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• Blueprints for Oracle NoSQL Database

  - by dan.mcclary

  I think that some of the most interesting analytic problems are graph problems.  I'm always interested in new ways to store and access graphs.  As such, I really like the work being done by Tinkerpop to create Open Source Software to make property graphs more accessible over a wide variety of datastores.  Since key-value stores like Oracle NoSQL Database are well-suited to storing property graphs, I decided to extend the Blueprints API to work with it.  Below I'll discuss some of the implementation details, but you can check out the finished product here: http://github.com/dwmclary/blueprints-oracle-nosqldb.  What's in a Property Graph?  In the most general sense, a graph is just a collection of vertices and edges.  Vertices and edges can have properties: weights, names, or any number of other traits.  In an undirected graph, edges connect vertices without direction.  A directed graph specifies that all edges have a head and a tail --- a direction.  A multi-graph allows multiple edges to connect two vertices.  A "property graph" encompasses all of these traits. Key-Value Stores for Property Graphs Key-Value stores like Oracle NoSQL Database tend to be ideal for implementing property graphs.  First, if any vertex or edge can have any number of traits, we can treat it as a hash map.  For example: Vertex["name"] = "Mary" Vertex["age"] = 28 Vertex["ID"] = 12345  and so on.  This is a natural key-value relationship: the key "name" maps to the value "Mary."  Moreover if we maintain two hash maps, one for vertex objects and one for edge objects, we've essentially captured the graph.  As such, any scalable key-value store is fertile ground for planting graphs. Oracle NoSQL Database as a Scalable Graph Database While Oracle NoSQL Database offers useful features like tunable consistency, what lends it to storing property graphs is the storage guarantees around its key structure.  Keys in Oracle NoSQL Database are divided into two parts: a major key and a minor key.  The storage guarantee is simple.  Major keys will be distributed across storage nodes, which could encompass a large number of servers.  However, all minor keys which are children of a given major key are guaranteed to be stored on the same storage node.  For example, the vertices: /Personnel/Vertex/1  and /Personnel/Vertex/2 May be stored on different servers, but /Personnel/Vertex/1-/name and  /Personnel/Vertex/1-/age will always be on the same server.  This means that we can structure our graph database such that retrieving all the properties for a vertex or edge requires I/O from only a single storage node.  Moreover, Oracle NoSQL Database provides a storeIterator which allows us to store a huge number of vertices and edges in a scalable fashion.  By storing the vertices and edges as major keys, we guarantee that they are distributed evenly across all storage nodes.  At the same time we can use a partial major key to iterate over all the vertices or edges (e.g. we search over /Personnel/Vertex to iterate over all vertices). Fork It! The Blueprints API and Oracle NoSQL Database present a great way to get started using a scalable key-value database to store and access graph data.  However, a graph store isn't useful without a good graph to work on.  I encourage you to fork or pull the repository, store some data, and try using Gremlin or any other language to explore.

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• Thoughts on C# Extension Methods

  - by Damon

  I'm not a huge fan of extension methods.  When they first came out, I remember seeing a method on an object that was fairly useful, but when I went to use it another piece of code that method wasn't available.  Turns out it was an extension method and I hadn't included the appropriate assembly and imports statement in my code to use it.  I remember being a bit confused at first about how the heck that could happen (hey, extension methods were new, cut me some slack) and it took a bit of time to track down exactly what it was that I needed to include to get that method back.  I just imagined a new developer trying to figure out why a method was missing and fruitlessly searching on MSDN for a method that didn't exist and it just didn't sit well with me. I am of the opinion that if you have an object, then you shouldn't have to include additional assemblies to get additional instance level methods out of that object.  That opinion applies to namespaces as well - I do not like it when the contents of a namespace are split out into multiple assemblies.  I prefer to have static utility classes instead of extension methods to keep things nicely packaged into a cohesive unit.  It also makes it abundantly clear where utility methods are used in code.  I will concede, however, that it can make code a bit more verbose and lengthy.  There is always a trade-off. Some people harp on extension methods because it breaks the tenants of object oriented development and allows you to add methods to sealed classes.  Whatever.  Extension methods are just utility methods that you can tack onto an object after the fact.  Extension methods do not give you any more access to an object than the developer of that object allows, so I say that those who cry OO foul on extension methods really don't have much of an argument on which to stand.  In fact, I have to concede that my dislike of them is really more about style than anything of great substance. One interesting thing that I found regarding extension methods is that you can call them on null objects. Take a look at this extension method: namespace ExtensionMethods {   public static class StringUtility   {     public static int WordCount(this string str)     {       if(str == null) return 0;       return str.Split(new char[] { ' ', '.', '?' },         StringSplitOptions.RemoveEmptyEntries).Length;     }   }   } Notice that the extension method checks to see if the incoming string parameter is null.  I was worried that the runtime would perform a check on the object instance to make sure it was not null before calling an extension method, but that is apparently not the case.  So, if you call the following code it runs just fine. string s = null; int words = s.WordCount(); I am a big fan of things working, but this seems to go against everything I've come to know about instance level methods.  However, an extension method is really a static method masquerading as an instance-level method, so I suppose it would be far more frustrating if it failed since there is really no reason it shouldn't succeed. Although I'm not a fan of extension methods, I will say that if you ever find yourself at an impasse with a die-hard fan of either the utility class or extension method approach, then there is a common ground.  Extension methods are defined in static classes, and you call them from those static classes as well as directly from the objects they extend.  So if you build your utility classes using extension methods, then you can have it your way and they can have it theirs. 

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• Abstracting entity caching in XNA

  - by Grofit

  I am in a situation where I am writing a framework in XNA and there will be quite a lot of static (ish) content which wont render that often. Now I am trying to take the same sort of approach I would use when doing non game development, where I don't even think about caching until I have finished my application and realise there is a performance problem and then implement a layer of caching over whatever needs it, but wrap it up so nothing is aware its happening. However in XNA the way we would usually cache would be drawing our objects to a texture and invalidating after a change occurs. So if you assume an interface like so: public interface IGameComponent { void Update(TimeSpan elapsedTime); void Render(GraphicsDevice graphicsDevice); } public class ContainerComponent : IGameComponent { public IList<IGameComponent> ChildComponents { get; private set; } // Assume constructor public void Update(TimeSpan elapsedTime) { // Update anything that needs it } public void Render(GraphicsDevice graphicsDevice) { foreach(var component in ChildComponents) { // draw every component } } } Then I was under the assumption that we just draw everything directly to the screen, then when performance becomes an issue we just add a new implementation of the above like so: public class CacheableContainerComponent : IGameComponent { private Texture2D cachedOutput; private bool hasChanged; public IList<IGameComponent> ChildComponents { get; private set; } // Assume constructor public void Update(TimeSpan elapsedTime) { // Update anything that needs it // set hasChanged to true if required } public void Render(GraphicsDevice graphicsDevice) { if(hasChanged) { CacheComponents(graphicsDevice); } // Draw cached output } private void CacheComponents(GraphicsDevice graphicsDevice) { // Clean up existing cache if needed var cachedOutput = new RenderTarget2D(...); graphicsDevice.SetRenderTarget(renderTarget); foreach(var component in ChildComponents) { // draw every component } graphicsDevice.SetRenderTarget(null); } } Now in this example you could inherit, but your Update may become a bit tricky then without changing your base class to alert you if you had changed, but it is up to each scenario to choose if its inheritance/implementation or composition. Also the above implementation will re-cache within the rendering cycle, which may cause performance stutters but its just an example of the scenario... Ignoring those facts as you can see that in this example you could use a cache-able component or a non cache-able one, the rest of the framework needs not know. The problem here is that if lets say this component is drawn mid way through the game rendering, other items will already be within the default drawing buffer, so me doing this would discard them, unless I set it to be persisted, which I hear is a big no no on the Xbox. So is there a way to have my cake and eat it here? One simple solution to this is make an ICacheable interface which exposes a cache method, but then to make any use of this interface you would need the rest of the framework to be cache aware, and check if it can cache, and to then do so. Which then means you are polluting and changing your main implementations to account for and deal with this cache... I am also employing Dependency Injection for alot of high level components so these new cache-able objects would be spat out from that, meaning no where in the actual game would they know they are caching... if that makes sense. Just incase anyone asked how I expected to keep it cache aware when I would need to new up a cachable entity.

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• SQL Azure: Notes on Building a Shard Technology

  - by Herve Roggero

  In Chapter 10 of the book on SQL Azure (http://www.apress.com/book/view/9781430229612) I am co-authoring, I am digging deeper in what it takes to write a Shard. It's actually a pretty cool exercise, and I wanted to share some thoughts on how I am designing the technology. A Shard is a technology that spreads the load of database requests over multiple databases, as transparently as possible. The type of shard I am building is called a Vertical Partition Shard  (VPS). A VPS is a mechanism by which the data is stored in one or more databases behind the scenes, but your code has no idea at design time which data is in which database. It's like having a mini cloud for records instead of services. Imagine you have three SQL Azure databases that have the same schema (DB1, DB2 and DB3), you would like to issue a SELECT * FROM Users on all three databases, concatenate the results into a single resultset, and order by last name. Imagine you want to ensure your code doesn't need to change if you add a new database to the shard (DB4). Now imagine that you want to make sure all three databases are queried at the same time, in a multi-threaded manner so your code doesn't have to wait for three database calls sequentially. Then, imagine you would like to obtain a breadcrumb (in the form of a new, virtual column) that gives you a hint as to which database a record came from, so that you could update it if needed. Now imagine all that is done through the standard SqlClient library... and you have the Shard I am currently building. Here are some lessons learned and techniques I am using with this shard: Parellel Processing: Querying databases in parallel is not too hard using the Task Parallel Library; all you need is to lock your resources when needed Deleting/Updating Data: That's not too bad either as long as you have a breadcrumb. However it becomes more difficult if you need to update a single record and you don't know in which database it is. Inserting Data: I am using a round-robin approach in which each new insert request is directed to the next database in the shard. Not sure how to deal with Bulk Loads just yet... Shard Databases:  I use a static collection of SqlConnection objects which needs to be loaded once; from there on all the Shard commands use this collection Extension Methods: In order to make it look like the Shard commands are part of the SqlClient class I use extension methods. For example I added ExecuteShardQuery and ExecuteShardNonQuery methods to SqlClient. Exceptions: Capturing exceptions in a multi-threaded code is interesting... but I kept it simple for now. I am using the ConcurrentQueue to store my exceptions. Database GUID: Every database in the shard is given a GUID, which is calculated based on the connection string's values. DataTable. The Shard methods return a DataTable object which can be bound to objects.  I will be sharing the code soon as an open-source project in CodePlex. Please stay tuned on twitter to know when it will be available (@hroggero). Or check www.bluesyntax.net for updates on the shard. Thanks!

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• How should an object that uses composition set its composed components?

  - by Casey

  After struggling with various problems and reading up on component-based systems and reading Bob Nystrom's excellent book "Game Programming Patterns" and in particular the chapter on Components I determined that this is a horrible idea: //Class intended to be inherited by all objects. Engine uses Objects exclusively. class Object : public IUpdatable, public IDrawable { public: Object(); Object(const Object& other); Object& operator=(const Object& rhs); virtual ~Object() =0; virtual void SetBody(const RigidBodyDef& body); virtual const RigidBody* GetBody() const; virtual RigidBody* GetBody(); //Inherited from IUpdatable virtual void Update(double deltaTime); //Inherited from IDrawable virtual void Draw(BITMAP* dest); protected: private: }; I'm attempting to refactor it into a more manageable system. Mr. Nystrom uses the constructor to set the individual components; CHANGING these components at run-time is impossible. It's intended to be derived and be used in derivative classes or factory methods where their constructors do not change at run-time. i.e. his Bjorne object is just a call to a factory method with a specific call to the GameObject constructor. Is this a good idea? Should the object have a default constructor and setters to facilitate run-time changes or no default constructor without setters and instead use a factory method? Given: class Object { public: //...See below for constructor implementation concerns. Object(const Object& other); Object& operator=(const Object& rhs); virtual ~Object() =0; //See below for Setter concerns IUpdatable* GetUpdater(); IDrawable* GetRenderer(); protected: IUpdatable* _updater; IDrawable* _renderer; private: }; Should the components be read-only and passed in to the constructor via: class Object { public: //No default constructor. Object(IUpdatable* updater, IDrawable* renderer); //...remainder is same as above... }; or Should a default constructor be provided and then the components can be set at run-time? class Object { public: Object(); //... SetUpdater(IUpdater* updater); SetRenderer(IDrawable* renderer); //...remainder is same as above... }; or both? class Object { public: Object(); Object(IUpdater* updater, IDrawable* renderer); //... SetUpdater(IUpdater* updater); SetRenderer(IDrawable* renderer); //...remainder is same as above... };

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• Build-time dependency resolving coming to Entity Framework. Now, how about those BI tools too?

  - by jamiet

  Three months ago I wrote a blog post entitled Some thoughts on Visual Studio database references and how they should be used for SQL Server BI where I shared some thoughts on a feature available to database developers in Visual Studio 2010 that I would love to see added to SQL Server Integration Services (SSIS), Analysis Services (SSAS) and Reporting Services (SSRS). In there I said: Over the past few weeks I have been making heavy use of the Database tools in Visual Studio 2010 and one of the features that has most impressed me has been database references.   Database references allow you to have stored procedures in your database project that refer to objects (tables, views, stored procedures etc…) that exist in other database projects and hence when you build your database project it is able to resolve those references.   It occurred to me that similar functionality would be incredibly useful for SQL Server Integration Services(SSIS), Analysis Services (SSAS) & Reporting Services (SSRS) projects. After all reports, packages and data source views are rife with references to database objects – why shouldn’t we be able to have design-time dependency checking in our BI projects the same way that database and .Net developers do? In that blog post I shared links to three Connect submissions where I requested this feature be added to SSIS, SSAS & SSRS. In addition I also submitted a request that the feature be extended to .Net projects so that any reference to a database object in a .Net assembly can be resolved at build time. That Connect submission is at [Entity FX] Use database references to constrain the EDM and overnight it received this comment from Microsoft: We have been working on this feature for a while and and will be available soon This is really good news - it improves the Microsoft developer ecosystem by ensuring invalid references to database references get caught at build time (ideally as part of a Continuous integration build) rather than run time. [Hopefully it might nip this code-first nonsense in the bud too (Ooo...way to incite flame comments :) ) ]. If you want to see this feature in action then check out a video from Teched Europe last month entitled SQL Server Developer Tools Code-named "Juneau" where it is demo'd by Lance Delano and Tim Laverty.   The point of this blog post though is not just to draw attention to this forthcoming feature for .Net developers, it is to ask you to petition Microsoft to get this feature added to SSIS/SSAS/SSRS too. After all, we already know (from the video above) that the feature is coming to this new code-name Juneau development environment plus we also know that Juneau will be the development environment for SSIS/SSAS/SSRS as well - is it really much of a stretch to expect the BI tools to have access to this great feature too? I don't think so and if you agree with me then I urge you to vote and add a comment to the Connection submissions that are requesting this feature. They are at: [SSAS] Declare Object Dependancies [SSRS] Declare Object Dependancies [SSIS] Declare Object Dependancies (Update, Apparently someone at Microsoft has deemed it necassary to set this to private and I am not able to change it back even though I submitted it. You can still vote on the other two though.) Let's close that SQL Developer Gap!   @Jamiet    

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• Problems implementing a screen space shadow ray tracing shader

  - by Grieverheart

  Here I previously asked for the possibility of ray tracing shadows in screen space in a deferred shader. Several problems were pointed out. One of the most important problem is that only visible objects can cast shadows and objects between the camera and the shadow caster can interfere. Still I thought it'd be a fun experiment. The idea is to calculate the view coordinates of pixels and cast a ray to the light. The ray is then traced pixel by pixel to the light and its depth is compared with the depth at the pixel. If a pixel is in front of the ray, a shadow is casted at the original pixel. At first I thought that I could use the DDA algorithm in 2D to calculate the distance 't' (in p = o + t d, where o origin, d direction) to the next pixel and use it in the 3D ray equation to find the ray's z coordinate at that pixel's position. For the 2D ray, I would use the projected and biased 3D ray direction and origin. The idea was that 't' would be the same in both 2D and 3D equations. Unfortunately, this is not the case since the projection matrix is 4D. Thus, some tweak needs to be done to make this work this way. I would like to ask if someone knows of a way to do what I described above, i.e. from a 2D ray in texture coordinate space to get the 3D ray in screen space. I did implement a simple version of the idea which you can see in the following video: video here Shadows may seem a bit pixelated, but that's mostly because of the size of the step in 't' I chose. And here is the shader: #version 330 core uniform sampler2D DepthMap; uniform vec2 projAB; uniform mat4 projectionMatrix; const vec3 light_p = vec3(-30.0, 30.0, -10.0); noperspective in vec2 pass_TexCoord; smooth in vec3 viewRay; layout(location = 0) out float out_AO; vec3 CalcPosition(void){ float depth = texture(DepthMap, pass_TexCoord).r; float linearDepth = projAB.y / (depth - projAB.x); vec3 ray = normalize(viewRay); ray = ray / ray.z; return linearDepth * ray; } void main(void){ vec3 origin = CalcPosition(); if(origin.z < -60) discard; vec2 pixOrigin = pass_TexCoord; //tex coords vec3 dir = normalize(light_p - origin); vec2 texel_size = vec2(1.0 / 600.0); float t = 0.1; ivec2 pixIndex = ivec2(pixOrigin / texel_size); out_AO = 1.0; while(true){ vec3 ray = origin + t * dir; vec4 temp = projectionMatrix * vec4(ray, 1.0); vec2 texCoord = (temp.xy / temp.w) * 0.5 + 0.5; ivec2 newIndex = ivec2(texCoord / texel_size); if(newIndex != pixIndex){ float depth = texture(DepthMap, texCoord).r; float linearDepth = projAB.y / (depth - projAB.x); if(linearDepth > ray.z + 0.1){ out_AO = 0.2; break; } pixIndex = newIndex; } t += 0.5; if(texCoord.x < 0 || texCoord.x > 1.0 || texCoord.y < 0 || texCoord.y > 1.0) break; } } As you can see, here I just increment 't' by some arbitrary factor, calculate the 3D ray and project it to get the pixel coordinates, which is not really optimal. Hopefully, I would like to optimize the code as much as possible and compare it with shadow mapping and how it scales with the number of lights. PS: Keep in mind that I reconstruct position from depth by interpolating rays through a full screen quad.

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• Undefined fireball movement behavior

  - by optimisez

  Demonstration video I try to do after the player shoot 10 times of fireball, then delete all the fireball objects and recreate a 10 new set of fireball objects. I did it but there is a weird bug happens that sometimes the fireball will come out from top and move to the right after shooting a few times. All the 10 fireballs should follow the player all the time and all the fireball should come out from player even after a new set of fireballs is recreated. Any ideas to fix it? Variables typedef struct gameObject{ float X; float Y; int length; int height; bool action; }; // Fireball #define FIREBALL_NUM 10 LPDIRECT3DTEXTURE9 fireball = NULL; RECT fireballRect; gameObject *fireballDest = new gameObject[FIREBALL_NUM]; int iFireBallAnimation; int fireballCount = 0; Set up Fireball void setUpFireBall() { // Initialize destination rectangle, rectangle height and length for (int i = 0; i < FIREBALL_NUM; i++) { fireballDest[i].X = 0; fireballDest[i].Y = 0; fireballDest[i].length = fireballRect.right - fireballRect.left; fireballDest[i].height = fireballRect.bottom - fireballRect.top; } iFireBallAnimation = fireballRect.right - fireballRect.left; // Initialize boolean for (int i = 0; i < FIREBALL_NUM; i++) { fireballDest[i].action = false; } } Initialize fireball void initFireball() { hr = D3DXCreateTextureFromFileEx(d3dDevice, "fireball.png", 512, 512, D3DX_DEFAULT, NULL, D3DFMT_A8R8G8B8, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, D3DCOLOR_XRGB(255, 255, 0), NULL, NULL, &fireball); // Initialize source rectangle fireballRect.left = 0; fireballRect.top = 256; fireballRect.right = 64; fireballRect.bottom = 320; setUpFireBall(); } Update fireball void update() { updateAnimation(); updateAI(); updatePhysics(); updateGameState(); } void updatePhysics() { motion(); collison(); } void motion() { playerMove(); playerJump(); playerGravity(); shootFireball(); fireballFollowPlayer(); } void shootFireball() { if (keyArr['Z']) fireballDest[fireballCount].action = true; if (fireballDest[fireballCount].action) { fireballDest[fireballCount].X += 10; if (fireballDest[fireballCount].X > 800) fireballCount++; } } void fireballFollowPlayer() { for (int i = 0; i < FIREBALL_NUM; i++) { if (fireballDest[i].action == false) { fireballDest[i].X = playerDest.X - 30; fireballDest[i].Y = playerDest.Y - 14; } } } void updateGameState() { // When no more fireball left, rearm fireball if (fireballCount == FIREBALL_NUM) { delete[] fireballDest; fireballDest = new gameObject[10]; fireballCount = 0; setUpFireBall(); } } Render fireball void renderFireball() { for (int i = 0; i < FIREBALL_NUM; i++) { if (fireballDest[i].action) sprite->Draw(fireball, &fireballRect, NULL, &D3DXVECTOR3(fireballDest[i].X, fireballDest[i].Y, 0), D3DCOLOR_XRGB(255,255, 255)); } }

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• how can I specify interleaved vertex attributes and vertex indices

  - by freefallr

  I'm writing a generic ShaderProgram class that compiles a set of Shader objects, passes args to the shader (like vertex position, vertex normal, tex coords etc), then links the shader components into a shader program, for use with glDrawArrays. My vertex data already exists in a VertexBufferObject that uses the following data structure to create a vertex buffer: class CustomVertex { public: float m_Position[3]; // x, y, z // offset 0, size = 3*sizeof(float) float m_TexCoords[2]; // u, v // offset 3*sizeof(float), size = 2*sizeof(float) float m_Normal[3]; // nx, ny, nz; float colour[4]; // r, g, b, a float padding[20]; // padded for performance }; I've already written a working VertexBufferObject class that creates a vertex buffer object from an array of CustomVertex objects. This array is said to be interleaved. It renders successfully with the following code: void VertexBufferObject::Draw() { if( ! m_bInitialized ) return; glBindBuffer( GL_ARRAY_BUFFER, m_nVboId ); glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, m_nVboIdIndex ); glEnableClientState( GL_VERTEX_ARRAY ); glEnableClientState( GL_TEXTURE_COORD_ARRAY ); glEnableClientState( GL_NORMAL_ARRAY ); glEnableClientState( GL_COLOR_ARRAY ); glVertexPointer( 3, GL_FLOAT, sizeof(CustomVertex), ((char*)NULL + 0) ); glTexCoordPointer(3, GL_FLOAT, sizeof(CustomVertex), ((char*)NULL + 12)); glNormalPointer(GL_FLOAT, sizeof(CustomVertex), ((char*)NULL + 20)); glColorPointer(3, GL_FLOAT, sizeof(CustomVertex), ((char*)NULL + 32)); glDrawElements( GL_TRIANGLES, m_nNumIndices, GL_UNSIGNED_INT, ((char*)NULL + 0) ); glDisableClientState( GL_VERTEX_ARRAY ); glDisableClientState( GL_TEXTURE_COORD_ARRAY ); glDisableClientState( GL_NORMAL_ARRAY ); glDisableClientState( GL_COLOR_ARRAY ); glBindBuffer( GL_ARRAY_BUFFER, 0 ); glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, 0 ); } Back to the Vertex Array Object though. My code for creating the Vertex Array object is as follows. This is performed before the ShaderProgram runtime linking stage, and no glErrors are reported after its steps. // Specify the shader arg locations (e.g. their order in the shader code) for( int n = 0; n < vShaderArgs.size(); n ++) glBindAttribLocation( m_nProgramId, n, vShaderArgs[n].sFieldName.c_str() ); // Create and bind to a vertex array object, which stores the relationship between // the buffer and the input attributes glGenVertexArrays( 1, &m_nVaoHandle ); glBindVertexArray( m_nVaoHandle ); // Enable the vertex attribute array (we're using interleaved array, since its faster) glBindBuffer( GL_ARRAY_BUFFER, vShaderArgs[0].nVboId ); glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, vShaderArgs[0].nVboIndexId ); // vertex data for( int n = 0; n < vShaderArgs.size(); n ++ ) { glEnableVertexAttribArray(n); glVertexAttribPointer( n, vShaderArgs[n].nFieldSize, GL_FLOAT, GL_FALSE, vShaderArgs[n].nStride, (GLubyte *) NULL + vShaderArgs[n].nFieldOffset ); AppLog::Ref().OutputGlErrors(); } This doesn't render correctly at all. I get a pattern of white specks onscreen, in the shape of the terrain rectangle, but there are no regular lines etc. Here's the code I use for rendering: void ShaderProgram::Draw() { using namespace AntiMatter; if( ! m_nShaderProgramId || ! m_nVaoHandle ) { AppLog::Ref().LogMsg("ShaderProgram::Draw() Couldn't draw object, as initialization of ShaderProgram is incomplete"); return; } glUseProgram( m_nShaderProgramId ); glBindVertexArray( m_nVaoHandle ); glDrawArrays( GL_TRIANGLES, 0, m_nNumTris ); glBindVertexArray(0); glUseProgram(0); } Can anyone see errors or omissions in either the VAO creation code or rendering code? thanks!

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• SSAS: Utility to export SQL code from your cube's Data Source View (DSV)

  - by DrJohn

  When you are working on a cube, particularly in a multi-person team, it is sometimes necessary to review what changes that have been done to the SQL queries in the cube's data source view (DSV). This can be a problem as the SQL editor in the DSV is not the best interface to review code. Now of course you can cut and paste the SQL into SSMS, but you have to do each query one-by-one. What is worse your DBA is unlikely to have BIDS installed, so you will have to manually export all the SQL yourself and send him the files. To make it easy to get hold of the SQL in a Data Source View, I developed a C# utility which connects to an OLAP database and uses Analysis Services Management Objects (AMO) to obtain and export all the SQL to a series of files. The added benefit of this approach is that these SQL files can be placed under source code control which means the DBA can easily compare one version with another. The Trick When I came to implement this utility, I quickly found that the AMO API does not give direct access to anything useful about the tables in the data source view. Iterating through the DSVs and tables is easy, but getting to the SQL proved to be much harder. My Google searches returned little of value, so I took a look at the idea of using the XmlDom to open the DSV’s XML and obtaining the SQL from that. This is when the breakthrough happened. Inspecting the DSV’s XML I saw the things I was interested in were called TableType DbTableName FriendlyName QueryDefinition Searching Google for FriendlyName returned this page: Programming AMO Fundamental Objects which hinted at the fact that I could use something called ExtendedProperties to obtain these XML attributes. This simplified my code tremendously to make the implementation almost trivial. So here is my code with appropriate comments. The full solution can be downloaded from here: ExportCubeDsvSQL.zip   using System;using System.Data;using System.IO;using Microsoft.AnalysisServices; ... class code removed for clarity// connect to the OLAP server Server olapServer = new Server();olapServer.Connect(config.olapServerName);if (olapServer != null){ // connected to server ok, so obtain reference to the OLAP databaseDatabase olapDatabase = olapServer.Databases.FindByName(config.olapDatabaseName);if (olapDatabase != null){ Console.WriteLine(string.Format("Succesfully connected to '{0}' on '{1}'",   config.olapDatabaseName,   config.olapServerName));// export SQL from each data source view (usually only one, but can be many!)foreach (DataSourceView dsv in olapDatabase.DataSourceViews){ Console.WriteLine(string.Format("Exporting SQL from DSV '{0}'", dsv.Name));// for each table in the DSV, export the SQL in a fileforeach (DataTable dt in dsv.Schema.Tables){ Console.WriteLine(string.Format("Exporting SQL from table '{0}'", dt.TableName)); // get name of the table in the DSV// use the FriendlyName as the user inputs this and therefore has control of itstring queryName = dt.ExtendedProperties["FriendlyName"].ToString().Replace(" ", "_");string sqlFilePath = Path.Combine(targetDir.FullName, queryName + ".sql"); // delete the sql file if it exists... file deletion code removed for clarity// write out the SQL to a fileif (dt.ExtendedProperties["TableType"].ToString() == "View"){ File.WriteAllText(sqlFilePath, dt.ExtendedProperties["QueryDefinition"].ToString());}if (dt.ExtendedProperties["TableType"].ToString() == "Table"){ File.WriteAllText(sqlFilePath, dt.ExtendedProperties["DbTableName"].ToString()); } } } Console.WriteLine(string.Format("Successfully written out SQL scripts to '{0}'", targetDir.FullName)); } }   Of course, if you are following industry best practice, you should be basing your cube on a series of views. This will mean that this utility will be of limited practical value unless of course you are inheriting a project and want to check if someone did the implementation correctly.

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• Determining explosion radius damage - Circle to Rectangle 2D

  - by Paul Renton

  One of the Cocos2D games I am working on has circular explosion effects. These explosion effects need to deal a percentage of their set maximum damage to all game characters (represented by rectangular bounding boxes as the objects in question are tanks) within the explosion radius. So this boils down to circle to rectangle collision and how far away the circle's radius is from the closest rectangle edge. I took a stab at figuring this out last night, but I believe there may be a better way. In particular, I don't know the best way to determine what percentage of damage to apply based on the distance calculated. Note : All tank objects have an anchor point of (0,0) so position is according to bottom left corner of bounding box. Explosion point is the center point of the circular explosion. TankObject * tank = (TankObject*) gameSprite; float distanceFromExplosionCenter; // IMPORTANT :: All GameCharacter have an assumed (0,0) anchor if (explosionPoint.x < tank.position.x) { // Explosion to WEST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, tank.position); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHWEST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = tank.position.x - explosionPoint.x; } // end if } else if (explosionPoint.x > (tank.position.x + tank.contentSize.width)) { // Explosion to EAST of tank if (explosionPoint.y <= tank.position.y) { //Explosion SOUTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y)); } else if (explosionPoint.y >= (tank.position.y + tank.contentSize.height)) { // Explosion NORTHEAST distanceFromExplosionCenter = ccpDistance(explosionPoint, ccp(tank.position.x + tank.contentSize.width, tank.position.y + tank.contentSize.height)); } else { // Exp center's y is between bottom and top corner of rect distanceFromExplosionCenter = explosionPoint.x - (tank.position.x + tank.contentSize.width); } // end if } else { // Tank is either north or south and is inbetween left and right corner of rect if (explosionPoint.y < tank.position.y) { // Explosion is South distanceFromExplosionCenter = tank.position.y - explosionPoint.y; } else { // Explosion is North distanceFromExplosionCenter = explosionPoint.y - (tank.position.y + tank.contentSize.height); } // end if } // end outer if if (distanceFromExplosionCenter < explosionRadius) { /* Collision :: Smaller distance larger the damage */ int damageToApply; if (self.directHit) { damageToApply = self.explosionMaxDamage + self.directHitBonusDamage; [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explsoion-> DIRECT HIT with total damage %d", damageToApply); } else { // TODO adjust this... turning out negative for some reason... damageToApply = (1 - (distanceFromExplosionCenter/explosionRadius) * explosionMaxDamage); [tank takeDamageAndAdjustHealthBar:damageToApply]; CCLOG(@"Explosion-> Non direct hit collision with tank"); CCLOG(@"Damage to apply is %d", damageToApply); } // end if } else { CCLOG(@"Explosion-> Explosion distance is larger than explosion radius"); } // end if } // end if Questions: 1) Can this circle to rect collision algorithm be done better? Do I have too many checks? 2) How to calculate the percentage based damage? My current method generates negative numbers occasionally and I don't understand why (Maybe I need more sleep!). But, in my if statement, I ask if distance < explosion radius. When control goes through, distance/radius must be < 1 right? So 1 - that intermediate calculation should not be negative. Appreciate any help/advice!

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• JDeveloper 11.1.2 : Command Link in Table Column Work Around

  - by Frank Nimphius

  Just figured that in Oracle JDeveloper 11.1.2, clicking on a command link in a table does not mark the table row as selected as it is the behavior in previous releases of Oracle JDeveloper. For the time being, the following work around can be used to achieve the "old" behavior: To mark the table row as selected, you need to build and queue the table selection event in the code executed by the command link action listener. To queue a selection event, you need to know about the rowKey of the row that the command link that you clicked on is located in. To get to this information, you add an f:attribute tag to the command link as shown below <af:column sortProperty="#{bindings.DepartmentsView1.hints.DepartmentId.name}" sortable="false"    headerText="#{bindings.DepartmentsView1.hints.DepartmentId.label}" id="c1">   <af:commandLink text="#{row.DepartmentId}" id="cl1" partialSubmit="true"       actionListener="#{BrowseBean.onCommandItemSelected}">     <f:attribute name="rowKey" value="#{row.rowKey}"/>   </af:commandLink>   ... </af:column> The f:attribute tag references #{row.rowKey} wich in ADF translates to JUCtrlHierNodeBinding.getRowKey(). This information can be used in the command link action listener to compose the RowKeySet you need to queue the selected row. For simplicitly reasons, I created a table "binding" reference to the managed bean that executes the command link action. The managed bean code that is referenced from the af:commandLink actionListener property is shown next: public void onCommandItemSelected(ActionEvent actionEvent) {   //get access to the clicked command link   RichCommandLink comp = (RichCommandLink)actionEvent.getComponent();   //read the added f:attribute value   Key rowKey = (Key) comp.getAttributes().get("rowKey");     //get the current selected RowKeySet from the table   RowKeySet oldSelection = table.getSelectedRowKeys();   //build an empty RowKeySet for the new selection   RowKeySetImpl newSelection = new RowKeySetImpl();     //RowKeySets contain List objects with key objects in them   ArrayList list = new ArrayList();   list.add(rowKey);   newSelection.add(list);     //create the selectionEvent and queue it   SelectionEvent selectionEvent = new SelectionEvent(oldSelection, newSelection, table);   selectionEvent.queue();     //refresh the table   AdfFacesContext.getCurrentInstance().addPartialTarget(table); }

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• dynamic? I'll never use that ... or then again, maybe it could ...

  - by adweigert

  So, I don't know about you, but I was highly skeptical of the dynamic keywork when it was announced. I thought to myself, oh great, just another move towards VB compliance. Well after seeing it being used in things like DynamicXml (which I use for this example) I then was working with a MVC controller and wanted to move some things like operation timeout of an action to a configuration file. Thinking big picture, it'd be really nice to have configuration for all my controllers like that. Ugh, I don't want to have to create all those ConfigurationElement objects... So, I started thinking self, use what you know and do something cool ... Well after a bit of zoning out, self came up with use a dynamic object duh! I was thinking of a config like this ...<controllers> <add type="MyApp.Web.Areas.ComputerManagement.Controllers.MyController, MyApp.Web"> <detail timeout="00:00:30" /> </add> </controllers> So, I ended up with a couple configuration classes like this ...blic abstract class DynamicConfigurationElement : ConfigurationElement { protected DynamicConfigurationElement() { this.DynamicObject = new DynamicConfiguration(); } public DynamicConfiguration DynamicObject { get; private set; } protected override bool OnDeserializeUnrecognizedAttribute(string name, string value) { this.DynamicObject.Add(name, value); return true; } protected override bool OnDeserializeUnrecognizedElement(string elementName, XmlReader reader) { this.DynamicObject.Add(elementName, new DynamicXml((XElement)XElement.ReadFrom(reader))); return true; } } public class ControllerConfigurationElement : DynamicConfigurationElement { [ConfigurationProperty("type", Options = ConfigurationPropertyOptions.IsRequired | ConfigurationPropertyOptions.IsKey)] public string TypeName { get { return (string)this["type"]; } } public Type Type { get { return Type.GetType(this.TypeName, true); } } } public class ControllerConfigurationElementCollection : ConfigurationElementCollection { protected override ConfigurationElement CreateNewElement() { return new ControllerConfigurationElement(); } protected override object GetElementKey(ConfigurationElement element) { return ((ControllerConfigurationElement)element).Type; } } And then had to create the meat of the DynamicConfiguration class which looks like this ...public class DynamicConfiguration : DynamicObject { private Dictionary<string, object> properties = new Dictionary<string, object>(StringComparer.CurrentCultureIgnoreCase); internal void Add<T>(string name, T value) { this.properties.Add(name, value); } public override bool TryGetMember(GetMemberBinder binder, out object result) { var propertyName = binder.Name; result = null; if (this.properties.ContainsKey(propertyName)) { result = this.properties[propertyName]; } return true; } } So all being said, I made a base controller class like a good little MVC-itizen ...public abstract class BaseController : Controller { protected BaseController() : base() { var configuration = ManagementConfigurationSection.GetInstance(); var controllerConfiguration = configuration.Controllers.ForType(this.GetType()); if (controllerConfiguration != null) { this.Configuration = controllerConfiguration.DynamicObject; } } public dynamic Configuration { get; private set; } } And used it like this ...public class MyController : BaseController { static readonly string DefaultDetailTimeout = TimeSpan.MaxValue.ToString(); public MyController() { this.DetailTimeout = TimeSpan.Parse(this.Configuration.Detail.Timeout ?? DefaultDetailTimeout); } public TimeSpan DetailTimeout { get; private set; } } And there I have an actual use for the dynamic keyword ... never thoguht I'd see the day when I first heard of it as I don't do much COM work ... oh dont' forget this little helper extension methods to find the controller configuration by the controller type.public static ControllerConfigurationElement ForType<T>(this ControllerConfigurationElementCollection collection) { Contract.Requires(collection != null); return ForType(collection, typeof(T)); } public static ControllerConfigurationElement ForType(this ControllerConfigurationElementCollection collection, Type type) { Contract.Requires(collection != null); Contract.Requires(type != null); return collection.Cast<ControllerConfigurationElement>().Where(element => element.Type == type).SingleOrDefault(); } Sure, it isn't perfect and I'm sure I can tweak it over time, but I thought it was a pretty cool way to take advantage of the dynamic keyword functionality. Just remember, it only validates you did it right at runtime, which isn't that bad ... is it? And yes, I did make it case-insensitive so my code didn't have to look like my XML objects, tweak it to your liking if you dare to use this creation.

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• Question on the implementation of my Entity System

  - by miguel.martin

  I am currently creating an Entity System, in C++, it is almost completed (I have all the code there, I just have to add a few things and test it). The only thing is, I can't figure out how to implement some features. This Entity System is based off a bit from the Artemis framework, however it is different. I'm not sure if I'll be able to type this out the way my head processing it. I'm going to basically ask whether I should do something over something else. Okay, now I'll give a little detail on my Entity System itself. Here are the basic classes that my Entity System uses to actually work: Entity - An Id (and some methods to add/remove/get/etc Components) Component - An empty abstract class ComponentManager - Manages ALL components for ALL entities within a Scene EntitySystem - Processes entities with specific components Aspect - The class that is used to help determine what Components an Entity must contain so a specific EntitySystem can process it EntitySystemManager - Manages all EntitySystems within a Scene EntityManager - Manages entities (i.e. holds all Entities, used to determine whether an Entity has been changed, enables/disables them, etc.) EntityFactory - Creates (and destroys) entities and assigns an ID to them Scene - Contains an EntityManager, EntityFactory, EntitySystemManager and ComponentManager. Has functions to update and initialise the scene. Now in order for an EntitySystem to efficiently know when to check if an Entity is valid for processing (so I can add it to a specific EntitySystem), it must recieve a message from the EntityManager (after a call of activate(Entity& e)). Similarly the EntityManager must know when an Entity is destroyed from the EntityFactory in the Scene, and also the ComponentManager must know when an Entity is created AND destroyed. I do have a Listener/Observer pattern implemented at the moment, but with this pattern I may remove a Listener (which is this case is dependent on the method being called). I mainly have this implemented for specific things related to a game, i.e. Teams, Tagging of entities, etc. So... I was thinking maybe I should call a private method (using friend classes) to send out when an Entity has been activated, deleted, etc. i.e. taken from my EntityFactory void EntityFactory::killEntity(Entity& e) { // if the entity doesn't exsist in the entity manager within the scene if(!getScene()->getEntityManager().doesExsist(e)) { return; // go back to the caller! (should throw an exception or something..) } // tell the ComponentManager and the EntityManager that we killed an Entity getScene()->getComponentManager().doOnEntityWillDie(e); getScene()->getEntityManager().doOnEntityWillDie(e); // notify the listners for(Mouth::iterator i = getMouth().begin(); i != getMouth().end(); ++i) { (*i)->onEntityWillDie(*this, e); } _idPool.addId(e.getId()); // add the ID to the pool delete &e; // delete the entity } As you can see on the lines where I am telling the ComponentManager and the EntityManager that an Entity will die, I am calling a method to make sure it handles it appropriately. Now I realise I could do this without calling it explicitly, with the help of that for loop notifying all listener objects connected to the EntityFactory's Mouth (an object used to tell listeners that there's an event), however is this a good idea (good design, or what)? I've gone over the PROS and CONS, I just can't decide what I want to do. Calling Explicitly: PROS Faster? Since these functions are explicitly called, they can't be "removed" CONS Not flexible Bad design? (friend functions) Calling through Listener objects (i.e. ComponentManager/EntityManager inherits from a EntityFactoryListener) PROS More Flexible? Better Design? CONS Slower? (virtual functions) Listeners can be removed, i.e. may be removed and not get called again during the program, which could cause in a crash. P.S. If you wish to view my current source code, I am hosting it on BitBucket.

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• SQL SERVER – Last Two Days to Get FREE Book – Joes 2 Pros Certification 70-433

  - by pinaldave

  Earlier this week we announced that we will be giving away FREE SQL Wait Stats book to everybody who will get SQL Server Joes 2 Pros Combo Kit. We had a fantastic response to the contest. We got an overwhelming response to the offer. We knew there would be a great response but we want to honestly say thank you to all of you for making it happen. Rick and I want to make sure that we express our special thanks to all of you who are reading our books. The offer is still on and there are two more days to avail this offer. We want to make sure that everybody who buys our most selling combo kits, we will send our other most popular SQL Wait Stats book. Please read all the details of the offer here. The books are great resources for anyone who wants to learn SQL Server from fundamentals and eventually go on the certification path of 70-433. Exam 70-433 contains following important subject and the book covers the subject of fundamental. If you are taking the exam or not taking the exam – this book is for every SQL Developer to learn the subject from fundamentals.  Create and alter tables. Create and alter views. Create and alter indexes. Create and modify constraints. Implement data types. Implement partitioning solutions. Create and alter stored procedures. Create and alter user-defined functions (UDFs). Create and alter DML triggers. Create and alter DDL triggers. Create and deploy CLR-based objects. Implement error handling. Manage transactions. Query data by using SELECT statements. Modify data by using INSERT, UPDATE, and DELETE statements. Return data by using the OUTPUT clause. Modify data by using MERGE statements. Implement aggregate queries. Combine datasets. INTERSECT, EXCEPT Implement subqueries. Implement CTE (common table expression) queries. Apply ranking functions. Control execution plans. Manage international considerations. Integrate Database Mail. Implement full-text search. Implement scripts by using Windows PowerShell and SQL Server Management Objects (SMOs). Implement Service Broker solutions. Track data changes. Data capture Retrieve relational data as XML. Transform XML data into relational data. Manage XML data. Capture execution plans. Collect output from the Database Engine Tuning Advisor. Collect information from system metadata. Availability of Book USA - Amazon | India - Flipkart | Indiaplaza Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Joes 2 Pros, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• How views are changing in future versions of SQL

  - by Rob Farley

  April is here, and this weekend, SQL v11.0 (previous known as Denali, now known as SQL Server 2012) reaches general availability. And so I thought I’d share some news about what’s coming next. I didn’t hear this at the MVP Summit earlier this year (where there was lots of NDA information given, but I didn’t go), so I think I’m free to share it. I’ve written before about CTEs being query-scoped views. Well, the actual story goes a bit further, and will continue to develop in future versions. A CTE is a like a “temporary temporary view”, scoped to a single query. Due to globally-scoped temporary objects using a two-hashes naming style, and session-scoped (or ‘local’) temporary objects a one-hash naming style, this query-scoped temporary object uses a cunning zero-hash naming style. We see this implied in Books Online in the CREATE TABLE page, but as we know, temporary views are not yet supported in the SQL Server. However, in a breakaway from ANSI-SQL, Microsoft is moving towards consistency with their naming. We know that a CTE is a “common table expression” – this is proving to be a more strategic than you may have appreciated. Within the Microsoft product group, the term “Table Expression” is far more widely used than just CTEs. Anything that can be used in a FROM clause is referred to as a Table Expression, so long as it doesn’t actually store data (which would make it a Table, rather than a Table Expression). You can see this is not just restricted to the product group by doing an internet search for how the term is used without ‘common’. In the past, Books Online has referred to a view as a “virtual table” (but notice that there is no SQL 2012 version of this page). However, it was generally decided that “virtual table” was a poor name because it wasn’t completely accurate, and it’s typically accepted that virtualisation and SQL is frowned upon. That page I linked to says “or stored query”, which is slightly better, but when the SQL 2012 version of that page is actually published, the line will be changed to read: “A view is a stored table expression (STE)”. This change will be the first of many. During the SQL 2012 R2 release, the keyword VIEW will become deprecated (this will be SQL v11 SP1.5). Three versions later, in SQL 14.5, you will need to be in compatibility mode 140 to allow “CREATE VIEW” to work. Also consistent with Microsoft’s deprecation policy, the execution of any query that refers to an object created as a view (rather than the new “CREATE STE”), will cause a Deprecation Event to fire. This will all be in preparation for the introduction of Single-Column Table Expressions (to be introduced in SQL 17.3 SP6) which will finally shut up those people waiting for a decent implementation of Inline Scalar Functions. And of course, CTEs are “Common” because the Table Expression definition needs to be repeated over and over throughout a stored procedure. ...or so I think I heard at some point. Oh, and congratulations to all the new MVPs on this April 1st. @rob_farley

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• Game Object Factory: Fixing Memory Leaks

  - by Bunkai.Satori

  Dear all, this is going to be tough: I have created a game object factory that generates objects of my wish. However, I get memory leaks which I can not fix. Memory leaks are generated by return new Object(); in the bottom part of the code sample. static BaseObject * CreateObjectFunc() { return new Object(); } How and where to delete the pointers? I wrote bool ReleaseClassType(). Despite the factory works well, ReleaseClassType() does not fix memory leaks. bool ReleaseClassTypes() { unsigned int nRecordCount = vFactories.size(); for (unsigned int nLoop = 0; nLoop < nRecordCount; nLoop++ ) { // if the object exists in the container and is valid, then render it if( vFactories[nLoop] != NULL) delete vFactories[nLoop](); } return true; } Before taking a look at the code below, let me help you in that my CGameObjectFactory creates pointers to functions creating particular object type. The pointers are stored within vFactories vector container. I have chosen this way because I parse an object map file. I have object type IDs (integer values) which I need to translate them into real objects. Because I have over 100 different object data types, I wished to avoid continuously traversing very long Switch() statement. Therefore, to create an object, I call vFactoriesnEnumObjectTypeID via CGameObjectFactory::create() to call stored function that generates desired object. The position of the appropriate function in the vFactories is identical to the nObjectTypeID, so I can use indexing to access the function. So the question remains, how to proceed with garbage collection and avoid reported memory leaks? #ifndef GAMEOBJECTFACTORY_H_UNIPIXELS #define GAMEOBJECTFACTORY_H_UNIPIXELS //#include "MemoryManager.h" #include <vector> template <typename BaseObject> class CGameObjectFactory { public: // cleanup and release registered object data types bool ReleaseClassTypes() { unsigned int nRecordCount = vFactories.size(); for (unsigned int nLoop = 0; nLoop < nRecordCount; nLoop++ ) { // if the object exists in the container and is valid, then render it if( vFactories[nLoop] != NULL) delete vFactories[nLoop](); } return true; } // register new object data type template <typename Object> bool RegisterClassType(unsigned int nObjectIDParam ) { if(vFactories.size() < nObjectIDParam) vFactories.resize(nObjectIDParam); vFactories[nObjectIDParam] = &CreateObjectFunc<Object>; return true; } // create new object by calling the pointer to the appropriate type function BaseObject* create(unsigned int nObjectIDParam) const { return vFactories[nObjectIDParam](); } // resize the vector array containing pointers to function calls bool resize(unsigned int nSizeParam) { vFactories.resize(nSizeParam); return true; } private: //DECLARE_HEAP; template <typename Object> static BaseObject * CreateObjectFunc() { return new Object(); } typedef BaseObject*(*factory)(); std::vector<factory> vFactories; }; //DEFINE_HEAP_T(CGameObjectFactory, "Game Object Factory"); #endif // GAMEOBJECTFACTORY_H_UNIPIXELS

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• How should I plan the inheritance structure for my game?

  - by Eric Thoma

  I am trying to write a platform shooter in C++ with a really good class structure for robustness. The game itself is secondary; it is the learning process of writing it that is primary. I am implementing an inheritance tree for all of the objects in my game, but I find myself unsure on some decisions. One specific issue that it bugging me is this: I have an Actor that is simply defined as anything in the game world. Under Actor is Character. Both of these classes are abstract. Under Character is the Philosopher, who is the main character that the user commands. Also under Character is NPC, which uses an AI module with stock routines for friendly, enemy and (maybe) neutral alignments. So under NPC I want to have three subclasses: FriendlyNPC, EnemyNPC and NeutralNPC. These classes are not abstract, and will often be subclassed in order to make different types of NPC's, like Engineer, Scientist and the most evil Programmer. Still, if I want to implement a generic NPC named Kevin, it would nice to be able to put him in without making a new class for him. I could just instantiate a FriendlyNPC and pass some values for the AI machine and for the dialogue; that would be ideal. But what if Kevin is the one benevolent Programmer in the whole world? Now we must make a class for him (but what should it be called?). Now we have a character that should inherit from Programmer (as Kevin has all the same abilities but just uses the friendly AI functions) but also should inherit from FriendlyNPC. Programmer and FriendlyNPC branched away from each other on the inheritance tree, so inheriting from both of them would have conflicts, because some of the same functions have been implemented in different ways on the two of them. 1) Is there a better way to order these classes to avoid these conflicts? Having three subclasses; Friendly, Enemy and Neutral; from each type of NPC; Engineer, Scientist, and Programmer; would amount to a huge number of classes. I would share specific implementation details, but I am writing the game slowly, piece by piece, and so I haven't implemented past Character yet. 2) Is there a place where I can learn these programming paradigms? I am already trying to take advantage of some good design patterns, like MVC architecture and Mediator objects. The whole point of this project is to write something in good style. It is difficult to tell what should become a subclass and what should become a state (i.e. Friendly boolean v. Friendly class). Having many states slows down code with if statements and makes classes long and unwieldy. On the other hand, having a class for everything isn't practical. 3) Are there good rules of thumb or resources to learn more about this? 4) Finally, where does templating come in to this? How should I coordinate templates into my class structure? I have never actually taken advantage of templating honestly, but I hear that it increases modularity, which means good code.

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• Notes - Part II - Play with JavaFX

  - by Silviu Turuga

  Open the project from last lesson Double click on NotesUI.fmxl, this will open the JavaFX Scene Builder On the left side you have a area called Hierarchy, from there press Del or Shift+Backspace on Mac to delete the Button and the Label. You'll receive a warning, that some components have been assigned an fx:id, click Delete as we don't need them anymore. Resize the AnchorPane to have enough room for our design, eg. 820x550px From the top left pick the Container called Accordion and drag over the AnchorPane design Chose then from Controls a List View and drag inside the Accordion. You'll notice that by default the Accordion has 2 TitledPane, and you can switch between them by clicking on their name. I'll let you the pleasure to do the rest in order to get the following result  Here is the list of objects used Save it and then return to NetBeans Run the application and it should be run without any issue. If you click on buttons they all are functional, but nothing happens as we didn't link them with any action. We'll see this in the next episode. Now, let's play a little bit with the application and try to resize it… Have you notice the behavior? If the form is too small, some objects aren't visible, if it is too large there is too much space . That's for sure something that your users won't like and you as a programmer have to care about this. From NetBeans double click NotesUI.fmxl so to return back to JavaFX Scene Builder Select the TextField from bottom left of Notes, the one where I put the text Category and then from the right part of JavaFX Scene Builder you'll notice a panel called Inspector. Chose Layout and then click on the dotted lines from left and bottom of the square, like you see in the below image This will make the textfield to have always the same distance from left and bottom no matter the size of the form. Save and run the application. Note that whenever the form is changing the Height, the Category TextField has the same distance from the bottom. Select Accordion and do the same steps but also check the top dotted line, because we want the Accordion to have the same height as the main form has. I'll let you the pleasure to do the same for the rest of components. It's very important to design an application that can be resize by user and in the same time, all the buttons are on place. Last step is to make sure our application is not getting smaller then a certain size, as this will hide parts of our layout. So select the AnchorPane and from Inspector go to Layout and note down the Width and Height. Go back to NetBeans and open the file Main.java and add the following code just after stage.setScene(scene); (around line 26) stage.setMinWidth(820); stage.setMinHeight(550); Use your own width and height. This will prevent user to reduce the width or height of your application to a value that will hide parts of your layout. So now you should have done most of the design part and next time we'll see how can we enter some data into our newly created application… Note: in case you miss something, here are the source files of the project till this point. 

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• Multithreading 2D gravity calculations

  - by Postman

  I'm building a space exploration game and I've currently started working on gravity ( In C# with XNA). The gravity still needs tweaking, but before I can do that, I need to address some performance issues with my physics calculations. This is using 100 objects, normally rendering 1000 of them with no physics calculations gets well over 300 FPS (which is my FPS cap), but any more than 10 or so objects brings the game (and the single thread it runs on) to its knees when doing physics calculations. I checked my thread usage and the first thread was killing itself from all the work, so I figured I just needed to do the physics calculation on another thread. However when I try to run the Gravity.cs class's Update method on another thread, even if Gravity's Update method has nothing in it, the game is still down to 2 FPS. Gravity.cs public void Update() { foreach (KeyValuePair<string, Entity> e in entityEngine.Entities) { Vector2 Force = new Vector2(); foreach (KeyValuePair<string, Entity> e2 in entityEngine.Entities) { if (e2.Key != e.Key) { float distance = Vector2.Distance(entityEngine.Entities[e.Key].Position, entityEngine.Entities[e2.Key].Position); if (distance > (entityEngine.Entities[e.Key].Texture.Width / 2 + entityEngine.Entities[e2.Key].Texture.Width / 2)) { double angle = Math.Atan2(entityEngine.Entities[e2.Key].Position.Y - entityEngine.Entities[e.Key].Position.Y, entityEngine.Entities[e2.Key].Position.X - entityEngine.Entities[e.Key].Position.X); float mult = 0.1f * (entityEngine.Entities[e.Key].Mass * entityEngine.Entities[e2.Key].Mass) / distance * distance; Vector2 VecForce = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); VecForce.Normalize(); Force = Vector2.Add(Force, VecForce * mult); } } } entityEngine.Entities[e.Key].Position += Force; } } Yeah, I know. It's a nested foreach loop, but I don't know how else to do the gravity calculation, and this seems to work, it's just so intensive that it needs its own thread. (Even if someone knows a super efficient way to do these calculations, I'd still like to know how I COULD do it on multiple threads instead) EntityEngine.cs (manages an instance of Gravity.cs) public class EntityEngine { public Dictionary<string, Entity> Entities = new Dictionary<string, Entity>(); public Gravity gravity; private Thread T; public EntityEngine() { gravity = new Gravity(this); } public void Update() { foreach (KeyValuePair<string, Entity> e in Entities) { Entities[e.Key].Update(); } T = new Thread(new ThreadStart(gravity.Update)); T.IsBackground = true; T.Start(); } } EntityEngine is created in Game1.cs, and its Update() method is called within Game1.cs. I need my physics calculation in Gravity.cs to run every time the game updates, in a separate thread so that the calculation doesn't slow the game down to horribly low (0-2) FPS. How would I go about making this threading work? (any suggestions for an improved Planetary Gravity system are welcome if anyone has them) I'm also not looking for a lesson in why I shouldn't use threading or the dangers of using it incorrectly, I'm looking for a straight answer on how to do it. I've already spent an hour googling this very question with little results that I understood or were helpful. I don't mean to come off rude, but it always seems hard as a programming noob to get a straight meaningful answer, I usually rather get an answer so complex I'd easily be able to solve my issue if I understood it, or someone saying why I shouldn't do what I want to do and offering no alternatives (that are helpful). Thank you for the help!

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• concurrency::extent<N> from amp.h

  - by Daniel Moth

  Overview We saw in a previous post how index<N> represents a point in N-dimensional space and in this post we'll see how to define the N-dimensional space itself. With C++ AMP, an N-dimensional space can be specified with the template class extent<N> where you define the size of each dimension. From a look and feel perspective, you'd expect the programmatic interface of a point type and size type to be similar (even though the concepts are different). Indeed, exactly like index<N>, extent<N> is essentially a coordinate vector of N integers ordered from most- to least- significant, BUT each integer represents the size for that dimension (and hence cannot be negative). So, if you read the description of index, you won't be surprised with the below description of extent<N> There is the rank field returning the value of N you passed as the template parameter. You can construct one extent from another (via the copy constructor or the assignment operator), you can construct it by passing an integer array, or via convenience constructor overloads for 1- 2- and 3- dimension extents. Note that the parameterless constructor creates an extent of the specified rank with all bounds initialized to 0. You can access the components of the extent through the subscript operator (passing it an integer). You can perform some arithmetic operations between extent objects through operator overloading, i.e. ==, !=, +=, -=, +, -. There are operator overloads so that you can perform operations between an extent and an integer: -- (pre- and post- decrement), ++ (pre- and post- increment), %=, *=, /=, +=, –= and, finally, there are additional overloads for plus and minus (+,-) between extent<N> and index<N> objects, returning a new extent object as the result. In addition to the usual suspects, extent offers a contains function that tests if an index is within the bounds of the extent (assuming an origin of zero). It also has a size function that returns the total linear size of this extent<N> in units of elements. Example code extent<2> e(3, 4); _ASSERT(e.rank == 2); _ASSERT(e.size() == 3 * 4); e += 3; e[1] += 6; e = e + index<2>(3,-4); _ASSERT(e == extent<2>(9, 9)); _ASSERT( e.contains(index<2>(8, 8))); _ASSERT(!e.contains(index<2>(8, 9))); grid<N> Our upcoming pre-release bits also have a similar type to extent, grid<N>. The way you create a grid is by passing it an extent, e.g. extent<3> e(4,2,6); grid<3> g(e); I am not going to dive deeper into grid, suffice for now to think of grid<N> simply as an alias for the extent<N> object, that you create when you encounter a function that expects a grid object instead of an extent object. Usage The extent class on its own simply defines the size of the N-dimensional space. We'll see in future posts that when you create containers (arrays) and wrappers (array_views) for your data, it is an extent<N> object that you'll need to use to create those (and use an index<N> object to index into them). We'll also see that it is a grid<N> object that you pass to the new parallel_for_each function that I'll cover in the next post. Comments about this post by Daniel Moth welcome at the original blog.

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• Broken Views

  - by Ajarn Mark Caldwell

  “SELECT *” isn’t just hazardous to performance, it can actually return blatantly wrong information. There are a number of blog posts and articles out there that actively discourage the use of the SELECT * FROM …syntax.  The two most common explanations that I have seen are: Performance:  The SELECT * syntax will return every column in the table, but frequently you really only need a few of the columns, and so by using SELECT * your are retrieving large volumes of data that you don’t need, but the system has to process, marshal across tiers, and so on.  It would be much more efficient to only select the specific columns that you need. Future-proof:  If you are taking other shortcuts in your code, along with using SELECT *, you are setting yourself up for trouble down the road when enhancements are made to the system.  For example, if you use SELECT * to return results from a table into a DataTable in .NET, and then reference columns positionally (e.g. myDataRow[5]) you could end up with bad data if someone happens to add a column into position 3 and skewing all the remaining columns’ ordinal position.  Or if you use INSERT…SELECT * then you will likely run into errors when a new column is added to the source table in any position. And if you use SELECT * in the definition of a view, you will run into a variation of the future-proof problem mentioned above.  One of the guys on my team, Mike Byther, ran across this in a project we were doing, but fortunately he caught it while we were still in development.  I asked him to put together a test to prove that this was related to the use of SELECT * and not some other anomaly.  I’ll walk you through the test script so you can see for yourself what happens. We are going to create a table and two views that are based on that table, one of them uses SELECT * and the other explicitly lists the column names.  The script to create these objects is listed below. IF OBJECT_ID('testtab') IS NOT NULL DROP TABLE testtabgoIF OBJECT_ID('testtab_vw') IS NOT NULL DROP VIEW testtab_vwgo IF OBJECT_ID('testtab_vw_named') IS NOT NULL DROP VIEW testtab_vw_namedgo CREATE TABLE testtab (col1 NVARCHAR(5) null, col2 NVARCHAR(5) null)INSERT INTO testtab(col1, col2)VALUES ('A','B'), ('A','B')GOCREATE VIEW testtab_vw AS SELECT * FROM testtabGOCREATE VIEW testtab_vw_named AS SELECT col1, col2 FROM testtabgo Now, to prove that the two views currently return equivalent results, select from them. SELECT 'star', col1, col2 FROM testtab_vwSELECT 'named', col1, col2 FROM testtab_vw_named OK, so far, so good.  Now, what happens if someone makes a change to the definition of the underlying table, and that change results in a new column being inserted between the two existing columns?  (Side note, I normally prefer to append new columns to the end of the table definition, but some people like to keep their columns alphabetized, and for clarity for later people reviewing the schema, it may make sense to group certain columns together.  Whatever the reason, it sometimes happens, and you need to protect yourself and your code from the repercussions.) DROP TABLE testtabgoCREATE TABLE testtab (col1 NVARCHAR(5) null, col3 NVARCHAR(5) NULL, col2 NVARCHAR(5) null)INSERT INTO testtab(col1, col3, col2)VALUES ('A','C','B'), ('A','C','B')goSELECT 'star', col1, col2 FROM testtab_vwSELECT 'named', col1, col2 FROM testtab_vw_named I would have expected that the view using SELECT * in its definition would essentially pass-through the column name and still retrieve the correct data, but that is not what happens.  When you run our two select statements again, you see that the View that is based on SELECT * actually retrieves the data based on the ordinal position of the columns at the time that the view was created.  Sure, one work-around is to recreate the View, but you can’t really count on other developers to know the dependencies you have built-in, and they won’t necessarily recreate the view when they refactor the table. I am sure that there are reasons and justifications for why Views behave this way, but I find it particularly disturbing that you can have code asking for col2, but actually be receiving data from col3.  By the way, for the record, this entire scenario and accompanying test script apply to SQL Server 2008 R2 with Service Pack 1. So, let the developer beware…know what assumptions are in effect around your code, and keep on discouraging people from using SELECT * syntax in anything but the simplest of ad-hoc queries. And of course, let’s clean up after ourselves.  To eliminate the database objects created during this test, run the following commands. DROP TABLE testtabDROP VIEW testtab_vwDROP VIEW testtab_vw_named

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• Is this over-abstraction? (And is there a name for it?)

  - by mwhite

  I work on a large Django application that uses CouchDB as a database and couchdbkit for mapping CouchDB documents to objects in Python, similar to Django's default ORM. It has dozens of model classes and a hundred or two CouchDB views. The application allows users to register a "domain", which gives them a unique URL containing the domain name that gives them access to a project whose data has no overlap with the data of other domains. Each document that is part of a domain has its domain property set to that domain's name. As far as relationships between the documents go, all domains are effectively mutually exclusive subsets of the data, except for a few edge cases (some users can be members of more than one domain, and there are some administrative reports that include all domains, etc.). The code is full of explicit references to the domain name, and I'm wondering if it would be worth the added complexity to abstract this out. I'd also like to know if there's a name for the sort of bound property approach I'm taking here. Basically, I have something like this in mind: Before in models.py class User(Document): domain = StringProperty() class Group(Document): domain = StringProperty() name = StringProperty() user_ids = StringListProperty() # method that returns related document set def users(self): return [User.get(id) for id in self.user_ids] # method that queries a couch view optimized for a specific lookup @classmethod def by_name(cls, domain, name): # the view method is provided by couchdbkit and handles # wrapping json CouchDB results as Python objects, and # can take various parameters modifying behavior return cls.view('groups/by_name', key=[domain, name]) # method that creates a related document def get_new_user(self): user = User(domain=self.domain) user.save() self.user_ids.append(user._id) return user in views.py: from models import User, Group # there are tons of views like this, (request, domain, ...) def create_new_user_in_group(request, domain, group_name): group = Group.by_name(domain, group_name)[0] user = User(domain=domain) user.save() group.user_ids.append(user._id) group.save() in group/by_name/map.js: function (doc) { if (doc.doc_type == "Group") { emit([doc.domain, doc.name], null); } } After models.py class DomainDocument(Document): domain = StringProperty() @classmethod def domain_view(cls, *args, **kwargs): kwargs['key'] = [cls.domain.default] + kwargs['key'] return super(DomainDocument, cls).view(*args, **kwargs) @classmethod def get(cls, *args, **kwargs, validate_domain=True): ret = super(DomainDocument, cls).get(*args, **kwargs) if validate_domain and ret.domain != cls.domain.default: raise Exception() return ret def models(self): # a mapping of all models in the application. accessing one returns the equivalent of class BoundUser(User): domain = StringProperty(default=self.domain) class User(DomainDocument): pass class Group(DomainDocument): name = StringProperty() user_ids = StringListProperty() def users(self): return [self.models.User.get(id) for id in self.user_ids] @classmethod def by_name(cls, name): return cls.domain_view('groups/by_name', key=[name]) def get_new_user(self): user = self.models.User() user.save() views.py @domain_view # decorator that sets request.models to the same sort of object that is returned by DomainDocument.models and removes the domain argument from the URL router def create_new_user_in_group(request, group_name): group = request.models.Group.by_name(group_name) user = request.models.User() user.save() group.user_ids.append(user._id) group.save() (Might be better to leave the abstraction leaky here in order to avoid having to deal with a couchapp-style //! include of a wrapper for emit that prepends doc.domain to the key or some other similar solution.) function (doc) { if (doc.doc_type == "Group") { emit([doc.name], null); } } Pros and Cons So what are the pros and cons of this? Pros: DRYer prevents you from creating related documents but forgetting to set the domain. prevents you from accidentally writing a django view - couch view execution path that leads to a security breach doesn't prevent you from accessing underlying self.domain and normal Document.view() method potentially gets rid of the need for a lot of sanity checks verifying whether two documents whose domains we expect to be equal are. Cons: adds some complexity hides what's really happening requires no model modules to have classes with the same name, or you would need to add sub-attributes to self.models for modules. However, requiring project-wide unique class names for models should actually be fine because they correspond to the doc_type property couchdbkit uses to decide which class to instantiate them as, which should be unique. removes explicit dependency documentation (from group.models import Group)

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• Is my class structure good enough?

  - by Rivten

  So I wanted to try out this challenge on reddit which is mostly about how you structure your data the best you can. I decided to challenge my C++ skills. Here's how I planned this. First, there's the Game class. It deals with time and is the only class main has access to. A game has a Forest. For now, this class does not have a lot of things, only a size and a Factory. Will be put in better use when it will come to SDL-stuff I guess A Factory is the thing that deals with the Game Objects (a.k.a. Trees, Lumberjack and Bears). It has a vector of all GameObjects and a queue of Events which will be managed at the end of one month. A GameObject is an abstract class which can be updated and which can notify the Event Listener The EventListener is a class which handles all the Events of a simulation. It can recieve events from a Game Object and notify the Factory if needed, the latter will manage correctly the event. So, the Tree, Lumberjack and Bear classes all inherits from GameObject. And Sapling and Elder Tree inherits from Tree. Finally, an Event is defined by an event_type enumeration (LUMBERJACK_MAWED, SAPPLING_EVOLUTION, ...) and an event_protagonists union (a GameObject or a pair of GameObject (who killed who ?)). I was quite happy at first with this because it seems quite logic and flexible. But I ended up questionning this structure. Here's why : I dislike the fact that a GameObject need to know about the Factory. Indeed, when a Bear moves somewhere, it needs to know if there's a Lumberjack ! Or it is the Factory which handles places and objects. It would be great if a GameObject could only interact with the EventListener... or maybe it's not that much of a big deal. Wouldn't it be better if I separate the Factory in three vectors ? One for each kind of GameObject. The idea would be to optimize research. If I'm looking do delete a dead lumberjack, I would only have to look in one shorter vector rather than a very long vector. Another problem arises when I want to know if there is any particular object in a given case because I have to look for all the gameObjects and see if they are at the given case. I would tend to think that the other idea would be to use a matrix but then the issue would be that I would have empty cases (and therefore unused space). I don't really know if Sapling and Elder Tree should inherit from Tree. Indeed, a Sapling is a Tree but what about its evolution ? Should I just delete the sapling and say to the factory to create a new Tree at the exact same place ? It doesn't seem natural to me to do so. How could I improve this ? Is the design of an Event quite good ? I've never used unions before in C++ but I didn't have any other ideas about what to use. Well, I hope I have been clear enough. Thank you for taking the time to help me !

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• WPF MVVM ComboBox SelectedItem or SelectedValue not working

  - by cjibo

  Update After a bit of investigating. What seems to be the issue is that the SelectedValue/SelectedItem is occurring before the Item source is finished loading. If I sit in a break point and weight a few seconds it works as expected. Don't know how I'm going to get around this one. End Update I have an application using in WPF using MVVM with a ComboBox. Below is the ViewModel Example. The issue I'm having is when we leave our page and migrate back the ComboBox is not selecting the current Value that is selected. View Model public class MyViewModel { private MyObject _selectedObject; private Collection<Object2> _objects; private IModel _model; public MyViewModel(IModel model) { _model = model; _objects = _model.GetObjects(); } public Collection<MyObject> Objects { get { return _objects; } private set { _objects = value; } } public MyObject SelectedObject { get { return _selectedObject; } set { _selectedObject = value; } } } For the sake of this example lets say MyObject has two properties (Text and Id). My XAML for the ComboBox looks like this. XAML <ComboBox Name="MyComboBox" Height="23" Width="auto" SelectedItem="{Binding Path=SelectedObject,Mode=TwoWay}" ItemsSource="{Binding Objects}" DisplayMemberPath="Text" SelectedValuePath="Id"> No matter which way I configure this when I come back to the page and the object is reassembled the ComboBox will not select the value. The object is returning the correct object via the get in the property though. I'm not sure if this is just an issue with the way the ComboBox and MVVM pattern works. The text box binding we are doing works correctly.

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