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• Optimal communication pattern to update subscribers

  - by hpc

  What is the optimal way to update the subscriber's local model on changes C on a central model M? ( M + C - M_c) The update can be done by the following methods: Publish the updated model M_c to all subscribers. Drawback: if the model is big in contrast to the change it results in much more data to be communicated. Publish change C to all subscribes. The subscribers will then update their local model in the same way as the server does. Drawback: The client needs to know the business logic to update the model in the same way as the server. It must be assured that the subscribed model stays equal to the central model. Calculate the delta (or patch) of the change (M_c - M = D_c) and transfer the delta. Drawback: This requires that calculating and applying the delta (M + D_c = M_c) is an cheap/easy operation. If a client newly subscribes it must be initialized. This involves sending the current model M. So method 1 is always required. Think of playing chess as a concrete example: Subscribers send moves and want to see the latest chess board state. The server checks validity of the move and applies it to the chess board. The server can then send the updated chessboard (method 1) or just send the move (method 2) or send the delta (method 3): remove piece on field D4, put tower on field D8.

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• "Programming error" exceptions - Is my approach sound?

  - by Medo42

  I am currently trying to improve my use of exceptions, and found the important distinction between exceptions that signify programming errors (e.g. someone passed null as argument, or called a method on an object after it was disposed) and those that signify a failure in the operation that is not the caller's fault (e.g. an I/O exception). As far as I understand, it makes little sense for an immediate caller to actually handle programming error exceptions, he should instead assure that the preconditions are met. Only "outer" exception handlers at task boundaries should catch them, so they can keep the system running if a task fails. In order to ensure that client code can cleanly catch "failure" exceptions without catching error exceptions by mistake, I create my own exception classes for all failure exceptions now, and document them in the methods that throw them. I would make them checked exceptions in Java. Now I have a few questions: Before, I tried to document all exceptions that a method could throw, but that sometimes creates an unwiedly list that needs to be documented in every method up the call chain until you can show that the error won't happen. Instead, I document the preconditions in the summary / parameter descriptions and don't even mention what happens if they are not met. The idea is that people should not try to catch these exceptions explicitly anyway, so there is no need to document their types. Would you agree that this is enough? Going further, do you think all preconditions even need to be documented for every method? For example, calling methods in IDisposable objects after calling Dispose is an error, but since IDisposable is such a widely used interface, can I just assume a programmer will know this? A similar case is with reference type parameters where passing null makes no conceivable sense: Should I document "non-null" anyway? IMO, documentation should only cover things that are not obvious, but I am not sure where "obvious" ends.

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• Can org.freedesktop.Notifications.CloseNotification(uint id) be triggered and invoked via DBus?

  - by george rowell

  ref: Close button on notify-osd? Bookmark: Can org.freedesktop.Notifications.CloseNotification(uint id) be triggered and invoked via DBus? Currently, this script dbus-monitor "interface='org.freedesktop.Notifications'" | \ grep --line-buffered "member=Notify" | \ sed -u -e 's/.*/killall notify-osd/g' | \ bash will kill all pending notifications. It would be better to finesse the specific target OSD notification to cancel, by using org.freedesktop.Notifications.CloseNotification(uint id). Is there an interface method that can put this on (in?) the DBus to fire when a particular notify event occurs? The method will need to get the notify PID to use as the argument for CloseNotification(uint id). Alternatively, qdbus org.freedesktop.Notifications \ /org/freedesktop/Notifications \ org.freedesktop.Notifications.CloseNotification(uint id) could be used from the shell, if the (uint id) argument could be determined. The actual command syntax would use an integer in place of (uint id). Perhaps a better question to ask first might be "How is the DBus address for a notification found?". In hindsight the previous question "How is the (uint id) for a notification found?" is rhetorical! This previous answer: http://askubuntu.com/a/186311/89468 provided details so either method below can be used: gdbus call --session --dest org.freedesktop.DBus \ --object-path / \ --method org.freedesktop.DBus.GetConnectionUnixProcessID :1.16 returning: (uint32 8957,) or qdbus --literal --session org.freedesktop.DBus / \ org.freedesktop.DBus.GetConnectionUnixProcessID :1.16 returning: 8957

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• preseeded installation keeps asking for confirmation while creating RAID-Partitions on certain hardware-platform

  - by Marc Shennon

  I am aware of the partman-md/confirm_nooverwrite thing, that was the solution to most of this problems in the past. The thing is, that the preseed-file works for almost all hardware-platforms I tested, but only for one (Primergy MX130) it keeps asking for confirmation, before writing the partition-layout to the disks. All machines I tested are running with two SATA Disks, nothing special. I'm not really sure, what information could be needed in order to investigate the cause of this behaviour, but I would of course be willing to provide more information, if someone has an idea. Relevant part of the preseed file is the following: d-i partman-auto/disk string /dev/sda /dev/sdb d-i partman-auto/method string raid d-i partman-md/confirm boolean true d-i partman-partitioning/confirm_write_new_label boolean true d-i partman-md/device_remove_md boolean true d-i partman/choose_partition select finish d-i partman-md/confirm_nooverwrite boolean true # Write the changes to disks? d-i partman/confirm boolean true d-i mdadm/boot_degraded boolean true # RECIPE # Next you need to specify the physical partitions that will be used. d-i partman-auto/expert_recipe string \ multiraid :: \ 500 10000 1000000000 raid $lvmignore{ }\ $primary{ } \ method{ raid } \ . \ 512 1000 786 raid $lvmignore{ }\ $primary{ } \ method{ raid } \ . \ 8192 10240 10240 raid $lvmignore{ }\ method{ raid } \ . # Parameters are: # <raidtype> <devcount> <sparecount> <fstype> <mountpoint> <devices> <sparedevices> d-i partman-auto-raid/recipe string \ 1 2 0 ext4 / /dev/sda1#/dev/sdb1 . \ 1 2 0 ext2 /boot /dev/sda2#/dev/sdb2 . \ 1 2 0 swap - /dev/sda5#/dev/sdb5 .

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• Assignments in mock return values

  - by zerkms

  (I will show examples using php and phpunit but this may be applied to any programming language) The case: let's say we have a method A::foo that delegates some work to class M and returns the value as-is. Which of these solutions would you choose: $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue('baz')); $obj = new A($mock); $this->assertEquals('baz', $obj->foo()); or $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue($result = 'baz')); $obj = new A($mock); $this->assertEquals($result, $obj->foo()); or $result = 'baz'; $mock = $this->getMock('M'); $mock->expects($this->once()) ->method('bar') ->will($this->returnValue($result)); $obj = new A($mock); $this->assertEquals($result, $obj->foo()); Personally I always follow the 2nd solution, but just 10 minutes ago I had a conversation with couple of developers who said that it is "too tricky" and chose 3rd or 1st. So what would you usually do? And do you have any conventions to follow in such cases?

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• Faster 2D Collision detection

  - by eShredder

  Recently I've been working on a fast-paced 2d shooter and I came across a mighty problem. Collision detection. Sure, it is working, but it is very slow. My goal is: Have lots of enemies on screen and have them to not touch each other. All of the enemies are chasing the player entity. Most of them have the same speed so sooner or later they all end up taking the same space while chasing the player. This really drops the fun factor since, for the player, it looks like you are being chased by one enemy only. To prevent them to take the same space I added a collision detection (a very basic 2D detection, the only method I know of) which is. Enemy class update method Loop through all enemies (continue; if the loop points at this object) If enemy object intersects with this object Push enemy object away from this enemy object This works fine. As long as I only have <200 enemy entities that is. When I get closer to 300-350 enemy entities my frame rate begins to drop heavily. First I thought it was bad rendering so I removed their draw call. This did not help at all so of course I realised it was the update method. The only heavy part in their update method is this each-enemy-loops-through-every-enemy part. When I get closer to 300 enemies the game does a 90000 (300x300) step itteration. My my~ I'm sure there must be another way to aproach this collision detection. Though I have no idea how. The pages I find is about how to actually do the collision between two objects or how to check collision between an object and a tile. I already know those two things. tl;dr? How do I aproach collision detection between LOTS of entities? Quick edit: If it is to any help, I'm using C# XNA.

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• Is this high coupling?

  - by Bono

  Question I'm currently working a on an assignment for school. The assignment is to create a puzzle/calculator program in which you learn how to work with different datastructures (such as Stacks). We have generate infix math strings suchs as "1 + 2 * 3 - 4" and then turn them in to postfix math strings such as "1 2 + 3 * 4 -". In my book the author creates a special class for converting the infix notation to postfix. I was planning on using this but whilst I was about to implement it I was wondering if the following is what you would call "high coupling". I have read something about this (nothing that is taught in the book or anything) and was wondering about the aspect (since I still have to grasp it). Problem I have created a PuzzleGenerator class which generates the infix notation of the puzzle (or math string, whatever you want to call it) when it's instantiated. I was going to make a method getAnswer() in which I would instantiate the InToPost class (the class from the book) to convert the infix to postfox notation and then calculate the answer. But whilst doing this I thought: "Is using the InToPost class inside this method a form a high coupling, and would it be better to place this in a different method?" (such as a "convertPostfixToInfix" method, inside the PuzzleGenerator class) Thanks in advance.

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• Java game design question (graphical objects)

  - by vemalsar

  Hello Guys, I'm beginner in game development, in Java and here on this site too and I have a game design question. Please comment my idea: I have a main loop which call update and draw method. I want to use an ArrayList which store graphical objects, they have coordinate and image or text to draw and my game objects extends this class. In update, I can choose which objects should be put in the array and in draw method I'll display the elements of array on the screen. I'm using a buffer and draw first there, but it is not important now I guess...Here is a simple (not full) code, only the logic: public class GamePanel extends JPanel implements KeyListener { ArrayList<graphicalObjects> graphArray = new ArrayList<graphicalObjects>(); public void update() { //change the game scene, update the graphArray, process input etc. } public void draw() { //draws every element of graphArray to a JPanel } public static main(String[] args) { while(true) { update(); draw(); } } } My questions: Should have I use interface or abstract class for graphicalObjects? graphicalObjects class and the ArrayList really needs or there is some better solution? How to draw objects? They draw themself with their own method or in the draw method I have to draw manually based on graphicalObjects variables (x,y coordinates, image etc.)? If this conception is wrong, please suggest another one! All comments are welcome and sorry if this is dumb question, thanks!

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• android shut-down errors / thread problems

  - by iQue

  Im starting to deal with some stuff in my game that I thought were "minor problems" and one of these are that I get an error every time I shut down my game that looks like this: 09-05 21:40:58.320: E/AndroidRuntime(30401): FATAL EXCEPTION: Thread-4898 09-05 21:40:58.320: E/AndroidRuntime(30401): java.lang.NullPointerException 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainGamePanel.render(MainGamePanel.java:94) 09-05 21:40:58.320: E/AndroidRuntime(30401): at nielsen.happy.shooter.MainThread.run(MainThread.java:101) on these lines is my GameViews rendering-method and the line in my Thread that calls my GameViews rendering-method. Im guessing Something in my surfaceDestroyed(SurfaceHolder holder) is wrong, or maybe Im not ending the tread in the right place. My surfaceDestroyed-method: public void surfaceDestroyed(SurfaceHolder holder) { Log.d(TAG, "Surface is being destroyed"); boolean retry = true; ((MainThread)thread).setRunning(false); while (retry) { try { ((MainThread)thread).join(); retry = false; } catch (InterruptedException e) { } } Log.d(TAG, "Thread was shut down cleanly"); } Also, In my activity for this View my onPaus, onDestoy and onStop are empty, do I maybe need to add something there? The crash occurs when I press my home-button on the phone, or any other button that makes the game stop. But as I understand it the onPaus is called when you press the Home-button.. This is really new territory for me so Im sorry if im missing something obvious or something really big. adding my surfaceCreated method asweel since that is where I start this thread: public void surfaceCreated(SurfaceHolder holder) { controls = new GameControls(this); setOnTouchListener(controls); timer1.schedule(new Task(this), 0, delay1); thread.setRunning(true); thread.start(); } and aslong as this is running, my game is rendering and updating.

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• Game engine lib and editor

  - by luke

  I would like to know the best way/best practice to handle the following situation. Suppose the project you are working on is split in two sub-projects: game engine lib editor gui. Now, you have a method bool Method( const MethodParams &params ) that will be called during game-level initialization. So it is a method belonging to the game engine lib. Now, the parameters of this method, passed as a reference the structure MethodParams can be decided via the editor, in the level design phase. Suppose the structure is the following: enum Enum1 { E1_VAL1, E1_VAL2, }; enum Enum2 { E2_VAL1, E2_VAL2, E2_VAL3, }; struct MethodParams { float value; Enum1 e1; Enum2 e2; // some other member } The editor should present a dialog that will let the user set the MethodParams struct. A text control for the field value. Furthermore, the editor needs to let the user set the fields e1 and e2 using, for example, two combo boxes (a combo box is a window control that has a list of choices). Obviously, every enum should be mapped to a string, so the user can make an informed selection (i have used E1_VAL1 etc.., but normally the enum would be more meaningful). One could even want to map every enum to a string more informative (E1_VAL1 to "Image union algorithm", E1_VAL2 to "Image intersection algorithm" and so on...). The editor will include all the relevant game egine lib files (.h etc...), but this mapping is not automatic and i am confused on how to handle it in a way that, if in future i add E1_VAL3 and E1_VAL4, the code change will be minimal.

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• Polygon is rotating too fast

  - by Manderin87

  I am going to be using a polygon collision detection method to test when objects collide. I am attempting to rotate a polygon to match the sprites rotation. However, the polygon is rotating too fast, much faster than the sprite is. I feel its a timing issue, but the sprite rotates like it is supposed to. Can anyone look at my code and tell me what could be causing this issue? public void rotate(float x0, float y0, double angle) { for(Point point : mPoints) { float x = (float) (x0 + (point.x - x0) * Math.cos(Utilities.toRadians(angle)) - (point.y - y0) * Math.sin(Utilities.toRadians(angle))); float y = (float) (y0 + (point.x - x0) * Math.sin(Utilities.toRadians(angle)) + (point.y - y0) * Math.cos(Utilities.toRadians(angle))); point.x = x; point.y = y; } } This algorithm works when done singly, but once I plug it into the update method the rotation is too fast. The Points used are: P1 608, 368 P2 640, 464 P3 672, 400 Origin x0 is: 640 400 The angle goes from 0 to 360 as the sprite rotates. When the codes executes the triangle looks like a star because its moving so fast. The rotation is done in the sprites update method. The rotation method just increases the sprites degree by .5 when it executes. public void update() { if(isActive()) { rotate(); mBounding.rotate(mPosition.x, mPosition.y, mDegree); } }

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• Should I use a seperate class per test?

  - by user460667

  Taking the following simple method, how would you suggest I write a unit test for it (I am using MSTest however concepts are similar in other tools). public void MyMethod(MyObject myObj, bool validInput) { if(!validInput) { // Do nothing } else { // Update the object myObj.CurrentDateTime = DateTime.Now; myObj.Name = "Hello World"; } } If I try and follow the rule of one assert per test, my logic would be that I should have a Class Initialise method which executes the method and then individual tests which check each property on myobj. public class void MyTest { MyObj myObj; [TestInitialize] public void MyTestInitialize() { this.myObj = new MyObj(); MyMethod(myObj, true); } [TestMethod] public void IsValidName() { Assert.AreEqual("Hello World", this.myObj.Name); } [TestMethod] public void IsDateNotNull() { Assert.IsNotNull(this.myObj.CurrentDateTime); } } Where I am confused is around the TestInitialize. If I execute the method under TestInitialize, I would need seperate classes per variation of parameter inputs. Is this correct? This would leave me with a huge number of files in my project (unless I have multiple classes per file). Thanks

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• Higher Performance With Spritesheets Than With Rotating Using C# and XNA 4.0?

  - by Manuel Maier

  I would like to know what the performance difference is between using multiple sprites in one file (sprite sheets) to draw a game-character being able to face in 4 directions and using one sprite per file but rotating that character to my needs. I am aware that the sprite sheet method restricts the character to only be able to look into predefined directions, whereas the rotation method would give the character the freedom of "looking everywhere". Here's an example of what I am doing: Single Sprite Method Assuming I have a 64x64 texture that points north. So I do the following if I wanted it to point east: spriteBatch.Draw( _sampleTexture, new Rectangle(200, 100, 64, 64), null, Color.White, (float)(Math.PI / 2), Vector2.Zero, SpriteEffects.None, 0); Multiple Sprite Method Now I got a sprite sheet (128x128) where the top-left 64x64 section contains a sprite pointing north, top-right 64x64 section points east, and so forth. And to make it point east, i do the following: spriteBatch.Draw( _sampleSpritesheet, new Rectangle(400, 100, 64, 64), new Rectangle(64, 0, 64, 64), Color.White); So which of these methods is using less CPU-time and what are the pro's and con's? Is .NET/XNA optimizing this in any way (e.g. it notices that the same call was done last frame and then just uses an already rendered/rotated image thats still in memory)?

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• Are super methods in JavaScript limited to functional inheritance, as per Crockford's book?

  - by kindohm

  In Douglas Crockford's "JavaScript: The Good Parts", he walks through three types of inheritance: classical, prototypal, and functional. In the part on functional inheritance he writes: "The functional pattern also gives us a way to deal with super methods." He then goes on to implement a method named "superior" on all Objects. However, in the way he uses the superior method, it just looks like he is copying the method on the super object for later use: // crockford's code: var coolcat = function(spec) { var that = cat(spec), super_get_name = that.superior('get_name'); that.get_name = function (n) { return 'like ' + super_get_name() + ' baby'; }; return that; }; The original get_name method is copied to super_get_name. I don't get what's so special about functional inheritance that makes this possible. Can't you do this with classical or prototypal inheritance? What's the difference between the code above and the code below: var CoolCat = function(name) { this.name = name; } CoolCat.prototype = new Cat(); CoolCat.prototype.super_get_name = CoolCat.prototype.get_name; CoolCat.prototype.get_name = function (n) { return 'like ' + this.super_get_name() + ' baby'; }; Doesn't this second example provide access to "super methods" too?

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• share code between check and process methods

  - by undu

  My job is to refactor an old library for GIS vector data processing. The main class encapsulates a collection of building outlines, and offers different methods for checking data consistency. Those checking functions have an optional parameter that allows to perform some process. For instance: std::vector<Point> checkIntersections(int process_mode = 0); This method tests if some building outlines are intersecting, and return the intersection points. But if you pass a non null argument, the method will modify the outlines to remove the intersection. I think it's pretty bad (at call site, a reader not familiar with the code base will assume that a method called checkSomething only performs a check and doesn't modifiy data) and I want to change this. I also want to avoid code duplication as check and process methods are mostly similar. So I was thinking to something like this: // a private worker std::vector<Point> workerIntersections(int process_mode = 0) { // it's the equivalent of the current checkIntersections, it may perform // a process depending on process_mode } // public interfaces for check and process std::vector<Point> checkIntersections() /* const */ { workerIntersections(0); } std::vector<Point> processIntersections(int process_mode /*I have different process modes*/) { workerIntersections(process_mode); } But that forces me to break const correctness as workerIntersections is a non-const method. How can I separate check and process, avoiding code duplication and keeping const-correctness?

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• Can not execute Sonar

  - by senzacionale

  my pom.xml <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>RCC</groupId> <artifactId>tmp</artifactId> <name>tmp</name> <version>1.0</version> <build> <sourceDirectory>C:\Projekti\KIS\Model\src </sourceDirectory> <outputDirectory>C:\Projekti\KIS\Model\classes</outputDirectory> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.5</source> <target>1.5</target> <excludes> <exclude>**/*.*</exclude> </excludes> </configuration> </plugin> </plugins> </build> <properties> <sonar.dynamicAnalysis>false</sonar.dynamicAnalysis> </properties> </project> running sonnar C:\Projekti\Metrics>mvn sonar:sonar -e + Error stacktraces are turned on. [INFO] Scanning for projects... [INFO] Searching repository for plugin with prefix: 'sonar'. [INFO] ------------------------------------------------------------------------ [INFO] Building tmp [INFO] task-segment: [sonar:sonar] (aggregator-style) [INFO] ------------------------------------------------------------------------ [INFO] [sonar:sonar {execution: default-cli}] [INFO] Sonar host: http://localhost:9000 [INFO] Sonar version: 2.1.2 [INFO] [sonar-core:internal {execution: default-internal}] [INFO] ------------------------------------------------------------------------ [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] Can not execute Sonar Embedded error: Can not analyze the project org.apache.derby.jdbc.ClientDriver [INFO] ------------------------------------------------------------------------ [INFO] Trace org.apache.maven.lifecycle.LifecycleExecutionException: Can not execute Sonar at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:719) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:569) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:539) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:387) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:284) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:180) at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:328) at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:138) at org.apache.maven.cli.MavenCli.main(MavenCli.java:362) at org.apache.maven.cli.compat.CompatibleMain.main(CompatibleMain.java:60) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315) at org.codehaus.classworlds.Launcher.launch(Launcher.java:255) at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430) at org.codehaus.classworlds.Launcher.main(Launcher.java:375) Caused by: org.apache.maven.plugin.MojoExecutionException: Can not execute Sonar at org.codehaus.mojo.sonar.Bootstraper.executeMojo(Bootstraper.java:87) at org.codehaus.mojo.sonar.Bootstraper.start(Bootstraper.java:65) at org.codehaus.mojo.sonar.SonarMojo.execute(SonarMojo.java:117) at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490) at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:694) ... 17 more Caused by: org.apache.maven.plugin.MojoExecutionException: Can not analyze the project at org.sonar.maven2.BatchMojo.executeBatch(BatchMojo.java:152) at org.sonar.maven2.BatchMojo.execute(BatchMojo.java:131) at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:490) at org.codehaus.mojo.sonar.Bootstraper.executeMojo(Bootstraper.java:82) ... 21 more Caused by: org.picocontainer.PicoLifecycleException: PicoLifecycleException: method 'public void org.sonar.api.database.AbstractDatabaseConnector.start()', instance 'org.sonar.api.database.DriverDatabaseConnector@c87621, java.lang.RuntimeException: wrapper at org.picocontainer.monitors.NullComponentMonitor.lifecycleInvocationFailed(NullComponentMonitor.java:77) at org.picocontainer.lifecycle.ReflectionLifecycleStrategy.monitorAndThrowReflectionLifecycleException(ReflectionLifecycleStrategy.java:132) at org.picocontainer.lifecycle.ReflectionLifecycleStrategy.invokeMethod(ReflectionLifecycleStrategy.java:115) at org.picocontainer.lifecycle.ReflectionLifecycleStrategy.start(ReflectionLifecycleStrategy.java:89) at org.picocontainer.injectors.AbstractInjectionFactory$LifecycleAdapter.start(AbstractInjectionFactory.java:84) at org.picocontainer.behaviors.AbstractBehavior.start(AbstractBehavior.java:169) at org.picocontainer.behaviors.Stored$RealComponentLifecycle.start(Stored.java:132) at org.picocontainer.behaviors.Stored.start(Stored.java:110) at org.picocontainer.DefaultPicoContainer.potentiallyStartAdapter(DefaultPicoContainer.java:996) at org.picocontainer.DefaultPicoContainer.startAdapters(DefaultPicoContainer.java:989) at org.picocontainer.DefaultPicoContainer.start(DefaultPicoContainer.java:746) at org.sonar.batch.AggregatorBatch.execute(AggregatorBatch.java:84) at org.sonar.maven2.BatchMojo.executeBatch(BatchMojo.java:149) ... 24 more Caused by: java.lang.RuntimeException: wrapper at org.picocontainer.lifecycle.ReflectionLifecycleStrategy.monitorAndThrowReflectionLifecycleException(ReflectionLifecycleStrategy.java:130) ... 35 more Caused by: org.sonar.api.database.DatabaseException: Cannot open connection to database: SQL driver not found org.apache.derby.jdbc.ClientDriver at org.sonar.api.database.AbstractDatabaseConnector.testConnection(AbstractDatabaseConnector.java:182) at org.sonar.api.database.AbstractDatabaseConnector.start(AbstractDatabaseConnector.java:94) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at org.picocontainer.lifecycle.ReflectionLifecycleStrategy.invokeMethod(ReflectionLifecycleStrategy.java:110) ... 34 more Caused by: java.sql.SQLException: SQL driver not found org.apache.derby.jdbc.ClientDriver at org.sonar.api.database.DriverDatabaseConnector.getConnection(DriverDatabaseConnector.java:70) at org.sonar.api.database.AbstractDatabaseConnector.testConnection(AbstractDatabaseConnector.java:178) ... 40 more Caused by: java.lang.ClassNotFoundException: org.apache.derby.jdbc.ClientDriver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at org.codehaus.classworlds.RealmClassLoader.loadClassDirect(RealmClassLoader.java:195) at org.codehaus.classworlds.DefaultClassRealm.loadClass(DefaultClassRealm.java:255) at org.codehaus.classworlds.DefaultClassRealm.loadClass(DefaultClassRealm.java:274) at org.codehaus.classworlds.RealmClassLoader.loadClass(RealmClassLoader.java:214) at java.lang.ClassLoader.loadClass(ClassLoader.java:251) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:164) at org.sonar.api.database.DriverDatabaseConnector.getConnection(DriverDatabaseConnector.java:68) ... 41 more [INFO] ------------------------------------------------------------------------ [INFO] Total time: 3 seconds [INFO] Finished at: Wed Jun 09 12:12:55 CEST 2010 [INFO] Final Memory: 12M/23M [INFO] ------------------------------------------------------------------------ any idea why not working Sonar with maven?

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• How to process images with paperclip on Heroku?

  - by Yuri

  I use Heroku for my app. I want to auto-orient image and then to resize it. So I do: class User < ActiveRecord::Base Paperclip.options[:swallow_stderr] = false has_attached_file :photo, :styles => { :square => "100%", :large => "100%" }, :convert_options => { :square => "-auto-orient -geometry 70X70#", :large => "-auto-orient -geometry X300" }, :storage => :s3, :s3_credentials => "#{RAILS_ROOT}/config/s3.yml", :path => ":attachment/:id/:style.:extension", :bucket => 'mybucket' validates_attachment_size :photo, :less_than => 5.megabyte end It does not work with error: There was an error processing the thumbnail for stream.20143 What am I doing wrong?

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• Vim: how to undo a regex with a new regex?

  - by Victor Tihomirov

  my I have here a text that has been encrypted in Vi this way: 1,$s/\(.\)\1/&&/g 1,$s/\(.\)\(.\)\2\2\2/\2\2\2\1\2/g 1,$s/\(.\)\(.\)\(.\)\(.\)/\3\1\4\2/g 1,$s/\(...\)\(...\)/\2\1/g The task is to write a new regex for each regex in order to undo the the changes, so-called decrypting of the text. I figured out how to undo the last 2 changes: :1,$s/\(...\)\(...\)/\2\1/g :1,$s/\(.\)\(.\)\(.\)\(.\)/\2\4\1\3/g I'd like you to explain me what do the first two regex do. What does \1 or \2\2\2 mean before the forward slash? I assume that after the slash they change place (but wouldn't it be enough to just write \2\1 instead of \2\2\2\1\2(what does it mean?)? I just don't get it). And what does & or && mean? Thank you

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• Is there any algebra calculation library for .NET?

  - by carter-boater

  For example, If I give the it a circle and a square, it can tell me how much area they overlaps.

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• Is there any algebra calculation library in C#?

  - by carter-boater

  For example, If I give the it a circle and a square, it can tell me how much area they overlaps. Thanks guys,

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• Neural Networks in C# using NeuronDotNet

  - by kingrichard2005

  Hello, I'm testing the NeuronDotNet library for a class assignment using C#. I have a very simple console application that I'm using to test some of the code snippets provided in the manual fro the library, the goal of the assignment is to teach the program how to distinguish between random points in a square which may or may not be within a circle that is also inside the square. So basically, which points inside the square are also inside the circle. Here is what I have so far: namespace _469_A7 { class Program { static void Main(string[] args) { //Initlaize the backpropogation network LinearLayer inputLayer = new LinearLayer(2); SigmoidLayer hiddenLayer = new SigmoidLayer(8); SigmoidLayer outputLayer = new SigmoidLayer(2); new BackpropagationConnector(inputLayer, hiddenLayer); new BackpropagationConnector(hiddenLayer, outputLayer); BackpropagationNetwork network = new BackpropagationNetwork(inputLayer, outputLayer); //Generate a training set for the ANN TrainingSet trainingSet = new TrainingSet(2, 2); //TEST: Generate random set of points and add to training set, //for testing purposes start with 10 samples; Point p; Program program = new Program(); //Used to access randdouble function Random rand = new Random(); for(int i = 0; i < 10; i++) { //These points will be within the circle radius Type A if(rand.NextDouble() > 0.5) { p = new Point(rand.NextDouble(), rand.NextDouble()); trainingSet.Add(new TrainingSample(new double[2] { p.getX(), p.getY() }, new double[2] { 1, 0 })); continue; } //These points will either be on the border or outside the circle Type B p = new Point(program.randdouble(1.0, 4.0), program.randdouble(1.0, 4.0)); trainingSet.Add(new TrainingSample(new double[2] { p.getX(), p.getY() }, new double[2] { 0, 1 })); } //Start network learning network.Learn(trainingSet, 100); //Stop network learning //network.StopLearning(); } //generates a psuedo-random double between min and max public double randdouble(double min, double max) { Random rand = new Random(); if (min > max) { return rand.NextDouble() * (min - max) + max; } else { return rand.NextDouble() * (max - min) + min; } } } //Class defines a point in X/Y coordinates public class Point { private double X; private double Y; public Point(double xVal, double yVal) { this.X = xVal; this.Y = yVal; } public double getX() { return X; } public double getY() { return Y; } } } This is basically all that I need, the only question I have is how to handle output?? More specifically, I need to output the value of the "step size" and the momentum, although it would be nice to output other information as well. Anyone with experience using NeuronDotNet, your input is appreciated.

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• jQuery slideToggle stay open on hover

  - by durilai

  I have a div that I have bound the jQuery hover event to activate a slideDown using slideToggle: <div class="Square"> <div class="RedSquare"></div> <div class="GraySquare"></div> </div> $("div.RedSquare").hover( function() { $(this).siblings("div.GraySquare").slideToggle("fast"); }, function() { $(this).siblings("div.GraySquare").slideToggle("fast"); } ); It toggles a div '.GraySquare' right below it. Basically making a gray box slide down from the red box. The problem I am facing is that when the mouse moves over the gray div the slide toggles up. I want it to remain down when hovering over the red or gray square. Any help is appreciated.

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• Trouble with OpenLayers Styles.

  - by Jenny

  So, tired of always seeing the bright orange default regular polygons, I'm trying to learn to style OpenLayers. I've had some success with: var layer_style = OpenLayers.Util.extend({},OpenLayers.Feature.Vector.style['default']); layer_style.fillColor = "#000000"; layer_style.strokeColor = "#000000"; polygonLayer = new OpenLayers.Layer.Vector("PolygonLayer"); polygonLayer.style = layer_style; But sine I am drawing my polygons with DrawFeature, my style only takes effect once I've finished drawing, and seeing it snap from bright orange to grey is sort of disconcerting. So, I learned about temporary styles, and tried: var layer_style = new OpenLayers.Style({"default": {fillColor: "#000000"}, "temporary": {fillColor: "#000000"}}) polygonLayer = new OpenLayers.Layer.Vector("PolygonLayer"); polygonLayer.style = layer_style; This got me a still orange square--until I stopped drawing, when it snapped into completely opaque black. I figured maybe I had to explicitly set the fillOpacity...no dice. Even when I changed both fill colors to be pink and blue, respectively, I still saw only orange and opaque black. I've tried messing with StyleMaps, since I read that if you only add one style to a style map, it uses the default one for everything, including the temporary style. var layer_style = OpenLayers.Util.extend({}, OpenLayers.Feature.Vector.style['default']); var style_map = new OpenLayers.StyleMap(layer_style); polygonLayer = new OpenLayers.Layer.Vector("PolygonLayer"); polygonLayer.style = style_map; That got me the black opaque square, too. (Even though that layer style works when not given to a map). Passing the map to the layer itself like so: polygonLayer = new OpenLayers.Layer.Vector("PolygonLayer", style_map); Didn't get me anything at all. Orange all the way, even after drawn. polygonLayer = new OpenLayers.Layer.Vector("PolygonLayer", {styleMap: style_map}); Is a lot more succesful: Orange while drawing, translucent black with black outline when drawn. Just like when I didn't use a map. Problem is, still no temporary... So, I tried initializing my map this way: var style_map = new OpenLayers.StyleMap({"default": layer_style, "temporary": layer_style}); No opaque square, but no dice for the temporary, either... Still orange snapping to black transparent. Even if I make a new Style (layer_style2), and set temporary to that, still no luck. And no luck with setting "select" style, either. What am I doing wrong? Temporary IS for styling things that are currently being sketched, correct? Is there some other way specific to the drawFeature Controller? Edit: setting extendDefault to be true doesn't seem to help, either... var style_map = new OpenLayers.StyleMap({"default": layer_style, "temporary": layer_style}, {"extendDefault": "true"});

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• SecurityException when accessing (ejb2-) session bean via local interface in JBoss 5

  - by sme

  I have the following problem with an EJB 2 SessionBean when deploying in JBoss 5: The SessionBean (called LVSKeepAliveDispatcher) requires a specific user role (called "LVSUser"), specified by <method-permission > <description></description> <role-name>LVSUser</role-name> <method > <description></description> <ejb-name>LVSKeepAliveDispatcher</ejb-name> <method-name>*</method-name> </method> </method-permission> in ejb-jar.xml. I now want to access this SessionBean from a Service (i.e. a class implementing the org.jboss.varia.scheduler.Schedulable interface that is then registered as a service) running inside the same JBoss instance. This is my jboss-service.xml: <server> <mbean code="org.jboss.varia.scheduler.Scheduler" name="lvs:service=TranslationService"> <attribute name="StartAtStartup">true</attribute> <attribute name="SchedulableClass">de.repower.lvs.server.service.translation.TranslationService</attribute> <attribute name="SchedulableArguments"></attribute> <attribute name="SchedulableArgumentTypes"></attribute> <attribute name="InitialStartDate">NOW</attribute> <attribute name="SchedulePeriod">60000</attribute> <attribute name="InitialRepetitions">1</attribute> <attribute name="TimerName">jboss:service=Timer,name=TranslationServiceTimer</attribute> <depends><mbean code="javax.management.timer.Timer" name="jboss:service=Timer,name=TranslationServiceTimer"/></depends> <depends>jboss.j2ee:service=EJB,jndiName=de/repower/lvs/i18n/sessionbeans/LVSTranslation</depends> </mbean> As the service is deployed in the same vm as the session bean I want to call the session bean via the local interface, but I get a SecurityException when I try to create an instance. When instead I do a lookup of the RemoteInterface it works. This is the code inside the perform method of my service class: public void perform(Date now, long remainingRepetitions) { try { final UsernamePasswordHandler handler = new UsernamePasswordHandler(USERNAME, PASSWORD); final LoginContext lc = new LoginContext("client-login", handler); lc.login(); // Trying to instantiate an LVSKeepAliveDispatcher via remote interface // This part works LVSKeepAliveDispatcher localvHome = LVSKeepAliveDispatcherUtil.getHome().create(); LOGGER.info("Successfully instantiated an LVSKeepAliveDispatcher " + localvHome.toString()); // Trying to instantiate an LVSKeepAliveDispatcherLocal via local interface LVSKeepAliveDispatcherLocal localvLocalHome = LVSKeepAliveDispatcherUtil.getLocalHome().create(); // this code is unforunately never reached LOGGER.info("Successfully instantiated an LVSKeepAliveDispatcherLocal " + localvLocalHome.toString()); lc.logout(); } catch (final Exception ex) { LOGGER.error("Error: ", ex); } } Exception: 2009-02-17 10:38:02,266 INFO [lvsi18n] (Timer-2) Successfully instantiated an LVSKeepAliveDispatcher de/repower/lvs/server/service/alive/sessionbeans/LVSKeepAliveDispatcher:Stateless 2009-02-17 10:38:02,297 ERROR [org.jboss.ejb.plugins.SecurityInterceptor] (Timer-2) Error in Security Interceptor java.lang.SecurityException: Authentication exception, principal=internalSystemUser at org.jboss.ejb.plugins.SecurityInterceptor.checkSecurityContext(SecurityInterceptor.java:321) at org.jboss.ejb.plugins.SecurityInterceptor.process(SecurityInterceptor.java:243) at org.jboss.ejb.plugins.SecurityInterceptor.invokeHome(SecurityInterceptor.java:205) at org.jboss.ejb.plugins.security.PreSecurityInterceptor.process(PreSecurityInterceptor.java:136) at org.jboss.ejb.plugins.security.PreSecurityInterceptor.invokeHome(PreSecurityInterceptor.java:88) at org.jboss.ejb.plugins.LogInterceptor.invokeHome(LogInterceptor.java:132) at org.jboss.ejb.plugins.ProxyFactoryFinderInterceptor.invokeHome(ProxyFactoryFinderInterceptor.java:107) at org.jboss.ejb.SessionContainer.internalInvokeHome(SessionContainer.java:639) at org.jboss.ejb.Container.invoke(Container.java:1046) at org.jboss.ejb.plugins.local.BaseLocalProxyFactory.invokeHome(BaseLocalProxyFactory.java:362) at org.jboss.ejb.plugins.local.LocalHomeProxy.invoke(LocalHomeProxy.java:133) at $Proxy193.create(Unknown Source) at de.repower.lvs.server.service.translation.TranslationService.perform(TranslationService.java:68) at org.jboss.varia.scheduler.Scheduler$PojoScheduler.invoke(Scheduler.java:1267) at org.jboss.varia.scheduler.Scheduler$BaseListener.handleNotification(Scheduler.java:1235) at sun.reflect.GeneratedMethodAccessor281.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.jboss.mx.notification.NotificationListenerProxy.invoke(NotificationListenerProxy.java:153) at $Proxy87.handleNotification(Unknown Source) at javax.management.NotificationBroadcasterSupport.handleNotification(NotificationBroadcasterSupport.java:257) at javax.management.NotificationBroadcasterSupport$SendNotifJob.run(NotificationBroadcasterSupport.java:322) at javax.management.NotificationBroadcasterSupport$1.execute(NotificationBroadcasterSupport.java:307) at javax.management.NotificationBroadcasterSupport.sendNotification(NotificationBroadcasterSupport.java:229) at javax.management.timer.Timer.sendNotification(Timer.java:1234) at javax.management.timer.Timer.notifyAlarmClock(Timer.java:1203) at javax.management.timer.TimerAlarmClock.run(Timer.java:1286) at java.util.TimerThread.mainLoop(Timer.java:512) at java.util.TimerThread.run(Timer.java:462) To further diagnose the error I debugged through the SecurityInterceptor and found that in the first case (successful creating an instance via the remote interface) the security context "lvs-security" (which I defined in login-config.xml) is being used whereas in the second case (failure when creating an instance via the local interface) the generic security context "CLIENT-LOGIN" is being used. This is the definition of the securit context "lvs-security" in login-config.xml: <application-policy name = "lvs-security"> <authentication> <login-module code = "org.jboss.security.ClientLoginModule" flag = "required"> </login-module> <login-module code = "de.repower.lvs.security.UsersRolesLoginModule" flag = "sufficient"> </login-module> <login-module code = "de.repower.lvs.security.login.LVSLoginModule" flag = "required"> <module-option name = "lvs-jboss-host">localhost</module-option> <module-option name = "lvs-jboss-jndi-port">1099</module-option> </login-module> </authentication> </application-policy> I'm now kind of stuck and hope someone can give me a hint about where to further look for the cause of the problem. This worked fine in JBoss 3.2.7. Edit: My current workaround for this problem: create a new container configuration in jboss.xml and remove the security interceptor stuff from this configuration use this newly created container configuration for all my session beans that I only use locally (i.e. via local interface).

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• Algorithm to detect no movable pieces in Stratego.

  - by maleki

  I am creating a Stratego Game and am having trouble creating an algorithm that can detect when there are no more possible moves because all your pieces are gone or the remaining pieces are unmovable or trapped by forbidden squares, unmovable pieces, or other trapped pieces. For simplicity you can think of the board as an array of Squares which can contain pieces. Square[][] gameBoard = new Square[10][10] Squares have easily checkable state such as hasPiece(), hasEnemyPiece(), hasUnMovablePiece(), hasMoveablePiece(), isBlocked(). It would also probably be nice if this algorithm wasn't run every time a player moved but maybe checked in the beginning and then only certain conditions were checked when the player moved.

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