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  • Structuring multi-threaded programs

    - by davidk01
    Are there any canonical sources for learning how to structure multi-threaded programs? Even with all the concurrency utility classes that Java provides I'm having a hard time properly structuring multi-threaded programs. Whenever threads are involved my code becomes very brittle, any little change can potentially break the program because the code that jumps back and forth between the threads tends to be very convoluted.

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  • Why Is Faulty Behaviour In The .NET Framework Not Fixed?

    - by Alois Kraus
    Here is the scenario: You have a Windows Form Application that calls a method via Invoke or BeginInvoke which throws exceptions. Now you want to find out where the error did occur and how the method has been called. Here is the output we do get when we call Begin/EndInvoke or simply Invoke The actual code that was executed was like this:         private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }            [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));   The faulting method is called GenerateError which does throw a NotImplementedException exception and wraps it in a NotSupportedException.           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         } It is clear that the method F2 and F1 did actually throw these exceptions but we do not see them in the call stack. If we directly call the InvokingFunction and catch and print the exception we can find out very easily how we did get into this situation. We see methods F1,F2,GenerateError and InvokingFunction directly in the stack trace and we see that actually two exceptions did occur. Here is for comparison what we get from Invoke/EndInvoke System.NotImplementedException: Inner Exception     StackTrace:    at System.Windows.Forms.Control.MarshaledInvoke(Control caller, Delegate method, Object[] args, Boolean synchronous)     at System.Windows.Forms.Control.Invoke(Delegate method, Object[] args)     at WindowsFormsApplication1.AppForm.InvokingFunction(CallMode mode)     at WindowsFormsApplication1.AppForm.cInvoke_Click(Object sender, EventArgs e)     at System.Windows.Forms.Control.OnClick(EventArgs e)     at System.Windows.Forms.Button.OnClick(EventArgs e) The exception message is kept but the stack starts running from our Invoke call and not from the faulting method F2. We have therefore no clue where this exception did occur! The stack starts running at the method MarshaledInvoke because the exception is rethrown with the throw catchedException which resets the stack trace. That is bad but things are even worse because if previously lets say 5 exceptions did occur .NET will return only the first (innermost) exception. That does mean that we do not only loose the original call stack but all other exceptions and all data contained therein as well. It is a pity that MS does know about this and simply closes this issue as not important. Programmers will play a lot more around with threads than before thanks to TPL, PLINQ that do come with .NET 4. Multithreading is hyped quit a lot in the press and everybody wants to use threads. But if the .NET Framework makes it nearly impossible to track down the easiest UI multithreading issue I have a problem with that. The problem has been reported but obviously not been solved. .NET 4 Beta 2 did not have changed that dreaded GetBaseException call in MarshaledInvoke to return only the innermost exception of the complete exception stack. It is really time to fix this. WPF on the other hand does the right thing and wraps the exceptions inside a TargetInvocationException which makes much more sense. But Not everybody uses WPF for its daily work and Windows forms applications will still be used for a long time. Below is the code to repro the issues shown and how the exceptions can be rendered in a meaningful way. The default Exception.ToString implementation generates a hard to interpret stack if several nested exceptions did occur. using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; using System.Globalization; using System.Runtime.CompilerServices;   namespace WindowsFormsApplication1 {     public partial class AppForm : Form     {         enum CallMode         {             Direct = 0,             BeginInvoke = 1,             Invoke = 2         };           public AppForm()         {             InitializeComponent();             Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;             Application.ThreadException += new System.Threading.ThreadExceptionEventHandler(Application_ThreadException);         }           void Application_ThreadException(object sender, System.Threading.ThreadExceptionEventArgs e)         {             cOutput.Text = PrintException(e.Exception, 0, null).ToString();         }           private void cDirectUnhandled_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Direct);         }           private void cDirectCall_Click(object sender, EventArgs e)         {             try             {                 InvokingFunction(CallMode.Direct);             }             catch (Exception ex)             {                 cOutput.Text = PrintException(ex, 0, null).ToString();             }         }           private void cInvoke_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.Invoke);         }           private void cBeginInvokeCall_Click(object sender, EventArgs e)         {             InvokingFunction(CallMode.BeginInvoke);         }           [MethodImpl(MethodImplOptions.NoInlining)]         void InvokingFunction(CallMode mode)         {             switch (mode)             {                 case CallMode.Direct:                     GenerateError();                     break;                 case CallMode.Invoke:                     this.Invoke(new MethodInvoker(GenerateError));                     break;                 case CallMode.BeginInvoke:                     IAsyncResult res = this.BeginInvoke(new MethodInvoker(GenerateError));                     this.EndInvoke(res);                     break;             }         }           [MethodImpl(MethodImplOptions.NoInlining)]         void GenerateError()         {             F1();         }           private void F1()         {             try             {                 F2();             }             catch (Exception ex)             {                 throw new NotSupportedException("Outer Exception", ex);             }         }           private void F2()         {            throw new NotImplementedException("Inner Exception");         }           StringBuilder PrintException(Exception ex, int identLevel, StringBuilder sb)         {             StringBuilder builtStr = sb;             if( builtStr == null )                 builtStr = new StringBuilder();               if( ex == null )                 return builtStr;                 WriteLine(builtStr, String.Format("{0}: {1}", ex.GetType().FullName, ex.Message), identLevel);             WriteLine(builtStr, String.Format("StackTrace: {0}", ShortenStack(ex.StackTrace)), identLevel + 1);             builtStr.AppendLine();               return PrintException(ex.InnerException, ++identLevel, builtStr);         }               void WriteLine(StringBuilder sb, string msg, int identLevel)         {             foreach (string trimmedLine in SplitToLines(msg)                                            .Select( (line) => line.Trim()) )             {                 for (int i = 0; i < identLevel; i++)                     sb.Append('\t');                 sb.Append(trimmedLine);                 sb.AppendLine();             }         }           string ShortenStack(string stack)         {             int nonAppFrames = 0;             // Skip stack frames not part of our app but include two foreign frames and skip the rest             // If our stack frame is encountered reset counter to 0             return SplitToLines(stack)                               .Where((line) =>                               {                                   nonAppFrames = line.Contains("WindowsFormsApplication1") ? 0 : nonAppFrames + 1;                                   return nonAppFrames < 3;                               })                              .Select((line) => line)                              .Aggregate("", (current, line) => current + line + Environment.NewLine);         }           static char[] NewLines = Environment.NewLine.ToCharArray();         string[] SplitToLines(string str)         {             return str.Split(NewLines, StringSplitOptions.RemoveEmptyEntries);         }     } }

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  • Library like ENet, but for TCP?

    - by Milo
    I'm not looking to use boost::asio, it is overly complex for my needs. I'm building a game that is cross platform, for desktop, iPhone and Android. I found a library called ENet which is pretty much what I need, but it uses UDP which does not seem to support encryption and a few other things. Given that the game is an event driven card game, TCP seems like the right fit. However, all I have found is WINSOCK / berkley sockets and bost::asio. Here is a sample client server application with ENet: #include <enet/enet.h> #include <stdlib.h> #include <string> #include <iostream> class Host { ENetAddress address; ENetHost * server; ENetHost* client; ENetEvent event; public: Host() :server(NULL) { enet_initialize(); setupServer(); } void setupServer() { if(server) { enet_host_destroy(server); server = NULL; } address.host = ENET_HOST_ANY; /* Bind the server to port 1234. */ address.port = 1721; server = enet_host_create (& address /* the address to bind the server host to */, 32 /* allow up to 32 clients and/or outgoing connections */, 2 /* allow up to 2 channels to be used, 0 and 1 */, 0 /* assume any amount of incoming bandwidth */, 0 /* assume any amount of outgoing bandwidth */); } void daLoop() { while(true) { /* Wait up to 1000 milliseconds for an event. */ while (enet_host_service (server, & event, 5000) > 0) { ENetPacket * packet; switch (event.type) { case ENET_EVENT_TYPE_CONNECT: printf ("A new client connected from %x:%u.\n", event.peer -> address.host, event.peer -> address.port); /* Store any relevant client information here. */ event.peer -> data = "Client information"; /* Create a reliable packet of size 7 containing "packet\0" */ packet = enet_packet_create ("packet", strlen ("packet") + 1, ENET_PACKET_FLAG_RELIABLE); /* Extend the packet so and append the string "foo", so it now */ /* contains "packetfoo\0" */ enet_packet_resize (packet, strlen ("packetfoo") + 1); strcpy ((char*)& packet -> data [strlen ("packet")], "foo"); /* Send the packet to the peer over channel id 0. */ /* One could also broadcast the packet by */ /* enet_host_broadcast (host, 0, packet); */ enet_peer_send (event.peer, 0, packet); /* One could just use enet_host_service() instead. */ enet_host_flush (server); break; case ENET_EVENT_TYPE_RECEIVE: printf ("A packet of length %u containing %s was received from %s on channel %u.\n", event.packet -> dataLength, event.packet -> data, event.peer -> data, event.channelID); /* Clean up the packet now that we're done using it. */ enet_packet_destroy (event.packet); break; case ENET_EVENT_TYPE_DISCONNECT: printf ("%s disconected.\n", event.peer -> data); /* Reset the peer's client information. */ event.peer -> data = NULL; } } } } ~Host() { if(server) { enet_host_destroy(server); server = NULL; } atexit (enet_deinitialize); } }; class Client { ENetAddress address; ENetEvent event; ENetPeer *peer; ENetHost* client; public: Client() :peer(NULL) { enet_initialize(); setupPeer(); } void setupPeer() { client = enet_host_create (NULL /* create a client host */, 1 /* only allow 1 outgoing connection */, 2 /* allow up 2 channels to be used, 0 and 1 */, 57600 / 8 /* 56K modem with 56 Kbps downstream bandwidth */, 14400 / 8 /* 56K modem with 14 Kbps upstream bandwidth */); if (client == NULL) { fprintf (stderr, "An error occurred while trying to create an ENet client host.\n"); exit (EXIT_FAILURE); } /* Connect to some.server.net:1234. */ enet_address_set_host (& address, "192.168.2.13"); address.port = 1721; /* Initiate the connection, allocating the two channels 0 and 1. */ peer = enet_host_connect (client, & address, 2, 0); if (peer == NULL) { fprintf (stderr, "No available peers for initiating an ENet connection.\n"); exit (EXIT_FAILURE); } /* Wait up to 5 seconds for the connection attempt to succeed. */ if (enet_host_service (client, & event, 20000) > 0 && event.type == ENET_EVENT_TYPE_CONNECT) { std::cout << "Connection to some.server.net:1234 succeeded." << std::endl; } else { /* Either the 5 seconds are up or a disconnect event was */ /* received. Reset the peer in the event the 5 seconds */ /* had run out without any significant event. */ enet_peer_reset (peer); puts ("Connection to some.server.net:1234 failed."); } } void daLoop() { ENetPacket* packet; /* Create a reliable packet of size 7 containing "packet\0" */ packet = enet_packet_create ("backet", strlen ("backet") + 1, ENET_PACKET_FLAG_RELIABLE); /* Extend the packet so and append the string "foo", so it now */ /* contains "packetfoo\0" */ enet_packet_resize (packet, strlen ("backetfoo") + 1); strcpy ((char*)& packet -> data [strlen ("backet")], "foo"); /* Send the packet to the peer over channel id 0. */ /* One could also broadcast the packet by */ /* enet_host_broadcast (host, 0, packet); */ enet_peer_send (event.peer, 0, packet); /* One could just use enet_host_service() instead. */ enet_host_flush (client); while(true) { /* Wait up to 1000 milliseconds for an event. */ while (enet_host_service (client, & event, 1000) > 0) { ENetPacket * packet; switch (event.type) { case ENET_EVENT_TYPE_RECEIVE: printf ("A packet of length %u containing %s was received from %s on channel %u.\n", event.packet -> dataLength, event.packet -> data, event.peer -> data, event.channelID); /* Clean up the packet now that we're done using it. */ enet_packet_destroy (event.packet); break; } } } } ~Client() { atexit (enet_deinitialize); } }; int main() { std::string a; std::cin >> a; if(a == "host") { Host host; host.daLoop(); } else { Client c; c.daLoop(); } return 0; } I looked at some socket tutorials and they seemed a bit too low level. I just need something that abstracts away the platform (eg, no WINSOCKS) and that has basic ability to keep track of connected clients and send them messages. Thanks

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  • 200th Post

    - by Tim Murphy
    I didn’t break any speed records getting getting to 200 posts, but I am here.  So what is the prize for getting here?  You have to put out the obligatory post announcing the achievement.  It also means that it is time to put “Yes, I’m a geek” on your business card.  Well, there it is.  Now go about your business.  Nothing to see here. del.icio.us Tags: 200th post

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  • Procedural, Semi-Procedural and Declarative Programming in SQL

    A lot of the time, the key to making SQL databases perform well is to take a break from the keyboard and rethink the way of approaching the problem; and rethinking in terms of a set-based declarative approach. Joe takes a simple discussion abut a problem with a UDF to illustrate the point that ingrained procedural reflexes can often prevent us from seeing simpler set-based techniques.

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  • SQL University: Parallelism Week - Introduction

    - by Adam Machanic
    Welcome to Parallelism Week at SQL University . My name is Adam Machanic, and I'm your professor. Imagine having 8 brains, or 16, or 32. Imagine being able to break up complex thoughts and distribute them across your many brains, so that you could solve problems faster. Now quit imagining that, because you're human and you're stuck with only one brain, and you only get access to the entire thing if you're lucky enough to have avoided abusing too many recreational drugs. For your database server,...(read more)

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  • SQL University: What and why of database testing

    - by Mladen Prajdic
    This is a post for a great idea called SQL University started by Jorge Segarra also famously known as SqlChicken on Twitter. It’s a collection of blog posts on different database related topics contributed by several smart people all over the world. So this week is mine and we’ll be talking about database testing and refactoring. In 3 posts we’ll cover: SQLU part 1 - What and why of database testing SQLU part 2 - What and why of database refactoring SQLU part 2 – Tools of the trade With that out of the way let us sharpen our pencils and get going. Why test a database The sad state of the industry today is that there is very little emphasis on testing in general. Test driven development is still a small niche of the programming world while refactoring is even smaller. The cause of this is the inability of developers to convince themselves and their managers that writing tests is beneficial. At the moment they are mostly viewed as waste of time. This is because the average person (let’s not fool ourselves, we’re all average) is unable to think about lower future costs in relation to little more current work. It’s orders of magnitude easier to know about the current costs in relation to current amount of work. That’s why programmers convince themselves testing is a waste of time. However we have to ask ourselves what tests are really about? Maybe finding bugs? No, not really. If we introduce bugs, we’re likely to write test around those bugs too. But yes we can find some bugs with tests. The main point of tests is to have reproducible repeatability in our systems. By having a code base largely covered by tests we can know with better certainty what a small code change can break in other parts of the system. By having repeatability we can make code changes with confidence, since we know we’ll see what breaks in other tests. And here comes the inability to estimate future costs. By spending just a few more hours writing those tests we’d know instantly what broke where. Imagine we fix a reported bug. We check-in the code, deploy it and the users are happy. Until we get a call 2 weeks later about a certain monthly process has stopped working. What we don’t know is that this process was developed by a long gone coworker and for some reason it relied on that same bug we’ve happily fixed. There’s no way we could’ve known that. We say OK and go in and fix the monthly process. But what we have no clue about is that there’s this ETL job that relied on data from that monthly process. Now that we’ve fixed the process it’s giving unexpected (yet correct since we fixed it) data to the ETL job. So we have to fix that too. But there’s this part of the app we coded that relies on data from that exact ETL job. And just like that we enter the “Loop of maintenance horror”. With the loop eventually comes blame. Here’s a nice tip for all developers and DBAs out there: If you make a mistake man up and admit to it. All of the above is valid for any kind of software development. Keeping this in mind the database is nothing other than just a part of the application. But a big part! One reason why testing a database is even more important than testing an application is that one database is usually accessed from multiple applications and processes. This makes it the central and vital part of the enterprise software infrastructure. Knowing all this can we really afford not to have tests? What to test in a database Now that we’ve decided we’ll dive into this testing thing we have to ask ourselves what needs to be tested? The short answer is: everything. The long answer is: read on! There are 2 main ways of doing tests: Black box and White box testing. Black box testing means we have no idea how the system internals are built and we only have access to it’s inputs and outputs. With it we test that the internal changes to the system haven’t caused the input/output behavior of the system to change. The most important thing to test here are the edge conditions. It’s where most programs break. Having good edge condition tests we can be more confident that the systems changes won’t break. White box testing has the full knowledge of the system internals. With it we test the internal system changes, different states of the application, etc… White and Black box tests should be complementary to each other as they are very much interconnected. Testing database routines includes testing stored procedures, views, user defined functions and anything you use to access the data with. Database routines are your input/output interface to the database system. They count as black box testing. We test then for 2 things: Data and schema. When testing schema we only care about the columns and the data types they’re returning. After all the schema is the contract to the out side systems. If it changes we usually have to change the applications accessing it. One helpful T-SQL command when doing schema tests is SET FMTONLY ON. It tells the SQL Server to return only empty results sets. This speeds up tests because it doesn’t return any data to the client. After we’ve validated the schema we have to test the returned data. There no other way to do this but to have expected data known before the tests executes and comparing that data to the database routine output. Testing Authentication and Authorization helps us validate who has access to the SQL Server box (Authentication) and who has access to certain database objects (Authorization). For desktop applications and windows authentication this works well. But the biggest problem here are web apps. They usually connect to the database as a single user. Please ensure that that user is not SA or an account with admin privileges. That is just bad. Load testing ensures us that our database can handle peak loads. One often overlooked tool for load testing is Microsoft’s OSTRESS tool. It’s part of RML utilities (x86, x64) for SQL Server and can help determine if our database server can handle loads like 100 simultaneous users each doing 10 requests per second. SQL Profiler can also help us here by looking at why certain queries are slow and what to do to fix them.   One particular problem to think about is how to begin testing existing databases. First thing we have to do is to get to know those databases. We can’t test something when we don’t know how it works. To do this we have to talk to the users of the applications accessing the database, run SQL Profiler to see what queries are being run, use existing documentation to decipher all the object relationships, etc… The way to approach this is to choose one part of the database (say a logical grouping of tables that go together) and filter our traces accordingly. Once we’ve done that we move on to the next grouping and so on until we’ve covered the whole database. Then we move on to the next one. Database Testing is a topic that we can spent many hours discussing but let this be a nice intro to the world of database testing. See you in the next post.

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  • Can someone help with indexing issues

    - by user631249
    Hi all I am on the first page of google for keywords concerned with MOVING, however i cant seem to break the carpet cleaning rankings. I have made changes and additions which havent been indexed yet. Should i wait for the run or please please can someone give me pointers on the carpet cleaning indexing. Also i have 53pages submitted and only 38 indexed, where could the problem be. Is there software to check indexing hiccups . Thanks.

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  • How In-Memory Database Objects Affect Database Design: The Conceptual Model

    - by drsql
    After a rather long break in the action to get through some heavy tech editing work (paid work before blogging, I always say!) it is time to start working on this presentation about In-Memory Databases. I have been trying to decide on the scope of the demo code in the back of my head, and I have added more and taken away bits and pieces over time trying to find the balance of "enough" complexity to show data integrity issues and joins, but not so much that we get lost in the process of trying to...(read more)

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  • Chrooting Apache2 With mod_chroot On Fedora 12

    <b>Howtoforge:</b> "This guide explains how to set up mod_chroot with Apache2 on a Fedora 12 system. With mod_chroot, you can run Apache2 in a secure chroot environment and make your server less vulnerable to break-in attempts that try to exploit vulnerabilities in Apache2 or your installed web applications."

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  • Does Ubuntu run on current Asus Transformer Prime?

    - by Ubuntu User
    I've read instructions about dual boot Android / Transformer Prime (a significant factor in ordering one). Also about not working with /latest/ Transformer Prime (firmware / BIOS?) Also about imminent Ubuntu ARM support. Will I be able to run Ubuntu in a day or two when Transformer arrives? Also, am I right to assume I can restore Transformer to factory status if I break something in the attempt?

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  • Procedural, Semi-Procedural and Declarative Programming in SQL

    A lot of the time, the key to making SQL databases perform well is to take a break from the keyboard and rethink the way of approaching the problem; and rethinking in terms of a set-based declarative approach. Joe takes a simple discussion abut a problem with a UDF to illustrate the point that ingrained procedural reflexes can often prevent us from seeing simpler set-based techniques.

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  • Star Wars – Battle of Hoth Recreated in Minecraft [Video]

    - by Asian Angel
    Star Wars and Minecraft each stand out on their own, but what if you combine the two into one awesome video? Enjoy the result with this video that YouTube user ParadiseDecay has created. Minecraft – Star Wars – Battle For Hoth [via Dorkly] HTG Explains: How Antivirus Software Works HTG Explains: Why Deleted Files Can Be Recovered and How You Can Prevent It HTG Explains: What Are the Sys Rq, Scroll Lock, and Pause/Break Keys on My Keyboard?

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  • WinAPI window taking 50% of CPU when idle

    - by henryprescott
    I'm currently working on a game that creates a window using WindowsAPI. However, at the moment the process is taking up 50% of my CPU. All I am doing is creating the window and looping using the code found below: int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) { MSG message = {0}; WNDCLASSEX wcl = {0}; wcl.cbSize = sizeof(wcl); wcl.style = CS_OWNDC | CS_HREDRAW | CS_VREDRAW; wcl.lpfnWndProc = WindowProc; wcl.cbClsExtra = 0; wcl.cbWndExtra = 0; wcl.hInstance = hInstance = hInstance; wcl.hIcon = LoadIcon(0, IDI_APPLICATION); wcl.hCursor = LoadCursor(0, IDC_ARROW); wcl.hbrBackground = 0; wcl.lpszMenuName = 0; wcl.lpszClassName = "GL2WindowClass"; wcl.hIconSm = 0; if (!RegisterClassEx(&wcl)) return 0; hWnd = CreateAppWindow(wcl, "Application"); if (hWnd) { if (Init()) { ShowWindow(hWnd, nShowCmd); UpdateWindow(hWnd); while (true) { while (PeekMessage(&message, 0, 0, 0, PM_REMOVE)) { if (message.message == WM_QUIT) break; TranslateMessage(&message); DispatchMessage(&message); } if (message.message == WM_QUIT) break; if (hasFocus) { elapsedTime = GetElapsedTimeInSeconds(); lastEarth += elapsedTime; lastUpdate += elapsedTime; lastFrame += elapsedTime; lastParticle += elapsedTime; if(lastUpdate >= (1.0f / 100.0f)) { Update(lastUpdate); lastUpdate = 0; } if(lastFrame >= (1.0f / 60.0f)) { UpdateFrameRate(lastFrame); lastFrame = 0; Render(); SwapBuffers(hDC); } if(lastEarth >= (1.0f / 10.0f)) { UpdateEarthAnimation(); lastEarth = 0; } if(lastParticle >= (1.0f / 30.0f)) { particleManager->rightBooster->Update(); particleManager->rightBoosterSmoke->Update(); particleManager->leftBooster->Update(); particleManager->leftBoosterSmoke->Update(); particleManager->breakUp->Update(); lastParticle = 0; } } else { WaitMessage(); } } } Cleanup(); UnregisterClass(wcl.lpszClassName, hInstance); } return static_cast<int>(message.wParam); } So even when I am not drawing anything when the window has focus it still takes up 50%. I don't understand how this is taking up so much system resources. Am I doing something wrong? Any help would be much appreciated, thank you!

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  • Friday Fun: The Milk Quest

    - by Asian Angel
    Glorious Friday is here once again, so why not take a break and have a quick bit of fun? In this week’s game your mission is to help a hungry kitten successfully travel through strange and dangerous lands to reach the milk treasure shown on his map.How To Encrypt Your Cloud-Based Drive with BoxcryptorHTG Explains: Photography with Film-Based CamerasHow to Clean Your Dirty Smartphone (Without Breaking Something)

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  • Push back rectangle where collision happens

    - by Tifa
    I have a tile collision on a game I am creating but the problem is once a collision happens for example a collision happens in right side my sprite cant move to up and bottom :( thats because i set the speed to 0. I thinks its wrong. here is my code: int startX, startY, endX, endY; float pushx = 0,pushy = 0; // move player if(Gdx.input.isKeyPressed(Input.Keys.LEFT)){ dx=-1; currentWalk = leftWalk; } if(Gdx.input.isKeyPressed(Input.Keys.RIGHT)){ dx=1; currentWalk = rightWalk; } if(Gdx.input.isKeyPressed(Input.Keys.DOWN)){ dy=-1; currentWalk = downWalk; } if(Gdx.input.isKeyPressed(Input.Keys.UP)){ dy=1; currentWalk = upWalk; } sr.setProjectionMatrix(camera.combined); sr.begin(ShapeRenderer.ShapeType.Line); Rectangle koalaRect = rectPool.obtain(); koalaRect.set(player.getX(), player.getY(), pw, ph /2 ); float oldX = player.getX(), oldY = player.getY(); // THIS LINE WAS ADDED player.setXY(player.getX() + dx * Gdx.graphics.getDeltaTime() * 4f, player.getY() + dy * Gdx.graphics.getDeltaTime() * 4f); // THIS LINE WAS MOVED HERE FROM DOWN BELOW if(dx> 0) { startX = endX = (int)(player.getX() + pw); } else { startX = endX = (int)(player.getX() ); } startY = (int)(player.getY()); endY = (int)(player.getY() + ph); getTiles(startX, startY, endX, endY, tiles); for(Rectangle tile: tiles) { sr.rect(tile.x,tile.y,tile.getWidth(),tile.getHeight()); if(koalaRect.overlaps(tile)) { //dx = 0; player.setX(oldX); // THIS LINE CHANGED Gdx.app.log("x","hit " + player.getX() + " " + oldX); break; } } if(dy > 0) { startY = endY = (int)(player.getY() + ph ); } else { startY = endY = (int)(player.getY() ); } startX = (int)(player.getX()); endX = (int)(player.getX() + pw); getTiles(startX, startY, endX, endY, tiles); for(Rectangle tile: tiles) { if(koalaRect.overlaps(tile)) { //dy = 0; player.setY(oldY); // THIS LINE CHANGED //Gdx.app.log("y","hit" + player.getY() + " " + oldY); break; } } sr.rect(koalaRect.x,koalaRect.y,koalaRect.getWidth(),koalaRect.getHeight() / 2); sr.setColor(Color.GREEN); sr.end(); I want to push back the sprite when a collision happens but i have no idea how :D pls help

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  • How to Become a Valuable Web Developer

    If you are new to web development and want to 'break into' the field then PHP is the programming language you should learn. There are many approaches to learning how to be a web developer, however, I believe the following approach makes the most sense.

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  • Why do iterators in Python raise an exception?

    - by NullUserException
    Here's the syntax for iterators in Java (somewhat similar syntax in C#): Iterator it = sequence.iterator(); while (it.hasNext()) { System.out.println(it.next()); } Which makes sense. Here's the equivalent syntax in Python: it = iter(sequence) while True: try: value = it.next() except StopIteration: break print(value) I thought Exceptions were supposed to be used only in, well, exceptional circumstances. Why does Python use exceptions to stop iteration?

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  • When you should and should not use the 'new' keyword?

    - by skizeey
    I watched a Google Tech Talk presentation on Unit Testing, given by Misko Hevery, and he said to avoid using the new keyword in business logic code. I wrote a program, and I did end up using the new keyword here and there, but they were mostly for instantiating objects that hold data (ie, they didn't have any functions or methods). I'm wondering, did I do something wrong when I used the new keyword for my program. And where can we break that 'rule'?

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  • How to create Custom ListForm WebPart

    - by DipeshBhanani
    Mostly all who works extensively on SharePoint (including meJ) don’t like to use out-of-box list forms (DispForm.aspx, EditForm.aspx, NewForm.aspx) as interface. Actually these OOB list forms bind hands of developers for the customization. It gives headache to developers to add just one post back event, for a dropdown field and to populate other fields in NewForm.aspx or EditForm.aspx. On top of that clients always ask such stuff. So here I am going to give you guys a flight for SharePoint Customization world. In this blog, I will explain, how to create CustomListForm WebPart. In my next blogs, I am going to explain easy deployment of List Forms through features and last, guidance on using SharePoint web controls. 1.       First thing, create a class library project through Visual Studio and inherit the class with WebPart class.     public class CustomListForm : WebPart   2.       Declare the public variables and properties which we are going to use throughout the class. You will get to know these once you see them in use.         #region "Variable Declaration"           Table spTableCntl;         FormToolBar formToolBar;         Literal ltAlertMessage;         Guid SiteId;         Guid ListId;         int ItemId;         string ListName;           #endregion           #region "Properties"           SPControlMode _ControlMode = SPControlMode.New;         [Personalizable(PersonalizationScope.Shared),          WebBrowsable(true),          WebDisplayName("Control Mode"),          WebDescription("Set Control Mode"),          DefaultValue(""),          Category("Miscellaneous")]         public SPControlMode ControlMode         {             get { return _ControlMode; }             set { _ControlMode = value; }         }           #endregion     The property “ControlMode” is used to identify the mode of the List Form. The property is of type SPControlMode which is an enum type with values (Display, Edit, New and Invalid). When we will add this WebPart to DispForm.aspx, EditForm.aspx and NewForm.aspx, we will set the WebPart property “ControlMode” to Display, Edit and New respectively.     3.       Now, we need to override the CreateChildControl method and write code to manually add SharePoint Web Controls related to each list fields as well as ToolBar controls.         protected override void CreateChildControls()         {             base.CreateChildControls();               try             {                 SiteId = SPContext.Current.Site.ID;                 ListId = SPContext.Current.ListId;                 ListName = SPContext.Current.List.Title;                   if (_ControlMode == SPControlMode.Display || _ControlMode == SPControlMode.Edit)                     ItemId = SPContext.Current.ItemId;                   SPSecurity.RunWithElevatedPrivileges(delegate()                 {                     using (SPSite site = new SPSite(SiteId))                     {                         //creating a new SPSite with credentials of System Account                         using (SPWeb web = site.OpenWeb())                         {                               //<Custom Code for creating form controls>                         }                     }                 });             }             catch (Exception ex)             {                 ShowError(ex, "CreateChildControls");             }         }   Here we are assuming that we are developing this WebPart to plug into List Forms. Hence we will get the List Id and List Name from the current context. We can have Item Id only in case of Display and Edit Mode. We are putting our code into “RunWithElevatedPrivileges” to elevate privileges to System Account. Now, let’s get deep down into the main code and expand “//<Custom Code for creating form controls>”. Before initiating any SharePoint control, we need to set context of SharePoint web controls explicitly so that it will be instantiated with elevated System Account user. Following line does the job.     //To create SharePoint controls with new web object and System Account credentials     SPControl.SetContextWeb(Context, web);   First thing, let’s add main table as container for all controls.     //Table to render webpart     Table spTableMain = new Table();     spTableMain.CellPadding = 0;     spTableMain.CellSpacing = 0;     spTableMain.Width = new Unit(100, UnitType.Percentage);     this.Controls.Add(spTableMain);   Now we need to add Top toolbar with Save and Cancel button at top as you see in the below screen shot.       // Add Row and Cell for Top ToolBar     TableRow spRowTopToolBar = new TableRow();     spTableMain.Rows.Add(spRowTopToolBar);     TableCell spCellTopToolBar = new TableCell();     spRowTopToolBar.Cells.Add(spCellTopToolBar);     spCellTopToolBar.Width = new Unit(100, UnitType.Percentage);         ToolBar toolBarTop = (ToolBar)Page.LoadControl("/_controltemplates/ToolBar.ascx");     toolBarTop.CssClass = "ms-formtoolbar";     toolBarTop.ID = "toolBarTbltop";     toolBarTop.RightButtons.SeparatorHtml = "<td class=ms-separator> </td>";       if (_ControlMode != SPControlMode.Display)     {         SaveButton btnSave = new SaveButton();         btnSave.ControlMode = _ControlMode;         btnSave.ListId = ListId;           if (_ControlMode == SPControlMode.New)             btnSave.RenderContext = SPContext.GetContext(web);         else         {             btnSave.RenderContext = SPContext.GetContext(this.Context, ItemId, ListId, web);             btnSave.ItemContext = SPContext.GetContext(this.Context, ItemId, ListId, web);             btnSave.ItemId = ItemId;         }         toolBarTop.RightButtons.Controls.Add(btnSave);     }       GoBackButton goBackButtonTop = new GoBackButton();     toolBarTop.RightButtons.Controls.Add(goBackButtonTop);     goBackButtonTop.ControlMode = SPControlMode.Display;       spCellTopToolBar.Controls.Add(toolBarTop);   Here we have use “SaveButton” and “GoBackButton” which are internal SharePoint web controls for save and cancel functionality. I have set some of the properties of Save Button with if-else condition because we will not have Item Id in case of New Mode. Item Id property is used to identify which SharePoint List Item need to be saved. Now, add Form Toolbar to the page which contains “Attach File”, “Delete Item” etc buttons.       // Add Row and Cell for FormToolBar     TableRow spRowFormToolBar = new TableRow();     spTableMain.Rows.Add(spRowFormToolBar);     TableCell spCellFormToolBar = new TableCell();     spRowFormToolBar.Cells.Add(spCellFormToolBar);     spCellFormToolBar.Width = new Unit(100, UnitType.Percentage);       FormToolBar formToolBar = new FormToolBar();     formToolBar.ID = "formToolBar";     formToolBar.ListId = ListId;     if (_ControlMode == SPControlMode.New)         formToolBar.RenderContext = SPContext.GetContext(web);     else     {         formToolBar.RenderContext = SPContext.GetContext(this.Context, ItemId, ListId, web);         formToolBar.ItemContext = SPContext.GetContext(this.Context, ItemId, ListId, web);         formToolBar.ItemId = ItemId;     }     formToolBar.ControlMode = _ControlMode;     formToolBar.EnableViewState = true;       spCellFormToolBar.Controls.Add(formToolBar);     The ControlMode property will take care of which button to be displayed on the toolbar. E.g. “Attach files”, “Delete Item” in new/edit forms and “New Item”, “Edit Item”, “Delete Item”, “Manage Permissions” etc in display forms. Now add main section which contains form field controls.     //Create Form Field controls and add them in Table "spCellCntl"     CreateFieldControls(web);     //Add public variable "spCellCntl" containing all form controls to the page     spRowCntl.Cells.Add(spCellCntl);     spCellCntl.Width = new Unit(100, UnitType.Percentage);     spCellCntl.Controls.Add(spTableCntl);       //Add a Blank Row with height of 5px to render space between ToolBar table and Control table     TableRow spRowLine1 = new TableRow();     spTableMain.Rows.Add(spRowLine1);     TableCell spCellLine1 = new TableCell();     spRowLine1.Cells.Add(spCellLine1);     spCellLine1.Height = new Unit(5, UnitType.Pixel);     spCellLine1.Controls.Add(new LiteralControl("<IMG SRC='/_layouts/images/blank.gif' width=1 height=1 alt=''>"));       //Add Row and Cell for Form Controls Section     TableRow spRowCntl = new TableRow();     spTableMain.Rows.Add(spRowCntl);     TableCell spCellCntl = new TableCell();       //Create Form Field controls and add them in Table "spCellCntl"     CreateFieldControls(web);     //Add public variable "spCellCntl" containing all form controls to the page     spRowCntl.Cells.Add(spCellCntl);     spCellCntl.Width = new Unit(100, UnitType.Percentage);     spCellCntl.Controls.Add(spTableCntl);       TableRow spRowLine2 = new TableRow();     spTableMain.Rows.Add(spRowLine2);     TableCell spCellLine2 = new TableCell();     spRowLine2.Cells.Add(spCellLine2);     spCellLine2.CssClass = "ms-formline";     spCellLine2.Controls.Add(new LiteralControl("<IMG SRC='/_layouts/images/blank.gif' width=1 height=1 alt=''>"));       // Add Blank row with height of 5 pixel     TableRow spRowLine3 = new TableRow();     spTableMain.Rows.Add(spRowLine3);     TableCell spCellLine3 = new TableCell();     spRowLine3.Cells.Add(spCellLine3);     spCellLine3.Height = new Unit(5, UnitType.Pixel);     spCellLine3.Controls.Add(new LiteralControl("<IMG SRC='/_layouts/images/blank.gif' width=1 height=1 alt=''>"));   You can add bottom toolbar also to get same look and feel as OOB forms. I am not adding here as the blog will be much lengthy. At last, you need to write following lines to allow unsafe updates for Save and Delete button.     // Allow unsafe update on web for save button and delete button     if (this.Page.IsPostBack && this.Page.Request["__EventTarget"] != null         && (this.Page.Request["__EventTarget"].Contains("IOSaveItem")         || this.Page.Request["__EventTarget"].Contains("IODeleteItem")))     {         SPContext.Current.Web.AllowUnsafeUpdates = true;     }   So that’s all. We have finished writing Custom Code for adding field control. But something most important is skipped. In above code, I have called function “CreateFieldControls(web);” to add SharePoint field controls to the page. Let’s see the implementation of the function:     private void CreateFieldControls(SPWeb pWeb)     {         SPList listMain = pWeb.Lists[ListId];         SPFieldCollection fields = listMain.Fields;           //Main Table to render all fields         spTableCntl = new Table();         spTableCntl.BorderWidth = new Unit(0);         spTableCntl.CellPadding = 0;         spTableCntl.CellSpacing = 0;         spTableCntl.Width = new Unit(100, UnitType.Percentage);         spTableCntl.CssClass = "ms-formtable";           SPContext controlContext = SPContext.GetContext(this.Context, ItemId, ListId, pWeb);           foreach (SPField listField in fields)         {             string fieldDisplayName = listField.Title;             string fieldInternalName = listField.InternalName;               //Skip if the field is system field or hidden             if (listField.Hidden || listField.ShowInVersionHistory == false)                 continue;               //Skip if the control mode is display and field is read-only             if (_ControlMode != SPControlMode.Display && listField.ReadOnlyField == true)                 continue;               FieldLabel fieldLabel = new FieldLabel();             fieldLabel.FieldName = listField.InternalName;             fieldLabel.ListId = ListId;               BaseFieldControl fieldControl = listField.FieldRenderingControl;             fieldControl.ListId = ListId;             //Assign unique id using Field Internal Name             fieldControl.ID = string.Format("Field_{0}", fieldInternalName);             fieldControl.EnableViewState = true;               //Assign control mode             fieldLabel.ControlMode = _ControlMode;             fieldControl.ControlMode = _ControlMode;             switch (_ControlMode)             {                 case SPControlMode.New:                     fieldLabel.RenderContext = SPContext.GetContext(pWeb);                     fieldControl.RenderContext = SPContext.GetContext(pWeb);                     break;                 case SPControlMode.Edit:                 case SPControlMode.Display:                     fieldLabel.RenderContext = controlContext;                     fieldLabel.ItemContext = controlContext;                     fieldLabel.ItemId = ItemId;                       fieldControl.RenderContext = controlContext;                     fieldControl.ItemContext = controlContext;                     fieldControl.ItemId = ItemId;                     break;             }               //Add row to display a field row             TableRow spCntlRow = new TableRow();             spTableCntl.Rows.Add(spCntlRow);               //Add the cells for containing field lable and control             TableCell spCellLabel = new TableCell();             spCellLabel.Width = new Unit(30, UnitType.Percentage);             spCellLabel.CssClass = "ms-formlabel";             spCntlRow.Cells.Add(spCellLabel);             TableCell spCellControl = new TableCell();             spCellControl.Width = new Unit(70, UnitType.Percentage);             spCellControl.CssClass = "ms-formbody";             spCntlRow.Cells.Add(spCellControl);               //Add the control to the table cells             spCellLabel.Controls.Add(fieldLabel);             spCellControl.Controls.Add(fieldControl);               //Add description if there is any in case of New and Edit Mode             if (_ControlMode != SPControlMode.Display && listField.Description != string.Empty)             {                 FieldDescription fieldDesc = new FieldDescription();                 fieldDesc.FieldName = fieldInternalName;                 fieldDesc.ListId = ListId;                 spCellControl.Controls.Add(fieldDesc);             }               //Disable Name(Title) in Edit Mode             if (_ControlMode == SPControlMode.Edit && fieldDisplayName == "Name")             {                 TextBox txtTitlefield = (TextBox)fieldControl.Controls[0].FindControl("TextField");                 txtTitlefield.Enabled = false;             }         }         fields = null;     }   First of all, I have declared List object and got list fields in field collection object called “fields”. Then I have added a table for the container of all controls and assign CSS class as "ms-formtable" so that it gives consistent look and feel of SharePoint. Now it’s time to navigate through all fields and add them if required. Here we don’t need to add hidden or system fields. We also don’t want to display read-only fields in new and edit forms. Following lines does this job.             //Skip if the field is system field or hidden             if (listField.Hidden || listField.ShowInVersionHistory == false)                 continue;               //Skip if the control mode is display and field is read-only             if (_ControlMode != SPControlMode.Display && listField.ReadOnlyField == true)                 continue;   Let’s move to the next line of code.             FieldLabel fieldLabel = new FieldLabel();             fieldLabel.FieldName = listField.InternalName;             fieldLabel.ListId = ListId;               BaseFieldControl fieldControl = listField.FieldRenderingControl;             fieldControl.ListId = ListId;             //Assign unique id using Field Internal Name             fieldControl.ID = string.Format("Field_{0}", fieldInternalName);             fieldControl.EnableViewState = true;               //Assign control mode             fieldLabel.ControlMode = _ControlMode;             fieldControl.ControlMode = _ControlMode;   We have used “FieldLabel” control for displaying field title. The advantage of using Field Label is, SharePoint automatically adds red star besides field label to identify it as mandatory field if there is any. Here is most important part to understand. The “BaseFieldControl”. It will render the respective web controls according to type of the field. For example, if it’s single line of text, then Textbox, if it’s look up then it renders dropdown. Additionally, the “ControlMode” property tells compiler that which mode (display/edit/new) controls need to be rendered with. In display mode, it will render label with field value. In edit mode, it will render respective control with item value and in new mode it will render respective control with empty value. Please note that, it’s not always the case when dropdown field will be rendered for Lookup field or Choice field. You need to understand which controls are rendered for which list fields. I am planning to write a separate blog which I hope to publish it very soon. Moreover, we also need to assign list field specific properties like List Id, Field Name etc to identify which SharePoint List field is attached with the control.             switch (_ControlMode)             {                 case SPControlMode.New:                     fieldLabel.RenderContext = SPContext.GetContext(pWeb);                     fieldControl.RenderContext = SPContext.GetContext(pWeb);                     break;                 case SPControlMode.Edit:                 case SPControlMode.Display:                     fieldLabel.RenderContext = controlContext;                     fieldLabel.ItemContext = controlContext;                     fieldLabel.ItemId = ItemId;                       fieldControl.RenderContext = controlContext;                     fieldControl.ItemContext = controlContext;                     fieldControl.ItemId = ItemId;                     break;             }   Here, I have separate code for new mode and Edit/Display mode because we will not have Item Id to assign in New Mode. We also need to set CSS class for cell containing Label and Controls so that those controls get rendered with SharePoint theme.             spCellLabel.CssClass = "ms-formlabel";             spCellControl.CssClass = "ms-formbody";   “FieldDescription” control is used to add field description if there is any.    Now it’s time to add some more customization,               //Disable Name(Title) in Edit Mode             if (_ControlMode == SPControlMode.Edit && fieldDisplayName == "Name")             {                 TextBox txtTitlefield = (TextBox)fieldControl.Controls[0].FindControl("TextField");                 txtTitlefield.Enabled = false;             }   The above code will disable the title field in edit mode. You can add more code here to achieve more customization according to your requirement. Some of the examples are as follow:             //Adding post back event on UserField to auto populate some other dependent field             //in new mode and disable it in edit mode             if (_ControlMode != SPControlMode.Display && fieldDisplayName == "Manager")             {                 if (fieldControl.Controls[0].FindControl("UserField") != null)                 {                     PeopleEditor pplEditor = (PeopleEditor)fieldControl.Controls[0].FindControl("UserField");                     if (_ControlMode == SPControlMode.New)                         pplEditor.AutoPostBack = true;                     else                         pplEditor.Enabled = false;                 }             }               //Add JavaScript Event on Dropdown field. Don't forget to add the JavaScript function on the page.             if (_ControlMode == SPControlMode.Edit && fieldDisplayName == "Designation")             {                 DropDownList ddlCategory = (DropDownList)fieldControl.Controls[0];                 ddlCategory.Attributes.Add("onchange", string.Format("javascript:DropdownChangeEvent('{0}');return false;", ddlCategory.ClientID));             }    Following are the screenshots of my Custom ListForm WebPart. Let’s play a game, check out your OOB List forms of SharePoint, compare with these screens and find out differences.   DispForm.aspx:   EditForm.aspx:   NewForm.aspx:   Enjoy the SharePoint Soup!!! ­­­­­­­­­­­­­­­­­­­­

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  • Forwarding non-www domain to other domain with dns

    - by Zen Savona
    Is it possible to forward firstdomain.com to www.seconddomain.com or seconddomain.com using surely dns records? I know how to forward www.firstdomain.com to seconddomain.com (with CNAME). What I am trying to do is move my site from one domain to another (new) one, and not break all the links which use the old domain name. I can't do a 301 redirect as it's hosted on Github Pages and I don't have access to the webserver. Thanks

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  • Exadata ROI cases

    - by Javier Puerta
    The following cases illustrate the type of ROI benefits that customers can obtain from their investment in Exadata infrastructure. Australian Finance Group will achieve a 42% ROI by and break even in three years by consolidating Oracle E-Business Suite and Siebel applications on Oracle Exadata.  Read the ROI case at: http://www.oracle.com/us/corporate/customers/afg-1-exadata-cs-1354807.pdf In addition to this study, there are Oracle Exadata Mainstay ROI Case Studies for the following: Merck -Pharma, Oracle Exadata Achieves Fivefold Performance Increase for Critical Product Research Platform Turkcell Accelerates Reporting Tenfold, Saves on Storage and Energy Costs with Consolidated Oracle Exadata Platform

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