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  • How to profile LINQ to Entities queries in your asp.net applications - part 1

    - by nikolaosk
    I have been teaching ASP.Net and EF in one of my classes and I have been asked on the various ways we can profile database activity. Everyone that I know that uses EF as its data access layer has the same question. "How can I see the T-SQL code that the LINQ to Entities engine generates on the fly?" I know a lot of people use VS studio built-in visualisers but that is not enough. A lot of developers use SQL Server Profiler. That is also a good solution since we can see the queries(generated from...(read more)

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  • Compilable modern alternatives to C/C++

    - by Jeremy French
    I am considering writing a new software product. Performance will be critical, so I am wary of using an interpreted or language or one that uses a emulation layer (read java). Which leads me to thinking of using C (or C++) however these are both rather long in the tooth. I haven't used either for a long time. I figure in the last 20 years someone should have created something which is reasonably popular and is nice to code in and is complied. What more modern alternatives are there to C for writing high performance code compiled code? edit in response to comments If C++ is a different beast than it was 15 years ago, I would consider it, I guess I had an assumption that it had some inherent problems. Parallelisation would be important, but probably not across multiple machines.

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  • Basic game architechture best practices in Cocos2D on iOS

    - by MrDatabase
    Consider the following simple game: 20 squares floating around an iPhone's screen. Tapping a square causes that square to disappear. What's the "best practices" way to set this up in Cocos2D? Here's my plan so far: One Objective-c GameState singleton class (maintains list of active squares) One CCScene (since there's no menus etc) One CCLayer (child node of the scene) Many CCSprite nodes (one for each square, all child nodes of the layer) Each sprite listens for a tap on itself. Receive tap = remove from GameState Since I'm relatively new to Cocos2D I'd like some feedback on this design. For example I'm unsure of the GameState singleton. Perhaps it's unnecessary.

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  • Issue with a point coordinates, which creates an unwanted triangle

    - by Paul
    I would like to connect the points from the red path, to the y-axis in blue. I figured out that the problem with my triangles came from the first point (V0) : it is not located where it should be. In the console, it says its location is at 0,0, but in the emulator, it is not. The code : for(int i = 1; i < 2; i++) { CCLOG(@"_polyVertices[i-1].x : %f, _polyVertices[i-1].y : %f", _polyVertices[i-1].x, _polyVertices[i-1].y); CCLOG(@"_polyVertices[i].x : %f, _polyVertices[i].y : %f", _polyVertices[i].x, _polyVertices[i].y); ccDrawLine(_polyVertices[i-1], _polyVertices[i]); } The output : _polyVertices[i-1].x : 0.000000, _polyVertices[i-1].y : 0.000000 _polyVertices[i].x : 50.000000, _polyVertices[i].y : 0.000000 And the result : (the layer goes up, i could not take the screenshot before the layer started to go up, but the first red point starts at y=0) : Then it creates an unwanted triangle when the code continues : Would you have any idea about this? (So to force the first blue point to start at 0,0, and not at 50,0 as it seems to be now) Here is the code : - (void)generatePath{ float x = 50; //first red point float y = 0; for(int i = 0; i < kMaxKeyPoints+1; i++) { if (i<3){ _hillKeyPoints[i] = CGPointMake(x, y); x = 150 + (random() % (int) 30); y += -40; } else if(i<20){ //going right _hillKeyPoints[i] = CGPointMake(x, y); x += (random() % (int) 30); y += -40; } else if(i<25){ //stabilize _hillKeyPoints[i] = CGPointMake(x, y); x = 150 + (random() % (int) 30); y += -40; } else if(i<30){ //going left _hillKeyPoints[i] = CGPointMake(x, y); //x -= (random() % (int) 10); x = 150 + (random() % (int) 30); y += -40; } else { //back to normal _hillKeyPoints[i] = CGPointMake(x, y); x = 150 + (random() % (int) 30); y += -40; } } } -(void)generatePolygons{ static int prevFromKeyPointI = -1; static int prevToKeyPointI = -1; // key points interval for drawing while (_hillKeyPoints[_fromKeyPointI].y > -_offsetY+winSizeTop) { _fromKeyPointI++; } while (_hillKeyPoints[_toKeyPointI].y > -_offsetY-winSizeBottom) { _toKeyPointI++; } if (prevFromKeyPointI != _fromKeyPointI || prevToKeyPointI != _toKeyPointI) { _nPolyVertices = 0; float x1 = 0; int keyPoints = _fromKeyPointI; for (int i=_fromKeyPointI; i<_toKeyPointI; i++){ //V0: at (0,0) _polyVertices[_nPolyVertices] = CGPointMake(x1, y1); //first blue point _polyTexCoords[_nPolyVertices++] = CGPointMake(x1, y1); //V1: to the first "point" _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); keyPoints++; //from point at index 0 to 1 //V2, same y as point n°2: _polyVertices[_nPolyVertices] = CGPointMake(0, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices++] = CGPointMake(0, _hillKeyPoints[keyPoints].y); //V1 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //V2 again _polyVertices[_nPolyVertices] = _polyVertices[_nPolyVertices-2]; _polyTexCoords[_nPolyVertices++] = _polyVertices[_nPolyVertices-2]; //CCLOG(@"_nPolyVertices V2 again : %i", _nPolyVertices); //V3 = same x,y as point at index 1 _polyVertices[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); _polyTexCoords[_nPolyVertices] = CGPointMake(_hillKeyPoints[keyPoints].x, _hillKeyPoints[keyPoints].y); y1 = _polyVertices[_nPolyVertices].y; _nPolyVertices++; } prevFromKeyPointI = _fromKeyPointI; prevToKeyPointI = _toKeyPointI; } } - (void) draw { //RED glColor4f(1, 1, 1, 1); for(int i = MAX(_fromKeyPointI, 1); i <= _toKeyPointI; ++i) { glColor4f(1.0, 0, 0, 1.0); ccDrawLine(_hillKeyPoints[i-1], _hillKeyPoints[i]); } //BLUE glColor4f(0, 0, 1, 1); for(int i = 1; i < 2; i++) { CCLOG(@"_polyVertices[i-1].x : %f, _polyVertices[i-1].y : %f", _polyVertices[i-1].x, _polyVertices[i-1].y); CCLOG(@"_polyVertices[i].x : %f, _polyVertices[i].y : %f", _polyVertices[i].x, _polyVertices[i].y); ccDrawLine(_polyVertices[i-1], _polyVertices[i]); } } Thanks

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  • How can I distribute a unique database already in production?

    - by JVerstry
    Let's assume a successful web Spring application running on a MySQL or PostgreSQL database. The traffic is becoming so high and the amount of data is becoming so big that a distributed database solution needs to be implemented to address scalability issue. Let's also assume this application is using Hibernate and the data access layer is cleanly separated with DAOs. Ideally, one should be able to add or remove databases easily. A failback solution is welcome too. What would be the best strategy to scale this database? Is it possible to minimize sharding code (Shard) in the application?

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  • Is it better to define all routes in the Global.asax than to define separately in the areas?

    - by Matthew Patrick Cashatt
    I am working on a MVC 4 project that will serve as an API layer of a larger application. The developers that came before me set up separate Areas to separate different API requests (i.e Search, Customers, Products, and so forth). I am noticing that each Area has separate Area registration classes that define routes for that area. However, the routes defined are not area-specific (i.e. {controller}/{action}/{id} might be defined redundantly in a couple of areas). My instinct would be to move all of these route definitions to a common place like the Global.asax to avoid redundancy and collisions, but I am not sure if I am correct about that.

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  • Is YQL still used?

    - by Andrea
    A few years ago, following the explosion of custom web APIs from various services around the world, Yahoo! launched the YQL service, which allows to query data from a variety of different providers with a unified Yahoo Query Language. Having worked with the APIs of Twitter, Instagram, Facebook, Google Maps, YouTube and more, I very much enjoy the idea. However, I do not see it mentioned often, and of course this is one of those efforts that makes sense when enough people follow it and expose their API through this layer. Are there some statitics of usage? Or some declarations from Yahoo about the destiny of YQL? I would also be interested in hearing your experience if you have tried it directly.

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  • What is it going here in my solution?

    - by bbb
    I am a asp.net mvc programmer and if I want to start a project I do this: I make a class library named Model for my models. I make a class library named Infrastructure.Repository for database processes I make a class library named Application for business logic layer And finally I make a MVC project for the UI. But now some things are confusing me. Am I using 3-tier programming? If yes so what is n-tier programming and which one is better? If no so what is 3-tier programming? Some where I see that the tiers namings are DAL and BIZ. Which one is correct according to the naming convention?

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  • The Most Important Person Is the One that Keeps Your PC Running [Comic]

    - by The Geek
    Fixing people’s computers usually makes them appreciate you more, though this might be a little too far. Latest Features How-To Geek ETC How To Create Your Own Custom ASCII Art from Any Image How To Process Camera Raw Without Paying for Adobe Photoshop How Do You Block Annoying Text Message (SMS) Spam? How to Use and Master the Notoriously Difficult Pen Tool in Photoshop HTG Explains: What Are the Differences Between All Those Audio Formats? How To Use Layer Masks and Vector Masks to Remove Complex Backgrounds in Photoshop Bring Summer Back to Your Desktop with the LandscapeTheme for Chrome and Iron The Prospector – Home Dash Extension Creates a Whole New Browsing Experience in Firefox KinEmote Links Kinect to Windows Why Nobody Reads Web Site Privacy Policies [Infographic] Asian Temple in the Snow Wallpaper 10 Weird Gaming Records from the Guinness Book

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  • What is the path to JavaScript mastery?

    - by Eric Wilson
    I know how we start with JavaScript, we cut-and-paste a snippit to gain a little client-side functionality or validation. But if you follow this path in trying to implement rich interactive behavior, it doesn't take long before you realize that you are creating a Big Ball Of Mud. So what is the path towards expertise in programming the interaction layer? What books, tutorials, exercises, and processes contribute towards the ability to program robust, maintainable JavaScript? We all know that practice is important in any endeavor, but I'm looking for a path similar to the answer here: http://stackoverflow.com/questions/2573135/

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  • Enhanced LINQ to SQL Compatible ORM Solution from Devart

    Devart has recently announced the release of LinqConnect - an enhanced LINQ to SQL compatible ORM solution with extended functionality, support for SQL Server, Oracle, MySQL, PostgreSQL, and SQLite, its own visual model designer, seamlessly integrating to Visual Studio, and SQL monitoring tool. LinqConnect allows you to quickly create mapping model and generate data access layer code for your application, greatly decreasing development time and eliminating the need to work over routine tasks. It...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How to profile LINQ to Entities queries in your asp.net applications - part 3

    - by nikolaosk
    In this post I will continue exploring ways on how to profile database activity when using the Entity Framework as the data access layer in our applications. If you want to read the first post of the series click here . If you want to read the second post of the series click here . In this post I will use the excellent (best tool for EF profiling) which is called Entity Framework Profiler. You can download the trial - fully functional edition of this tool from here . I will use the previous example...(read more)

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  • 2D Particle Explosion

    - by TheBroodian
    I'm developing a 2D action game, and in said game I've given my primary character an ability he can use to throw a fireball. I'm trying to design an effect so that when said fireball collides (be it with terrain or with an enemy) that the fireball will explode. For the explosion effect I've created a particle that once placed into game space will follow random, yet autonomic behavior based on random variables. Here is my question: When I generate my explosion (essentially 90 of these particles) I get one of two behaviors, 1) They are all generated with the same random variables, and don't resemble an explosion at all, more like a large mass of clumped sprites that all follow the same randomly generated path. 2) If I assign each particle a unique seed to its random number generator, they are a little bit -more- spread out, yet clumping is still visible (they seem to fork out into 3 different directions) Does anybody have any tips for producing particle-based 2D explosions? I'll include the code for my particle and the event I'm generating them in. Fire particle class: public FireParticle(xTile.Dimensions.Location StartLocation, ContentManager content) { worldLocation = StartLocation; fireParticleAnimation = new FireParticleAnimation(content); random = new Random(); int rightorleft = random.Next(0, 3); int upordown = random.Next(1, 3); int xVelocity = random.Next(0, 101); int yVelocity = random.Next(0, 101); Vector2 tempVector2 = new Vector2(0,0); if (rightorleft == 1) { tempVector2 = new Vector2(xVelocity, tempVector2.Y); } else if (rightorleft == 2) { tempVector2 = new Vector2(-xVelocity, tempVector2.Y); } if (upordown == 1) { tempVector2 = new Vector2(tempVector2.X, -yVelocity); } else if (upordown == 2) { tempVector2 = new Vector2(tempVector2.X, yVelocity); } velocity = tempVector2; scale = random.Next(1, 11); upwardForce = -10; dead = false; } public FireParticle(xTile.Dimensions.Location StartLocation, ContentManager content, int seed) { worldLocation = StartLocation; fireParticleAnimation = new FireParticleAnimation(content); random = new Random(seed); int rightorleft = random.Next(0, 3); int upordown = random.Next(1, 3); int xVelocity = random.Next(0, 101); int yVelocity = random.Next(0, 101); Vector2 tempVector2 = new Vector2(0, 0); if (rightorleft == 1) { tempVector2 = new Vector2(xVelocity, tempVector2.Y); } else if (rightorleft == 2) { tempVector2 = new Vector2(-xVelocity, tempVector2.Y); } if (upordown == 1) { tempVector2 = new Vector2(tempVector2.X, -yVelocity); } else if (upordown == 2) { tempVector2 = new Vector2(tempVector2.X, yVelocity); } velocity = tempVector2; scale = random.Next(1, 11); upwardForce = -10; dead = false; } #endregion #region Update and Draw public void Update(GameTime gameTime) { elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; fireParticleAnimation.Update(gameTime); Vector2 moveAmount = velocity * elapsed; xTile.Dimensions.Location newPosition = new xTile.Dimensions.Location(worldLocation.X + (int)moveAmount.X, worldLocation.Y + (int)moveAmount.Y); worldLocation = newPosition; velocity.Y += upwardForce; if (fireParticleAnimation.finishedPlaying) { dead = true; } } public void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw( fireParticleAnimation.image.Image, new Rectangle((int)drawLocation.X, (int)drawLocation.Y, scale, scale), fireParticleAnimation.image.SizeAndsource, Color.White * fireParticleAnimation.image.Alpha); } Fireball explosion event: public override void Update(GameTime gameTime) { if (enabled) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; foreach (Heart_of_Fire.World_Objects.Particles.FireParticle particle in explosionParticles.ToList()) { particle.Update(gameTime); if (particle.Dead) { explosionParticles.Remove(particle); } } collisionRectangle = new Microsoft.Xna.Framework.Rectangle((int)wrldPstn.X, (int)wrldPstn.Y, 5, 5); explosionCheck = exploded; if (!exploded) { coreGraphic.Update(gameTime); tailGraphic.Update(gameTime); Vector2 moveAmount = velocity * elapsed; moveAmount = horizontalCollision(moveAmount, layer); moveAmount = verticalCollision(moveAmount, layer); Vector2 newPosition = new Vector2(wrldPstn.X + moveAmount.X, wrldPstn.Y + moveAmount.Y); if (hasCollidedHorizontally || hasCollidedVertically) { exploded = true; } wrldPstn = newPosition; worldLocation = new xTile.Dimensions.Location((int)wrldPstn.X, (int)wrldPstn.Y); } if (explosionCheck != exploded) { for (int i = 0; i < 90; i++) { explosionParticles.Add(new World_Objects.Particles.FireParticle( new Location( collisionRectangle.X + random.Next(0, 6), collisionRectangle.Y + random.Next(0, 6)), contentMgr)); } } if (exploded && explosionParticles.Count() == 0) { //enabled = false; } } }

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  • Online Poker Game Programming

    - by Eyal
    I am trying to write a massive online multiplayer client for a poker site, where one user can be on a Flash client and the other on say an iOS client (iPhone / iPad), and would like to know how can interaction between two users be visible on both clients. What would be better to use? Should I use MSMQ? AJAX? Something other? I need the messaging layer (client interaction messages) to scale up to 100K+ online users to begin with. In other words; What scalable technology can I use to make game interactions between online users visible to all game participants?

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  • SQL Server Express Profiler

    - by David Turner
    During a recent project, while waiting for our Development Database to be provisioned on the clients corporate SQL Server Environment (these things can sometimes take weeks or months to be setup), we began our initial development against a local instance on SQL Server Express, just as an interim measure until the Development database was live.  This was going just fine, until we found that we needed to do some profiling to understand a problem we were having with the performance of our ORM generated Data Access Layer.  The full version of SQL Server Management Studio includes a profiler, that we could use to help with this kind of problem, however the Express version does not, so I was really pleased to find that there is a freely available Profiler for SQL Server Express imaginatively titled ‘SQL Server Express Profiler’, and it worked great for us.  http://sites.google.com/site/sqlprofiler/

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  • Online Poker Game Programng

    - by Eyal
    I am trying to write a massive multiplayer online (mmo) for a poker site, where one user can be on a Flash client and the other on say an iOS client (iPhone / iPad), and would like to know how can interaction between two users be visible on both clients. Do I use MSMQ? AJAX? Other? I need the messaging layer (client interaction messages) to scale up to 100K+ online users to begin with. In other words; What scaleable technology can I use to make game interactions between online users visible to all game participants? Thank you much in advance! Eyal

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  • Ask the Readers: The Two-Step Login Verification Process – Security Boost or Just Another Hassle?

    - by Asian Angel
    Google recently introduced a new optional two-step login verification process for Google accounts to help increase account security. What we would like to know this week is if you think this will really help improve account security, should be implemented by others in addition to Google, or would simply add a new layer of hassle to using your accounts Latest Features How-To Geek ETC How To Remove People and Objects From Photographs In Photoshop Ask How-To Geek: How Can I Monitor My Bandwidth Usage? Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Here’s a Super Simple Trick to Defeating Fake Anti-Virus Malware How to Change the Default Application for Android Tasks Stop Believing TV’s Lies: The Real Truth About "Enhancing" Images The Legend of Zelda – 1980s High School Style [Video] Suspended Sentence is a Free Cross-Platform Point and Click Game Build a Batman-Style Hidden Bust Switch Make Your Clock Creates a Custom Clock for your Android Homescreen Download the Anime Angels Theme for Windows 7 CyanogenMod Updates; Rolls out Android 2.3 to the Less Fortunate

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  • AndEngine Foreground Sprite

    - by McGrey
    I'm developing an Android game and have some troubles: I want to add some foreground sprites, that must obstruct my player. Se the following example: Its a screenshot from "Shinobi 3". We can see the player, the enemy, the background and two foreground trees, that hide the player's arm and part of the enemy. I'm using AndEngine GLES2 Anchor Center and I am trying to add a new layer to my scene. Sprite Forest = new Sprite(getWidth() * 0.5f, textureHeightForest * 0.5f + 100, ResourcesManager.getInstance().foreground_forest_region, vbom); Entity foregroundLayer = new Entity(); foregroundLayer.attachChild(hillFurthest); attachChild(foregroundLayer); But it still shows behind my player sprite. I am trying to find something in HUD-class (it's always shown in the foreground), but got no results. Can anyone help please?

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  • The underlying mechanism in 'yield return www' of Unity3D Game Engine

    - by thyandrecardoso
    In the Unity3D game engine, a common code sequence for getting remote data is this: WWW www = new WWW("http://remote.com/data/location/with/texture.png"); yield return www; What is the underlying mechanism here? I know we use the yield mechanism in order to allow the next frame to be processed, while the download is being completed. But what is going on under the hood when we do the yield return www ? What method is being called (if any, on the WWW class)? Is Unity using threads? Is the "upper" Unity layer getting hold of www instance and doing something?

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  • Can it be useful to build an application starting with the GUI?

    - by Grant Palin
    The trend in application design and development seems to be starting with the "guts": the domain, then data access, then infrastructure, etc. The GUI seems to usually come later in the process. I wonder if it could ever be useful to build the GUI first... My rationale is that by building at least a prototype GUI, you gain a better idea of what needs to happen behind the scenes, and so are in a better position to start work on the domain and supporting code. I can see an issue with this practice in that if the supporting code is not yet written, there won't be much for the GUI layer to actually do. Perhaps building mock objects or throwaway classes (somewhat like is done in unit testing) would provide just enough of a foundation to build the GUI on initially. Might this be a feasible idea for a real project? Maybe we could add GDD (GUI Driven Development) to the acronym stable...

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  • How to distribute a unique database already in production?

    - by JVerstry
    Let's assume a successful web spring application running on a MySql or PostGre kind of database. The traffic is becoming so high and the amount of data is becoming so big that a distributed dataase solution needs to be implemented. It is a scalability issue. Let's assume this application is using Hibernate and the data access layer is cleanly separated with DAO objects. What would be the best strategy to scale this database? Does anyone have hands on experience to share? Is it possible to minimize sharding code (Shard) in the application? Ideally, one should be able to add or remove databases easily. A failback solution is welcome too. I am not looking for you could go for sharding or you could go no sql kind of answers. I am looking for deeper answers from people with experience.

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  • Iterating selected rows in an ADF Faces table

    - by Frank Nimphius
    In OTN Harvest May 2012; http://www.oracle.com/technetwork/developer-tools/adf/learnmore/may2012-otn-harvest-1652358.pdf I wrote about "Common mistake when iterating <af:table> rows". In this entry I showed code to access the row associated with a selected table row from the binding layer to avoid the problem of having to programmatically change the selected table row. As it turns out, my solution only worked fro selected table rows that are in the current iterator query range. So here's a solution that works for all ranges public String onButtonPress() { RowKeySet rks = table.getSelectedRowKeys(); Iterator it = rks.iterator(); while (it.hasNext()) { List selectedRowKeyPath = (List)it.next(); //table is the JSF component reference created using the table's binding //property Row row = ((JUCtrlHierNodeBinding)table.getRowData(selectedRowKeyPath)).getRow(); System.out.println("Print Test: " + row.getAttribute(1)); } return null; }

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  • How can I improve my Animation

    - by sharethis
    The first approaches in animation for my game relied mostly on sine and cosine functions with the time as parameter. Here is an example of a very basic jump I implemented. if(jumping) { height = sin(time); if(height < 0) jumping = false; // player landed player.position.z = height; } if(keydown(SPACE) && !jumping) { jumping = true; time = now(); // store the starting time } So my player jumped in a perfect sine function. That seems quite natural, because he slows down when he reached the top position, and in the fall he speeds up again. But patching every animation out of sine and cosine is stretched to its limits soon. So can I improve my animation and provide a more abstract layer?

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  • Wireless suddenly dropping with a Ralink RT2870

    - by cwwk
    I have a Linksys WUSB600N v1 Dual-Band Wireless-N Network Adapter Ralink RT2870 USB dongle that worked flawlessly in 11.10. Since upgrading, I can't keep a connection for more than five minutes. The wild world of Google was unable to provide a solution, and I would rather not downgrade although that remains a possibility. Results of syslog: slack@slack:~$ tail /var/log/syslog Apr 26 20:26:10 slack AptDaemon: INFO: Initializing daemon Apr 26 20:26:10 slack AptDaemon.PackageKit: INFO: Initializing PackageKit compat layer Apr 26 20:26:10 slack dbus[972]: [system] Successfully activated service 'org.freedesktop.PackageKit' Apr 26 20:26:10 slack AptDaemon.PackageKit: INFO: Initializing PackageKit transaction Apr 26 20:26:10 slack AptDaemon.Worker: INFO: Simulating trans: /org/debian/apt/transaction/aaed4e38eb3c41ad86d2bab6ca03ee7c Apr 26 20:26:10 slack AptDaemon.Worker: INFO: Processing transaction /org/debian/apt/transaction/aaed4e38eb3c41ad86d2bab6ca03ee7c Apr 26 20:26:12 slack dbus[972]: [system] Activating service name='com.ubuntu.SystemService' (using servicehelper) Apr 26 20:26:12 slack dbus[972]: [system] Successfully activated service 'com.ubuntu.SystemService' Apr 26 20:30:26 slack AptDaemon.PackageKit: INFO: Get updates() Apr 26 20:30:27 slack AptDaemon.Worker: INFO: Finished transaction /org/debian/apt/transaction/aaed4e38eb3c41ad86d2bab6ca03ee7c Any suggestions?

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  • Proxied calls not working as expected

    - by AndyH
    I have been modifying an application to have a cleaner client/server split to allow for load splitting and resource sharing etc. Everything is written to an interface so it was easy to add a remoting layer to the interface using a proxy. Everything worked fine. The next phase was to add a caching layer to the interface and again this worked fine and speed was improved but not as much as I would have expected. On inspection it became very clear what was going on. I feel sure that this behavior has been seen many times before and there is probably a design pattern to solve the problem but it eludes me and I'm not even sure how to describe it. It is easiest explained with an example. Let's imagine the interface is interface IMyCode { List<IThing> getLots( List<String> ); IThing getOne( String id ); } The getLots() method calls getOne() and fills up the list before returning. The interface is implemented at the client which is proxied to a remoting client which then calls the remoting server which in turn calls the implementation at the server. At the client and the server layers there is also a cache. So we have :- Client interface | Client cache | Remote client | Remote server | Server cache | Server interface If we call getOne("A") at the client interface, the call is passed to the client cache which faults. This then calls the remote client which passes the call to the remote server. This then calls the server cache which also faults and so the call is eventually passed to the server interface which actually gets the IThing. In turn the server cache is filled and finally the client cache also. If getOne("A") is again called at the client interface the client cache has the data and it gets returned immediately. If a second client called getOne("B") it would fill the server cache with "B" as well as it's own client cache. Then, when the first client calls getOne("B") the client cache faults but the server cache has the data. This is all as one would expect and works well. Now lets call getLots( [ "C", "D" ] ). This works as you would expect by calling getOne() twice but there is a subtlety here. The call to getLots() cannot directly make use of the cache. Therefore the sequence is to call the client interface which in turn calls the remote client, then the remote server and eventually the server interface. This then calls getOne() to fill the list before returning. The problem is that the getOne() calls are being satisfied at the server when ideally they should be satisfied at the client. If you imagine that the client/server link is really slow then it becomes clear why the client call is more efficient than the server call once the client cache has the data. This example is contrived to illustrate the point. The more general problem is that you cannot just keep adding proxied layers to an interface and expect it to work as you would imagine. As soon as the call goes 'through' the proxy any subsequent calls are on the proxied side rather than 'self' side. Have I failed to learn or not learned something correctly? All this is implemented in Java and I haven't used EJBs. It seems that the example may be confusing. The problem is nothing to do with cache efficiencies. It is more to do with an illusion created by the use of proxies or AOP techniques in general. When you have an object whose class implements an interface there is an assumption that a call on that object might make further calls on that same object. For example, public String getInternalString() { return InetAddress.getLocalHost().toString(); } public String getString() { return getInternalString(); } If you get an object and call getString() the result depends where the code is running. If you add a remoting proxy to the class then the result could be different for calls to getString() and getInternalString() on the same object. This is because the initial call gets 'deproxied' before the actual method is called. I find this not only confusing but I wonder how I can control this behavior especially as the use of the proxy may be by a third party. The concept is fine but the practice is certainly not what I expected. Have I missed the point somewhere?

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