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• How to implement a 2d collision detection for Android

  - by Michael Seun Araromi

  I am making a 2d space shooter using opengl ES. Can someone please show me how to implement a collision detection between the enemy ship and player ship. The code for the two classes are below: Player Ship Class: package com.proandroidgames; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import javax.microedition.khronos.opengles.GL10; public class SSGoodGuy { public boolean isDestroyed = false; private int damage = 0; private FloatBuffer vertexBuffer; private FloatBuffer textureBuffer; private ByteBuffer indexBuffer; private float vertices[] = { 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, }; private float texture[] = { 0.0f, 0.0f, 0.25f, 0.0f, 0.25f, 0.25f, 0.0f, 0.25f, }; private byte indices[] = { 0, 1, 2, 0, 2, 3, }; public void applyDamage(){ damage++; if (damage == SSEngine.PLAYER_SHIELDS){ isDestroyed = true; } } public SSGoodGuy() { ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); vertexBuffer = byteBuf.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(texture.length * 4); byteBuf.order(ByteOrder.nativeOrder()); textureBuffer = byteBuf.asFloatBuffer(); textureBuffer.put(texture); textureBuffer.position(0); indexBuffer = ByteBuffer.allocateDirect(indices.length); indexBuffer.put(indices); indexBuffer.position(0); } public void draw(GL10 gl, int[] spriteSheet) { gl.glBindTexture(GL10.GL_TEXTURE_2D, spriteSheet[0]); gl.glFrontFace(GL10.GL_CCW); gl.glEnable(GL10.GL_CULL_FACE); gl.glCullFace(GL10.GL_BACK); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glDisable(GL10.GL_CULL_FACE); } } Enemy Ship Class: package com.proandroidgames; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import java.util.Random; import javax.microedition.khronos.opengles.GL10; public class SSEnemy { public float posY = 0f; public float posX = 0f; public float posT = 0f; public float incrementXToTarget = 0f; public float incrementYToTarget = 0f; public int attackDirection = 0; public boolean isDestroyed = false; private int damage = 0; public int enemyType = 0; public boolean isLockedOn = false; public float lockOnPosX = 0f; public float lockOnPosY = 0f; private Random randomPos = new Random(); private FloatBuffer vertexBuffer; private FloatBuffer textureBuffer; private ByteBuffer indexBuffer; private float vertices[] = { 0.0f, 0.0f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f, 0.0f, }; private float texture[] = { 0.0f, 0.0f, 0.25f, 0.0f, 0.25f, 0.25f, 0.0f, 0.25f, }; private byte indices[] = { 0, 1, 2, 0, 2, 3, }; public void applyDamage() { damage++; switch (enemyType) { case SSEngine.TYPE_INTERCEPTOR: if (damage == SSEngine.INTERCEPTOR_SHIELDS) { isDestroyed = true; } break; case SSEngine.TYPE_SCOUT: if (damage == SSEngine.SCOUT_SHIELDS) { isDestroyed = true; } break; case SSEngine.TYPE_WARSHIP: if (damage == SSEngine.WARSHIP_SHIELDS) { isDestroyed = true; } break; } } public SSEnemy(int type, int direction) { enemyType = type; attackDirection = direction; posY = (randomPos.nextFloat() * 4) + 4; switch (attackDirection) { case SSEngine.ATTACK_LEFT: posX = 0; break; case SSEngine.ATTACK_RANDOM: posX = randomPos.nextFloat() * 3; break; case SSEngine.ATTACK_RIGHT: posX = 3; break; } posT = SSEngine.SCOUT_SPEED; ByteBuffer byteBuf = ByteBuffer.allocateDirect(vertices.length * 4); byteBuf.order(ByteOrder.nativeOrder()); vertexBuffer = byteBuf.asFloatBuffer(); vertexBuffer.put(vertices); vertexBuffer.position(0); byteBuf = ByteBuffer.allocateDirect(texture.length * 4); byteBuf.order(ByteOrder.nativeOrder()); textureBuffer = byteBuf.asFloatBuffer(); textureBuffer.put(texture); textureBuffer.position(0); indexBuffer = ByteBuffer.allocateDirect(indices.length); indexBuffer.put(indices); indexBuffer.position(0); } public float getNextScoutX() { if (attackDirection == SSEngine.ATTACK_LEFT) { return (float) ((SSEngine.BEZIER_X_4 * (posT * posT * posT)) + (SSEngine.BEZIER_X_3 * 3 * (posT * posT) * (1 - posT)) + (SSEngine.BEZIER_X_2 * 3 * posT * ((1 - posT) * (1 - posT))) + (SSEngine.BEZIER_X_1 * ((1 - posT) * (1 - posT) * (1 - posT)))); } else { return (float) ((SSEngine.BEZIER_X_1 * (posT * posT * posT)) + (SSEngine.BEZIER_X_2 * 3 * (posT * posT) * (1 - posT)) + (SSEngine.BEZIER_X_3 * 3 * posT * ((1 - posT) * (1 - posT))) + (SSEngine.BEZIER_X_4 * ((1 - posT) * (1 - posT) * (1 - posT)))); } } public float getNextScoutY() { return (float) ((SSEngine.BEZIER_Y_1 * (posT * posT * posT)) + (SSEngine.BEZIER_Y_2 * 3 * (posT * posT) * (1 - posT)) + (SSEngine.BEZIER_Y_3 * 3 * posT * ((1 - posT) * (1 - posT))) + (SSEngine.BEZIER_Y_4 * ((1 - posT) * (1 - posT) * (1 - posT)))); } public void draw(GL10 gl, int[] spriteSheet) { gl.glBindTexture(GL10.GL_TEXTURE_2D, spriteSheet[0]); gl.glFrontFace(GL10.GL_CCW); gl.glEnable(GL10.GL_CULL_FACE); gl.glCullFace(GL10.GL_BACK); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); gl.glTexCoordPointer(2, GL10.GL_FLOAT, 0, textureBuffer); gl.glDrawElements(GL10.GL_TRIANGLES, indices.length, GL10.GL_UNSIGNED_BYTE, indexBuffer); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glDisableClientState(GL10.GL_TEXTURE_COORD_ARRAY); gl.glDisable(GL10.GL_CULL_FACE); } }

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• Functions inside page using Razor View Engine – ASP.NET MVC

  - by hajan

  As we already know, Razor is probably the best view engine for ASP.NET MVC so far. It keeps your code fluid and very expressive. Besides the other functionalities Razor has, it also supports writing local functions. If you want to write a function, you can’t just open new @{ } razor block and write it there… it won’t work. Instead, you should specify @functions { } so that inside the brackets you will write your own C#/VB.NET functions/methods. Lets see an example: 1. I have the following loop that prints data using Razor <ul> @{     int N = 10;     for (int i = 1; i<=N; i++)     {         <li>Number @i</li>     }     } </ul> This code will print the numbers from 1 to 10: Number 1 Number 2 Number 3 Number 4 Number 5 Number 6 Number 7 Number 8 Number 9 Number 10 So, now lets write a function that will check if current number is even, if yes… add Even before Number word. Function in Razor @functions{     public bool isEven(int number)     {         return number % 2 == 0 ? true : false;     } } The modified code which creates unordered list is: <ul> @{     int N = 10;     for (int i = 1; i<=N; i++)     {         if (isEven(@i)) {             <li>Even number @i</li>         }         else {             <li>Number @i</li>         }                 }             } </ul> As you can see, in the modified code we use the isEven(@i) function to check if the current number is even or not… The result is: Number 1 Even number 2 Number 3 Even number 4 Number 5 Even number 6 Number 7 Even number 8 Number 9 Even number 10 So, the main point of this blog was to show how you can define your own functions inside page using Razor View Engine. Of course you can define multiple functions inside the same @functions { } defined razor statement. The complete code: @{     Layout = null; } <!DOCTYPE html> <html> <head>     <title>ASP.NET MVC - Razor View Engine :: Functions</title> </head> <body>     <div>         <ul>         @{             int N = 10;             for (int i = 1; i<=N; i++)             {                 if (isEven(@i)) {                     <li>Even number @i</li>                 }                 else {                     <li>Number @i</li>                 }                         }                     }         </ul>         @functions{             public bool isEven(int number)             {                 return number % 2 == 0 ? true : false;             }         }     </div> </body> </html> Hope you like it. Regards, Hajan

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• C#/.NET Little Wonders: Using &lsquo;default&rsquo; to Get Default Values

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Today’s little wonder is another of those small items that can help a lot in certain situations, especially when writing generics.  In particular, it is useful in determining what the default value of a given type would be. The Problem: what’s the default value for a generic type? There comes a time when you’re writing generic code where you may want to set an item of a given generic type.  Seems simple enough, right?  We’ll let’s see! Let’s say we want to query a Dictionary<TKey, TValue> for a given key and get back the value, but if the key doesn’t exist, we’d like a default value instead of throwing an exception. So, for example, we might have a the following dictionary defined: 1: var lookup = new Dictionary<int, string> 2: { 3: { 1, "Apple" }, 4: { 2, "Orange" }, 5: { 3, "Banana" }, 6: { 4, "Pear" }, 7: { 9, "Peach" } 8: }; And using those definitions, perhaps we want to do something like this: 1: // assume a default 2: string value = "Unknown"; 3:  4: // if the item exists in dictionary, get its value 5: if (lookup.ContainsKey(5)) 6: { 7: value = lookup[5]; 8: } But that’s inefficient, because then we’re double-hashing (once for ContainsKey() and once for the indexer).  Well, to avoid the double-hashing, we could use TryGetValue() instead: 1: string value; 2:  3: // if key exists, value will be put in value, if not default it 4: if (!lookup.TryGetValue(5, out value)) 5: { 6: value = "Unknown"; 7: } But the “flow” of using of TryGetValue() can get clunky at times when you just want to assign either the value or a default to a variable.  Essentially it’s 3-ish lines (depending on formatting) for 1 assignment.  So perhaps instead we’d like to write an extension method to support a cleaner interface that will return a default if the item isn’t found: 1: public static class DictionaryExtensions 2: { 3: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 4: TKey key, TValue defaultIfNotFound) 5: { 6: TValue value; 7:  8: // value will be the result or the default for TValue 9: if (!dict.TryGetValue(key, out value)) 10: { 11: value = defaultIfNotFound; 12: } 13:  14: return value; 15: } 16: } 17:  So this creates an extension method on Dictionary<TKey, TValue> that will attempt to get a value using the given key, and will return the defaultIfNotFound as a stand-in if the key does not exist. This code compiles, fine, but what if we would like to go one step further and allow them to specify a default if not found, or accept the default for the type?  Obviously, we could overload the method to take the default or not, but that would be duplicated code and a bit heavy for just specifying a default.  It seems reasonable that we could set the not found value to be either the default for the type, or the specified value. So what if we defaulted the type to null? 1: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 2: TKey key, TValue defaultIfNotFound = null) // ... No, this won’t work, because only reference types (and Nullable<T> wrapped types due to syntactical sugar) can be assigned to null.  So what about a calling parameterless constructor? 1: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 2: TKey key, TValue defaultIfNotFound = new TValue()) // ... No, this won’t work either for several reasons.  First, we’d expect a reference type to return null, not an “empty” instance.  Secondly, not all reference types have a parameter-less constructor (string for example does not).  And finally, a constructor cannot be determined at compile-time, while default values can. The Solution: default(T) – returns the default value for type T Many of us know the default keyword for its uses in switch statements as the default case.  But it has another use as well: it can return us the default value for a given type.  And since it generates the same defaults that default field initialization uses, it can be determined at compile-time as well. For example: 1: var x = default(int); // x is 0 2:  3: var y = default(bool); // y is false 4:  5: var z = default(string); // z is null 6:  7: var t = default(TimeSpan); // t is a TimeSpan with Ticks == 0 8:  9: var n = default(int?); // n is a Nullable<int> with HasValue == false Notice that for numeric types the default is 0, and for reference types the default is null.  In addition, for struct types, the value is a default-constructed struct – which simply means a struct where every field has their default value (hence 0 Ticks for TimeSpan, etc.). So using this, we could modify our code to this: 1: public static class DictionaryExtensions 2: { 3: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 4: TKey key, TValue defaultIfNotFound = default(TValue)) 5: { 6: TValue value; 7:  8: // value will be the result or the default for TValue 9: if (!dict.TryGetValue(key, out value)) 10: { 11: value = defaultIfNotFound; 12: } 13:  14: return value; 15: } 16: } Now, if defaultIfNotFound is unspecified, it will use default(TValue) which will be the default value for whatever value type the dictionary holds.  So let’s consider how we could use this: 1: lookup.GetValueOrDefault(1); // returns “Apple” 2:  3: lookup.GetValueOrDefault(5); // returns null 4:  5: lookup.GetValueOrDefault(5, “Unknown”); // returns “Unknown” 6:  Again, do not confuse a parameter-less constructor with the default value for a type.  Remember that the default value for any type is the compile-time default for any instance of that type (0 for numeric, false for bool, null for reference types, and struct will all default fields for struct).  Consider the difference: 1: // both zero 2: int i1 = default(int); 3: int i2 = new int(); 4:  5: // both “zeroed” structs 6: var dt1 = default(DateTime); 7: var dt2 = new DateTime(); 8:  9: // sb1 is null, sb2 is an “empty” string builder 10: var sb1 = default(StringBuilder()); 11: var sb2 = new StringBuilder(); So in the above code, notice that the value types all resolve the same whether using default or parameter-less construction.  This is because a value type is never null (even Nullable<T> wrapped types are never “null” in a reference sense), they will just by default contain fields with all default values. However, for reference types, the default is null and not a constructed instance.  Also it should be noted that not all classes have parameter-less constructors (string, for instance, doesn’t have one – and doesn’t need one). Summary Whenever you need to get the default value for a type, especially a generic type, consider using the default keyword.  This handy word will give you the default value for the given type at compile-time, which can then be used for initialization, optional parameters, etc. Technorati Tags: C#,CSharp,.NET,Little Wonders,default

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• C#: Does an IDisposable in a Halted Iterator Dispose?

  - by James Michael Hare

  If that sounds confusing, let me give you an example. Let's say you expose a method to read a database of products, and instead of returning a List<Product> you return an IEnumerable<Product> in iterator form (yield return). This accomplishes several good things: The IDataReader is not passed out of the Data Access Layer which prevents abstraction leak and resource leak potentials. You don't need to construct a full List<Product> in memory (which could be very big) if you just want to forward iterate once. If you only want to consume up to a certain point in the list, you won't incur the database cost of looking up the other items. This could give us an example like: 1: // a sample data access object class to do standard CRUD operations. 2: public class ProductDao 3: { 4: private DbProviderFactory _factory = SqlClientFactory.Instance 5:  6: // a method that would retrieve all available products 7: public IEnumerable<Product> GetAvailableProducts() 8: { 9: // must create the connection 10: using (var con = _factory.CreateConnection()) 11: { 12: con.ConnectionString = _productsConnectionString; 13: con.Open(); 14:  15: // create the command 16: using (var cmd = _factory.CreateCommand()) 17: { 18: cmd.Connection = con; 19: cmd.CommandText = _getAllProductsStoredProc; 20: cmd.CommandType = CommandType.StoredProcedure; 21:  22: // get a reader and pass back all results 23: using (var reader = cmd.ExecuteReader()) 24: { 25: while(reader.Read()) 26: { 27: yield return new Product 28: { 29: Name = reader["product_name"].ToString(), 30: ... 31: }; 32: } 33: } 34: } 35: } 36: } 37: } The database details themselves are irrelevant. I will say, though, that I'm a big fan of using the System.Data.Common classes instead of your provider specific counterparts directly (SqlCommand, OracleCommand, etc). This lets you mock your data sources easily in unit testing and also allows you to swap out your provider in one line of code. In fact, one of the shared components I'm most proud of implementing was our group's DatabaseUtility library that simplifies all the database access above into one line of code in a thread-safe and provider-neutral way. I went with my own flavor instead of the EL due to the fact I didn't want to force internal company consumers to use the EL if they didn't want to, and it made it easy to allow them to mock their database for unit testing by providing a MockCommand, MockConnection, etc that followed the System.Data.Common model. One of these days I'll blog on that if anyone's interested. Regardless, you often have situations like the above where you are consuming and iterating through a resource that must be closed once you are finished iterating. For the reasons stated above, I didn't want to return IDataReader (that would force them to remember to Dispose it), and I didn't want to return List<Product> (that would force them to hold all products in memory) -- but the first time I wrote this, I was worried. What if you never consume the last item and exit the loop? Are the reader, command, and connection all disposed correctly? Of course, I was 99.999999% sure the creators of C# had already thought of this and taken care of it, but inspection in Reflector was difficult due to the nature of the state machines yield return generates, so I decided to try a quick example program to verify whether or not Dispose() will be called when an iterator is broken from outside the iterator itself -- i.e. before the iterator reports there are no more items. So I wrote a quick Sequencer class with a Dispose() method and an iterator for it. Yes, it is COMPLETELY contrived: 1: // A disposable sequence of int -- yes this is completely contrived... 2: internal class Sequencer : IDisposable 3: { 4: private int _i = 0; 5: private readonly object _mutex = new object(); 6:  7: // Constructs an int sequence. 8: public Sequencer(int start) 9: { 10: _i = start; 11: } 12:  13: // Gets the next integer 14: public int GetNext() 15: { 16: lock (_mutex) 17: { 18: return _i++; 19: } 20: } 21:  22: // Dispose the sequence of integers. 23: public void Dispose() 24: { 25: // force output immediately (flush the buffer) 26: Console.WriteLine("Disposed with last sequence number of {0}!", _i); 27: Console.Out.Flush(); 28: } 29: } And then I created a generator (infinite-loop iterator) that did the using block for auto-Disposal: 1: // simply defines an extension method off of an int to start a sequence 2: public static class SequencerExtensions 3: { 4: // generates an infinite sequence starting at the specified number 5: public static IEnumerable<int> GetSequence(this int starter) 6: { 7: // note the using here, will call Dispose() when block terminated. 8: using (var seq = new Sequencer(starter)) 9: { 10: // infinite loop on this generator, means must be bounded by caller! 11: while(true) 12: { 13: yield return seq.GetNext(); 14: } 15: } 16: } 17: } This is really the same conundrum as the database problem originally posed. Here we are using iteration (yield return) over a large collection (infinite sequence of integers). If we cut the sequence short by breaking iteration, will that using block exit and hence, Dispose be called? Well, let's see: 1: // The test program class 2: public class IteratorTest 3: { 4: // The main test method. 5: public static void Main() 6: { 7: Console.WriteLine("Going to consume 10 of infinite items"); 8: Console.Out.Flush(); 9:  10: foreach(var i in 0.GetSequence()) 11: { 12: // could use TakeWhile, but wanted to output right at break... 13: if(i >= 10) 14: { 15: Console.WriteLine("Breaking now!"); 16: Console.Out.Flush(); 17: break; 18: } 19:  20: Console.WriteLine(i); 21: Console.Out.Flush(); 22: } 23:  24: Console.WriteLine("Done with loop."); 25: Console.Out.Flush(); 26: } 27: } So, what do we see? Do we see the "Disposed" message from our dispose, or did the Dispose get skipped because from an "eyeball" perspective we should be locked in that infinite generator loop? Here's the results: 1: Going to consume 10 of infinite items 2: 0 3: 1 4: 2 5: 3 6: 4 7: 5 8: 6 9: 7 10: 8 11: 9 12: Breaking now! 13: Disposed with last sequence number of 11! 14: Done with loop. Yes indeed, when we break the loop, the state machine that C# generates for yield iterate exits the iteration through the using blocks and auto-disposes the IDisposable correctly. I must admit, though, the first time I wrote one, I began to wonder and that led to this test. If you've never seen iterators before (I wrote a previous entry here) the infinite loop may throw you, but you have to keep in mind it is not a linear piece of code, that every time you hit a "yield return" it cedes control back to the state machine generated for the iterator. And this state machine, I'm happy to say, is smart enough to clean up the using blocks correctly. I suspected those wily guys and gals at Microsoft engineered it well, and I wasn't disappointed. But, I've been bitten by assumptions before, so it's good to test and see. Yes, maybe you knew it would or figured it would, but isn't it nice to know? And as those campy 80s G.I. Joe cartoon public service reminders always taught us, "Knowing is half the battle...". Technorati Tags: C#,.NET

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• Collide with rotation of the object

  - by Lahiru

  I'm developing a mirror for lazer beam(Ball sprite). There I'm trying to redirect the laze beam according to the ration degree of the mirror(Rectangle). How can I collide the ball to the correct angle if the colliding object is with some angle(45 deg) rather than colliding back. here is an screen shot of my work here is my code using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace collision { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; Texture2D ballTexture; Rectangle ballBounds; Vector2 ballPosition; Vector2 ballVelocity; float ballSpeed = 30f; Texture2D blockTexture; Rectangle blockBounds; Vector2 blockPosition; private Vector2 origin; KeyboardState keyboardState; //Font SpriteFont Font1; Vector2 FontPos; private String displayText; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here ballPosition = new Vector2(this.GraphicsDevice.Viewport.Width / 2, this.GraphicsDevice.Viewport.Height * 0.25f); blockPosition = new Vector2(this.GraphicsDevice.Viewport.Width / 2, this.GraphicsDevice.Viewport.Height /2); ballVelocity = new Vector2(0, 1); base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); ballTexture = Content.Load<Texture2D>("ball"); blockTexture = Content.Load<Texture2D>("mirror"); //create rectangles based off the size of the textures ballBounds = new Rectangle((int)(ballPosition.X - ballTexture.Width / 2), (int)(ballPosition.Y - ballTexture.Height / 2), ballTexture.Width, ballTexture.Height); blockBounds = new Rectangle((int)(blockPosition.X - blockTexture.Width / 2), (int)(blockPosition.Y - blockTexture.Height / 2), blockTexture.Width, blockTexture.Height); origin.X = blockTexture.Width / 2; origin.Y = blockTexture.Height / 2; // TODO: use this.Content to load your game content here Font1 = Content.Load<SpriteFont>("SpriteFont1"); FontPos = new Vector2(graphics.GraphicsDevice.Viewport.Width - 100, 20); } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> /// private float RotationAngle; float circle = MathHelper.Pi * 2; float angle; protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); // TODO: Add your update logic here //check for collision between the ball and the block, or if the ball is outside the bounds of the screen if (ballBounds.Intersects(blockBounds) || !GraphicsDevice.Viewport.Bounds.Contains(ballBounds)) { //we have a simple collision! //if it has hit, swap the direction of the ball, and update it's position ballVelocity = -ballVelocity; ballPosition += ballVelocity * ballSpeed; } else { //move the ball a bit ballPosition += ballVelocity * ballSpeed; } //update bounding boxes ballBounds.X = (int)ballPosition.X; ballBounds.Y = (int)ballPosition.Y; blockBounds.X = (int)blockPosition.X; blockBounds.Y = (int)blockPosition.Y; keyboardState = Keyboard.GetState(); float val = 1.568017f/90; if (keyboardState.IsKeyDown(Keys.Space)) RotationAngle = RotationAngle + (float)Math.PI; if (keyboardState.IsKeyDown(Keys.Left)) RotationAngle = RotationAngle - val; angle = (float)Math.PI / 4.0f; // 90 degrees RotationAngle = angle; // RotationAngle = RotationAngle % circle; displayText = RotationAngle.ToString(); base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); // TODO: Add your drawing code here spriteBatch.Begin(); // Find the center of the string Vector2 FontOrigin = Font1.MeasureString(displayText) / 2; spriteBatch.DrawString(Font1, displayText, FontPos, Color.White, 0, FontOrigin, 1.0f, SpriteEffects.None, 0.5f); spriteBatch.Draw(ballTexture, ballPosition, Color.White); spriteBatch.Draw(blockTexture, blockPosition,null, Color.White, RotationAngle,origin, 1.0f, SpriteEffects.None, 0f); spriteBatch.End(); base.Draw(gameTime); } } }

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• tile_static, tile_barrier, and tiled matrix multiplication with C++ AMP

  - by Daniel Moth

  We ended the previous post with a mechanical transformation of the C++ AMP matrix multiplication example to the tiled model and in the process introduced tiled_index and tiled_grid. This is part 2. tile_static memory You all know that in regular CPU code, static variables have the same value regardless of which thread accesses the static variable. This is in contrast with non-static local variables, where each thread has its own copy. Back to C++ AMP, the same rules apply and each thread has its own value for local variables in your lambda, whereas all threads see the same global memory, which is the data they have access to via the array and array_view. In addition, on an accelerator like the GPU, there is a programmable cache, a third kind of memory type if you'd like to think of it that way (some call it shared memory, others call it scratchpad memory). Variables stored in that memory share the same value for every thread in the same tile. So, when you use the tiled model, you can have variables where each thread in the same tile sees the same value for that variable, that threads from other tiles do not. The new storage class for local variables introduced for this purpose is called tile_static. You can only use tile_static in restrict(direct3d) functions, and only when explicitly using the tiled model. What this looks like in code should be no surprise, but here is a snippet to confirm your mental image, using a good old regular C array // each tile of threads has its own copy of locA, // shared among the threads of the tile tile_static float locA[16][16]; Note that tile_static variables are scoped and have the lifetime of the tile, and they cannot have constructors or destructors. tile_barrier In amp.h one of the types introduced is tile_barrier. You cannot construct this object yourself (although if you had one, you could use a copy constructor to create another one). So how do you get one of these? You get it, from a tiled_index object. Beyond the 4 properties returning index objects, tiled_index has another property, barrier, that returns a tile_barrier object. The tile_barrier class exposes a single member, the method wait. 15: // Given a tiled_index object named t_idx 16: t_idx.barrier.wait(); 17: // more code …in the code above, all threads in the tile will reach line 16 before a single one progresses to line 17. Note that all threads must be able to reach the barrier, i.e. if you had branchy code in such a way which meant that there is a chance that not all threads could reach line 16, then the code above would be illegal. Tiled Matrix Multiplication Example – part 2 So now that we added to our understanding the concepts of tile_static and tile_barrier, let me obfuscate rewrite the matrix multiplication code so that it takes advantage of tiling. Before you start reading this, I suggest you get a cup of your favorite non-alcoholic beverage to enjoy while you try to fully understand the code. 01: void MatrixMultiplyTiled(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W) 02: { 03: static const int TS = 16; 04: array_view<const float,2> a(M, W, vA); 05: array_view<const float,2> b(W, N, vB); 06: array_view<writeonly<float>,2> c(M,N,vC); 07: parallel_for_each(c.grid.tile< TS, TS >(), 08: [=] (tiled_index< TS, TS> t_idx) restrict(direct3d) 09: { 10: int row = t_idx.local[0]; int col = t_idx.local[1]; 11: float sum = 0.0f; 12: for (int i = 0; i < W; i += TS) { 13: tile_static float locA[TS][TS], locB[TS][TS]; 14: locA[row][col] = a(t_idx.global[0], col + i); 15: locB[row][col] = b(row + i, t_idx.global[1]); 16: t_idx.barrier.wait(); 17: for (int k = 0; k < TS; k++) 18: sum += locA[row][k] * locB[k][col]; 19: t_idx.barrier.wait(); 20: } 21: c[t_idx.global] = sum; 22: }); 23: } Notice that all the code up to line 9 is the same as per the changes we made in part 1 of tiling introduction. If you squint, the body of the lambda itself preserves the original algorithm on lines 10, 11, and 17, 18, and 21. The difference being that those lines use new indexing and the tile_static arrays; the tile_static arrays are declared and initialized on the brand new lines 13-15. On those lines we copy from the global memory represented by the array_view objects (a and b), to the tile_static vanilla arrays (locA and locB) – we are copying enough to fit a tile. Because in the code that follows on line 18 we expect the data for this tile to be in the tile_static storage, we need to synchronize the threads within each tile with a barrier, which we do on line 16 (to avoid accessing uninitialized memory on line 18). We also need to synchronize the threads within a tile on line 19, again to avoid the race between lines 14, 15 (retrieving the next set of data for each tile and overwriting the previous set) and line 18 (not being done processing the previous set of data). Luckily, as part of the awesome C++ AMP debugger in Visual Studio there is an option that helps you find such races, but that is a story for another blog post another time. May I suggest reading the next section, and then coming back to re-read and walk through this code with pen and paper to really grok what is going on, if you haven't already? Cool. Why would I introduce this tiling complexity into my code? Funny you should ask that, I was just about to tell you. There is only one reason we tiled our extent, had to deal with finding a good tile size, ensure the number of threads we schedule are correctly divisible with the tile size, had to use a tiled_index instead of a normal index, and had to understand tile_barrier and to figure out where we need to use it, and double the size of our lambda in terms of lines of code: the reason is to be able to use tile_static memory. Why do we want to use tile_static memory? Because accessing tile_static memory is around 10 times faster than accessing the global memory on an accelerator like the GPU, e.g. in the code above, if you can get 150GB/second accessing data from the array_view a, you can get 1500GB/second accessing the tile_static array locA. And since by definition you are dealing with really large data sets, the savings really pay off. We have seen tiled implementations being twice as fast as their non-tiled counterparts. Now, some algorithms will not have performance benefits from tiling (and in fact may deteriorate), e.g. algorithms that require you to go only once to global memory will not benefit from tiling, since with tiling you already have to fetch the data once from global memory! Other algorithms may benefit, but you may decide that you are happy with your code being 150 times faster than the serial-version you had, and you do not need to invest to make it 250 times faster. Also algorithms with more than 3 dimensions, which C++ AMP supports in the non-tiled model, cannot be tiled. Also note that in future releases, we may invest in making the non-tiled model, which already uses tiling under the covers, go the extra step and use tile_static memory on your behalf, but it is obviously way to early to commit to anything like that, and we certainly don't do any of that today. Comments about this post by Daniel Moth welcome at the original blog.

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• Scheduling thread tiles with C++ AMP

  - by Daniel Moth

  This post assumes you are totally comfortable with, what some of us call, the simple model of C++ AMP, i.e. you could write your own matrix multiplication. We are now ready to explore the tiled model, which builds on top of the non-tiled one. Tiling the extent We know that when we pass a grid (which is just an extent under the covers) to the parallel_for_each call, it determines the number of threads to schedule and their index values (including dimensionality). For the single-, two-, and three- dimensional cases you can go a step further and subdivide the threads into what we call tiles of threads (others may call them thread groups). So here is a single-dimensional example: extent<1> e(20); // 20 units in a single dimension with indices from 0-19 grid<1> g(e);      // same as extent tiled_grid<4> tg = g.tile<4>(); …on the 3rd line we subdivided the single-dimensional space into 5 single-dimensional tiles each having 4 elements, and we captured that result in a concurrency::tiled_grid (a new class in amp.h). Let's move on swiftly to another example, in pictures, this time 2-dimensional: So we start on the left with a grid of a 2-dimensional extent which has 8*6=48 threads. We then have two different examples of tiling. In the first case, in the middle, we subdivide the 48 threads into tiles where each has 4*3=12 threads, hence we have 2*2=4 tiles. In the second example, on the right, we subdivide the original input into tiles where each has 2*2=4 threads, hence we have 4*3=12 tiles. Notice how you can play with the tile size and achieve different number of tiles. The numbers you pick must be such that the original total number of threads (in our example 48), remains the same, and every tile must have the same size. Of course, you still have no clue why you would do that, but stick with me. First, we should see how we can use this tiled_grid, since the parallel_for_each function that we know expects a grid. Tiled parallel_for_each and tiled_index It turns out that we have additional overloads of parallel_for_each that accept a tiled_grid instead of a grid. However, those overloads, also expect that the lambda you pass in accepts a concurrency::tiled_index (new in amp.h), not an index<N>. So how is a tiled_index different to an index? A tiled_index object, can have only 1 or 2 or 3 dimensions (matching exactly the tiled_grid), and consists of 4 index objects that are accessible via properties: global, local, tile_origin, and tile. The global index is the same as the index we know and love: the global thread ID. The local index is the local thread ID within the tile. The tile_origin index returns the global index of the thread that is at position 0,0 of this tile, and the tile index is the position of the tile in relation to the overall grid. Confused? Here is an example accompanied by a picture that hopefully clarifies things: array_view<int, 2> data(8, 6, p_my_data); parallel_for_each(data.grid.tile<2,2>(), [=] (tiled_index<2,2> t_idx) restrict(direct3d) { /* todo */ }); Given the code above and the picture on the right, what are the values of each of the 4 index objects that the t_idx variables exposes, when the lambda is executed by T (highlighted in the picture on the right)? If you can't work it out yourselves, the solution follows: t_idx.global       = index<2> (6,3) t_idx.local          = index<2> (0,1) t_idx.tile_origin = index<2> (6,2) t_idx.tile             = index<2> (3,1) Don't move on until you are comfortable with this… the picture really helps, so use it. Tiled Matrix Multiplication Example – part 1 Let's paste here the C++ AMP matrix multiplication example, bolding the lines we are going to change (can you guess what the changes will be?) 01: void MatrixMultiplyTiled_Part1(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W) 02: { 03: 04: array_view<const float,2> a(M, W, vA); 05: array_view<const float,2> b(W, N, vB); 06: array_view<writeonly<float>,2> c(M, N, vC); 07: parallel_for_each(c.grid, 08: [=](index<2> idx) restrict(direct3d) { 09: 10: int row = idx[0]; int col = idx[1]; 11: float sum = 0.0f; 12: for(int i = 0; i < W; i++) 13: sum += a(row, i) * b(i, col); 14: c[idx] = sum; 15: }); 16: } To turn this into a tiled example, first we need to decide our tile size. Let's say we want each tile to be 16*16 (which assumes that we'll have at least 256 threads to process, and that c.grid.extent.size() is divisible by 256, and moreover that c.grid.extent[0] and c.grid.extent[1] are divisible by 16). So we insert at line 03 the tile size (which must be a compile time constant). 03: static const int TS = 16; ...then we need to tile the grid to have tiles where each one has 16*16 threads, so we change line 07 to be as follows 07: parallel_for_each(c.grid.tile<TS,TS>(), ...that means that our index now has to be a tiled_index with the same characteristics as the tiled_grid, so we change line 08 08: [=](tiled_index<TS, TS> t_idx) restrict(direct3d) { ...which means, without changing our core algorithm, we need to be using the global index that the tiled_index gives us access to, so we insert line 09 as follows 09: index<2> idx = t_idx.global; ...and now this code just works and it is tiled! Closing thoughts on part 1 The process we followed just shows the mechanical transformation that can take place from the simple model to the tiled model (think of this as step 1). In fact, when we wrote the matrix multiplication example originally, the compiler was doing this mechanical transformation under the covers for us (and it has additional smarts to deal with the cases where the total number of threads scheduled cannot be divisible by the tile size). The point is that the thread scheduling is always tiled, even when you use the non-tiled model. But with this mechanical transformation, we haven't gained anything… Hint: our goal with explicitly using the tiled model is to gain even more performance. In the next post, we'll evolve this further (beyond what the compiler can automatically do for us, in this first release), so you can see the full usage of the tiled model and its benefits… Comments about this post by Daniel Moth welcome at the original blog.

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• Applications: The Mathematics of Movement, Part 2

  - by TechTwaddle

  In part 1 of this series we saw how we can make the marble move towards the click point, with a fixed speed. In this post we’ll see, first, how to get rid of Atan2(), sine() and cosine() in our calculations, and, second, reducing the speed of the marble as it approaches the destination, so it looks like the marble is easing into it’s final position. As I mentioned in one of the previous posts, this is achieved by making the speed of the marble a function of the distance between the marble and the destination point. Getting rid of Atan2(), sine() and cosine() Ok, to be fair we are not exactly getting rid of these trigonometric functions, rather, replacing one form with another. So instead of writing sin(?), we write y/length. You see the point. So instead of using the trig functions as below, double x = destX - marble1.x; double y = destY - marble1.y; //distance between destination and current position, before updating marble position distanceSqrd = x * x + y * y; double angle = Math.Atan2(y, x); //Cos and Sin give us the unit vector, 6 is the value we use to magnify the unit vector along the same direction incrX = speed * Math.Cos(angle); incrY = speed * Math.Sin(angle); marble1.x += incrX; marble1.y += incrY; we use the following, double x = destX - marble1.x; double y = destY - marble1.y; //distance between destination and marble (before updating marble position) lengthSqrd = x * x + y * y; length = Math.Sqrt(lengthSqrd); //unit vector along the same direction as vector(x, y) unitX = x / length; unitY = y / length; //update marble position incrX = speed * unitX; incrY = speed * unitY; marble1.x += incrX; marble1.y += incrY; so we replaced cos(?) with x/length and sin(?) with y/length. The result is the same.   Adding oomph to the way it moves In the last post we had the speed of the marble fixed at 6, double speed = 6; to make the marble decelerate as it moves, we have to keep updating the speed of the marble in every frame such that the speed is calculated as a function of the length. So we may have, speed = length/12; ‘length’ keeps decreasing as the marble moves and so does speed. The Form1_MouseUp() function remains the same as before, here is the UpdatePosition() method, private void UpdatePosition() {     double incrX = 0, incrY = 0;     double lengthSqrd = 0, length = 0, lengthSqrdNew = 0;     double unitX = 0, unitY = 0;     double speed = 0;     double x = destX - marble1.x;     double y = destY - marble1.y;     //distance between destination and marble (before updating marble position)     lengthSqrd = x * x + y * y;     length = Math.Sqrt(lengthSqrd);     //unit vector along the same direction as vector(x, y)     unitX = x / length;     unitY = y / length;     //speed as a function of length     speed = length / 12;     //update marble position     incrX = speed * unitX;     incrY = speed * unitY;     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;     }     //distance between destination and marble (after updating marble position)     x = destX - (marble1.x);     y = destY - (marble1.y);     lengthSqrdNew = x * x + y * y;     /*      * End Condition:      * 1. If there is not much difference between lengthSqrd and lengthSqrdNew      * 2. If the marble has moved more than or equal to a distance of totLenToTravel (see Form1_MouseUp)      */     x = startPosX - marble1.x;     y = startPosY - marble1.y;     double totLenTraveledSqrd = x * x + y * y;     if ((int)totLenTraveledSqrd >= (int)totLenToTravelSqrd)     {         System.Console.WriteLine("Stopping because Total Len has been traveled");         timer1.Enabled = false;     }     else if (Math.Abs((int)lengthSqrd - (int)lengthSqrdNew) < 4)     {         System.Console.WriteLine("Stopping because no change in Old and New");         timer1.Enabled = false;     } } A point to note here is that, in this implementation, the marble never stops because it travelled a distance of totLenToTravelSqrd (first if condition). This happens because speed is a function of the length. During the final few frames length becomes very small and so does speed; and so the amount by which the marble shifts is quite small, and the second if condition always hits true first. I’ll end this series with a third post. In part 3 we will cover two things, one, when the user clicks, the marble keeps moving in that direction, rebounding off the screen edges and keeps moving forever. Two, when the user clicks on the screen, the marble moves towards it, with it’s speed reducing by every frame. It doesn’t come to a halt when the destination point is reached, instead, it continues to move, rebounds off the screen edges and slowly comes to halt. The amount of time that the marble keeps moving depends on how far the user clicks from the marble. I had mentioned this second situation here. Finally, here’s a video of this program running,

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• JBox2D Polygon Collisions Acting Strange

  - by andy

  I have been playing around with JBox2D and Slick2D and made a little demo with a ground object, a box object, and two different polygons. The problem I am facing is that the collision-detection for the polygons seems to be off (see picture below), but the box's collision works fine. My Code: Main Class package main; import org.jbox2d.common.Vec2; import org.jbox2d.dynamics.BodyType; import org.jbox2d.dynamics.World; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.SlickException; import org.newdawn.slick.state.BasicGameState; import org.newdawn.slick.state.StateBasedGame; import shapes.Box; import shapes.Polygon; public class State1 extends BasicGameState{ World world; int velocityIterations; int positionIterations; float pixelsPerMeter; int state; Box ground; Box box1; Polygon poly1; Polygon poly2; Renderer renderer; public State1(int state) { this.state = state; } @Override public void init(GameContainer gc, StateBasedGame game) throws SlickException { velocityIterations = 10; positionIterations = 10; pixelsPerMeter = 1f; world = new World(new Vec2(0.f, -9.8f)); renderer = new Renderer(gc, gc.getGraphics(), pixelsPerMeter, world); box1 = new Box(-100f, 200f, 40, 50, BodyType.DYNAMIC, world); ground = new Box(-14, -275, 50, 900, BodyType.STATIC, world); poly1 = new Polygon(50f, 10f, new Vec2[] { new Vec2(-6f, -14f), new Vec2(0f, -20f), new Vec2(6f, -14f), new Vec2(10f, 10f), new Vec2(-10f, 10f) }, BodyType.DYNAMIC, world); poly2 = new Polygon(0f, 10f, new Vec2[] { new Vec2(10f, 0f), new Vec2(20f, 0f), new Vec2(30f, 10f), new Vec2(30f, 20f), new Vec2(20f, 30f), new Vec2(10f, 30f), new Vec2(0f, 20f), new Vec2(0f, 10f) }, BodyType.DYNAMIC, world); } @Override public void update(GameContainer gc, StateBasedGame game, int delta) throws SlickException { world.step((float)delta / 180f, velocityIterations, positionIterations); } @Override public void render(GameContainer gc, StateBasedGame game, Graphics g) throws SlickException { renderer.render(); } @Override public int getID() { return this.state; } } Polygon Class package shapes; import org.jbox2d.collision.shapes.PolygonShape; import org.jbox2d.common.Vec2; import org.jbox2d.dynamics.Body; import org.jbox2d.dynamics.BodyDef; import org.jbox2d.dynamics.BodyType; import org.jbox2d.dynamics.FixtureDef; import org.jbox2d.dynamics.World; import org.newdawn.slick.Color; public class Polygon { public float x, y; public Color color; public BodyType bodyType; org.newdawn.slick.geom.Polygon poly; BodyDef def; PolygonShape ps; FixtureDef fd; Body body; World world; Vec2[] verts; public Polygon(float x, float y, Vec2[] verts, BodyType bodyType, World world) { this.verts = verts; this.x = x; this.y = y; this.bodyType = bodyType; this.world = world; init(); } public void init() { def = new BodyDef(); def.type = bodyType; def.position.set(x, y); ps = new PolygonShape(); ps.set(verts, verts.length); fd = new FixtureDef(); fd.shape = ps; fd.density = 2.0f; fd.friction = 0.7f; fd.restitution = 0.5f; body = world.createBody(def); body.createFixture(fd); } } Rendering Class package main; import org.jbox2d.collision.shapes.PolygonShape; import org.jbox2d.collision.shapes.ShapeType; import org.jbox2d.common.MathUtils; import org.jbox2d.common.Vec2; import org.jbox2d.dynamics.Body; import org.jbox2d.dynamics.Fixture; import org.jbox2d.dynamics.World; import org.newdawn.slick.Color; import org.newdawn.slick.GameContainer; import org.newdawn.slick.Graphics; import org.newdawn.slick.geom.Polygon; import org.newdawn.slick.geom.Transform; public class Renderer { World world; float pixelsPerMeter; GameContainer gc; Graphics g; public Renderer(GameContainer gc, Graphics g, float ppm, World world) { this.world = world; this.pixelsPerMeter = ppm; this.g = g; this.gc = gc; } public void render() { Body current = world.getBodyList(); Vec2 center = current.getLocalCenter(); while(current != null) { Vec2 pos = current.getPosition(); g.pushTransform(); g.translate(pos.x * pixelsPerMeter + (0.5f * gc.getWidth()), -pos.y * pixelsPerMeter + (0.5f * gc.getHeight())); Fixture f = current.getFixtureList(); while(f != null) { ShapeType type = f.getType(); g.setColor(getColor(current)); switch(type) { case POLYGON: { PolygonShape shape = (PolygonShape)f.getShape(); Vec2[] verts = shape.getVertices(); int count = shape.getVertexCount(); Polygon p = new Polygon(); for(int i = 0; i < count; i++) { p.addPoint(verts[i].x, verts[i].y); } p.setCenterX(center.x); p.setCenterY(center.y); p = (Polygon)p.transform(Transform.createRotateTransform(current.getAngle() + MathUtils.PI, center.x, center.y)); p = (Polygon)p.transform(Transform.createScaleTransform(pixelsPerMeter, pixelsPerMeter)); g.draw(p); break; } case CIRCLE: { f.getShape(); } default: } f = f.getNext(); } g.popTransform(); current = current.getNext(); } } public Color getColor(Body b) { Color c = new Color(1f, 1f, 1f); switch(b.m_type) { case DYNAMIC: if(b.isActive()) { c = new Color(255, 123, 0); } else { c = new Color(99, 99, 99); } break; case KINEMATIC: break; case STATIC: c = new Color(111, 111, 111); break; default: break; } return c; } } Any help with fixing the collisions would be greatly appreciated, and if you need any other code snippets I would be happy to provide them.

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• How do I increase moving speed of body?

  - by Siddharth

  How to move ball speedily on the screen using box2d in libGDX? package com.badlogic.box2ddemo; import com.badlogic.gdx.ApplicationListener; import com.badlogic.gdx.Gdx; import com.badlogic.gdx.graphics.GL10; import com.badlogic.gdx.graphics.Texture; import com.badlogic.gdx.graphics.g2d.Sprite; import com.badlogic.gdx.graphics.g2d.SpriteBatch; import com.badlogic.gdx.graphics.g2d.TextureRegion; import com.badlogic.gdx.math.Matrix4; import com.badlogic.gdx.math.Vector2; import com.badlogic.gdx.physics.box2d.Body; import com.badlogic.gdx.physics.box2d.BodyDef; import com.badlogic.gdx.physics.box2d.BodyDef.BodyType; import com.badlogic.gdx.physics.box2d.Box2DDebugRenderer; import com.badlogic.gdx.physics.box2d.CircleShape; import com.badlogic.gdx.physics.box2d.Fixture; import com.badlogic.gdx.physics.box2d.FixtureDef; import com.badlogic.gdx.physics.box2d.PolygonShape; import com.badlogic.gdx.physics.box2d.World; public class Box2DDemo implements ApplicationListener { private SpriteBatch batch; private TextureRegion texture; private World world; private Body groundDownBody, groundUpBody, groundLeftBody, groundRightBody, ballBody; private BodyDef groundBodyDef1, groundBodyDef2, groundBodyDef3, groundBodyDef4, ballBodyDef; private PolygonShape groundDownPoly, groundUpPoly, groundLeftPoly, groundRightPoly; private CircleShape ballPoly; private Sprite sprite; private FixtureDef fixtureDef; private Vector2 ballPosition; private Box2DDebugRenderer renderer; Vector2 vector2; @Override public void create() { texture = new TextureRegion(new Texture( Gdx.files.internal("img/red_ring.png"))); sprite = new Sprite(texture); sprite.setOrigin(sprite.getWidth() / 2, sprite.getHeight() / 2); batch = new SpriteBatch(); world = new World(new Vector2(0.0f, 0.0f), false); groundBodyDef1 = new BodyDef(); groundBodyDef1.type = BodyType.StaticBody; groundBodyDef1.position.x = 0.0f; groundBodyDef1.position.y = 0.0f; groundDownBody = world.createBody(groundBodyDef1); groundBodyDef2 = new BodyDef(); groundBodyDef2.type = BodyType.StaticBody; groundBodyDef2.position.x = 0f; groundBodyDef2.position.y = Gdx.graphics.getHeight(); groundUpBody = world.createBody(groundBodyDef2); groundBodyDef3 = new BodyDef(); groundBodyDef3.type = BodyType.StaticBody; groundBodyDef3.position.x = 0f; groundBodyDef3.position.y = 0f; groundLeftBody = world.createBody(groundBodyDef3); groundBodyDef4 = new BodyDef(); groundBodyDef4.type = BodyType.StaticBody; groundBodyDef4.position.x = Gdx.graphics.getWidth(); groundBodyDef4.position.y = 0f; groundRightBody = world.createBody(groundBodyDef4); groundDownPoly = new PolygonShape(); groundDownPoly.setAsBox(480.0f, 10f); fixtureDef = new FixtureDef(); fixtureDef.density = 0f; fixtureDef.restitution = 1f; fixtureDef.friction = 0f; fixtureDef.shape = groundDownPoly; fixtureDef.filter.groupIndex = 0; groundDownBody.createFixture(fixtureDef); groundUpPoly = new PolygonShape(); groundUpPoly.setAsBox(480.0f, 10f); fixtureDef = new FixtureDef(); fixtureDef.friction = 0f; fixtureDef.restitution = 0f; fixtureDef.density = 0f; fixtureDef.shape = groundUpPoly; fixtureDef.filter.groupIndex = 0; groundUpBody.createFixture(fixtureDef); groundLeftPoly = new PolygonShape(); groundLeftPoly.setAsBox(10f, 320f); fixtureDef = new FixtureDef(); fixtureDef.friction = 0f; fixtureDef.restitution = 0f; fixtureDef.density = 0f; fixtureDef.shape = groundLeftPoly; fixtureDef.filter.groupIndex = 0; groundLeftBody.createFixture(fixtureDef); groundRightPoly = new PolygonShape(); groundRightPoly.setAsBox(10f, 320f); fixtureDef = new FixtureDef(); fixtureDef.friction = 0f; fixtureDef.restitution = 0f; fixtureDef.density = 0f; fixtureDef.shape = groundRightPoly; fixtureDef.filter.groupIndex = 0; groundRightBody.createFixture(fixtureDef); ballPoly = new CircleShape(); ballPoly.setRadius(16f); fixtureDef = new FixtureDef(); fixtureDef.shape = ballPoly; fixtureDef.density = 1f; fixtureDef.friction = 1f; fixtureDef.restitution = 1f; ballBodyDef = new BodyDef(); ballBodyDef.type = BodyType.DynamicBody; ballBodyDef.position.x = (int) 200; ballBodyDef.position.y = (int) 200; ballBody = world.createBody(ballBodyDef); ballBody.setLinearVelocity(200f, 200f); // ballBody.applyLinearImpulse(new Vector2(250f, 250f), // ballBody.getLocalCenter()); ballBody.createFixture(fixtureDef); renderer = new Box2DDebugRenderer(true, false, false); } @Override public void dispose() { ballPoly.dispose(); groundLeftPoly.dispose(); groundUpPoly.dispose(); groundDownPoly.dispose(); groundRightPoly.dispose(); world.destroyBody(ballBody); world.dispose(); } @Override public void pause() { } @Override public void render() { world.step(1f/30f, 3, 3); Gdx.gl.glClearColor(1f, 1f, 1f, 1f); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); batch.begin(); vector2 = ballBody.getLinearVelocity(); System.out.println("X=" + vector2.x + " Y=" + vector2.y); ballPosition = ballBody.getPosition(); renderer.render(world,batch.getProjectionMatrix()); // int preX = (int) (vector2.x / Math.abs(vector2.x)); // int preY = (int) (vector2.y / Math.abs(vector2.y)); // // if (Math.abs(vector2.x) == 0.0f) // ballBody1.setLinearVelocity(1.4142137f, vector2.y); // else if (Math.abs(vector2.x) < 1.4142137f) // ballBody1.setLinearVelocity(preX * 5, vector2.y); // // if (Math.abs(vector2.y) == 0.0f) // ballBody1.setLinearVelocity(vector2.x, 1.4142137f); // else if (Math.abs(vector2.y) < 1.4142137f) // ballBody1.setLinearVelocity(vector2.x, preY * 5); batch.draw(sprite, (ballPosition.x - (texture.getRegionWidth() / 2)), (ballPosition.y - (texture.getRegionHeight() / 2))); batch.end(); } @Override public void resize(int arg0, int arg1) { } @Override public void resume() { } } I implement above code but I can not achieve higher moving speed of the ball

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• How to implement smooth flocking

  - by Craig

  I'm working on a simple survival game, avoid the big guy and chase the the small guys to stay alive for as long as possible. I have taken the chase and evade example from MSDN create and drawn 20 mice on the screen. I want the small guys to flock when they arent evading. They are doing this, but it isnt as smooth as I would like it to be. How do i make the movement smoother? Its very jittery.# Below is what I have going at the moment, flocking code is within the IF statement, when it isnt set to evading. Any help would be greatly appreciated! :) namespace ChaseAndEvade { class MouseSprite { public enum MouseAiState { // evading the cat Evading, // the mouse can't see the "cat", and it's wandering around. Wander } // how fast can the mouse move? public float MaxMouseSpeed = 4.5f; // and how fast can it turn? public float MouseTurnSpeed = 0.20f; // MouseEvadeDistance controls the distance at which the mouse will flee from // cat. If the mouse is further than "MouseEvadeDistance" pixels away, he will // consider himself safe. public float MouseEvadeDistance = 100.0f; // this constant is similar to TankHysteresis. The value is larger than the // tank's hysteresis value because the mouse is faster than the tank: with a // higher velocity, small fluctuations are much more visible. public float MouseHysteresis = 60.0f; public Texture2D mouseTexture; public Vector2 mouseTextureCenter; public Vector2 mousePosition; public MouseAiState mouseState = MouseAiState.Wander; public float mouseOrientation; public Vector2 mouseWanderDirection; int separationImpact = 4; int cohesionImpact = 6; int alignmentImpact = 2; int sensorDistance = 50; public void UpdateMouse(Vector2 position, MouseSprite [] mice, int numberMice, int index) { Vector2 catPosition = position; int enemies = numberMice; // first, calculate how far away the mouse is from the cat, and use that // information to decide how to behave. If they are too close, the mouse // will switch to "active" mode - fleeing. if they are far apart, the mouse // will switch to "idle" mode, where it roams around the screen. // we use a hysteresis constant in the decision making process, as described // in the accompanying doc file. float distanceFromCat = Vector2.Distance(mousePosition, catPosition); // the cat is a safe distance away, so the mouse should idle: if (distanceFromCat > MouseEvadeDistance + MouseHysteresis) { mouseState = MouseAiState.Wander; } // the cat is too close; the mouse should run: else if (distanceFromCat < MouseEvadeDistance - MouseHysteresis) { mouseState = MouseAiState.Evading; } // if neither of those if blocks hit, we are in the "hysteresis" range, // and the mouse will continue doing whatever it is doing now. // the mouse will move at a different speed depending on what state it // is in. when idle it won't move at full speed, but when actively evading // it will move as fast as it can. this variable is used to track which // speed the mouse should be moving. float currentMouseSpeed; // the second step of the Update is to change the mouse's orientation based // on its current state. if (mouseState == MouseAiState.Evading) { // If the mouse is "active," it is trying to evade the cat. The evasion // behavior is accomplished by using the TurnToFace function to turn // towards a point on a straight line facing away from the cat. In other // words, if the cat is point A, and the mouse is point B, the "seek // point" is C. // C // B // A Vector2 seekPosition = 2 * mousePosition - catPosition; // Use the TurnToFace function, which we introduced in the AI Series 1: // Aiming sample, to turn the mouse towards the seekPosition. Now when // the mouse moves forward, it'll be trying to move in a straight line // away from the cat. mouseOrientation = ChaseAndEvadeGame.TurnToFace(mousePosition, seekPosition, mouseOrientation, MouseTurnSpeed); // set currentMouseSpeed to MaxMouseSpeed - the mouse should run as fast // as it can. currentMouseSpeed = MaxMouseSpeed; } else { // if the mouse isn't trying to evade the cat, it should just meander // around the screen. we'll use the Wander function, which the mouse and // tank share, to accomplish this. mouseWanderDirection and // mouseOrientation are passed by ref so that the wander function can // modify them. for more information on ref parameters, see // http://msdn2.microsoft.com/en-us/library/14akc2c7(VS.80).aspx ChaseAndEvadeGame.Wander(mousePosition, ref mouseWanderDirection, ref mouseOrientation, MouseTurnSpeed); // if the mouse is wandering, it should only move at 25% of its maximum // speed. currentMouseSpeed = .25f * MaxMouseSpeed; Vector2 separate = Vector2.Zero; Vector2 moveCloser = Vector2.Zero; Vector2 moveAligned = Vector2.Zero; // What the AI does when it sees other AIs for (int j = 0; j < enemies; j++) { if (index != j) { // Calculate a vector towards another AI Vector2 separation = mice[index].mousePosition - mice[j].mousePosition; // Only react if other AI is within a certain distance if ((separation.Length() < this.sensorDistance) & (separation.Length()> 0) ) { moveAligned += mice[j].mouseWanderDirection; float distance = Math.Abs(separation.Length()); if (distance == 0) distance = 1; moveCloser += mice[j].mousePosition; separation.Normalize(); separate += separation / distance; } } } if (moveAligned.LengthSquared() != 0) { moveAligned.Normalize(); } if (moveCloser.LengthSquared() != 0) { moveCloser.Normalize(); } moveCloser /= enemies; mice[index].mousePosition += (separate * separationImpact) + (moveCloser * cohesionImpact) + (moveAligned * alignmentImpact); } // The final step is to move the mouse forward based on its current // orientation. First, we construct a "heading" vector from the orientation // angle. To do this, we'll use Cosine and Sine to tell us the x and y // components of the heading vector. See the accompanying doc for more // information. Vector2 heading = new Vector2( (float)Math.Cos(mouseOrientation), (float)Math.Sin(mouseOrientation)); // by multiplying the heading and speed, we can get a velocity vector. the // velocity vector is then added to the mouse's current position, moving him // forward. mousePosition += heading * currentMouseSpeed; } } }

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• Increase moving speed of body

  - by Siddharth

  How to move ball speedily on the screen using box2d in libGDX? public class Box2DDemo implements ApplicationListener { private SpriteBatch batch; private TextureRegion texture; private World world; private Body groundDownBody, groundUpBody, groundLeftBody, groundRightBody, ballBody; private BodyDef groundBodyDef1, groundBodyDef2, groundBodyDef3, groundBodyDef4, ballBodyDef; private PolygonShape groundDownPoly, groundUpPoly, groundLeftPoly, groundRightPoly; private CircleShape ballPoly; private Sprite sprite; private FixtureDef fixtureDef; private Vector2 ballPosition; private Box2DDebugRenderer renderer; Vector2 vector2; @Override public void create() { texture = new TextureRegion(new Texture( Gdx.files.internal("img/red_ring.png"))); sprite = new Sprite(texture); sprite.setOrigin(sprite.getWidth() / 2, sprite.getHeight() / 2); batch = new SpriteBatch(); world = new World(new Vector2(0.0f, -10.0f), false); groundBodyDef1 = new BodyDef(); groundBodyDef1.type = BodyType.StaticBody; groundBodyDef1.position.x = 0.0f; groundBodyDef1.position.y = 0.0f; groundDownBody = world.createBody(groundBodyDef1); groundBodyDef2 = new BodyDef(); groundBodyDef2.type = BodyType.StaticBody; groundBodyDef2.position.x = 0f; groundBodyDef2.position.y = Gdx.graphics.getHeight(); groundUpBody = world.createBody(groundBodyDef2); groundBodyDef3 = new BodyDef(); groundBodyDef3.type = BodyType.StaticBody; groundBodyDef3.position.x = 0f; groundBodyDef3.position.y = 0f; groundLeftBody = world.createBody(groundBodyDef3); groundBodyDef4 = new BodyDef(); groundBodyDef4.type = BodyType.StaticBody; groundBodyDef4.position.x = Gdx.graphics.getWidth(); groundBodyDef4.position.y = 0f; groundRightBody = world.createBody(groundBodyDef4); groundDownPoly = new PolygonShape(); groundDownPoly.setAsBox(480.0f, 10f); fixtureDef = new FixtureDef(); fixtureDef.density = 0f; fixtureDef.restitution = 1f; fixtureDef.friction = 0f; fixtureDef.shape = groundDownPoly; fixtureDef.filter.groupIndex = 0; groundDownBody.createFixture(fixtureDef); groundUpPoly = new PolygonShape(); groundUpPoly.setAsBox(480.0f, 10f); fixtureDef = new FixtureDef(); fixtureDef.friction = 0f; fixtureDef.restitution = 0f; fixtureDef.density = 0f; fixtureDef.shape = groundUpPoly; fixtureDef.filter.groupIndex = 0; groundUpBody.createFixture(fixtureDef); groundLeftPoly = new PolygonShape(); groundLeftPoly.setAsBox(10f, 320f); fixtureDef = new FixtureDef(); fixtureDef.friction = 0f; fixtureDef.restitution = 0f; fixtureDef.density = 0f; fixtureDef.shape = groundLeftPoly; fixtureDef.filter.groupIndex = 0; groundLeftBody.createFixture(fixtureDef); groundRightPoly = new PolygonShape(); groundRightPoly.setAsBox(10f, 320f); fixtureDef = new FixtureDef(); fixtureDef.friction = 0f; fixtureDef.restitution = 0f; fixtureDef.density = 0f; fixtureDef.shape = groundRightPoly; fixtureDef.filter.groupIndex = 0; groundRightBody.createFixture(fixtureDef); ballPoly = new CircleShape(); ballPoly.setRadius(16f); fixtureDef = new FixtureDef(); fixtureDef.shape = ballPoly; fixtureDef.density = 1f; fixtureDef.friction = 1f; fixtureDef.restitution = 1f; ballBodyDef = new BodyDef(); ballBodyDef.type = BodyType.DynamicBody; ballBodyDef.position.x = (int) 200; ballBodyDef.position.y = (int) 200; ballBody = world.createBody(ballBodyDef); // ballBody.setLinearVelocity(200f, 200f); // ballBody.applyLinearImpulse(new Vector2(250f, 250f), // ballBody.getLocalCenter()); ballBody.createFixture(fixtureDef); renderer = new Box2DDebugRenderer(true, false, false); } @Override public void dispose() { ballPoly.dispose(); groundLeftPoly.dispose(); groundUpPoly.dispose(); groundDownPoly.dispose(); groundRightPoly.dispose(); world.destroyBody(ballBody); world.dispose(); } @Override public void pause() { } @Override public void render() { world.step(1f/30f, 3, 3); Gdx.gl.glClearColor(1f, 1f, 1f, 1f); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); batch.begin(); vector2 = ballBody.getLinearVelocity(); System.out.println("X=" + vector2.x + " Y=" + vector2.y); ballPosition = ballBody.getPosition(); renderer.render(world,batch.getProjectionMatrix()); // int preX = (int) (vector2.x / Math.abs(vector2.x)); // int preY = (int) (vector2.y / Math.abs(vector2.y)); // // if (Math.abs(vector2.x) == 0.0f) // ballBody1.setLinearVelocity(1.4142137f, vector2.y); // else if (Math.abs(vector2.x) < 1.4142137f) // ballBody1.setLinearVelocity(preX * 5, vector2.y); // // if (Math.abs(vector2.y) == 0.0f) // ballBody1.setLinearVelocity(vector2.x, 1.4142137f); // else if (Math.abs(vector2.y) < 1.4142137f) // ballBody1.setLinearVelocity(vector2.x, preY * 5); batch.draw(sprite, (ballPosition.x - (texture.getRegionWidth() / 2)), (ballPosition.y - (texture.getRegionHeight() / 2))); batch.end(); } @Override public void resize(int arg0, int arg1) { } @Override public void resume() { } } I implement above code but I can not achieve higher moving speed of the ball

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• Make a lives display in HUD, Flash AS3 (not text!)

  - by user40404

  I've been searching the internet all day and I can't find the answer I'm looking for. In my HUD I want to use orange dots to represent lives. The user starts off with 5 lives and every time they die, I want a dot to be removed. Pretty straight forward. So far my idea is to make a movie clip that has the five dots in a line. There would be 5 frames on the timeline (because after the last life it goes to a game over screen right away). I would have a variable set up to store the number of lives and a function to keep track of lives. So every hit of an obstacle would result in livesCounter--;. Then I would set up something like this: switch(livesCounter){ case 5: livesDisplay.gotoAndPlay(1); break; case 4: livesDisplay.gotoAndPlay(2); break; case 3: livesDisplay.gotoAndPlay(3); break; case 2: livesDisplay.gotoAndPlay(4); break; case 1: livesDisplay.gotoAndPlay(5); break; } I feel like there has to be an easier way to do this where I could just have a movie clip of a single orange dot that I could replicate across an x value based on the number of lives. Maybe the dots would be stored in an array? When the user loses a life, a dot on the right end of the line is removed. So in the end the counter would look like this: * * * * * * * * * * * * * * * (last life lost results in the end game screen) EDIT: code based on suggestions by Zhafur and Arthur Wolf White package { import flash.display.MovieClip; import flash.events.*; import flash.ui.Multitouch; import flash.ui.MultitouchInputMode; import flash.display.Sprite; import flash.text.*; import flash.utils.getTimer; public class CollisionMouse extends MovieClip{ public var mySprite:Sprite = new Sprite(); Multitouch.inputMode = MultitouchInputMode.TOUCH_POINT; public var replacement:newSprite = new newSprite; public var score:int = 0; public var obstScore:int = -50; public var targetScore:int = 200; public var startTime:uint = 0; public var gameTime:uint; public var pauseScreen:PauseScreen = new PauseScreen(); public var hitTarget:Boolean = false; public var hitObj:Boolean = false; public var currLevel:Number = 1; public var heroLives:int = 5; public var life:Sprite; public function CollisionMouse() { mySprite.graphics.beginFill(0xff0000); mySprite.graphics.drawRect(0,0,40,40); addChild(mySprite); mySprite.x = 200; mySprite.y = 200; pauseScreen.x = stage.width/2; pauseScreen.y = stage.height/2; life = new Sprite(); life.x = 210; stage.addEventListener(MouseEvent.MOUSE_MOVE,followMouse); /*mySprite.addEventListener(TouchEvent.TOUCH_END, onTouchEnd);*/ //checkLevel(); timeCheck(); trackLives(); } public function timeCheck(){ addEventListener(Event.ENTER_FRAME, showTime); } public function showTime(e:Event) { gameTime = getTimer()-startTime; rm1_mc.timeDisplay.text = clockTime(gameTime); rm1_mc.livesDisplay.text = String(heroLives); } public function clockTime(ms:int) { var seconds:int = Math.floor(ms/1000); var minutes:int = Math.floor(seconds/60); seconds -= minutes*60; var timeString:String = minutes+":"+String(seconds+100).substr(1,2); return timeString; } public function trackLives(){ for(var i:int=0; i<heroLives; i++){ life.graphics.lineStyle(1, 0xff9900); life.graphics.beginFill(0xff9900, 1); life.graphics.drawCircle(i*15, 45, 6); life.graphics.endFill(); addChild(life); } } function followMouse(e:MouseEvent){ mySprite.x=mouseX; mySprite.y=mouseY; trackCollisions(); } function trackCollisions(){ if(mySprite.hitTestObject(rm1_mc.obst1) || mySprite.hitTestObject(rm1_mc.obst2)){ hitObjects(); } else if(mySprite.hitTestObject(rm1_mc.target_mc)){ hitTarg(); } } function hitObjects(){ addChild(replacement); mySprite.x ^= replacement.x; replacement.x ^= mySprite.x; mySprite.x ^= replacement.x; mySprite.y ^= replacement.y; replacement.y ^= mySprite.y; mySprite.y ^= replacement.y; stage.removeEventListener(MouseEvent.MOUSE_MOVE, followMouse); removeChild(mySprite); hitObj = true; checkScore(); } function hitTarg(){ addChild(replacement); mySprite.x ^= replacement.x; replacement.x ^= mySprite.x; mySprite.x ^= replacement.x; mySprite.y ^= replacement.y; replacement.y ^= mySprite.y; mySprite.y ^= replacement.y; stage.removeEventListener(MouseEvent.MOUSE_MOVE, followMouse); removeEventListener(Event.ENTER_FRAME, showTime); removeChild(mySprite); hitTarget = true; currLevel++; checkScore(); } function checkScore(){ if(hitObj){ score += obstScore; heroLives--; removeChild(life); } else if(hitTarget){ score += targetScore; } rm1_mc.scoreDisplay.text = String(score); rm1_mc.livesDisplay.text = String(heroLives); trackLives(); } } }

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• printing reverse in singly link list using pointers

  - by theoneabhinav

  i have been trying this code. i think the logic is ok but the program terminates abruptly when the display_rev function is called here is code of display_rev void display_rev(emp_node *head) { emp_node *p=head, *q; while(p->next != NULL) p=p->next; while(p!=head || p==head){ q=head; display_rec(p); while(q->next != p) q=q->next; p=q; } } here is my whole code #include<stdio.h> #include<stdlib.h> #include<ctype.h> #include<string.h> //Declarations=============================================================== typedef struct //employee record { int emp_id; char name[150]; char mob_no[11]; float salary; int proj[5]; struct emp_node *next; } emp_node; emp_node* add_rec(emp_node*); emp_node* create_db(emp_node*); emp_node* search_db(emp_node*, int); emp_node* delete_rec(emp_node*, int); void read_name(emp_node*); void read_mob(emp_node*); void display_db(emp_node*); void display_rec(emp_node*); void display_rev(emp_node*); void modify_rec(emp_node*); void swtch(emp_node*); //=========================================================================== int main() { char ans; emp_node *head = NULL; head = create_db(head); display_db(head); do { swtch(head); printf("\n\n\tDo you want to continue (y/n) : "); getchar(); scanf("%c", &ans); } while (ans == 'y' || ans == 'Y'); return 0; } //Definitions================================================================ emp_node* create_db(emp_node *head) //database creation { int i = 1, no; emp_node *p; printf("Enter number of employees:"); scanf("%d", &no); printf("\n\n"); head = (emp_node *) malloc(sizeof(emp_node)); head = add_rec(head); head->next = NULL; p = head; while (i < no) { p->next = (emp_node *) malloc(sizeof(emp_node)); p = p->next; p = add_rec(p); p->next = NULL; i++; } return head; } emp_node* add_rec(emp_node *p) //new record { int j; printf("\n\tEmployee ID : "); scanf("%d", &(p->emp_id)); printf("\n\tFirst Name:"); read_name(p); printf("\n\tMobile No.:"); read_mob(p); printf("\n\tSalary :"); scanf("%f", &(p->salary)); printf( "\n\tEnter \"1\" for the projects employee is working on, otherwise enter \"0\": \n"); for (j = 0; j < 5; j++) { printf("\n\t\tProject No. %d : ", j + 1); scanf("%d", &(p->proj[j])); while (p->proj[j] != 1 && p->proj[j] != 0) { printf("\n\nInvalid entry!! Please re-enter."); printf("\n\t\tProject No. %d : ", j + 1); scanf("%d", &(p->proj[j])); } } printf("\n\n\n"); return p; } void read_name(emp_node *p) //validation for name { int j, len; scanf("%s", p->name); len = strlen(p->name); for (j = 0; j < len; j++) { if (!isalpha(p->name[j])) { printf( "\n\n\tInvalid name!!Can contain only characters. Please Re-enter.\n"); printf("\n\tName : "); read_name(p); } } } void read_mob(emp_node *p) //validation for mobile no. { int j; scanf("%s", p->mob_no); while (strlen(p->mob_no) != 10) { printf("\n\nInvalid Mobile No!!Please Re-enter"); printf("\n\n\tMobile No.:"); read_mob(p); } for (j = 0; j < 10; j++) { if (!(48 <= p->mob_no[j] && p->mob_no[j] <= 57)) { printf( "\n\nInvalid Mobile No!!Can contain only digits. Please Re-enter."); printf("\n\n\tMobile No.:"); read_mob(p); } } } void display_db(emp_node *head) //displaying whole database { emp_node *p; p = head; printf("\n\n\t\t****** EMPLOYEE DATABASE ******\n"); printf( "\n=============================================================================="); printf("\n Id.\t Name\t\t Mobile No\t Salary\t Projects\n"); while (p != NULL) { display_rec(p); p = p->next; printf("\n\n\n"); } printf( "\n=============================================================================="); } void swtch(emp_node *head) //function for menu and switch case { int cho, x; emp_node *p; printf("\n\n\t\t****** MENU ******"); printf( "\n\n\t1. insert Record\n\t2. Search Record\n\t3. Modify Record\n\t4. Delete Record\n\t5. Display Reverse\n\t6. Exit"); printf("\n\tWhich operation do you want to perform? "); scanf("%d", &cho); switch (cho) { case 1: p=head; while(p->next != NULL) p=p->next; p->next = (emp_node *) malloc(sizeof(emp_node)); p=p->next; p = add_rec(p); p->next = NULL; display_db(head); break; case 2: printf("\n\n\tEnter employee ID whose record is to be Searched :"); scanf("%d", &x); p = search_db(head, x); if (p == NULL) printf("\n\nRecord not found."); else display_rec(p); break; case 3: printf("\n\n\tEnter employee ID whose record is to be modified :"); scanf("%d", &x); p = search_db(head, x); if (p == NULL) printf("\n\nRecord not found."); else modify_rec(p); display_db(head); break; case 4: printf("\n\n\tEnter employee ID whose record is to be deleted :"); scanf("%d", &x); head = delete_rec(head, x); display_db(head); break; case 5: display_rev(head); case 6: exit(0); default: printf("Invalid Choice!! Please try again."); } } emp_node* search_db(emp_node *head, int id) //search database { emp_node *p = head; while (p != NULL) { if (p->emp_id == id) return p; p = p->next; } return NULL; } void display_rec(emp_node *p) //display a single record { int j; printf("\n %d", p->emp_id); printf("\t %10s", p->name); printf("\t %10s", p->mob_no); printf("\t %05.2f", p->salary); printf("\t "); for (j = 0; j < 5; j++) { if (p->proj[j] == 1) printf(" %d,", j + 1); } } void modify_rec(emp_node *p) //modifying a record { int j, cho; char ch1, edt; do { printf( "\n\t1. Name\n\t2. Email Address\n\t3. Mobile No.\n\t4. Salary\n\t5. Date of birth\n\t6. Projects\n"); printf("Enter your choice : "); scanf("%d", &cho); switch (cho) { case 1: printf("\n\tPrevious name:%s", p->name); printf("\n\tDo you want to edit ? (y/n)"); getchar(); scanf("%c", &ch1); if (ch1 == 'y' || ch1 == 'Y') { printf("\n\tEnter New Name:"); read_name(p); } break; case 2: printf("\n\tPrevious Mobile No. : %s", p->mob_no); printf("\n\tDo you want to edit ? (y/n)"); getchar(); scanf("%c", &ch1); if (ch1 == 'y' || ch1 == 'Y') { printf("\n\tEnter New Mobile No. :"); read_mob(p); } break; case 3: printf("\n\tPrevious salary is : %f", p->salary); printf("\n\tDo you want to edit ? (y/n)"); getchar(); scanf("%c", &ch1); if (ch1 == 'y' || ch1 == 'Y') { printf("\n\tEnter New salary:"); scanf("%f", &(p->salary)); } break; case 4: printf("the employee is currently working on project no. "); for (j = 0; j < 5; j++) { if (p->proj[j] == 1) printf(" %d,", j + 1); } printf("\n\tDo you want to edit ? (y/n)"); getchar(); scanf("%c", &ch1); if (ch1 == 'y' || ch1 == 'Y') { printf( "\n\tEnter \"1\" for the projects employee is working on : \n"); for (j = 0; j < 5; j++) { printf("\n\t\tProject No. %d : ", j + 1); scanf("%d", &(p->proj[j])); while (p->proj[j] != 1) { printf("\n\nInvalid entry!! Please re-enter."); printf("\n\t\tProject No. %d : ", j + 1); scanf("%d", &(p->proj[j])); } } } break; default: printf("\n\nInvalid Choice!! Please Try again."); } printf("\n\nDo you want to edit any other fields ?(y/n)"); getchar(); scanf("%c", &edt); } while (edt == 'y' || edt == 'Y'); } emp_node* delete_rec(emp_node *head, int id) //physical deletion of record { emp_node *p = head, *q; if (head->emp_id == id) { head = head->next; free(p); return head; } else { q = p->next; while (q->emp_id != id) { p = p->next; q = q->next; } if (q->next == NULL) p->next = NULL; else p->next = q->next; free(q); return head; } } void display_rev(emp_node *head) { emp_node *p=head, *q; while(p->next != NULL) p=p->next; while(p!=head || p==head){ q=head; display_rec(p); while(q->next != p) q=q->next; p=q; } }

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• Can I alias all directory requests to a single file in nginx?

  - by user749618

  I'm trying to figure out how to take all requests made to a particular directory and return a json string without a redirect, in nginx. Example: curl -i http://example.com/api/call1/ Expected result: HTTP/1.1 200 OK Accept-Ranges: bytes Content-Type: application/json Date: Fri, 13 Apr 2012 23:48:21 GMT Last-Modified: Fri, 13 Apr 2012 22:58:56 GMT Server: nginx X-UA-Compatible: IE=Edge,chrome=1 Content-Length: 38 Connection: keep-alive {"logout": true} Here's what I have so far in my nginx conf: location ~ ^/api/(.*)$ { index /api_logout.json; alias /path/to/file/api_logout.json; types { } default_type "application/json; charset=utf-8"; break; } However, when I try to make the request the Content-Type doesn't stick: $ curl -i http://example.com/api/call1/ HTTP/1.1 200 OK Accept-Ranges: bytes Content-Type: application/octet-stream Date: Fri, 13 Apr 2012 23:48:21 GMT Last-Modified: Fri, 13 Apr 2012 22:58:56 GMT Server: nginx X-UA-Compatible: IE=Edge,chrome=1 Content-Length: 38 Connection: keep-alive {"logout": true} Is there a better way to do this? How can I get the application/json type to stick?

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• C# 4.0: Dynamic Programming

  - by Paulo Morgado

  The major feature of C# 4.0 is dynamic programming. Not just dynamic typing, but dynamic in broader sense, which means talking to anything that is not statically typed to be a .NET object. Dynamic Language Runtime The Dynamic Language Runtime (DLR) is piece of technology that unifies dynamic programming on the .NET platform, the same way the Common Language Runtime (CLR) has been a common platform for statically typed languages. The CLR always had dynamic capabilities. You could always use reflection, but its main goal was never to be a dynamic programming environment and there were some features missing. The DLR is built on top of the CLR and adds those missing features to the .NET platform. The Dynamic Language Runtime is the core infrastructure that consists of: Expression Trees The same expression trees used in LINQ, now improved to support statements. Dynamic Dispatch Dispatches invocations to the appropriate binder. Call Site Caching For improved efficiency. Dynamic languages and languages with dynamic capabilities are built on top of the DLR. IronPython and IronRuby were already built on top of the DLR, and now, the support for using the DLR is being added to C# and Visual Basic. Other languages built on top of the CLR are expected to also use the DLR in the future. Underneath the DLR there are binders that talk to a variety of different technologies: .NET Binder Allows to talk to .NET objects. JavaScript Binder Allows to talk to JavaScript in SilverLight. IronPython Binder Allows to talk to IronPython. IronRuby Binder Allows to talk to IronRuby. COM Binder Allows to talk to COM. Whit all these binders it is possible to have a single programming experience to talk to all these environments that are not statically typed .NET objects. The dynamic Static Type Let’s take this traditional statically typed code: Calculator calculator = GetCalculator(); int sum = calculator.Sum(10, 20); Because the variable that receives the return value of the GetCalulator method is statically typed to be of type Calculator and, because the Calculator type has an Add method that receives two integers and returns an integer, it is possible to call that Sum method and assign its return value to a variable statically typed as integer. Now lets suppose the calculator was not a statically typed .NET class, but, instead, a COM object or some .NET code we don’t know he type of. All of the sudden it gets very painful to call the Add method: object calculator = GetCalculator(); Type calculatorType = calculator.GetType(); object res = calculatorType.InvokeMember("Add", BindingFlags.InvokeMethod, null, calculator, new object[] { 10, 20 }); int sum = Convert.ToInt32(res); And what if the calculator was a JavaScript object? ScriptObject calculator = GetCalculator(); object res = calculator.Invoke("Add", 10, 20); int sum = Convert.ToInt32(res); For each dynamic domain we have a different programming experience and that makes it very hard to unify the code. With C# 4.0 it becomes possible to write code this way: dynamic calculator = GetCalculator(); int sum = calculator.Add(10, 20); You simply declare a variable who’s static type is dynamic. dynamic is a pseudo-keyword (like var) that indicates to the compiler that operations on the calculator object will be done dynamically. The way you should look at dynamic is that it’s just like object (System.Object) with dynamic semantics associated. Anything can be assigned to a dynamic. dynamic x = 1; dynamic y = "Hello"; dynamic z = new List<int> { 1, 2, 3 }; At run-time, all object will have a type. In the above example x is of type System.Int32. When one or more operands in an operation are typed dynamic, member selection is deferred to run-time instead of compile-time. Then the run-time type is substituted in all variables and normal overload resolution is done, just like it would happen at compile-time. The result of any dynamic operation is always dynamic and, when a dynamic object is assigned to something else, a dynamic conversion will occur. Code Resolution Method double x = 1.75; double y = Math.Abs(x); compile-time double Abs(double x) dynamic x = 1.75; dynamic y = Math.Abs(x); run-time double Abs(double x) dynamic x = 2; dynamic y = Math.Abs(x); run-time int Abs(int x) The above code will always be strongly typed. The difference is that, in the first case the method resolution is done at compile-time, and the others it’s done ate run-time. IDynamicMetaObjectObject The DLR is pre-wired to know .NET objects, COM objects and so forth but any dynamic language can implement their own objects or you can implement your own objects in C# through the implementation of the IDynamicMetaObjectProvider interface. When an object implements IDynamicMetaObjectProvider, it can participate in the resolution of how method calls and property access is done. The .NET Framework already provides two implementations of IDynamicMetaObjectProvider: DynamicObject : IDynamicMetaObjectProvider The DynamicObject class enables you to define which operations can be performed on dynamic objects and how to perform those operations. For example, you can define what happens when you try to get or set an object property, call a method, or perform standard mathematical operations such as addition and multiplication. ExpandoObject : IDynamicMetaObjectProvider The ExpandoObject class enables you to add and delete members of its instances at run time and also to set and get values of these members. This class supports dynamic binding, which enables you to use standard syntax like sampleObject.sampleMember, instead of more complex syntax like sampleObject.GetAttribute("sampleMember").

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• iPhone - UIImage Leak, CGBitmapContextCreateImage Leak

  - by bbullis21

  Alright I am having a world of difficulty tracking down this memory leak. When running this script I do not see any memory leaking, but my objectalloc is climbing. Instruments points to CGBitmapContextCreateImage create_bitmap_data_provider malloc, this takes up 60% of my objectalloc. This code is called several times with a NSTimer. //GET IMAGE FROM RESOURCE DIR NSString * fileLocation = [[NSBundle mainBundle] pathForResource:imgMain ofType:@"jpg"]; NSData * imageData = [NSData dataWithContentsOfFile:fileLocation]; UIImage * blurMe = [UIImage imageWithData:imageData]; NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; UIImage * scaledImage = [blurMe _imageScaledToSize:CGSizeMake(blurMe.size.width / dblBlurLevel, blurMe.size.width / dblBlurLevel) interpolationQuality:3.0]; UIImage * labelImage = [scaledImage _imageScaledToSize:blurMe.size interpolationQuality:3.0]; UIImage * imageCopy = [[UIImage alloc] initWithCGImage:labelImage.CGImage]; [pool drain]; // deallocates scaledImage and labelImage imgView.image = imageCopy; [imageCopy release]; Below is the blur function. I believe the objectalloc issue is located in here. Maybe I just need a pair of fresh eyes. Would be great if someone could figure this out. Sorry it is kind of long... I'll try and shorten it. @implementation UIImage(Blur) - (UIImage *)blurredCopy:(int)pixelRadius { //VARS unsigned char *srcData, *destData, *finalData; CGContextRef context = NULL; CGColorSpaceRef colorSpace; void * bitmapData; int bitmapByteCount; int bitmapBytesPerRow; //IMAGE SIZE size_t pixelsWide = CGImageGetWidth(self.CGImage); size_t pixelsHigh = CGImageGetHeight(self.CGImage); bitmapBytesPerRow = (pixelsWide * 4); bitmapByteCount = (bitmapBytesPerRow * pixelsHigh); colorSpace = CGColorSpaceCreateDeviceRGB(); if (colorSpace == NULL) { return NULL; } bitmapData = malloc( bitmapByteCount ); if (bitmapData == NULL) { CGColorSpaceRelease( colorSpace ); } context = CGBitmapContextCreate (bitmapData, pixelsWide, pixelsHigh, 8, bitmapBytesPerRow, colorSpace, kCGImageAlphaPremultipliedFirst ); if (context == NULL) { free (bitmapData); } CGColorSpaceRelease( colorSpace ); free (bitmapData); if (context == NULL) { return NULL; } //PREPARE BLUR size_t width = CGBitmapContextGetWidth(context); size_t height = CGBitmapContextGetHeight(context); size_t bpr = CGBitmapContextGetBytesPerRow(context); size_t bpp = (CGBitmapContextGetBitsPerPixel(context) / 8); CGRect rect = {{0,0},{width,height}}; CGContextDrawImage(context, rect, self.CGImage); // Now we can get a pointer to the image data associated with the bitmap // context. srcData = (unsigned char *)CGBitmapContextGetData (context); if (srcData != NULL) { size_t dataSize = bpr * height; finalData = malloc(dataSize); destData = malloc(dataSize); memcpy(finalData, srcData, dataSize); memcpy(destData, srcData, dataSize); int sums[5]; int i, x, y, k; int gauss_sum=0; int radius = pixelRadius * 2 + 1; int *gauss_fact = malloc(radius * sizeof(int)); for (i = 0; i < pixelRadius; i++) { .....blah blah blah... THIS IS JUST LONG CODE THE CREATES INT FIGURES ........blah blah blah...... } if (gauss_fact) { free(gauss_fact); } } size_t bitmapByteCount2 = bpr * height; //CREATE DATA PROVIDER CGDataProviderRef dataProvider = CGDataProviderCreateWithData(NULL, srcData, bitmapByteCount2, NULL); //CREATE IMAGE CGImageRef cgImage = CGImageCreate( width, height, CGBitmapContextGetBitsPerComponent(context), CGBitmapContextGetBitsPerPixel(context), CGBitmapContextGetBytesPerRow(context), CGBitmapContextGetColorSpace(context), CGBitmapContextGetBitmapInfo(context), dataProvider, NULL, true, kCGRenderingIntentDefault ); //RELEASE INFORMATION CGDataProviderRelease(dataProvider); CGContextRelease(context); if (destData) { free(destData); } if (finalData) { free(finalData); } if (srcData) { free(srcData); } UIImage *retUIImage = [UIImage imageWithCGImage:cgImage]; CGImageRelease(cgImage); return retUIImage; } The only thing I can think of that is holding up the objectalloc is this UIImage *retUIImage = [UIImage imageWithCGImage:cgImage];...but how to do I release that after it has been returned? Hopefully someone can help please.

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• Numerology with Python And Django

  - by Asinox

  Hi guys, i have a function that give me the result that im expecting in console mode, but if i try to use the function with Django, the page never load and just have a loop calculating and never end. Any idea ? *sorry with my english Console function (WORK GREAT): def sum_digitos(n): sum = 0; while n != 0: sum += n % 10 n /= 10 if sum > 9: x = str(sum) y =list(x) sum = int(y[0]) + int(y[1]) return sum print sum_digitos(2461978) Django views: def Calcular(request): if request.method == 'POST': form = NumerologiaForm(request.POST) if form.is_valid(): sum = 0; ano = str(request.POST['fecha_year']) mes = str(request.POST['fecha_month']) dia = str(request.POST['fecha_day']) data = dia + mes + ano fecha = int(data) while fecha != 0: f = fecha sum += f % 10 f /= 10 if sum > 9: x = str(sum) y =list(x) sum = int(y[0]) + int(y[1]) resultado = get_object_or_404(Numero,numero = sum) return HttpResponseRedirect(resultado.get_absolute_url()) else: form = NumerologiaForm() return render_to_response('numerologiaForm.html',{'form':form})

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• CUDA linking error - Visual Express 2008 - nvcc fatal due to (null) configuration file

  - by Josh

  Hi, I've been searching extensively for a possible solution to my error for the past 2 weeks. I have successfully installed the Cuda 64-bit compiler (tools) and SDK as well as the 64-bit version of Visual Studio Express 2008 and Windows 7 SDK with Framework 3.5. I'm using windows XP 64-bit. I have confirmed that VSE is able to compile in 64-bit as I have all of the 64-bit options available to me using the steps on the following website: (since Visual Express does not inherently include the 64-bit packages) http://jenshuebel.wordpress.com/2009/02/12/visual-c-2008-express-edition-and-64-bit-targets/ I have confirmed the 64-bit compile ability since the "x64" is available from the pull-down menu under "Tools-Options-VC++ Directories" and compiling in 64-bit does not result in the entire project being "skipped". I have included all the needed directories for 64-bit cuda tools, 64 SDK and Visual Express (\VC\bin\amd64). Here's the error message I receive when trying to compile in 64-bit: 1>------ Build started: Project: New, Configuration: Release x64 ------ 1>Compiling with CUDA Build Rule... 1>"C:\CUDA\bin64\nvcc.exe" -arch sm_10 -ccbin "C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\bin" -Xcompiler "/EHsc /W3 /nologo /O2 /Zi /MT " -maxrregcount=32 --compile -o "x64\Release\template.cu.obj" "c:\Documents and Settings\All Users\Application Data\NVIDIA Corporation\NVIDIA GPU Computing SDK\C\src\CUDA_Walkthrough_DeviceKernels\template.cu" 1>nvcc fatal : Visual Studio configuration file '(null)' could not be found for installation at 'C:/Program Files (x86)/Microsoft Visual Studio 9.0/VC/bin/../..' 1>Linking... 1>LINK : fatal error LNK1181: cannot open input file '.\x64\Release\template.cu.obj' 1>Build log was saved at "file://c:\Documents and Settings\Administrator\My Documents\Visual Studio 2008\Projects\New\New\x64\Release\BuildLog.htm" 1>New - 1 error(s), 0 warning(s) ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Here's the simple code I'm trying to compile/run in 64-bit: #include <stdlib.h> #include <stdio.h> #include <string.h> #include <math.h> #include <cuda.h> void mypause () { printf ( "Press [Enter] to continue . . ." ); fflush ( stdout ); getchar(); } __global__ void VecAdd1_Kernel(float* A, float* B, float* C, int N) { int i = blockDim.x*blockIdx.x+threadIdx.x; if (i<N) C[i] = A[i] + B[i]; //result should be a 16x1 array of 250s } __global__ void VecAdd2_Kernel(float* B, float* C, int N) { int i = blockDim.x*blockIdx.x+threadIdx.x; if (i<N) C[i] = C[i] + B[i]; //result should be a 16x1 array of 400s } int main() { int N = 16; float A[16];float B[16]; size_t size = N*sizeof(float); for(int i=0; i<N; i++) { A[i] = 100.0; B[i] = 150.0; } // Allocate input vectors h_A and h_B in host memory float* h_A = (float*)malloc(size); float* h_B = (float*)malloc(size); float* h_C = (float*)malloc(size); //Initialize Input Vectors memset(h_A,0,size);memset(h_B,0,size); h_A = A;h_B = B; printf("SUM = %f\n",A[1]+B[1]); //simple check for initialization //Allocate vectors in device memory float* d_A; cudaMalloc((void**)&d_A,size); float* d_B; cudaMalloc((void**)&d_B,size); float* d_C; cudaMalloc((void**)&d_C,size); //Copy vectors from host memory to device memory cudaMemcpy(d_A,h_A,size,cudaMemcpyHostToDevice); cudaMemcpy(d_B,h_B,size,cudaMemcpyHostToDevice); //Invoke kernel int threadsPerBlock = 256; int blocksPerGrid = (N+threadsPerBlock-1)/threadsPerBlock; VecAdd1(blocksPerGrid, threadsPerBlock,d_A,d_B,d_C,N); VecAdd2(blocksPerGrid, threadsPerBlock,d_B,d_C,N); //Copy results from device memory to host memory //h_C contains the result in host memory cudaMemcpy(h_C,d_C,size,cudaMemcpyDeviceToHost); for(int i=0; i<N; i++) //output result from the kernel "VecAdd" { printf("%f ", h_C[i] ); printf("\n"); } printf("\n"); cudaFree(d_A); cudaFree(d_B); cudaFree(d_C); free(h_A); free(h_B); free(h_C); mypause(); return 0; }

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• Nullable One To One Relationships with Integer Keys in LINQ-to-SQL

  - by Craig Walker

  I have two objects (Foo and Bar) that have a one-to-zero-or-one relationship between them. So, Foo has a nullable foreign key reference to Bar.ID and a (nullbusted) unique index to enforce the "1" side. Bar.ID is an int, and so Foo.BarID is a nullable int. The problem occurs in the LINQ-to-SQL DBML mapping of .NET types to SQL datatypes. Since int is not a nullable type in .NET, it gets wrapped in a Nullable<int>. However, this is not the same type as int, and so Visual Studio gives me this error message when I try to create the OneToOne Association between them: Cannot create an association "Bar_Foo". Properties do not have matching types: "ID", "BarID". Is there a way around this?

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• new[n] and delete every location with delete instead the whole chunk with delete[]

  - by pmr

  Is this valid C++ (e.g. not invoking UB) and does it achieve what I want without leaking memory? valgrinds complains about mismatching free and delete but says "no leaks are possible" in the end. int main() { int* a = new int[5]; for(int i = 0; i < 5; ++i) a[i] = i; for(int i = 0; i < 5; ++i) delete &a[i]; } The reason I'm asking: I have a class that uses boost::intrusive::list and I new every object that is added to that list. Sometimes I know how many objects I want to add to the list and was thinking about using new[] to allocate a chunk and still be able to delete every object on its own with the Disposer-style of boost::intrusive.

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• Binding collection indexes to a WPF DataGrid at runtime

  - by bearda

  After trying to develop our own control to display a table of data we stumbled on the WPF toolkit DataGrid and thought we were saved. A couple hours later I'm scratching my head trying to figure out if it can do what we really want it to do. The DataGrid seems to be based on displaying various properties of a single object, where I think I need something that can display a collection's items, I want to display a table of strings with a variable number of rows and a variable number of columns. Each row represents the state of a number of inputs at a given time. The number of samples may change, and the number of inputs may change at runtime. As a result, I can't create a custom object that represents a row with a property for each input. This makes the DataGrid binding more complicated, since I can't bind to a fixed property for each column. I thought I found a workaround for this by binding to ".[" + channelIndex + ]" but it hasn't worked out quite the way I wanted. Right now I have a collection of a collection of strings that represents the two-dimensional array of strings. I'm using ObservableCollection so string change event notifications work, but I can use any collection type needed. It looked like everything was working great until I realized that every row was showing the same line of data. Binding in C# is not my strong suit, so I'm kind of lost on what's going wrong. Is what I'm trying to do overall even possible with the WPF Toolkit DataGrid? using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Data; using System.Windows.Documents; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Imaging; using System.Windows.Navigation; using System.Windows.Shapes; using Microsoft.Windows.Controls; using System.ComponentModel; using System.Collections; using System.Collections.ObjectModel; namespace WRE.NGDAS.UILayer { /// <summary> /// Interaction logic for DataTableControl.xaml /// </summary> public partial class DataTableControl : UserControl { #region Constants private const int lineHeight = 25; #endregion #region Type Definitions private class TableChannelInfo { internal string ChannelName = string.Empty; internal int Column = 0; public override string ToString() { return ChannelName; } } internal class NotifyString : INotifyPropertyChanged { private string text = String.Empty; public event PropertyChangedEventHandler PropertyChanged; public string Text { get { return text; } set { text = value; NotifyPropertyChanged( "Text" ); } } public NotifyString(string newText) { text = newText; } protected void NotifyPropertyChanged( string propertyChanged ) { if ( PropertyChanged != null ) { PropertyChanged(this, new PropertyChangedEventArgs(propertyChanged)); } } } #endregion #region Private Data Members string[] channels = null; int numberFixed = 0; int numberOfRows = 0; ObservableCollection<ObservableCollection<NotifyString>> tableText = null; #endregion public DataTableControl( List<string> channelNames, List<string> nameToolTips, int numberFixedColumns, int numberRows ) { InitializeComponent(); numberFixed = numberFixedColumns; numberOfRows = numberRows; tableText = new ObservableCollection<ObservableCollection<NotifyString>>(); dataGrid.ItemsSource = tableText; channels = new string[channelNames.Count]; for (int channelIndex = 0; channelIndex < channelNames.Count; channelIndex++) { channels[channelIndex] = channelNames[channelIndex]; tableText.Add(new ObservableCollection<NotifyString>()); for (int i = 0; i < numberOfRows; i++) { tableText[channelIndex].Add( new NotifyString(String.Empty) ); } Binding textBinding = new Binding( ".[" + channelIndex + "]" ); textBinding.Mode = BindingMode.OneWay; textBinding.UpdateSourceTrigger = UpdateSourceTrigger.PropertyChanged; textBinding.Source = tableText[channelIndex]; DataGridTextColumn newColumn = new DataGridTextColumn(); newColumn.Header = channelNames[channelIndex]; newColumn.DisplayIndex = channelIndex; newColumn.Binding = textBinding; if ( channelIndex < numberFixed ) { newColumn.CanUserReorder = false; } dataGrid.Columns.Add(newColumn); } //Height = lineHeight + numberOfRows * lineHeight; } internal void UpdateChannelRow( int rowNumber, List<string> channelValues, DisplayColors color ) { if ( rowNumber < numberOfRows ) { for (int column = 0; column < channelValues.Count; column++) { if ( column < channels.GetLength(0) ) { tableText[column][rowNumber].Text = channelValues[column]; } } } } } }

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• Getting stored procedure's return value with iBatis.NET

  - by MikeWyatt

  How can I retrieve the return value of a stored procedure using iBatis.NET? The below code successfully calls the stored procedure, but the QueryForObject<int> call returns 0. SqlMap <procedure id="MyProc" parameterMap="MyProcParameters" resultClass="int"> MyProc </procedure> <parameterMap id="MyProcParameters"> <parameter property="num"/> </parameterMap> C# code public int RunMyProc( string num ) { return QueryForObject < int > ( "MyProc", new Hashtable { { "num", num } } ); } Stored Procedure create procedure MyProc @num nvarchar(512) as begin return convert(int, @num) end FYI, I'm using iBatis 1.6.1.0, .NET 3.5, and SQL Server 2008.

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• RDLC (VS 2010) How to access nested class or arrays on DataObjects

  - by gerard

  How can I access the TD.SubNumber property and Numbers[] on RDLC? I keep getting #Error on my expressions "=Fields!TD.Value.SubNumber" and "=Fields!Numbers.Value(0)". public class TestData { TestSubData tdata = new TestSubData(); public TestSubData TD { get { return tdata; } set { tdata = value; } } string m_Description; public string Description { get { return m_Description; } set { m_Description = value; } } int[] m_Numbers = new int[12]; public int?[] Numbers { get { return m_Numbers; } } } public class TestSubData { int x; public TestSubData() { } public int SubNumber { get { return x; } set { x = value; } } }

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• Thread scheduling Round Robin / scheduling dispatch

  - by MRP

  #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <semaphore.h> #define NUM_THREADS 4 #define COUNT_LIMIT 13 int done = 0; int count = 0; int quantum = 2; int thread_ids[4] = {0,1,2,3}; int thread_runtime[4] = {0,5,4,7}; pthread_mutex_t count_mutex; pthread_cond_t count_threshold_cv; void * inc_count(void * arg); static sem_t count_sem; int quit = 0; ///////// Inc_Count//////////////// void *inc_count(void *t) { long my_id = (long)t; int i; sem_wait(&count_sem); /////////////CRIT SECTION////////////////////////////////// printf("run_thread = %d\n",my_id); printf("%d \n",thread_runtime[my_id]); for( i=0; i < thread_runtime[my_id];i++) { printf("runtime= %d\n",thread_runtime[my_id]); pthread_mutex_lock(&count_mutex); count++; if (count == COUNT_LIMIT) { pthread_cond_signal(&count_threshold_cv); printf("inc_count(): thread %ld, count = %d Threshold reached.\n", my_id, count); } printf("inc_count(): thread %ld, count = %d, unlocking mutex\n",my_id, count); pthread_mutex_unlock(&count_mutex); sleep(1) ; }//End For sem_post(&count_sem); // Next Thread Enters Crit Section pthread_exit(NULL); } /////////// Count_Watch //////////////// void *watch_count(void *t) { long my_id = (long)t; printf("Starting watch_count(): thread %ld\n", my_id); pthread_mutex_lock(&count_mutex); if (count<COUNT_LIMIT) { pthread_cond_wait(&count_threshold_cv, &count_mutex); printf("watch_count(): thread %ld Condition signal received.\n", my_id); printf("watch_count(): thread %ld count now = %d.\n", my_id, count); } pthread_mutex_unlock(&count_mutex); pthread_exit(NULL); } ////////////////// Main //////////////// int main (int argc, char *argv[]) { int i; long t1=0, t2=1, t3=2, t4=3; pthread_t threads[4]; pthread_attr_t attr; sem_init(&count_sem, 0, 1); /* Initialize mutex and condition variable objects */ pthread_mutex_init(&count_mutex, NULL); pthread_cond_init (&count_threshold_cv, NULL); /* For portability, explicitly create threads in a joinable state */ pthread_attr_init(&attr); pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE); pthread_create(&threads[0], &attr, watch_count, (void *)t1); pthread_create(&threads[1], &attr, inc_count, (void *)t2); pthread_create(&threads[2], &attr, inc_count, (void *)t3); pthread_create(&threads[3], &attr, inc_count, (void *)t4); /* Wait for all threads to complete */ for (i=0; i<NUM_THREADS; i++) { pthread_join(threads[i], NULL); } printf ("Main(): Waited on %d threads. Done.\n", NUM_THREADS); /* Clean up and exit */ pthread_attr_destroy(&attr); pthread_mutex_destroy(&count_mutex); pthread_cond_destroy(&count_threshold_cv); pthread_exit(NULL); } I am trying to learn thread scheduling, there is a lot of technical coding that I don't know. I do know in theory how it should work, but having trouble getting started in code... I know, at least I think, this program is not real time and its not meant to be. Some how I need to create a scheduler dispatch to control the threads in the order they should run... RR FCFS SJF ect. Right now I don't have a dispatcher. What I do have is semaphores/ mutex to control the threads. This code does run FCFS... and I have been trying to use semaphores to create a RR.. but having a lot of trouble. I believe it would be easier to create a dispatcher but I dont know how. I need help, I am not looking for answers just direction.. some sample code will help to understand a bit more. Thank you.

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