and it’s main job is to process messages from the windows message pump (for a more thorough explanation, see my Visual Studio Magazine article on multithreading in WinForms).  If you put a Thread.Sleep in the middle of that code, your UI will be locked up and unresponsive for those 15 seconds.  Not a good UX and something that needs to be fixed.  Sure, I could throw an “Application.DoEvents()” in there, but that’s hacky. The Windows Timer Then I think, “I can solve that.  I’ll use the Windows Timer to handle the timing in the background and simply notify me when the time has changed”.  Let’s see how I could accomplish this with a Windows timer (WindowsApplication02 in the solution): public partial class Form1 : Form { private readonly Timer clockTimer; private int counter;   public Form1() { InitializeComponent(); clockTimer = new Timer {Interval = 1000}; clockTimer.Tick += UpdateLabel; }   private void UpdateLabel(object sender, EventArgs e) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); counter++; if (counter == 15) { clockTimer.Enabled = false; lblTime.ForeColor = SystemColors.ControlText; } }   private void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; counter = 0; clockTimer.Start(); } } Holy cow – things got pretty complicated here.  I use the timer to fire off a Tick event every second.  Inside there, I can update the label.  Granted, I can’t use a simple for/loop and have to maintain a global counter for the number of iterations.  And my “end” code (when the loop is finished) is now buried inside the bottom of the Tick event (inside an “if” statement).  I do, however, get a responsive application that doesn’t hang or stop repainting while the 15 seconds are ticking away. But doesn’t .NET have something that makes background processing easier? The BackgroundWorker Next I try .NET’s BackgroundWorker component – it’s specifically designed to do processing in a background thread (leaving the UI thread free to process the windows message pump) and allows updates to be performed on the main UI thread (WindowsApplication03 in the solution): public partial class Form1 : Form { private readonly BackgroundWorker worker;   public Form1() { InitializeComponent(); worker = new BackgroundWorker {WorkerReportsProgress = true}; worker.DoWork += StartUpdating; worker.ProgressChanged += UpdateLabel; worker.RunWorkerCompleted += ResetLabelColor; }   private void StartUpdating(object sender, DoWorkEventArgs e) { var workerObject = (BackgroundWorker) sender; for (int x = 0; x < 15; x++) { workerObject.ReportProgress(0); Thread.Sleep(1000); } }   private void UpdateLabel(object sender, ProgressChangedEventArgs e) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); }   private void ResetLabelColor(object sender, RunWorkerCompletedEventArgs e) { lblTime.ForeColor = SystemColors.ControlText; }   private void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; worker.RunWorkerAsync(); } } Well, this got a little better (I think).  At least I now have my simple for/next loop back.  Unfortunately, I’m still dealing with event handlers spread throughout my code to co-ordinate all of this stuff in the right order. Time to look into the future. The async way Using the Async CTP, I can go back to much simpler code (WindowsApplication04 in the solution): private async void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; for (var x = 0; x < 15; x++) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); await TaskEx.Delay(1000); } lblTime.ForeColor = SystemColors.ControlText; } This code will run just like the Timer or BackgroundWorker versions – fully responsive during the updates – yet is way easier to implement.  In fact, it’s almost a line-for-line copy of the original version of this code.  All of the async plumbing is handled by the compiler and the framework.  My code goes back to representing the “what” of what I want to do, not the “how”. I urge you to download the Async CTP.  All you need is .NET 4.0 and Visual Studio 2010 sp1 – no need to set up a virtual machine with the VS2011 beta (unless, of course, you want to dive right in to the C# 5.0 stuff!).  Starting playing around with this today and see how much easier it will be in the future to write async-enabled applications.

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• What happened to PolicyKit?

  - by Jo-Erlend Schinstad

  Back in 8.04 or so, when PolicyKit was new, we had a GUI "browser" that enabled us to easily decide things like whether a user should be allowed to shutdown the system when other users were logged in and if it should always be allowed or only while on the console, etc. Then those things suddenly disappeared and though it seems PolicyKit is still in use, I haven't been able to find any similar GUI to actually configure the policies. What happened?

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• Minimizing Dependencies For GUIs

  - by tuba09

  I've been working on a project, and have been charged with designing the projects GUI front-end. I'm coding in Java and using the Swing toolkit. Usability-wise, the GUI front-end follows all of Nielsen's heuristics. Users can easily get to where they want to go through the click of a button / JComboBox. Essentially, in Swing terms, what happens is their actions drive the creation/deletion of custom panels. The GUI is coming along fine for the most part. However, I have to admit to being utterly dismayed at the tight web of dependencies my code is being smothered in. The main problem that I've encountered, that I haven't been able to fix as of yet, is how to keep a reference to the panels/buttons being changed. I'll give an example: Say there's a button A Say there's a panel B displaying picture C Say there's another picture D (not currently being displayed by panel B) When user clicks A, panel B should remove picture C and display picture D My question is, what's the best way of keeping track of panel B? Since I need a global point of access to panel B, my solution has so far been to just shoehorn it into a static variable, and access it through a series of static getters and setters. And this static variable is usually stored in the reference's original class. I.e. UserPanel has a static variable that stores a reference to itself. Is there an easy, tried-and-true way of dealing with these kinds of situations? Like my GUI works fine, but it is not modular and/or robust at all. To add to this, the dreaded 'cyclical dependencies' issue that's shunned by so many programmers is out here in full effect. I'm fairly new to development and just want to make sure that my code will be fairly extensible and won't cause much of a headache to the next person that decides to get a try at it. I know there's loads of books out there that probably have a nice elegant solution to this, but unfortunately I just don't have the time to leisure read right now. I need something that's quick and dirty. Thanks in advance

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• C# Dev - I've tried Lisps, but I don't get it.

  - by Jonathan Mitchem

  After a few months of learning about and playing with lisps, both CL and a bit of Clojure, I'm still not seeing a compelling reason to write anything in it instead of C#. I would really like some compelling reasons, or for someone to point out that I'm missing something really big. The strengths of a Lisp (per my research): Compact, expressive notation - More so than C#, yes... but I seem to be able to express those ideas in C# too. Implicit support for functional programming - C# with LINQ extension methods: mapcar = .Select( lambda ) mapcan = .Select( lambda ).Aggregate( (a,b) = a.Union(b) ) car/first = .First() cdr/rest = .Skip(1) .... etc. Lambda and higher-order function support - C# has this, and the syntax is arguably simpler: "(lambda (x) ( body ))" versus "x = ( body )" "#(" with "%", "%1", "%2" is nice in Clojure Method dispatch separated from the objects - C# has this through extension methods Multimethod dispatch - C# does not have this natively, but I could implement it as a function call in a few hours Code is Data (and Macros) - Maybe I haven't "gotten" macros, but I haven't seen a single example where the idea of a macro couldn't be implemented as a function; it doesn't change the "language", but I'm not sure that's a strength DSLs - Can only do it through function composition... but it works Untyped "exploratory" programming - for structs/classes, C#'s autoproperties and "object" work quite well, and you can easily escalate into stronger typing as you go along Runs on non-Windows hardware - Yeah, so? Outside of college, I've only known one person who doesn't run Windows at home, or at least a VM of Windows on *nix/Mac. (Then again, maybe this is more important than I thought and I've just been brainwashed...) The REPL for bottom-up design - Ok, I admit this is really really nice, and I miss it in C#. Things I'm missing in a Lisp (due to a mix of C#, .NET, Visual Studio, Resharper): Namespaces. Even with static methods, I like to tie them to a "class" to categorize their context (Clojure seems to have this, CL doesn't seem to.) Great compile and design-time support the type system allows me to determine "correctness" of the datastructures I pass around anything misspelled is underlined realtime; I don't have to wait until runtime to know code improvements (such as using an FP approach instead of an imperative one) are autosuggested GUI development tools: WinForms and WPF (I know Clojure has access to the Java GUI libraries, but they're entirely foreign to me.) GUI Debugging tools: breakpoints, step-in, step-over, value inspectors (text, xml, custom), watches, debug-by-thread, conditional breakpoints, call-stack window with the ability to jump to the code at any level in the stack (To be fair, my stint with Emacs+Slime seemed to provide some of this, but I'm partial to the VS GUI-driven approach) I really like the hype surrounding Lisps and I gave it a chance. But is there anything I can do in a Lisp that I can't do as well in C#? It might be a bit more verbose in C#, but I also have autocomplete. What am I missing? Why should I use Clojure/CL?

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• WebLogic Server??????????

  - by Masa.Sasaki

  ???2?9??54?????! ?????????????8?WebLogic Server???@???????????WebLogic Server?3?????????????????????????????????????WebLogic Server???????????! WebLogic Server?MBean???????????2?????? ???????????????????????????????????????????????????????????????????????????????WebLogic Server?JRockit??????????????????????????????JRockit???????????&??????????????????????????WebLogic Server????????????????????????????????????????????????????????????????? ??????????????????????????????? ?????JMX MBean??????????GUI??????????????????????WLST (WebLogic Scripting Tool)????????Jython??????????????????????????MBean????????GUI???????????????????????????????????WebLogic Server???????????????????????????????????????????????????? ???????????2?16?(?)???6?:30?????14? WebLogic Server???@????????????????????????????????????????????(??????????)?

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• VB alternative/equivalent for development of Windows apps in Ubuntu

  - by Nirmik

  I want to develop a simple form for an Invoice for the user to use on Windows. I learnt how to do it using Visual basic in Windows. It's the simplest way to make a GUI for Windows I suppose. I am going to link it to a database at the backend. I want an alternative or equivalent software that will provide me with similar drag-and-drop feature enabled programing and GUI designing that will help me crate an application that will run on Windows.

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• change texture at runtime

  - by user1509674

  How can I change the texture at runtime. I have done changing the label(text) at runtime. The following code is used using UnityEngine; using System.Collections; public class switchtime : MonoBehaviour { // Use this for initialization private bool showLabel = false; private bool showLabe2 = false; private bool showLabe3 = false; private bool showLabe4 = false; public void Start() { Invoke("ToggleLabel", 1); Invoke("ToggleLabel2", 3); Invoke("ToggleLabel3",6 ); Invoke("ToggleLabel4", 9); } public void ToggleLabel() { showLabel = !showLabel; } public void ToggleLabel2() { showLabe2 = !showLabe2; } public void ToggleLabel3() { showLabe3 = !showLabe3; } public void ToggleLabel4() { showLabe4 = !showLabe4; } public void OnGUI() { if (showLabel) { GUI.Label(new Rect(300, 200, 100, 20), "Copying window file.."); } if (showLabe2) { GUI.Label(new Rect(40, 40, 100, 20), "Epanding windows file.."); } if (showLabe3) { GUI.Label(new Rect(80, 80, 100, 20), "Installing Feature.."); } if (showLabe4) { GUI.Label(new Rect(100, 100, 100, 20), "Installing Updates"); } } } Now I need to change the GUITexture at runtime. How can do this? Can anybody help me in coding? Here is some changes I made. I worked on changing the gameObject when mouse is placed on it. This is the code I applied and its working for me using UnityEngine; using System.Collections; public class change : MonoBehaviour { // Use this for initialization public GameObject newSprite; private Vector3 currentSpritePosition; void update() { } void Start() { newSprite.renderer.enabled = false; currentSpritePosition = transform.position; //then make it invisible renderer.enabled = false; //give the new sprite the position of the latter newSprite.transform.position = currentSpritePosition; //then make it visible newSprite.renderer.enabled = true; } void OnMouseExit(){ //just the reverse process renderer.enabled = true; newSprite.renderer.enabled = false; } } Now the problem is that, in same code I need to set a time so that the text get loaded without the mouse click. I mean a particular time to load each text one after the another. Here is my screen shot Here I have placed the image one below the another,when the mouse is hovered on it it will change the text from bold to normal text.Changes process stated in (image 2,3).That code I posted is working for me.

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• ????????SQL Developer?Data Modeler?????????????

  - by Yusuke.Yamamoto

  ????? ??:2010/05/18 ??:?????? Oracle ?GUI?????????···??????????????????SQL Developer ? Data Modeler ???????GUI???????????????????????????SQL Developer ? Data Modeler ?????????????????? ????Oracle SQL Developer Data Modeler ??Oracle SQL Developer Data Modeler ????Oracle SQL Developer ???Oracle SQL Developer ???????? ????????? ????????????????? http://www.oracle.com/technology/global/jp/ondemand/otn-seminar/pdf/100518_sqldeveloper_evening.pdf

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• ??????????Oracle???????????????????????·????! |WebLogic Channel|??????

  - by ???02

  ?? ???????·??·?????????????????????????????????????????????????????????????????????????????????????????????????!?????????????????????·????????????????!???????????!????????????????????????????? ????????????????????GUI??? Oracle Enterprise Manager Grid Control??????????????·???????GUI????JRockit Flight Recorder??????????????2??????????WebLogic Server ? Oracle Database ???????????????????????????????????????????????????¦Database?Application Server??????¦????????????????????¦???????????????????????¦?????????·????????¦Oracle Enterprise Manager Grid Control????????????¦JRockit Flight Recorder????????????????????????????????????????????2???????????????????????http://www.oracle.com/technetwork/jp/ondemand/application-grid/id-000954-404639-ja.pdf<wmv> http://otndnld.oracle.co.jp/ondemand/otn-seminar/movie/id_000948.wmv<mp4> http://otndnld.oracle.co.jp/ondemand/otn-seminar/movie/mp4/id_000948.mp4

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• Getting problem in collision detection in Java Game

  - by chetans

  Hi I am developing Spaceship Game in which i am getting problem in collision detection of moving images Game has a spaceship and number of asteroids(obstacles) i want to detect the collision between them How can i do this?`package Game; import java.applet.Applet; import java.awt.Color; import java.awt.Dimension; import java.awt.Graphics; import java.awt.Image; import java.awt.MediaTracker; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.net.MalformedURLException; import java.net.URL; public class ThreadInApplet extends Applet implements KeyListener { private static final long serialVersionUID = 1L; Image[] asteroidImage; Image spaceshipImage; int[] XPosObst,YPosObst; int numberOfObstacles=0,XPosOfSpaceship,YPosOfSpaceship; int spaceButtnCntr=0,noOfObstaclesLevel=20; boolean gameStart=false,collideUp=false,collideDown=false,collideLeft=false,collideRight=false; private Image offScreenImage; private Dimension offScreenSize,d; private Graphics offScreenGraphics; int speedObstacles=1; String spaceshipImagePath="images/spaceship.png",obstacleImagepath="images/asteroid.png"; String buttonToStart="Press Space to start"; public void init() { try { asteroidImage=new Image[noOfObstaclesLevel]; XPosObst=new int[noOfObstaclesLevel]; YPosObst=new int[noOfObstaclesLevel]; XPosOfSpaceship=getWidth()/2-35; YPosOfSpaceship=getHeight()-100; spaceshipImage=getImage(new URL(getCodeBase(),spaceshipImagePath)); for(int i=0;i<noOfObstaclesLevel;i++) { asteroidImage[i]=getImage(new URL(getCodeBase(),obstacleImagepath)); XPosObst[i]=(int) (Math.random()*700); YPosObst[i]=0; } MediaTracker tracker = new MediaTracker (this); for(int i=0;i<noOfObstaclesLevel;i++) { tracker.addImage (asteroidImage[i], 0); } } catch (MalformedURLException e) { e.printStackTrace(); } setBackground(Color.black); addKeyListener(this); } public void paint(Graphics g) { g.setColor(Color.white); if(gameStart==false) { g.drawString(buttonToStart, (getWidth()/2)-60, getHeight()/2); } g.drawString("HEADfitted Solutions Pvt.Ltd.", (getWidth()/2)-80, getHeight()-20); for(int n=0;n<numberOfObstacles;n++) { if(n>0) g.drawImage(asteroidImage[n],XPosObst[n],YPosObst[n],this); } g.drawImage(spaceshipImage,XPosOfSpaceship,YPosOfSpaceship,this); } @SuppressWarnings("deprecation") public void update(Graphics g) { d = size(); if((offScreenImage == null) || (d.width != offScreenSize.width) || (d.height != offScreenSize.height)) { offScreenImage = createImage(d.width, d.height); offScreenSize = d; offScreenGraphics = offScreenImage.getGraphics(); } offScreenGraphics.clearRect(0, 0, d.width, d.height); paint(offScreenGraphics); g.drawImage(offScreenImage, 0, 0, null); } public void keyReleased(KeyEvent arg0){} public void keyTyped(KeyEvent arg0) {} Thread mainThread=new Thread() { synchronized public void run () { try { //System.out.println("in main thread"); if (gameStart==true) { moveObstacles.start(); if(collide()==false) { createObsThread.start(); } } } catch (Exception e) { e.printStackTrace(); } } }; Thread createObsThread=new Thread() { synchronized public void run () { if (spaceButtnCntr==1) { if (collide()==false) { for(int g=0;g<noOfObstaclesLevel;g++) { try { sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } numberOfObstacles++; } } } } }; Thread moveObstacles=new Thread() // Moving Obstacle images downwards after every 10 ms { synchronized public void run () { while(YPosObst[19]!=600) { if (collide()==false) { //createObsThread.start(); for(int l=0;l } repaint(); try { sleep(10); } catch (InterruptedException e) { e.printStackTrace(); } } } } }; public void keyPressed(KeyEvent e) { if(e.getKeyCode()==32) { gameStart=true; spaceButtnCntr++; if (spaceButtnCntr==1) { mainThread.start(); } } if(gameStart==true) { if(e.getKeyCode()==37 && collideLeft==false)//Spaceship movement left { new Thread () { synchronized public void run () { XPosOfSpaceship-=10; repaint(); } }.start(); } if(e.getKeyCode()==38 && collideUp==false)//Spaceship movement up { new Thread () { synchronized public void run () { YPosOfSpaceship-=10; repaint(); } }.start(); } if(e.getKeyCode()==39 && collideRight==false)//Spaceship movement right { new Thread () { synchronized public void run () { XPosOfSpaceship+=10; repaint(); } }.start(); } if(e.getKeyCode()==40 && collideDown==false)//Spaceship movement down { new Thread () { synchronized public void run () { YPosOfSpaceship+=10; repaint(); } }.start(); } } } /*public boolean collide() { int x0, y0, w0, h0, x2, y2, w2, h2; x0=XPosOfSpaceship; y0=YPosOfSpaceship; h0=spaceshipImage.getHeight(null); w0=spaceshipImage.getWidth(null); for(int i=0;i<20;i++) { x2=XPosObst[i]; y2=YPosObst[i]; h2=asteroidImage[i].getHeight(null); w2=asteroidImage[i].getWidth(null); if ((x0 > (x2 + w2)) || ((x0 + w0) < x2)) return false; System.out.println(x2+" "+y2+" "+h2+" "+w2); if ((y0 > (y2 + h2)) || ((y0 + h0) < y2)) return false; } return true; }*/ public boolean collide() { int x1,y1,x2,y2,x3,y3,x4,y4; //coordinates of obstacles int a1,b1,a2,b2,a3,b3,a4,b4; //coordinates of spaceship a1 =XPosOfSpaceship; b1=YPosOfSpaceship; a2=a1+spaceshipImage.getWidth(this); b2=b1; a3=a1; b3=b1+spaceshipImage.getHeight(this); a4=a2; b4=b3; for(int a=0;a if(x1>=a1 && x1<=a2 && x1<=b3 && x1>=b1) return (true); if(x2>=a1 && x2<=a2 && x2<=b3 && x2>=b1) return(true); //********checking asteroid touch spaceship from up direction******** if(y3==b1 && x4>=a1 && x4<=a2) { collideUp = true; return(true); } if(y3==b1 && x3>=a1 && x3<=a2) { collideUp = true; return(true); } //********checking asteroid touch spaceship from left direction****** if(x2==a1 && y4>=b1 && y4<=b3) { collideLeft=true; return(true); } if(x2==a1 && y2>=b1 && y2<=b3) { collideLeft=true; return(true); } //********checking asteroid touch spaceship from right direction***** if(x1==a2 && y3>=b2 && y3<=b4) { collideRight=true; return(true); } if(x1==a2 && y1>=b2 && y1<=b4) { collideRight=true; return(true); } //********checking asteroid touch spaceship from down direction***** if(y1==b3 && x2>=a3 && x2<=a4) { collideDown=true; return(true); } if(y1==b3 && x1>=a3 && x1<=a4) { collideDown=true; return(true); } else { collideUp=false; collideDown=false; collideLeft=false; collideRight=false; } } return(false); } } `

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• ASP.NET WebAPI Security 2: Identity Architecture

  - by Your DisplayName here!

  Pedro has beaten me to the punch with a detailed post (and diagram) about the WebAPI hosting architecture. So go read his post first, then come back so we can have a closer look at what that means for security. The first important takeaway is that WebAPI is hosting independent-  currently it ships with two host integration implementations – one for ASP.NET (aka web host) and WCF (aka self host). Pedro nicely shows the integration into the web host. Self hosting is not done yet so we will mainly focus on the web hosting case and I will point out security related differences when they exist. The interesting part for security (amongst other things of course) is the HttpControllerHandler (see Pedro’s diagram) – this is where the host specific representation of an HTTP request gets converted to the WebAPI abstraction (called HttpRequestMessage). The ConvertRequest method does the following: Create a new HttpRequestMessage. Copy URI, method and headers from the HttpContext. Copies HttpContext.User to the Properties<string, object> dictionary on the HttpRequestMessage. The key used for that can be found on HttpPropertyKeys.UserPrincipalKey (which resolves to “MS_UserPrincipal”). So the consequence is that WebAPI receives whatever IPrincipal has been set by the ASP.NET pipeline (in the web hosting case). Common questions are: Are there situations where is property does not get set? Not in ASP.NET – the DefaultAuthenticationModule in the HTTP pipeline makes sure HttpContext.User (and Thread.CurrentPrincipal – more on that later) are always set. Either to some authenticated user – or to an anonymous principal. This may be different in other hosting environments (again more on that later). Why so generic? Keep in mind that WebAPI is hosting independent and may run on a host that materializes identity completely different compared to ASP.NET (or .NET in general). This gives them a way to evolve the system in the future. How does WebAPI code retrieve the current client identity? HttpRequestMessage has an extension method called GetUserPrincipal() which returns the property as an IPrincipal. A quick look at self hosting shows that the moral equivalent of HttpControllerHandler.ConvertRequest() is HttpSelfHostServer.ProcessRequestContext(). Here the principal property gets only set when the host is configured for Windows authentication (inconsisteny). Do I like that? Well – yes and no. Here are my thoughts: I like that it is very straightforward to let WebAPI inherit the client identity context of the host. This might not always be what you want – think of an ASP.NET app that consists of UI and APIs – the UI might use Forms authentication, the APIs token based authentication. So it would be good if the two parts would live in a separate security world. It makes total sense to have this generic hand off point for identity between the host and WebAPI. It also makes total sense for WebAPI plumbing code (especially handlers) to use the WebAPI specific identity abstraction. But – c’mon we are running on .NET. And the way .NET represents identity is via IPrincipal/IIdentity. That’s what every .NET developer on this planet is used to. So I would like to see a User property of type IPrincipal on ApiController. I don’t like the fact that Thread.CurrentPrincipal is not populated. T.CP is a well established pattern as a one stop shop to retrieve client identity on .NET.  That makes a lot of sense – even if the name is misleading at best. There might be existing library code you want to call from WebAPI that makes use of T.CP (e.g. PrincipalPermission, or a simple .Name or .IsInRole()). Having the client identity as an ambient property is useful for code that does not have access to the current HTTP request (for calling GetUserPrincipal()). I don’t like the fact that that the client identity conversion from host to WebAPI is inconsistent. This makes writing security plumbing code harder. I think the logic should always be: If the host has a client identity representation, copy it. If not, set an anonymous principal on the request message. Btw – please don’t annoy me with the “but T.CP is static, and static is bad for testing” chant. T.CP is a getter/setter and, in fact I find it beneficial to be able to set different security contexts in unit tests before calling in some logic. And, in case you have wondered – T.CP is indeed thread static (and the name comes from a time where a logical operation was bound to a thread – which is not true anymore). But all thread creation APIs in .NET actually copy T.CP to the new thread they create. This is the case since .NET 2.0 and is certainly an improvement compared to how Win32 does things. So to sum it up: The host plumbing copies the host client identity to WebAPI (this is not perfect yet, but will surely be improved). or in other words: The current WebAPI bits don’t ship with any authentication plumbing, but solely use whatever authentication (and thus client identity) is set up by the host. WebAPI developers can retrieve the client identity from the HttpRequestMessage. Hopefully my proposed changes around T.CP and the User property on ApiController will be added. In the next post, I will detail how to add WebAPI specific authentication support, e.g. for Basic Authentication and tokens. This includes integrating the notion of claims based identity. After that we will look at the built-in authorization bits and how to improve them as well. Stay tuned.

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• Code Trivia #6

  - by João Angelo

  It’s time for yet another code trivia and it’s business as usual. What will the following program output to the console? using System; using System.Drawing; using System.Threading; class Program { [ThreadStatic] static Point Mark = new Point(1, 1); static void Main() { Thread.CurrentThread.Name = "A"; MoveMarkUp(); var helperThread = new Thread(MoveMarkUp) { Name = "B" }; helperThread.Start(); helperThread.Join(); } static void MoveMarkUp() { Mark.Y++; Console.WriteLine("{0}:{1}", Thread.CurrentThread.Name, Mark); } }

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• PTLQueue : a scalable bounded-capacity MPMC queue

  - by Dave

  Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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• A Method for Reducing Contention and Overhead in Worker Queues for Multithreaded Java Applications

  - by Janice J. Heiss

  A java.net article, rich in practical resources, by IBM India Labs’ Sathiskumar Palaniappan, Kavitha Varadarajan, and Jayashree Viswanathan, explores the challenge of writing code in a way that that effectively makes use of the resources of modern multicore processors and multiprocessor servers.As the article states: “Many server applications, such as Web servers, application servers, database servers, file servers, and mail servers, maintain worker queues and thread pools to handle large numbers of short tasks that arrive from remote sources. In general, a ‘worker queue’ holds all the short tasks that need to be executed, and the threads in the thread pool retrieve the tasks from the worker queue and complete the tasks. Since multiple threads act on the worker queue, adding tasks to and deleting tasks from the worker queue needs to be synchronized, which introduces contention in the worker queue.” The article goes on to explain ways that developers can reduce contention by maintaining one queue per thread. It also demonstrates a work-stealing technique that helps in effectively utilizing the CPU in multicore systems. Read the rest of the article here.

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• Error java.lang.OutOfMemoryError: getNewTla using Oracle EPM products

  - by Marc Schumacher

  Running into a Java out of memory error, it is very common behaviour in the field that the Java heap size will be increased. While this might help to solve a heap space out of memory error, it might not help to fix an out of memory error for the Thread Local Area (TLA). Increasing the available heap space from 1 GB to 16 GB might not even help in this situation. The Thread Local Area (TLA) is part of the Java heap, but as the name already indicates, this memory area is local to a specific thread so there is no need to synchronize with other threads using this memory area. For optimization purposes the TLA size is configurable using the Java command line option “-XXtlasize”. Depending on the JRockit version and the available Java heap, the default values vary. Using Oracle EPM System (mainly 11.1.2.x) the following setting was tested successfully: -XXtlasize:min=8k,preferred=128k More information about the “-XXtlasize” parameter can be found in the JRockit documentation: http://docs.oracle.com/cd/E13150_01/jrockit_jvm/jrockit/jrdocs/refman/optionXX.html

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• How To Get Web Site Thumbnail Image In ASP.NET

  - by SAMIR BHOGAYTA

  Overview One very common requirement of many web applications is to display a thumbnail image of a web site. A typical example is to provide a link to a dynamic website displaying its current thumbnail image, or displaying images of websites with their links as a result of search (I love to see it on Google). Microsoft .NET Framework 2.0 makes it quite easier to do it in a ASP.NET application. Background In order to generate image of a web page, first we need to load the web page to get their html code, and then this html needs to be rendered in a web browser. After that, a screen shot can be taken easily. I think there is no easier way to do this. Before .NET framework 2.0 it was quite difficult to use a web browser in C# or VB.NET because we either have to use COM+ interoperability or third party controls which becomes headache later. WebBrowser control in .NET framework 2.0 In .NET framework 2.0 we have a new Windows Forms WebBrowser control which is a wrapper around old shwdoc.dll. All you really need to do is to drop a WebBrowser control from your Toolbox on your form in .NET framework 2.0. If you have not used WebBrowser control yet, it's quite easy to use and very consistent with other Windows Forms controls. Some important methods of WebBrowser control are. public bool GoBack(); public bool GoForward(); public void GoHome(); public void GoSearch(); public void Navigate(Uri url); public void DrawToBitmap(Bitmap bitmap, Rectangle targetBounds); These methods are self explanatory with their names like Navigate function which redirects browser to provided URL. It also has a number of useful overloads. The DrawToBitmap (inherited from Control) draws the current image of WebBrowser to the provided bitmap. Using WebBrowser control in ASP.NET 2.0 The Solution Let's start to implement the solution which we discussed above. First we will define a static method to get the web site thumbnail image. public static Bitmap GetWebSiteThumbnail(string Url, int BrowserWidth, int BrowserHeight, int ThumbnailWidth, int ThumbnailHeight) { WebsiteThumbnailImage thumbnailGenerator = new WebsiteThumbnailImage(Url, BrowserWidth, BrowserHeight, ThumbnailWidth, ThumbnailHeight); return thumbnailGenerator.GenerateWebSiteThumbnailImage(); } The WebsiteThumbnailImage class will have a public method named GenerateWebSiteThumbnailImage which will generate the website thumbnail image in a separate STA thread and wait for the thread to exit. In this case, I decided to Join method of Thread class to block the initial calling thread until the bitmap is actually available, and then return the generated web site thumbnail. public Bitmap GenerateWebSiteThumbnailImage() { Thread m_thread = new Thread(new ThreadStart(_GenerateWebSiteThumbnailImage)); m_thread.SetApartmentState(ApartmentState.STA); m_thread.Start(); m_thread.Join(); return m_Bitmap; } The _GenerateWebSiteThumbnailImage will create a WebBrowser control object and navigate to the provided Url. We also register for the DocumentCompleted event of the web browser control to take screen shot of the web page. To pass the flow to the other controls we need to perform a method call to Application.DoEvents(); and wait for the completion of the navigation until the browser state changes to Complete in a loop. private void _GenerateWebSiteThumbnailImage() { WebBrowser m_WebBrowser = new WebBrowser(); m_WebBrowser.ScrollBarsEnabled = false; m_WebBrowser.Navigate(m_Url); m_WebBrowser.DocumentCompleted += new WebBrowserDocument CompletedEventHandler(WebBrowser_DocumentCompleted); while (m_WebBrowser.ReadyState != WebBrowserReadyState.Complete) Application.DoEvents(); m_WebBrowser.Dispose(); } The DocumentCompleted event will be fired when the navigation is completed and the browser is ready for screen shot. We will get screen shot using DrawToBitmap method as described previously which will return the bitmap of the web browser. Then the thumbnail image is generated using GetThumbnailImage method of Bitmap class passing it the required thumbnail image width and height. private void WebBrowser_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { WebBrowser m_WebBrowser = (WebBrowser)sender; m_WebBrowser.ClientSize = new Size(this.m_BrowserWidth, this.m_BrowserHeight); m_WebBrowser.ScrollBarsEnabled = false; m_Bitmap = new Bitmap(m_WebBrowser.Bounds.Width, m_WebBrowser.Bounds.Height); m_WebBrowser.BringToFront(); m_WebBrowser.DrawToBitmap(m_Bitmap, m_WebBrowser.Bounds); m_Bitmap = (Bitmap)m_Bitmap.GetThumbnailImage(m_ThumbnailWidth, m_ThumbnailHeight, null, IntPtr.Zero); } One more example here : http://www.codeproject.com/KB/aspnet/Website_URL_Screenshot.aspx

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• Actor based concurrency and cancellation

  - by Akash

  I'm reading about actor based concurrency and I appreciate the simplicity of actors sequentially processing messages on a single thread. However there is one scenario that doesn't seen possible. Suppose that actor A sends a message to actor B, who then performs some long running task and returns a completion message to actor A. How can actor A force actor B to cancel the long running task after it has started? If actor B is running the task in its message queue thread, it won't pick up the cancellation message until it had completed the task; if actor B runs the task in a background thread then it seems to be violating the principle of actors. Is there a common way that this scenario is handled with actors? Or does each actor language/framework take a different approach? Or is this not a suitable problem to tackle via actors?

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• Rewrite Generic URLs into real URLs on Google Analytics

  - by valdroni

  I have an iPhone app for a forum which also has a limited Google Analytics reporting. This app reports the page views in following generic form: /forum/67 /thread/29036 etc... The numbers above represent forum and thread ID's I am trying to set an Advanced filter, which will rewrite/report the page views in Google Analytics in following form: http://www.mysite.com/forum-67.html http://www.mysite.com/thread-29036.html Can someone please assist me in creating an Advanced Google Analytics filter which will enable me to see URL's so they can be live and send to correct page. Is there another method to achieve what I'm looking for ? Obviously there will be a need for some RegExp matches, but I cannot get around it.

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• One True Event Loop

  - by CyberShadow

  Simple programs that collect data from only one system need only one event loop. For example, Windows applications have the message loop, POSIX network programs usually have a select/epoll/etc. loop at their core, pure SDL games use SDL's event loop. But what if you need to collect events from several subsystems? Such as an SDL game which doesn't use SDL_net for networking. I can think of several solutions: Polling (ugh) Put each event loop in its own thread, and: Send messages to the main thread, which collects and processes the events, or Place the event-processing code of each thread in a critical section, so that the threads can wait for events asynchronously but process them synchronously Choose one subsystem for the main event loop, and pass events from other subsystems via that subsystem as custom messages (for example, the Windows message loop and custom messages, or a socket select() loop and passing events via a loopback connection). Option 2.1 is more interesting on platforms where message-passing is a well-developed threading primitive (e.g. in the D programming language), but 2.2 looks like the best option to me.

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• What is So Unique About Node.js?

  - by Adrian Shum

  Recently there has been a lot of praise for Node.js. I am not a developer that has had much exposure to network application. From my bare understanding of Nodes.js, its strength is: we have only one thread handling multiple connections, providing an event-based architecture. However, for example in Java, I can create only one thread using NIO/AIO (which is non-blocking APIs from my bare understanding), and handle multiple connections using that thread, and I provide an event-based architecture to implement the data handling logic (shouldn't be that difficult by providing some callback etc) ? Given JVM being a even more mature VM than V8 (I expect it to run faster too), and event-based handling architecture seems to be something not difficult to create, I am not sure why Node.js is attracting so much attention. Did I miss some important points?

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• Why Nodes.js being that "unique"?

  - by Adrian Shum

  Recently years there are lots of praise to Nodes.js. I am not a developer that have much exposure on network application. From my bare understanding of Nodes.js, its strength is: We are having only on thread handling multiple connections, providing a event-based architecture. However, for example in Java, what if I am having only one thread, using NIO/AIO (which is non-blocking APIs from my bare understanding), and handle multiple connections using that thread, and I provide an event-based architecture to implement the data handling logic (shouldn't be that difficult by providing some callback etc) ? Given JVM being a even more mature VM than V8 (I expect it run faster too), and event-based handling architecture seems not something difficult to create. I am not sure why Nodes.js is attracting so much attention. Did I miss some important points?

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• DIY Touch Screen Mod Makes Regular Gloves Smartphone-friendly

  - by Jason Fitzpatrick

  Smartphone-friendly winter gloves are expensive (and often ugly). Skip shelling out for store-bought gloves when, armed with a needle and thread, you can turn any gloves into smartphone-friendly ones. Over at Popular Science, Taylor Kubota shares the simple trick: 1. Order silver-plated nylon thread (silver conducts electricity). This can be difficult to find in stores, but major online retailers carry it. 2. Pick a pair of gloves to modify. Although leather works, it’s harder to push a needle through. 3. Stitch the figure of a star or other solid shape onto the glove’s index finger with the thread, making sure it will contact both the touchscreen and your skin. Our Geek Trivia App for Windows 8 is Now Available Everywhere How To Boot Your Android Phone or Tablet Into Safe Mode HTG Explains: Does Your Android Phone Need an Antivirus?

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