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  • Run Jar in Background on Linux

    - by Benny
    I have a jar that runs forever (infinite loop with socket listening thread) and need it to run in the background at all times. An example would be: "java -jar test.jar" How do I do this? Thanks in advance!

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  • Question about RewriteRule and HTTP_HOST server variable

    - by SeancoJr
    In evaluating a rewrite rule that redirects to a specific URL and say the rewrite condition is met, would it be possible to use HTTP_HOST as part of the URL to be redirected to? Example in question: RewriteRule .*\.(jpg|jpe?g|gif|png|bmp)$ http://%{HTTP_HOST}/no-leech.jpg [R,NC] The motive behind this question is a desire to create a single htaccess file that would match against an addon domain (on a shared hosting account) and an infinite amount of subdomains below it to prevent hotlinking of images.

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  • What's the utility of the return command in autohotkey?

    - by Shashank Sawant
    In the instances where the return command returns a value, the utility is obvious. I have seen the return command being used even when it is seemingly unnecessary. Let me show the following examples: Example 1: Loop { if a_index > 25 break ; Terminate the loop if a_index < 20 continue ; Skip the below and start a new iteration MsgBox, a_index = %a_index% ; This will display only the numbers 20 through 25 } Example 2: IfWinExist, Untitled - Notepad { WinActivate ; Automatically uses the window found above. return } Why is the return command used in Example 2 but is not used in Example 1? Both examples are copy-pasted/modified-pasted from the autohotkey.com's documentation.

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  • Sun Grid Engine : jobs are not well balanced

    - by GlinesMome
    I use Open Grid Scheduler (a fork/copy of Sun Grid Engine). I have tried this configuration from master: # qconf -mattr exechost complex_values slots=8 slave2 # qconf -mq all.q | grep slots slots 100,[slave1=1],[slave2=8] slave1 is down, then I run 10 qsub with a sleep example (so no CPU consumption) but only 4 jobs are run at the same time on slave2 instead of I have put 8 slots. What does I missed ? PS: my goal is to provide infinite slots to force SGE to schedule only via consummable ressources.

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  • Can't `mount -o loop` an ISO from an NFS share (RHEL)

    - by warren
    I have a large NFS share with a variety of software ISOs on it. I've only tried this on Red Hat Enterprise Linux, but when trying to do the following, the mount comes back with an error indicating no permissions to mount. Why would this be happening? NFS is mounted thusly: mediaserver:path/to/isos /media/nfs This is the mount call that fails mount -o loop /media/nfs/product.iso /tmp/product If I copy the ISO, there is no issue. The NFS share is mounted rw. How can I loop mount the ISO from the NFS share without copying it first?

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  • VMware vSwitches and spanning tree

    - by dunxd
    I have two redundant core switches I want to connect to a new vSwitch I am setting up on a VMware ESX host. The switch will have two physical NICs each of which will connect to one of the core switches. The core switches are connected. If this was a physical switch, I would worry about connecting it to both core switches, because this would create a network loop. Do I need to worry about this for a VMware virtual switch? VMware's documentation says it is not possible to connect two vSwitches in a loop, therefore STP is not required. However, I am worried about connecting two physical switches together via a vSwitch.

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  • SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best

    - by pinaldave
    This is followup post of my earlier article SQL SERVER – Convert IN to EXISTS – Performance Talk, after reading all the comments I have received I felt that I could write more on the same subject to clear few things out. First let us run following four queries, all of them are giving exactly same resultset. USE AdventureWorks GO -- use of = SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of in SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- use of exists SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA WHERE EA.EmployeeID = E.EmployeeID) GO -- Use of Join SELECT * FROM HumanResources.Employee E INNER JOIN HumanResources.EmployeeAddress EA ON E.EmployeeID = EA.EmployeeID GO Let us compare the execution plan of the queries listed above. Click on image to see larger image. It is quite clear from the execution plan that in case of IN, EXISTS and JOIN SQL Server Engines is smart enough to figure out what is the best optimal plan of Merge Join for the same query and execute the same. However, in the case of use of Equal (=) Operator, SQL Server is forced to use Nested Loop and test each result of the inner query and compare to outer query, leading to cut the performance. Please note that here I no mean suggesting that Nested Loop is bad or Merge Join is better. This can very well vary on your machine and amount of resources available on your computer. When I see Equal (=) operator used in query like above, I usually recommend to see if user can use IN or EXISTS or JOIN. As I said, this can very much vary on different system. What is your take in above query? I believe SQL Server Engines is usually pretty smart to figure out what is ideal execution plan and use it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Is recursion really bad?

    - by dotneteer
    After my previous post about the stack space, it appears that there is perception from the feedback that recursion is bad and we should avoid deep recursion. After writing a compiler, I know that the modern computer and compiler are complex enough and one cannot automatically assume that a hand crafted code would out-perform the compiler optimization. The only way is to do some prototype to find out. So why recursive code may not perform as well? Compilers place frames on a stack. In additional to arguments and local variables, compiles also need to place frame and program pointers on the frame, resulting in overheads. So why hand-crafted code may not performance as well? The stack used by a compiler is a simpler data structure and can grow and shrink cleanly. To replace recursion with out own stack, our stack is allocated in the heap that is far more complicated to manage. There could be overhead as well if the compiler needs to mark objects for garbage collection. Compiler also needs to worry about the memory fragmentation. Then there is additional complexity: CPUs have registers and multiple levels of cache. Register access is a few times faster than in-CPU cache access and is a few 10s times than on-board memory access. So it is up to the OS and compiler to maximize the use of register and in-CPU cache. For my particular problem, I did an experiment to rewrite my c# version of recursive code with a loop and stack approach. So here are the outcomes of the two approaches:   Recursive call Loop and Stack Lines of code for the algorithm 17 46 Speed Baseline 3% faster Readability Clean Far more complex So at the end, I was able to achieve 3% better performance with other drawbacks. My message is never assuming your sophisticated approach would automatically work out better than a simpler approach with a modern computer and compiler. Gage carefully before committing to a more complex approach.

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  • How does an optimizing compiler react to a program with nested loops?

    - by D.Singh
    Say you have a bunch of nested loops. public void testMethod() { for(int i = 0; i<1203; i++){ //some computation for(int k=2; k<123; k++){ //some computation for(int j=2; j<12312; j++){ //some computation for(int l=2; l<123123; l++){ //some computation for(int p=2; p<12312; p++){ //some computation } } } } } } When the above code reaches the stage where the compiler will try to optimize it (I believe it's when the intermediate language needs to converted to machine code?), what will the compiler try to do? Is there any significant optimization that will take place? I understand that the optimizer will break up the loops by means of loop fission. But this is only per loop isn't it? What I mean with my question is will it take any action exclusively based on seeing the nested loops? Or will it just optimize the loops one by one? If the Java VM complicates the explanation then please just assume that it's C or C++ code.

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  • C string question

    - by user208454
    I am writing a simple c program which reverses a string, taking the string from argv[1]. Here is the code: #include <stdio.h> #include <stdlib.h> #include <string.h> char* flip_string(char *string){ int i = strlen(string); int j = 0; // Doesn't really matter all I wanted was the same size string for temp. char* temp = string; puts("This is the original string"); puts(string); puts("This is the \"temp\" string"); puts(temp); for(i; i>=0; i--){ temp[j] = string[i] if (j <= strlen(string)) { j++; } } return(temp); } int main(int argc, char *argv[]){ puts(flip_string(argv[1])); printf("This is the end of the program\n"); } That's basically it, the program compiles and everything but does not return the temp string in the end (just blank space). In the beginning it prints temp fine when its equal to string. Furthermore if I do a character by character printf of temp in the for loop the correct temp string in printed i.e. string - reversed. just when I try to print it to standard out (after the for loop/ or in the main) nothing happens only blank space is printed.

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  • 2D Procedural Terrain with box2d Assets

    - by Alex
    I'm making a game that invloves a tire moving through terrain that is generated randomly over 1000 points. The terrain is always a downwards incline like so: The actual box2d terrain extends one screen width behind and infront of the circular character. I'm now at a stage where I need to add gameplay elements to the terrain such as chasms or physical objects (like the demo polygon in the picture) and am not sure of the best way to structure the procedural generation of the terrain and objects. I currently have a very simple for loop like so: for(int i = 0; i < kMaxHillPoints; i++) { hillKeyPoints[i] = CGPointMake(terrainX, terrainY); if(i%50 == 0) { i += [self generateCasmAtIndex:i]; } terrainX += winsize.width/20; terrainY -= random() % ((int) winsize.height/20); } With the generateCasmAtIndex function add points to the hillKeyPoints array and incrementing the for loop by the required amount. If I want to generate box2d objects as well for specific terrain elements, I'll also have to keep track of the current position of the player and have some sort of array of box2d objects that need to be created at certain locations. I am not sure of an efficient way to accomplish this procedural generation of terrain elements with accompanying box2d objects. My thoughts are: 1) Have many functions for each terrain element (chasm, jump etc.) which add elements to be drawn to an array that is check on each game step - similar to what I've shown above. 2) Create an array of terrain element objects that string together and are looped over to create the terrain and generate the box2d objects. Each object would hold an array of points to be drawn and and array of accompanying box2d objects. Any help on this is much appreciated as I cannot see a 'clean' solution.

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  • Glenn Fiedler's fixed timestep with fake threads

    - by kaoD
    I've implemented Glenn Fiedler's Fix Your Timestep! quite a few times in single-threaded games. Now I'm facing a different situation: I'm trying to do this in JavaScript. I know JS is single-threaded, but I plan on using requestAnimationFrame for the rendering part. This leaves me with two independent fake threads: simulation and rendering (I suppose requestAnimationFrame isn't really threaded, is it? I don't think so, it would BREAK JS.) Timing in these threads is independent too: dt for simulation and render is not the same. If I'm not mistaken, simulation should be up to Fiedler's while loop end. After the while loop, accumulator < dt so I'm left with some unspent time (dt) in the simulation thread. The problem comes in the draw/interpolation phase: const double alpha = accumulator / dt; State state = currentState*alpha + previousState * ( 1.0 - alpha ); render( state ); In my render callback, I have the current timestamp to which I can subtract the last-simulated-in-physics-timestamp to have a dt for the current frame. Should I just forget about this dt and draw using the physics thread's dt? It seems weird, since, well, I want to interpolate for the unspent time between simulation and render too, right? Of course, I want simulation and rendering to be completely independent, but I can't get around the fact that in Glenn's implementation the renderer produces time and the simulation consumes it in discrete dt sized chunks. A similar question was asked in Semi Fixed-timestep ported to javascript but the question doesn't really get to the point, and answers there point to removing physics from the render thread (which is what I'm trying to do) or just keeping physics in the render callback too (which is what I'm trying to avoid.)

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  • Adding objects to the environment at timed intervals

    - by david
    I am using an ArrayList to handle objects and at each interval of 120 frames, I am adding a new object of the same type at a random location along the z-axis of 60. The problem is, it doesn't add just 1. It depends on how many are in the list. If I kill the Fox before the time interval when one is supposed to spawn comes, then no Fox will be spawned. If I don't kill any foxes, it grows exponentially. I only want one Fox to be added every 120 frames. This problem never happened before when I created new ones and added them to the environment. Any insights? Here is my code: /**** FOX CLASS ****/ import env3d.EnvObject; import java.util.ArrayList; public class Fox extends Creature { private int frame = 0; public Fox(double x, double y, double z) { super(x, y, z); // Must use the mutator as the fields have private access // in the parent class setTexture("models/fox/fox.png"); setModel("models/fox/fox.obj"); setScale(1.4); } public void move(ArrayList<Creature> creatures, ArrayList<Creature> dead_creatures, ArrayList<Creature> new_creatures) { frame++; setX(getX()-0.2); setRotateY(270); if (frame > 120) { Fox f = new Fox(60, 1, (int)(Math.random()*28)+1); new_creatures.add(f); frame = 0; } for (Creature c : creatures) { if (this.distance(c) < this.getScale()+c.getScale() && c instanceof Tux) { dead_creatures.add(c); } } for (Creature c : creatures) { if (c.getX() < 1 && c instanceof Fox) { dead_creatures.add(c); } } } } import env3d.Env; import java.util.ArrayList; import org.lwjgl.input.Keyboard; /** * A predator and prey simulation. Fox is the predator and Tux is the prey. */ public class Game { private Env env; private boolean finished; private ArrayList<Creature> creatures; private KingTux king; private Snowball ball; private int tuxcounter; private int kills; /** * Constructor for the Game class. It sets up the foxes and tuxes. */ public Game() { // we use a separate ArrayList to keep track of each animal. // our room is 50 x 50. creatures = new ArrayList<Creature>(); for (int i = 0; i < 10; i++) { creatures.add(new Tux((int)(Math.random()*10)+1, 1, (int)(Math.random()*28)+1)); } for (int i = 0; i < 1; i++) { creatures.add(new Fox(60, 1, (int)(Math.random()*28)+1)); } king = new KingTux(25, 1, 35); ball = new Snowball(-400, -400, -400); } /** * Play the game */ public void play() { finished = false; // Create the new environment. Must be done in the same // method as the game loop env = new Env(); // Make the room 50 x 50. env.setRoom(new Room()); // Add all the animals into to the environment for display for (Creature c : creatures) { env.addObject(c); } for (Creature c : creatures) { if (c instanceof Tux) { tuxcounter++; } } env.addObject(king); env.addObject(ball); // Sets up the camera env.setCameraXYZ(30, 50, 55); env.setCameraPitch(-63); // Turn off the default controls env.setDefaultControl(false); // A list to keep track of dead tuxes. ArrayList<Creature> dead_creatures = new ArrayList<Creature>(); ArrayList<Creature> new_creatures = new ArrayList<Creature>(); // The main game loop while (!finished) { if (env.getKey() == 1 || tuxcounter == 0) { finished = true; } env.setDisplayStr("Tuxes: " + tuxcounter, 15, 0); env.setDisplayStr("Kills: " + kills, 140, 0); processInput(); ball.move(); king.check(); // Move each fox and tux. for (Creature c : creatures) { c.move(creatures, dead_creatures, new_creatures); } for (Creature c : creatures) { if (c.distance(ball) < c.getScale()+ball.getScale() && c instanceof Fox) { dead_creatures.add(c); ball.setX(-400); ball.setY(-400); ball.setZ(-400); kills++; } } // Clean up of the dead tuxes. for (Creature c : dead_creatures) { if (c instanceof Tux) { tuxcounter--; } env.removeObject(c); creatures.remove(c); } for (Creature c : new_creatures) { creatures.add(c); env.addObject(c); } // we clear the ArrayList for the next loop. We could create a new one // every loop but that would be very inefficient. dead_creatures.clear(); new_creatures.clear(); // Update display env.advanceOneFrame(); } // Just a little clean up env.exit(); } private void processInput() { int keyDown = env.getKeyDown(); int key = env.getKey(); if (keyDown == 203) { king.setX(king.getX()-1); } else if (keyDown == 205) { king.setX(king.getX()+1); } if (ball.getX() <= -400 && key == Keyboard.KEY_S) { ball.setX(king.getX()); ball.setY(king.getY()); ball.setZ(king.getZ()); } } /** * Main method to launch the program. */ public static void main(String args[]) { (new Game()).play(); } } /**** CREATURE CLASS ****/ /* (Parent class to Tux, Fox, and KingTux) */ import env3d.EnvObject; import java.util.ArrayList; abstract public class Creature extends EnvObject { private int frame; private double rand; /** * Constructor for objects of class Creature */ public Creature(double x, double y, double z) { setX(x); setY(y); setZ(z); setScale(1); rand = Math.random(); } private void randomGenerator() { rand = Math.random(); } public void move(ArrayList<Creature> creatures, ArrayList<Creature> dead_creatures, ArrayList<Creature> new_creatures) { frame++; if (frame > 12) { randomGenerator(); frame = 0; } // if (rand < 0.25) { // setX(getX()+0.3); // setRotateY(90); // } else if (rand < 0.5) { // setX(getX()-0.3); // setRotateY(270); // } else if (rand < 0.75) { // setZ(getZ()+0.3); // setRotateY(0); // } else if (rand < 1) { // setZ(getZ()-0.3); // setRotateY(180); // } if (rand < 0.5) { setRotateY(getRotateY()-7); } else if (rand < 1) { setRotateY(getRotateY()+7); } setX(getX()+Math.sin(Math.toRadians(getRotateY()))*0.5); setZ(getZ()+Math.cos(Math.toRadians(getRotateY()))*0.5); if (getX() < getScale()) setX(getScale()); if (getX() > 50-getScale()) setX(50 - getScale()); if (getZ() < getScale()) setZ(getScale()); if (getZ() > 50-getScale()) setZ(50 - getScale()); // The move method now handles collision detection if (this instanceof Fox) { for (Creature c : creatures) { if (c.distance(this) < c.getScale()+this.getScale() && c instanceof Tux) { dead_creatures.add(c); } } } } } The rest of the classes are a bit trivial to this specific problem.

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  • javascript fixed timestep gameloop with requestanimation frame

    - by coffeecup
    hello i just started to read through several articles, including http://gafferongames.com/game-physics/fix-your-timestep/ ...://gamedev.stackexchange.com/questions/1589/fixed-time-step-vs-variable-time-step/ ...//dewitters.koonsolo.com/gameloop.html ...://nokarma.org/2011/02/02/javascript-game-development-the-game-loop/index.html my understanding of this is that i need the currentTime and the timeStep size and integrate all states to the next state the time which is left is then passed into the render function to do interpolation i tried to implement glenn fiedlers "the final touch", whats troubling me is that each FrameTime is about 15 (ms) and the update loop runs at about 1500 fps which seems a little bit off? heres my code this.t = 0 this.dt = 0.01 this.currTime = new Date().getTime() this.accumulator = 0.0 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if ( frameTime > 0.25 ) frameTime = 0.25 this.currTime = newTime this.accumulator += frameTime while (this.accumulator >= this.dt ) { this.prev_state = this.curr_state this.update(this.t,this.dt) this.t += this.dt this.accumulator -= this.dt } alpha = this.accumulator / this.dt this.render( this.t, this.dt, alpha) requestAnimationFrame( this.animate ) } also i would like to know, are there differences between glenn fiedlers implementation and the last solution presented here ? gameloop1 gameloop2 [ sorry couldnt post more than 2 links.. ] edit : i looked into it again and adjusted the values this.currTime = new Date().getTime() this.accumulator = 0 this.p_t = 0 this.p_step = 1000/100 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if(frameTime > 25) frameTime = 25 this.currTime = newTime this.accumulator += frameTime while(this.accumulator >= this.p_step){ // prevstate = currState this.update() this.p_t+=this.p_step this.accumulator -= this.p_step } alpha = this.accumulator / this.p_step this.render(alpha) requestAnimationFrame( this.animate ) now i can set the physics update rate, render runs at 60 fps and physics update at 100 fps, maybe someone could confirm this because its the first time i'm playing around with game development :-)

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  • how to think like a computer scientist java edition exercise 7.2 [on hold]

    - by James Canfield
    I cannot figure out how to write this program, can someone please help me?! The purpose of this method is to practice manipulating St rings. Create a new program called Name.java. This program will take a name string consisting of EITHER a first name followed by a last name (nonstandar d format) or a last name followed by a comma then a first name (standard format). Ie . “Joe Smith” vs. “Smith, Joe”. This program will convert the string to standard format if it is not already in standard format. Write a method called hasComma that takes a name as an argument and that returns a boolean indicating whether it contains a comma. If i t does, you can assume that it is in last name first format. You can use the indexOf String m ethod to help you. Write a method called convertName that takes a name as an argument. It should check whether it contains a comma by calling your hasComma method. If it does, it should just return the string. If not, then it should assume th at the name is in first name first format, and it should return a new string that contains the name converted to last name comma first format. Uses charAt, length, substring, and indexOf methods. In your main program, loop, asking the user for a n ame string. If the string is not blank, call convertName and print the results. The loop terminat es when the string is blank. HINTS/SUGGESTIONS: Use the charAt, length, substring, and indexOf Str ing methods. Use scanner for your input. To get the full line, complete with spaces, use reader.nextLine()

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  • Why are SW engineering interviews disproportionately difficult?

    - by stackoverflowuser2010
    First, some background on me. I have a PhD in CS and have had jobs both as a software engineer and as an R&D research scientist, both at Very Large Corporations You Know Very Well. I recently changed jobs and interviewed for both types of jobs (as I have done in the past). My observation: SW engineer job interviews are way, way disproportionately more difficult than CS researcher job interviews, but the researcher job is higher paying, more competitive, more rewarding, more interesting, and has a higher upside. Here's a typical interview loop for researcher: Phone interview to see if my research is in alignment with the lab's researcher In-person, give presentation on my recent research for one hour (which represents maybe 9 month's worth of work), answer questions In-person one-on-one interviews with about 5 researchers, where they ask me very reasonable questions on my work/publications/patents, including: technical questions, where my work fits into related work, and how I can extend my work to new areas Here's a typical interview loop for SW engineer: Phone interview where I'm asked algorithm questions and maybe do some coding. Pretty standard. In-person interviews at the whiteboard where they drill the F*** out of you on esoteric C++ minutia (e.g. how does a polymorphic virtual function call work), algorithms (make all-pairs-shortest-path algorithm work for 1B vertices), system design (design a database load balancer), etc. This goes on for six or seven interviews. Ridiculous. Why would anyone be willing to put up with this? What is the point of asking about C++ trivia or writing code to prove yourself? Why not make the SE interview more like the researcher interview where you give a talk about what you've done? How are technical job interviews for other fields, like physics, chemistry, civil engineering, mechanical engineering?

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  • Constant game speed independent of variable FPS in OpenGL with GLUT?

    - by Nazgulled
    I've been reading Koen Witters detailed article about different game loop solutions but I'm having some problems implementing the last one with GLUT, which is the recommended one. After reading a couple of articles, tutorials and code from other people on how to achieve a constant game speed, I think that what I currently have implemented (I'll post the code below) is what Koen Witters called Game Speed dependent on Variable FPS, the second on his article. First, through my searching experience, there's a couple of people that probably have the knowledge to help out on this but don't know what GLUT is and I'm going to try and explain (feel free to correct me) the relevant functions for my problem of this OpenGL toolkit. Skip this section if you know what GLUT is and how to play with it. GLUT Toolkit: GLUT is an OpenGL toolkit and helps with common tasks in OpenGL. The glutDisplayFunc(renderScene) takes a pointer to a renderScene() function callback, which will be responsible for rendering everything. The renderScene() function will only be called once after the callback registration. The glutTimerFunc(TIMER_MILLISECONDS, processAnimationTimer, 0) takes the number of milliseconds to pass before calling the callback processAnimationTimer(). The last argument is just a value to pass to the timer callback. The processAnimationTimer() will not be called each TIMER_MILLISECONDS but just once. The glutPostRedisplay() function requests GLUT to render a new frame so we need call this every time we change something in the scene. The glutIdleFunc(renderScene) could be used to register a callback to renderScene() (this does not make glutDisplayFunc() irrelevant) but this function should be avoided because the idle callback is continuously called when events are not being received, increasing the CPU load. The glutGet(GLUT_ELAPSED_TIME) function returns the number of milliseconds since glutInit was called (or first call to glutGet(GLUT_ELAPSED_TIME)). That's the timer we have with GLUT. I know there are better alternatives for high resolution timers, but let's keep with this one for now. I think this is enough information on how GLUT renders frames so people that didn't know about it could also pitch in this question to try and help if they fell like it. Current Implementation: Now, I'm not sure I have correctly implemented the second solution proposed by Koen, Game Speed dependent on Variable FPS. The relevant code for that goes like this: #define TICKS_PER_SECOND 30 #define MOVEMENT_SPEED 2.0f const int TIMER_MILLISECONDS = 1000 / TICKS_PER_SECOND; int previousTime; int currentTime; int elapsedTime; void renderScene(void) { (...) // Setup the camera position and looking point SceneCamera.LookAt(); // Do all drawing below... (...) } void processAnimationTimer(int value) { // setups the timer to be called again glutTimerFunc(TIMER_MILLISECONDS, processAnimationTimer, 0); // Get the time when the previous frame was rendered previousTime = currentTime; // Get the current time (in milliseconds) and calculate the elapsed time currentTime = glutGet(GLUT_ELAPSED_TIME); elapsedTime = currentTime - previousTime; /* Multiply the camera direction vector by constant speed then by the elapsed time (in seconds) and then move the camera */ SceneCamera.Move(cameraDirection * MOVEMENT_SPEED * (elapsedTime / 1000.0f)); // Requests to render a new frame (this will call my renderScene() once) glutPostRedisplay(); } void main(int argc, char **argv) { glutInit(&argc, argv); (...) glutDisplayFunc(renderScene); (...) // Setup the timer to be called one first time glutTimerFunc(TIMER_MILLISECONDS, processAnimationTimer, 0); // Read the current time since glutInit was called currentTime = glutGet(GLUT_ELAPSED_TIME); glutMainLoop(); } This implementation doesn't fell right. It works in the sense that helps the game speed to be constant dependent on the FPS. So that moving from point A to point B takes the same time no matter the high/low framerate. However, I believe I'm limiting the game framerate with this approach. Each frame will only be rendered when the time callback is called, that means the framerate will be roughly around TICKS_PER_SECOND frames per second. This doesn't feel right, you shouldn't limit your powerful hardware, it's wrong. It's my understanding though, that I still need to calculate the elapsedTime. Just because I'm telling GLUT to call the timer callback every TIMER_MILLISECONDS, it doesn't mean it will always do that on time. I'm not sure how can I fix this and to be completely honest, I have no idea what is the game loop in GLUT, you know, the while( game_is_running ) loop in Koen's article. But it's my understanding that GLUT is event-driven and that game loop starts when I call glutMainLoop() (which never returns), yes? I thought I could register an idle callback with glutIdleFunc() and use that as replacement of glutTimerFunc(), only rendering when necessary (instead of all the time as usual) but when I tested this with an empty callback (like void gameLoop() {}) and it was basically doing nothing, only a black screen, the CPU spiked to 25% and remained there until I killed the game and it went back to normal. So I don't think that's the path to follow. Using glutTimerFunc() is definitely not a good approach to perform all movements/animations based on that, as I'm limiting my game to a constant FPS, not cool. Or maybe I'm using it wrong and my implementation is not right? How exactly can I have a constant game speed with variable FPS? More exactly, how do I correctly implement Koen's Constant Game Speed with Maximum FPS solution (the fourth one on his article) with GLUT? Maybe this is not possible at all with GLUT? If not, what are my alternatives? What is the best approach to this problem (constant game speed) with GLUT? I originally posted this question on Stack Overflow before being pointed out about this site. The following is a different approach I tried after creating the question in SO, so I'm posting it here too. Another Approach: I've been experimenting and here's what I was able to achieve now. Instead of calculating the elapsed time on a timed function (which limits my game's framerate) I'm now doing it in renderScene(). Whenever changes to the scene happen I call glutPostRedisplay() (ie: camera moving, some object animation, etc...) which will make a call to renderScene(). I can use the elapsed time in this function to move my camera for instance. My code has now turned into this: int previousTime; int currentTime; int elapsedTime; void renderScene(void) { (...) // Setup the camera position and looking point SceneCamera.LookAt(); // Do all drawing below... (...) } void renderScene(void) { (...) // Get the time when the previous frame was rendered previousTime = currentTime; // Get the current time (in milliseconds) and calculate the elapsed time currentTime = glutGet(GLUT_ELAPSED_TIME); elapsedTime = currentTime - previousTime; /* Multiply the camera direction vector by constant speed then by the elapsed time (in seconds) and then move the camera */ SceneCamera.Move(cameraDirection * MOVEMENT_SPEED * (elapsedTime / 1000.0f)); // Setup the camera position and looking point SceneCamera.LookAt(); // All drawing code goes inside this function drawCompleteScene(); glutSwapBuffers(); /* Redraw the frame ONLY if the user is moving the camera (similar code will be needed to redraw the frame for other events) */ if(!IsTupleEmpty(cameraDirection)) { glutPostRedisplay(); } } void main(int argc, char **argv) { glutInit(&argc, argv); (...) glutDisplayFunc(renderScene); (...) currentTime = glutGet(GLUT_ELAPSED_TIME); glutMainLoop(); } Conclusion, it's working, or so it seems. If I don't move the camera, the CPU usage is low, nothing is being rendered (for testing purposes I only have a grid extending for 4000.0f, while zFar is set to 1000.0f). When I start moving the camera the scene starts redrawing itself. If I keep pressing the move keys, the CPU usage will increase; this is normal behavior. It drops back when I stop moving. Unless I'm missing something, it seems like a good approach for now. I did find this interesting article on iDevGames and this implementation is probably affected by the problem described on that article. What's your thoughts on that? Please note that I'm just doing this for fun, I have no intentions of creating some game to distribute or something like that, not in the near future at least. If I did, I would probably go with something else besides GLUT. But since I'm using GLUT, and other than the problem described on iDevGames, do you think this latest implementation is sufficient for GLUT? The only real issue I can think of right now is that I'll need to keep calling glutPostRedisplay() every time the scene changes something and keep calling it until there's nothing new to redraw. A little complexity added to the code for a better cause, I think. What do you think?

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  • case-specific mod rewrite on Wordpress subdomain multisite

    - by Steve
    I have split a Wordpress blog into multiple category-specific blogs using subdomains, as the topics in the original blog were too broad to be lumped together effectively. Posts were exported from the parent www blog and imported into the subject-specific subdomain blogs. I believe .htaccess provides mod rewrite for all subdomains (including the original www) in a single .htaccess file. I use .htaccess to perform 301 redirect on post categories to the relevant post on the subdomain's blog. eg: RedirectMatch 301 ^/auto/(.*)$ http://auto.example.com/$1 The problem I have is that the category has been retained in the permalink structure in the subdomain blog, so that www.example.com/auto/mercedes is now auto.example.com/auto/mercedes. The 1st URL is redirect to the 2nd, but unfortunately, the 2nd URL is redirected to auto.example.com/mercedes using the same rewrite rule, which is not found, as the permalink on the subdomain's blog retains the parent category of auto. The solution would be to adjust the permalink structure in the subdomain's WP settings, so that the top level category does not duplicate the subdomain. My question would be: how do I then strip a section of the original (www) blog's post URL from the subdomain's URL when redirecting? eg: How do I redirect www.example.com/auto/mercedes to auto.example.com/mercedes? I'm assuming this would be a regular expression trick, which I am not great at. Update: I might have to use: RewriteCond %{HTTP_HOST} !auto.example.com$ in the default Wordpress if loop in .htaccess, and seperate my custom subdomain redirections into a second if loop section.

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  • Oracle Warehouse Builder és Enterprise ETL

    - by Fekete Zoltán
    Friss és ropogós az adatlap!!! Fogyasszátok egészséggel: ODI Enterprise Edition: Warehouse Builder Enterprise ETL white paper. A jó hír: minden megvásárolt Oracle Database-hez ingyenese használható az Oracle Warehouse Builder alap (core) funkcionalitása. Mi is az az OWB core funkcionalitás, és mit használhatunk az opciókban? Az Enterprise ETL funkcionalitás az Oracle Data Integrator Enterprise Edition licensz részeként érheto el az OWB-hez. Azok a funkciók, amik csak az ODI EE licensszel érhetok el (a korábbi OWB Enterprise ETL opció is ennek a része) megtekinthetok itt is a szöveg alján. Ezek: - Transportable ETL modules, multiple configurations, and pluggable mappings - Operators for pluggable mapping, pluggable mapping input signature, pluggable mapping output signature - Design Environment Support for RAC - Metadata change propagation - Schedulable Mappings and Process Flows - Slowing Changing Dimensions (SCD) Type 2 and 3 - XML Files as a target - Target load ordering - Seeded spatial and streams transformations - Process Flow Activity templates - Process Flow variables support - Process Flow looping activities such as For Loop and While Loop - Process Flow Route and Notification activities - Metadata lineage and impact analysis - Metadata Extensibility - Deployment to Discoverer EUL - Deployment to Oracle BI Beans catalog Tehát ha komolyabb környezetben szeretném használni az OWB-t, több környezetbe deployálni, stb, akkor szükség van az ODI EE licenszre is. ODI Enterprise Edition: Warehouse Builder Enterprise ETL white paper.

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  • Android threads trouble wrapping my head around design

    - by semajhan
    I am having trouble wrapping my head around game design. On the android platform, I have an activity and set its content view with a custom surface view. The custom surface view acts as my panel and I create instances of all classes and do all the drawing and calculation in there. Question: Should I instead create the instances of other classes in my activity? Now I create a custom thread class that handles the game loop. Question: How do I use this one class in all my activities? Or do I have to create a separate instance of the extended thread class each time? In my previous game, I had multiple levels that had to create an instance of the thread class and in the thread class I had to set constructor methods for each separate level and in the loop use a switch statement to check which level it needs to render and update. Sorry if that sounds confusing. I just want to know if the method I am using is inefficient (which it probably is) and how to go about designing it the correct way. I have read many tutorials out there and I am still having lots of trouble with this particular topic. Maybe a link to a some tutorials that explain this? Thanks.

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  • How to determine if you should use full or differential backup?

    - by Peter Larsson
    Or ask yourself, "How much of the database has changed since last backup?". Here is a simple script that will tell you how much (in percent) have changed in the database since last backup. -- Prepare staging table for all DBCC outputs DECLARE @Sample TABLE         (             Col1 VARCHAR(MAX) NOT NULL,             Col2 VARCHAR(MAX) NOT NULL,             Col3 VARCHAR(MAX) NOT NULL,             Col4 VARCHAR(MAX) NOT NULL,             Col5 VARCHAR(MAX)         )   -- Some intermediate variables for controlling loop DECLARE @FileNum BIGINT = 1,         @PageNum BIGINT = 6,         @SQL VARCHAR(100),         @Error INT,         @DatabaseName SYSNAME = 'Yoda'   -- Loop all files to the very end WHILE 1 = 1     BEGIN         BEGIN TRY             -- Build the SQL string to execute             SET     @SQL = 'DBCC PAGE(' + QUOTENAME(@DatabaseName) + ', ' + CAST(@FileNum AS VARCHAR(50)) + ', '                             + CAST(@PageNum AS VARCHAR(50)) + ', 3) WITH TABLERESULTS'               -- Insert the DBCC output in the staging table             INSERT  @Sample                     (                         Col1,                         Col2,                         Col3,                         Col4                     )             EXEC    (@SQL)               -- DCM pages exists at an interval             SET    @PageNum += 511232         END TRY           BEGIN CATCH             -- If error and first DCM page does not exist, all files are read             IF @PageNum = 6                 BREAK             ELSE                 -- If no more DCM, increase filenum and start over                 SELECT  @FileNum += 1,                         @PageNum = 6         END CATCH     END   -- Delete all records not related to diff information DELETE FROM    @Sample WHERE   Col1 NOT LIKE 'DIFF%'   -- Split the range UPDATE  @Sample SET     Col5 = PARSENAME(REPLACE(Col3, ' - ', '.'), 1),         Col3 = PARSENAME(REPLACE(Col3, ' - ', '.'), 2)   -- Remove last paranthesis UPDATE  @Sample SET     Col3 = RTRIM(REPLACE(Col3, ')', '')),         Col5 = RTRIM(REPLACE(Col5, ')', ''))   -- Remove initial information about filenum UPDATE  @Sample SET     Col3 = SUBSTRING(Col3, CHARINDEX(':', Col3) + 1, 8000),         Col5 = SUBSTRING(Col5, CHARINDEX(':', Col5) + 1, 8000)   -- Prepare data outtake ;WITH cteSource(Changed, [PageCount]) AS (     SELECT      Changed,                 SUM(COALESCE(ToPage, FromPage) - FromPage + 1) AS [PageCount]     FROM        (                     SELECT CAST(Col3 AS INT) AS FromPage,                             CAST(NULLIF(Col5, '') AS INT) AS ToPage,                             LTRIM(Col4) AS Changed                     FROM    @Sample                 ) AS d     GROUP BY    Changed     WITH ROLLUP ) -- Present the final result SELECT  COALESCE(Changed, 'TOTAL PAGES') AS Changed,         [PageCount],         100.E * [PageCount] / SUM(CASE WHEN Changed IS NULL THEN 0 ELSE [PageCount] END) OVER () AS Percentage FROM    cteSource

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  • python Velocity control of the player, why doesn't this work?

    - by Dominic Grenier
    I have the following code inside a while True loop: if abs(playerx) < MAXSPEED: if moveLeft: playerx -= 1 if moveRight: playerx += 1 if abs(playery) < MAXSPEED: if moveDown: playery += 1 if moveUp: playery -= 1 if moveLeft == False and abs(playerx) > 0: playerx += 1 if moveRight == False and abs(playerx) > 0: playerx -= 1 if moveUp == False and abs(playery) > 0: playery += 1 if moveDown == False and abs(playery) > 0: playery -= 1 player.x += playerx player.y += playery if player.left < 0 or player.right > 1000: player.x -= playerx if player.top < 0 or player.bottom > 600: player.y -= playery The intended result is that while an arrow key is pressed, playerx or y increments by one at every loop until it reaches MAXSPEED and stays at MAXSPEED. And that when the player stops pressing that arrow key, his speed decreases. Until it reaches 0. To me, this code explicitly says that... But what actually happens is that playerx or y keeps incrementing regardless of MAXSPEED and continues moving even after the player stops pressing the arrow key. I keep rereading but I'm completely baffled by this weird behavior. Any insights? Thanks.

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  • "Accumulate" buffer results in XNA4?

    - by Utkarsh Sinha
    I'm trying to simulate a "heightmap" buffer in XNA4.0 but the results don't look correct. Here's what I'm hoping to achieve: http://www.youtube.com/watch?feature=player_detailpage&v=-Q6ISVaM5Ww#t=517s (8:38). From what I understand, here are the steps to reach there: Pass height buffer + current entity's heightmap Generate a stencil and update the height buffer Render sprite+stencil For now, I'm just trying to get the height buffer thing to work. So here's the problem. Inside the draw loop, I do the following: Create a new render target & set it Draw the heightmap with a sprite batch(no shaders) graphicsDevice.SetRenderTarget(null) Draw the rendertarget with SpriteBatch I expected to see all entities' heightmaps. But only the last entity's heightmap is visible. Any hints on what I'm doing wrong? Here's the code inside the draw loop: RenderTarget2D tempDepthStencil = new RenderTarget2D(graphicsDevice, graphicsDevice.Viewport.Width, graphicsDevice.Viewport.Height, false, graphicsDevice.DisplayMode.Format, DepthFormat.None); graphicsDevice.SetRenderTarget(tempDepthStencil); // Gather depth information SpriteBatch depthStencilSpriteBatch = new SpriteBatch(graphicsDevice); depthStencilSpriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, SamplerState.LinearClamp, DepthStencilState.None, RasterizerState.CullCounterClockwise); depthStencilSpriteBatch.Draw(texHeightmap, pos, null, Color.White, 0, Vector2.Zero, 1, spriteEffects, 1); depthStencilSpriteBatch.End(); graphicsDevice.SetRenderTarget(null); SpriteBatch b1 = new SpriteBatch(graphicsDevice); b1.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, null, null, null, null); b1.Draw((Texture2D)tempDepthStencil, Vector2.Zero, null, Color.White, 0, Vector2.Zero, 1, spriteEffects, 1); b1.End();

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  • Android threads trouble wrapping my head around design

    - by semajhan
    I am having trouble wrapping my head around game design. On the android platform, I have an activity and set its content view with a custom surface view. The custom surface view acts as my panel and I create instances of all classes and do all the drawing and calculation in there. Question: Should I instead create the instances of other classes in my activity? Now I create a custom thread class that handles the game loop. Question: How do I use this one class in all my activities? Or do I have to create a separate thread each time? In my previous game, I had multiple levels that had to create an instance of the thread class and in the thread class I had to set constructor methods for each separate level and in the loop use a switch statement to check which level it needs to render and update. Sorry if that sounds confusing. I just want to know if the method I am using is inefficient (which it probably is) and how to go about designing it the correct way. I have read many tutorials out there and I am still having lots of trouble with this particular topic. Maybe a link to a some tutorials that explain this? Thanks.

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  • 2D platformers: why make the physics dependent on the framerate?

    - by Archagon
    "Super Meat Boy" is a difficult platformer that recently came out for PC, requiring exceptional control and pixel-perfect jumping. The physics code in the game is dependent on the framerate, which is locked to 60fps; this means that if your computer can't run the game at full speed, the physics will go insane, causing (among other things) your character to run slower and fall through the ground. Furthermore, if vsync is off, the game runs extremely fast. Could those experienced with 2D game programming help explain why the game was coded this way? Wouldn't a physics loop running at a constant rate be a better solution? (Actually, I think a physics loop is used for parts of the game, since some of the entities continue to move normally regardless of the framerate. Your character, on the other hand, runs exactly [fps/60] as fast.) What bothers me about this implementation is the loss of abstraction between the game engine and the graphics rendering, which depends on system-specific things like the monitor, graphics card, and CPU. If, for whatever reason, your computer can't handle vsync, or can't run the game at exactly 60fps, it'll break spectacularly. Why should the rendering step in any way influence the physics calculations? (Most games nowadays would either slow down the game or skip frames.) On the other hand, I understand that old-school platformers on the NES and SNES depended on a fixed framerate for much of their control and physics. Why is this, and would it be possible to create a patformer in that vein without having the framerate dependency? Is there necessarily a loss of precision if you separate the graphics rendering from the rest of the engine? Thank you, and sorry if the question was confusing.

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