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• The code works but when using printf it gives me a weird answer. Help please [closed]

  - by user71458

  //Programmer-William Chen //Seventh Period Computer Science II //Problem Statement - First get the elapsed times and the program will find the //split times for the user to see. // //Algorithm- First the programmer makes the prototype and calls them in the //main function. The programmer then asks the user to input lap time data. //Secondly, you convert the splits into seconds and subtract them so you can //find the splits. Then the average is all the lap time's in seconds. Finally, //the programmer printf all the results for the user to see. #include <iostream> #include <stdlib.h> #include <math.h> #include <conio.h> #include <stdio.h> using namespace std; void thisgetsElapsedTimes( int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5); //this is prototype void thisconvertstoseconds ( int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5, int &split1, int &split2, int &split3, int &split4, int &split5);//this too void thisfindsSplits(int &m1, int &m2, int &m3, int &m4, int &m5, int &split1, int &split2, int &split3, int &split4, int &split5, int &split6, int &split7, int &split8, int &split9, int &split10);// this is part of prototype void thisisthesecondconversation (int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S,int &split2S, int &split3S, int &split4S, int &split5S, int &split1, int &split2, int &split3, int &split4, int &split5);//this gets a value void thisfindstheaverage(double &average, int &split1, int &split2, int &split3, int &split4, int &split5);//and this void thisprintsstuff( int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S, int &split2S, int &split3S, int &split4S, int &split5S, double &average); //this prints int main(int argc, char *argv[]) { int m1, m2, m3, m4, m5, s1, s2, s3, s4, s5, split1, split2, split3, split4, split5, split1M, split2M, split3M, split4M, split5M, split1S, split2S, split3S, split4S, split5S; int split6, split7, split8, split9, split10; double average; char thistakescolon; thisgetsElapsedTimes ( m1, m2, m3, m4, m5, s1, s2, s3, s4, s5); thisconvertstoseconds ( m1, m2, m3, m4, m5, s1, s2, s3, s4, s5, split1, split2, split3, split4, split5); thisfindsSplits ( m1, m2, m3, m4, m5, split1, split2, split3, split4, split5, split6, split7, split8, split9, split10); thisisthesecondconversation ( split1M, split2M, split3M, split4M, split5M, split1S, split2S, split3S, split4S, split5S, split1, split2, split3, split4, split5); thisfindstheaverage ( average, split1, split2, split3, split4, split5); thisprintsstuff ( split1M, split2M, split3M, split4M, split5M, split1S, split2S, split3S, split4S, split5S, average); // these are calling statements and they call from the main function to the other functions. system("PAUSE"); return 0; } void thisgetsElapsedTimes(int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5) { char thistakescolon; cout << "Enter the elapsed time:" << endl; cout << " Kilometer 1 "; cin m1 thistakescolon s1; cout << " Kilometer 2 "; cin m2 thistakescolon s2; cout << " Kilometer 3 " ; cin m3 thistakescolon s3; cout << " Kilometer 4 "; cin m4 thistakescolon s4; cout << " Kilometer 5 "; cin m5 thistakescolon s5; // this gets the data required to get the results needed for the user to see // . } void thisconvertstoseconds (int &m1, int &m2, int &m3, int &m4, int &m5, int &s1, int &s2, int &s3, int &s4, int &s5, int &split1, int &split2, int &split3, int &split4, int &split5) { split1 = (m1 * 60) + s1;//this converts for minutes to seconds for m1 split2 = (m2 * 60) + s2;//this converts for minutes to seconds for m2 split3 = (m3 * 60) + s3;//this converts for minutes to seconds for m3 split4 = (m4 * 60) + s4;//this converts for minutes to seconds for m4 split5 = (m5 * 60) + s5;//this converts for minutes to seconds for m5 } void thisfindsSplits (int &m1, int &m2, int &m3, int &m4, int &m5,int &split1, int &split2, int &split3, int &split4, int &split5, int &split6, int &split7, int &split8, int &split9, int &split10)//this is function heading { split6 = split1; //this is split for the first lap. split7 = split2 - split1;//this is split for the second lap. split8 = split3 - split2;//this is split for the third lap. split9 = split4 - split3;//this is split for the fourth lap. split10 = split5 - split4;//this is split for the fifth lap. } void thisfindstheaverage(double &average, int &split1, int &split2, int &split3, int &split4, int &split5) { average = (split1 + split2 + split3 + split4 + split5)/5; // this finds the average from all the splits in seconds } void thisisthesecondconversation (int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S,int &split2S, int &split3S, int &split4S, int &split5S, int &split1, int &split2, int &split3, int &split4, int &split5) { split1M = split1 * 60; //this finds the split times split1S = split1M - split1 * 60; //then this finds split2M = split2 * 60; //and all of this split2S = split2M - split2 * 60; //does basically split3M = split3 * 60; //the same thing split3S = split3M - split3 * 60; //all of it split4M = split4 * 60; //it's also a split4S = split4M - split4 * 60; //function split5M = split5 * 60; //and it finds the splits split5S = split5M - split5 * 60; //for each lap. } void thisprintsstuff (int &split1M, int &split2M, int &split3M, int &split4M, int &split5M, int &split1S, int &split2S, int &split3S, int &split4S, int &split5S, double &average)// this is function heading { printf("\n kilometer 1 %d" , ":02%d",'split1M','split1S'); printf("\n kilometer 2 %d" , ":02%d",'split2M','split2S'); printf("\n kilometer 3 %d" , ":02%d",'split3M','split3S'); printf("\n kilometer 4 %d" , ":02%d",'split4M','split4S'); printf("\n kilometer 5 %d" , ":02%d",'split5M','split5S'); printf("\n your average pace is ",'average',"per kilometer \n", "William Chen\n"); // this printf so the programmer // can allow the user to see // the results from the data gathered. }

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• Problem Implementing Texture on Libgdx Mesh of Randomized Terrain

  - by BrotherJack

  I'm having problems understanding how to apply a texture to a non-rectangular object. The following code creates textures such as this: from the debug renderer I think I've got the physical shape of the "earth" correct. However, I don't know how to apply a texture to it. I have a 50x50 pixel image (in the environment constructor as "dirt.png"), that I want to apply to the hills. I have a vague idea that this seems to involve the mesh class and possibly a ShapeRenderer, but the little i'm finding online is just confusing me. Bellow is code from the class that makes and regulates the terrain and the code in a separate file that is supposed to render it (but crashes on the mesh.render() call). Any pointers would be appreciated. public class Environment extends Actor{ Pixmap sky; public Texture groundTexture; Texture skyTexture; double tankypos; //TODO delete, temp public Tank etank; //TODO delete, temp int destructionRes; // how wide is a static pixel private final float viewWidth; private final float viewHeight; private ChainShape terrain; public Texture dirtTexture; private World world; public Mesh terrainMesh; private static final String LOG = Environment.class.getSimpleName(); // Constructor public Environment(Tank tank, FileHandle sfileHandle, float w, float h, int destructionRes) { world = new World(new Vector2(0, -10), true); this.destructionRes = destructionRes; sky = new Pixmap(sfileHandle); viewWidth = w; viewHeight = h; skyTexture = new Texture(sky); terrain = new ChainShape(); genTerrain((int)w, (int)h, 6); Texture tankSprite = new Texture(Gdx.files.internal("TankSpriteBase.png")); Texture turretSprite = new Texture(Gdx.files.internal("TankSpriteTurret.png")); tank = new Tank(0, true, tankSprite, turretSprite); Rectangle tankrect = new Rectangle(300, (int)tankypos, 44, 45); tank.setRect(tankrect); BodyDef terrainDef = new BodyDef(); terrainDef.type = BodyType.StaticBody; terrainDef.position.set(0, 0); Body terrainBody = world.createBody(terrainDef); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = terrain; terrainBody.createFixture(fixtureDef); BodyDef tankDef = new BodyDef(); Rectangle rect = tank.getRect(); tankDef.type = BodyType.DynamicBody; tankDef.position.set(0,0); tankDef.position.x = rect.x; tankDef.position.y = rect.y; Body tankBody = world.createBody(tankDef); FixtureDef tankFixture = new FixtureDef(); PolygonShape shape = new PolygonShape(); shape.setAsBox(rect.width*WORLD_TO_BOX, rect.height*WORLD_TO_BOX); fixtureDef.shape = shape; dirtTexture = new Texture(Gdx.files.internal("dirt.png")); etank = tank; } private void genTerrain(int w, int h, int hillnessFactor){ int width = w; int height = h; Random rand = new Random(); //min and max bracket the freq's of the sin/cos series //The higher the max the hillier the environment int min = 1; //allocating horizon for screen width Vector2[] horizon = new Vector2[width+2]; horizon[0] = new Vector2(0,0); double[] skyline = new double[width]; //TODO skyline necessary as an array? //ratio of amplitude of screen height to landscape variation double r = (int) 2.0/5.0; //number of terms to be used in sine/cosine series int n = 4; int[] f = new int[n*2]; //calculating omegas for sine series for(int i = 0; i < n*2 ; i ++){ f[i] = rand.nextInt(hillnessFactor - min + 1) + min; } //amp is the amplitude of the series int amp = (int) (r*height); double lastPoint = 0.0; for(int i = 0 ; i < width; i ++){ skyline[i] = 0; for(int j = 0; j < n; j++){ skyline[i] += ( Math.sin( (f[j]*Math.PI*i/height) ) + Math.cos(f[j+n]*Math.PI*i/height) ); } skyline[i] *= amp/(n*2); skyline[i] += (height/2); skyline[i] = (int)skyline[i]; //TODO Possible un-necessary float to int to float conversions tankypos = skyline[i]; horizon[i+1] = new Vector2((float)i, (float)skyline[i]); if(i == width) lastPoint = skyline[i]; } horizon[width+1] = new Vector2(800, (float)lastPoint); terrain.createChain(horizon); terrain.createLoop(horizon); //I have no idea if the following does anything useful :( terrainMesh = new Mesh(true, (width+2)*2, (width+2)*2, new VertexAttribute(Usage.Position, (width+2)*2, "a_position")); float[] vertices = new float[(width+2)*2]; short[] indices = new short[(width+2)*2]; for(int i=0; i < (width+2); i+=2){ vertices[i] = horizon[i].x; vertices[i+1] = horizon[i].y; indices[i] = (short)i; indices[i+1] = (short)(i+1); } terrainMesh.setVertices(vertices); terrainMesh.setIndices(indices); } Here is the code that is (supposed to) render the terrain. @Override public void render(float delta) { Gdx.gl.glClearColor(1, 1, 1, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); // tell the camera to update its matrices. camera.update(); // tell the SpriteBatch to render in the // coordinate system specified by the camera. backgroundStage.draw(); backgroundStage.act(delta); uistage.draw(); uistage.act(delta); batch.begin(); debugRenderer.render(this.ground.getWorld(), camera.combined); batch.end(); //Gdx.graphics.getGL10().glEnable(GL10.GL_TEXTURE_2D); ground.dirtTexture.bind(); ground.terrainMesh.render(GL10.GL_TRIANGLE_FAN); //I'm particularly lost on this ground.step(); }

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• Issues with signal handling [closed]

  - by user34790

  I am trying to actually study the signal handling behavior in multiprocess system. I have a system where there are three signal generating processes generating signals of type SIGUSR1 and SIGUSR1. I have two handler processes that handle a particular type of signal. I have another monitoring process that also receives the signals and then does its work. I have a certain issue. Whenever my signal handling processes generate a signal of a particular type, it is sent to the process group so it is received by the signal handling processes as well as the monitoring processes. Whenever the signal handlers of monitoring and signal handling processes are called, I have printed to indicate the signal handling. I was expecting a uniform series of calls for the signal handlers of the monitoring and handling processes. However, looking at the output I could see like at the beginning the monitoring and signal handling processes's signal handlers are called uniformly. However, after I could see like signal handler processes handlers being called in a burst followed by the signal handler of monitoring process being called in a burst. Here is my code and output #include <iostream> #include <sys/types.h> #include <sys/wait.h> #include <sys/time.h> #include <signal.h> #include <cstdio> #include <stdlib.h> #include <sys/ipc.h> #include <sys/shm.h> #define NUM_SENDER_PROCESSES 3 #define NUM_HANDLER_PROCESSES 4 #define NUM_SIGNAL_REPORT 10 #define MAX_SIGNAL_COUNT 100000 using namespace std; volatile int *usrsig1_handler_count; volatile int *usrsig2_handler_count; volatile int *usrsig1_sender_count; volatile int *usrsig2_sender_count; volatile int *lock_1; volatile int *lock_2; volatile int *lock_3; volatile int *lock_4; volatile int *lock_5; volatile int *lock_6; //Used only by the monitoring process volatile int monitor_count; volatile int usrsig1_monitor_count; volatile int usrsig2_monitor_count; double time_1[NUM_SIGNAL_REPORT]; double time_2[NUM_SIGNAL_REPORT]; //Used only by the main process int total_signal_count; //For shared memory int shmid; const int shareSize = sizeof(int) * (10); double timestamp() { struct timeval tp; gettimeofday(&tp, NULL); return (double)tp.tv_sec + tp.tv_usec / 1000000.; } pid_t senders[NUM_SENDER_PROCESSES]; pid_t handlers[NUM_HANDLER_PROCESSES]; pid_t reporter; void signal_catcher_1(int); void signal_catcher_2(int); void signal_catcher_int(int); void signal_catcher_monitor(int); void signal_catcher_main(int); void terminate_processes() { //Kill the child processes int status; cout << "Time up terminating the child processes" << endl; for(int i=0; i<NUM_SENDER_PROCESSES; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); //Wait for the child processes to finish for(int i=0; i<NUM_SENDER_PROCESSES; i++) { waitpid(senders[i], &status, 0); } for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { waitpid(handlers[i], &status, 0); } waitpid(reporter, &status, 0); } int main(int argc, char *argv[]) { if(argc != 2) { cout << "Required parameters missing. " << endl; cout << "Option 1 = 1 which means run for 30 seconds" << endl; cout << "Option 2 = 2 which means run until 100000 signals" << endl; exit(0); } int option = atoi(argv[1]); pid_t pid; if(option == 2) { if(signal(SIGUSR1, signal_catcher_main) == SIG_ERR) { perror("1"); exit(1); } if(signal(SIGUSR2, signal_catcher_main) == SIG_ERR) { perror("2"); exit(1); } } else { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); exit(1); } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); exit(1); } } if(signal(SIGINT, signal_catcher_int) == SIG_ERR) { perror("3"); exit(1); } /////////////////////////////////////////////////////////////////////////////////////// ////////////////////// Initializing the shared memory ///////////////////////////////// /////////////////////////////////////////////////////////////////////////////////////// cout << "Initializing the shared memory" << endl; if ((shmid=shmget(IPC_PRIVATE,shareSize,IPC_CREAT|0660))< 0) { perror("shmget fail"); exit(1); } usrsig1_handler_count = (int *) shmat(shmid, NULL, 0); usrsig2_handler_count = usrsig1_handler_count + 1; usrsig1_sender_count = usrsig2_handler_count + 1; usrsig2_sender_count = usrsig1_sender_count + 1; lock_1 = usrsig2_sender_count + 1; lock_2 = lock_1 + 1; lock_3 = lock_2 + 1; lock_4 = lock_3 + 1; lock_5 = lock_4 + 1; lock_6 = lock_5 + 1; //Initialize them to be zero *usrsig1_handler_count = 0; *usrsig2_handler_count = 0; *usrsig1_sender_count = 0; *usrsig2_sender_count = 0; *lock_1 = 0; *lock_2 = 0; *lock_3 = 0; *lock_4 = 0; *lock_5 = 0; *lock_6 = 0; cout << "End of initializing the shared memory" << endl; ///////////////////////////////////////////////////////////////////////////////////////////// /////////////////// End of initializing the shared memory /////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////// /////////////////////////////////////////////////////////////////////////////////////////// /////////////////////////////Registering the signal handlers/////////////////////////////// /////////////////////////////////////////////////////////////////////////////////////////// cout << "Registering the signal handlers" << endl; for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { if((pid = fork()) == 0) { if(i%2 == 0) { struct sigaction action; action.sa_handler = signal_catcher_1; sigset_t block_mask; action.sa_flags = 0; sigaction(SIGUSR1,&action,NULL); if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); exit(1); } } else { if(signal(SIGUSR1 ,SIG_IGN) == SIG_ERR) { perror("1"); exit(1); } struct sigaction action; action.sa_handler = signal_catcher_2; action.sa_flags = 0; sigaction(SIGUSR2,&action,NULL); } if(signal(SIGINT, SIG_DFL) == SIG_ERR) { perror("2"); exit(1); } while(true) { pause(); } exit(0); } else { //cout << "Registerd the handler " << pid << endl; handlers[i] = pid; } } cout << "End of registering the signal handlers" << endl; ///////////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////////End of registering the signal handlers ////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////////////////////////////////// ///////////////////////////Registering the monitoring process ////////////////////////////////////// //////////////////////////////////////////////////////////////////////////////////////////////////// cout << "Registering the monitoring process" << endl; if((pid = fork()) == 0) { struct sigaction action; action.sa_handler = signal_catcher_monitor; sigemptyset(&action.sa_mask); sigset_t block_mask; sigemptyset(&block_mask); sigaddset(&block_mask,SIGUSR1); sigaddset(&block_mask,SIGUSR2); action.sa_flags = 0; action.sa_mask = block_mask; sigaction(SIGUSR1,&action,NULL); sigaction(SIGUSR2,&action,NULL); if(signal(SIGINT, SIG_DFL) == SIG_ERR) { perror("2"); exit(1); } while(true) { pause(); } exit(0); } else { cout << "Monitor's pid is " << pid << endl; reporter = pid; } cout << "End of registering the monitoring process" << endl; ///////////////////////////////////////////////////////////////////////////////////////////////////// ////////////////////////End of registering the monitoring process//////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// //Sleep to make sure that the monitor and handler processes are well initialized and ready to handle signals sleep(5); ////////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////////////Registering the signal generators/////////////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// cout << "Registering the signal generators" << endl; for(int i=0; i<NUM_SENDER_PROCESSES; i++) { if((pid = fork()) == 0) { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); exit(1); } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); exit(1); } if(signal(SIGINT, SIG_DFL) == SIG_ERR) { perror("2"); exit(1); } srand(i); while(true) { int signal_id = rand()%2 + 1; if(signal_id == 1) { killpg(getpgid(getpid()), SIGUSR1); while(__sync_lock_test_and_set(lock_4,1) != 0) { } (*usrsig1_sender_count)++; *lock_4 = 0; } else { killpg(getpgid(getpid()), SIGUSR2); while(__sync_lock_test_and_set(lock_5,1) != 0) { } (*usrsig2_sender_count)++; *lock_5=0; } int r = rand()%10 + 1; double s = (double)r/100; sleep(s); } exit(0); } else { //cout << "Registered the sender " << pid << endl; senders[i] = pid; } } //cout << "End of registering the signal generators" << endl; ///////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////////////End of registering the signal generators/////////////////////////////////// ///////////////////////////////////////////////////////////////////////////////////////////////////// //Either sleep for 30 seconds and terminate the program or if the number of signals generated reaches 10000, terminate the program if(option = 1) { sleep(90); terminate_processes(); } else { while(true) { if(total_signal_count >= MAX_SIGNAL_COUNT) { terminate_processes(); } else { sleep(0.001); } } } } void signal_catcher_1(int the_sig) { while(__sync_lock_test_and_set(lock_1,1) != 0) { } (*usrsig1_handler_count) = (*usrsig1_handler_count) + 1; cout << "Signal Handler 1 " << *usrsig1_handler_count << endl; __sync_lock_release(lock_1); } void signal_catcher_2(int the_sig) { while(__sync_lock_test_and_set(lock_2,1) != 0) { } (*usrsig2_handler_count) = (*usrsig2_handler_count) + 1; __sync_lock_release(lock_2); } void signal_catcher_main(int the_sig) { while(__sync_lock_test_and_set(lock_6,1) != 0) { } total_signal_count++; *lock_6 = 0; } void signal_catcher_int(int the_sig) { for(int i=0; i<NUM_SENDER_PROCESSES; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<NUM_HANDLER_PROCESSES; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); exit(3); } void signal_catcher_monitor(int the_sig) { cout << "Monitoring process " << *usrsig1_handler_count << endl; } Here is the initial segment of output Monitoring process 0 Monitoring process 0 Monitoring process 0 Monitoring process 0 Signal Handler 1 1 Monitoring process 2 Signal Handler 1 2 Signal Handler 1 3 Signal Handler 1 4 Monitoring process 4 Monitoring process Signal Handler 1 6 Signal Handler 1 7 Monitoring process 7 Monitoring process 8 Monitoring process 8 Signal Handler 1 9 Monitoring process 9 Monitoring process 9 Monitoring process 10 Signal Handler 1 11 Monitoring process 11 Monitoring process 12 Signal Handler 1 13 Signal Handler 1 14 Signal Handler 1 15 Signal Handler 1 16 Signal Handler 1 17 Signal Handler 1 18 Monitoring process 19 Signal Handler 1 20 Monitoring process 20 Signal Handler 1 21 Monitoring process 21 Monitoring process 21 Monitoring process 22 Monitoring process 22 Monitoring process 23 Signal Handler 1 24 Signal Handler 1 25 Monitoring process 25 Signal Handler 1 27 Signal Handler 1 28 Signal Handler 1 29 Here is the segment when the signal handler processes signal handlers are called in a burst Signal Handler 1 456 Signal Handler 1 457 Signal Handler 1 458 Signal Handler 1 459 Signal Handler 1 460 Signal Handler 1 461 Signal Handler 1 462 Signal Handler 1 463 Signal Handler 1 464 Signal Handler 1 465 Signal Handler 1 466 Signal Handler 1 467 Signal Handler 1 468 Signal Handler 1 469 Signal Handler 1 470 Signal Handler 1 471 Signal Handler 1 472 Signal Handler 1 473 Signal Handler 1 474 Signal Handler 1 475 Signal Handler 1 476 Signal Handler 1 477 Signal Handler 1 478 Signal Handler 1 479 Signal Handler 1 480 Signal Handler 1 481 Signal Handler 1 482 Signal Handler 1 483 Signal Handler 1 484 Signal Handler 1 485 Signal Handler 1 486 Signal Handler 1 487 Signal Handler 1 488 Signal Handler 1 489 Signal Handler 1 490 Signal Handler 1 491 Signal Handler 1 492 Signal Handler 1 493 Signal Handler 1 494 Signal Handler 1 495 Signal Handler 1 496 Signal Handler 1 497 Signal Handler 1 498 Signal Handler 1 499 Signal Handler 1 500 Signal Handler 1 501 Signal Handler 1 502 Signal Handler 1 503 Signal Handler 1 504 Signal Handler 1 505 Signal Handler 1 506 Here is the segment when the monitoring processes signal handlers are called in a burst Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Monitoring process 140 Why isn't it uniform afterwards. Why are they called in a burst?

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• C#/.NET Little Wonders: Interlocked CompareExchange()

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Two posts ago, I discussed the Interlocked Add(), Increment(), and Decrement() methods (here) for adding and subtracting values in a thread-safe, lightweight manner.  Then, last post I talked about the Interlocked Read() and Exchange() methods (here) for safely and efficiently reading and setting 32 or 64 bit values (or references).  This week, we’ll round out the discussion by talking about the Interlocked CompareExchange() method and how it can be put to use to exchange a value if the current value is what you expected it to be. Dirty reads can lead to bad results Many of the uses of Interlocked that we’ve explored so far have centered around either reading, setting, or adding values.  But what happens if you want to do something more complex such as setting a value based on the previous value in some manner? Perhaps you were creating an application that reads a current balance, applies a deposit, and then saves the new modified balance, where of course you’d want that to happen atomically.  If you read the balance, then go to save the new balance and between that time the previous balance has already changed, you’ll have an issue!  Think about it, if we read the current balance as $400, and we are applying a new deposit of $50.75, but meanwhile someone else deposits $200 and sets the total to $600, but then we write a total of $450.75 we’ve lost $200! Now, certainly for int and long values we can use Interlocked.Add() to handles these cases, and it works well for that.  But what if we want to work with doubles, for example?  Let’s say we wanted to add the numbers from 0 to 99,999 in parallel.  We could do this by spawning several parallel tasks to continuously add to a total: 1: double total = 0; 2:  3: Parallel.For(0, 10000, next => 4: { 5: total += next; 6: }); Were this run on one thread using a standard for loop, we’d expect an answer of 4,999,950,000 (the sum of all numbers from 0 to 99,999).  But when we run this in parallel as written above, we’ll likely get something far off.  The result of one of my runs, for example, was 1,281,880,740.  That is way off!  If this were banking software we’d be in big trouble with our clients.  So what happened?  The += operator is not atomic, it will read in the current value, add the result, then store it back into the total.  At any point in all of this another thread could read a “dirty” current total and accidentally “skip” our add.   So, to clean this up, we could use a lock to guarantee concurrency: 1: double total = 0.0; 2: object locker = new object(); 3:  4: Parallel.For(0, count, next => 5: { 6: lock (locker) 7: { 8: total += next; 9: } 10: }); Which will give us the correct result of 4,999,950,000.  One thing to note is that locking can be heavy, especially if the operation being locked over is trivial, or the life of the lock is a high percentage of the work being performed concurrently.  In the case above, the lock consumes pretty much all of the time of each parallel task – and the task being locked on is relatively trivial. Now, let me put in a disclaimer here before we go further: For most uses, lock is more than sufficient for your needs, and is often the simplest solution!    So, if lock is sufficient for most needs, why would we ever consider another solution?  The problem with locking is that it can suspend execution of your thread while it waits for the signal that the lock is free.  Moreover, if the operation being locked over is trivial, the lock can add a very high level of overhead.  This is why things like Interlocked.Increment() perform so well, instead of locking just to perform an increment, we perform the increment with an atomic, lockless method. As with all things performance related, it’s important to profile before jumping to the conclusion that you should optimize everything in your path.  If your profiling shows that locking is causing a high level of waiting in your application, then it’s time to consider lighter alternatives such as Interlocked. CompareExchange() – Exchange existing value if equal some value So let’s look at how we could use CompareExchange() to solve our problem above.  The general syntax of CompareExchange() is: T CompareExchange<T>(ref T location, T newValue, T expectedValue) If the value in location == expectedValue, then newValue is exchanged.  Either way, the value in location (before exchange) is returned. Actually, CompareExchange() is not one method, but a family of overloaded methods that can take int, long, float, double, pointers, or references.  It cannot take other value types (that is, can’t CompareExchange() two DateTime instances directly).  Also keep in mind that the version that takes any reference type (the generic overload) only checks for reference equality, it does not call any overridden Equals(). So how does this help us?  Well, we can grab the current total, and exchange the new value if total hasn’t changed.  This would look like this: 1: // grab the snapshot 2: double current = total; 3:  4: // if the total hasn’t changed since I grabbed the snapshot, then 5: // set it to the new total 6: Interlocked.CompareExchange(ref total, current + next, current); So what the code above says is: if the amount in total (1st arg) is the same as the amount in current (3rd arg), then set total to current + next (2nd arg).  This check and exchange pair is atomic (and thus thread-safe). This works if total is the same as our snapshot in current, but the problem, is what happens if they aren’t the same?  Well, we know that in either case we will get the previous value of total (before the exchange), back as a result.  Thus, we can test this against our snapshot to see if it was the value we expected: 1: // if the value returned is != current, then our snapshot must be out of date 2: // which means we didn't (and shouldn't) apply current + next 3: if (Interlocked.CompareExchange(ref total, current + next, current) != current) 4: { 5: // ooops, total was not equal to our snapshot in current, what should we do??? 6: } So what do we do if we fail?  That’s up to you and the problem you are trying to solve.  It’s possible you would decide to abort the whole transaction, or perhaps do a lightweight spin and try again.  Let’s try that: 1: double current = total; 2:  3: // make first attempt... 4: if (Interlocked.CompareExchange(ref total, current + i, current) != current) 5: { 6: // if we fail, go into a spin wait, spin, and try again until succeed 7: var spinner = new SpinWait(); 8:  9: do 10: { 11: spinner.SpinOnce(); 12: current = total; 13: } 14: while (Interlocked.CompareExchange(ref total, current + i, current) != current); 15: } 16:  This is not trivial code, but it illustrates a possible use of CompareExchange().  What we are doing is first checking to see if we succeed on the first try, and if so great!  If not, we create a SpinWait and then repeat the process of SpinOnce(), grab a fresh snapshot, and repeat until CompareExchnage() succeeds.  You may wonder why not a simple do-while here, and the reason it’s more efficient to only create the SpinWait until we absolutely know we need one, for optimal efficiency. Though not as simple (or maintainable) as a simple lock, this will perform better in many situations.  Comparing an unlocked (and wrong) version, a version using lock, and the Interlocked of the code, we get the following average times for multiple iterations of adding the sum of 100,000 numbers: 1: Unlocked money average time: 2.1 ms 2: Locked money average time: 5.1 ms 3: Interlocked money average time: 3 ms So the Interlocked.CompareExchange(), while heavier to code, came in lighter than the lock, offering a good compromise of safety and performance when we need to reduce contention. CompareExchange() - it’s not just for adding stuff… So that was one simple use of CompareExchange() in the context of adding double values -- which meant we couldn’t have used the simpler Interlocked.Add() -- but it has other uses as well. If you think about it, this really works anytime you want to create something new based on a current value without using a full lock.  For example, you could use it to create a simple lazy instantiation implementation.  In this case, we want to set the lazy instance only if the previous value was null: 1: public static class Lazy<T> where T : class, new() 2: { 3: private static T _instance; 4:  5: public static T Instance 6: { 7: get 8: { 9: // if current is null, we need to create new instance 10: if (_instance == null) 11: { 12: // attempt create, it will only set if previous was null 13: Interlocked.CompareExchange(ref _instance, new T(), (T)null); 14: } 15:  16: return _instance; 17: } 18: } 19: } So, if _instance == null, this will create a new T() and attempt to exchange it with _instance.  If _instance is not null, then it does nothing and we discard the new T() we created. This is a way to create lazy instances of a type where we are more concerned about locking overhead than creating an accidental duplicate which is not used.  In fact, the BCL implementation of Lazy<T> offers a similar thread-safety choice for Publication thread safety, where it will not guarantee only one instance was created, but it will guarantee that all readers get the same instance.  Another possible use would be in concurrent collections.  Let’s say, for example, that you are creating your own brand new super stack that uses a linked list paradigm and is “lock free”.  We could use Interlocked.CompareExchange() to be able to do a lockless Push() which could be more efficient in multi-threaded applications where several threads are pushing and popping on the stack concurrently. Yes, there are already concurrent collections in the BCL (in .NET 4.0 as part of the TPL), but it’s a fun exercise!  So let’s assume we have a node like this: 1: public sealed class Node<T> 2: { 3: // the data for this node 4: public T Data { get; set; } 5:  6: // the link to the next instance 7: internal Node<T> Next { get; set; } 8: } Then, perhaps, our stack’s Push() operation might look something like: 1: public sealed class SuperStack<T> 2: { 3: private volatile T _head; 4:  5: public void Push(T value) 6: { 7: var newNode = new Node<int> { Data = value, Next = _head }; 8:  9: if (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next) 10: { 11: var spinner = new SpinWait(); 12:  13: do 14: { 15: spinner.SpinOnce(); 16: newNode.Next = _head; 17: } 18: while (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next); 19: } 20: } 21:  22: // ... 23: } Notice a similar paradigm here as with adding our doubles before.  What we are doing is creating the new Node with the data to push, and with a Next value being the original node referenced by _head.  This will create our stack behavior (LIFO – Last In, First Out).  Now, we have to set _head to now refer to the newNode, but we must first make sure it hasn’t changed! So we check to see if _head has the same value we saved in our snapshot as newNode.Next, and if so, we set _head to newNode.  This is all done atomically, and the result is _head’s original value, as long as the original value was what we assumed it was with newNode.Next, then we are good and we set it without a lock!  If not, we SpinWait and try again. Once again, this is much lighter than locking in highly parallelized code with lots of contention.  If I compare the method above with a similar class using lock, I get the following results for pushing 100,000 items: 1: Locked SuperStack average time: 6 ms 2: Interlocked SuperStack average time: 4.5 ms So, once again, we can get more efficient than a lock, though there is the cost of added code complexity.  Fortunately for you, most of the concurrent collection you’d ever need are already created for you in the System.Collections.Concurrent (here) namespace – for more information, see my Little Wonders – The Concurent Collections Part 1 (here), Part 2 (here), and Part 3 (here). Summary We’ve seen before how the Interlocked class can be used to safely and efficiently add, increment, decrement, read, and exchange values in a multi-threaded environment.  In addition to these, Interlocked CompareExchange() can be used to perform more complex logic without the need of a lock when lock contention is a concern. The added efficiency, though, comes at the cost of more complex code.  As such, the standard lock is often sufficient for most thread-safety needs.  But if profiling indicates you spend a lot of time waiting for locks, or if you just need a lock for something simple such as an increment, decrement, read, exchange, etc., then consider using the Interlocked class’s methods to reduce wait. Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked,CompareExchange,threading,concurrency

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• Adding Polynomials (Linked Lists)......Bug Help

  - by Brian

  I have written a program that creates nodes that in this class are parts of polynomials and then the two polynomials get added together to become one polynomial (list of nodes). All my code compiles so the only problem I am having is that the nodes are not inserting into the polynomial via the insert method I have in polynomial.java and when running the program it does create nodes and displays them in the 2x^2 format but when it comes to add the polynomials together it displays o as the polynomials, so if anyone can figure out whats wrong and what I can do to fix it it would be much appreciated. Here is the code: import java.util.Scanner; class Polynomial{ public termNode head; public Polynomial() { head = null; } public boolean isEmpty() { return (head == null); } public void display() { if (head == null) System.out.print("0"); else for(termNode cur = head; cur != null; cur = cur.getNext()) { System.out.println(cur); } } public void insert(termNode newNode) { termNode prev = null; termNode cur = head; while (cur!=null && (newNode.compareTo(cur)<0)) { prev = null; cur = cur.getNext(); } if (prev == null) { newNode.setNext(head); head = newNode; } else { newNode.setNext(cur); prev.setNext(newNode); } } public void readPolynomial(Scanner kb) { boolean done = false; double coefficient; int exponent; termNode term; head = null; //UNLINK ANY PREVIOUS POLYNOMIAL System.out.println("Enter 0 and 0 to end."); System.out.print("coefficient: "); coefficient = kb.nextDouble(); System.out.println(coefficient); System.out.print("exponent: "); exponent = kb.nextInt(); System.out.println(exponent); done = (coefficient == 0 && exponent == 0); while(!done) { Polynomial poly = new Polynomial(); term = new termNode(coefficient,exponent); System.out.println(term); poly.insert(term); System.out.println("Enter 0 and 0 to end."); System.out.print("coefficient: "); coefficient = kb.nextDouble(); System.out.println(coefficient); System.out.print("exponent: "); exponent = kb.nextInt(); System.out.println(exponent); done = (coefficient==0 && exponent==0); } } public static Polynomial add(Polynomial p, Polynomial q) { Polynomial r = new Polynomial(); double coefficient; int exponent; termNode first = p.head; termNode second = q.head; termNode sum = r.head; termNode term; while (first != null && second != null) { if (first.getExp() == second.getExp()) { if (first.getCoeff() != 0 && second.getCoeff() != 0); { double addCoeff = first.getCoeff() + second.getCoeff(); term = new termNode(addCoeff,first.getExp()); sum.setNext(term); first.getNext(); second.getNext(); } } else if (first.getExp() < second.getExp()) { sum.setNext(second); term = new termNode(second.getCoeff(),second.getExp()); sum.setNext(term); second.getNext(); } else { sum.setNext(first); term = new termNode(first.getNext()); sum.setNext(term); first.getNext(); } } while (first != null) { sum.setNext(first); } while (second != null) { sum.setNext(second); } return r; } } Here is my Node class: class termNode implements Comparable { private int exp; private double coeff; private termNode next; public termNode(double coefficient, int exponent) { coeff = coefficient; exp = exponent; next = null; } public termNode(termNode inTermNode) { coeff = inTermNode.coeff; exp = inTermNode.exp; } public void setData(double coefficient, int exponent) { coefficient = coeff; exponent = exp; } public double getCoeff() { return coeff; } public int getExp() { return exp; } public void setNext(termNode link) { next = link; } public termNode getNext() { return next; } public String toString() { if (exp == 0) { return(coeff + " "); } else if (exp == 1) { return(coeff + "x"); } else { return(coeff + "x^" + exp); } } public int compareTo(Object other) { if(exp ==((termNode) other).exp) return 0; else if(exp < ((termNode) other).exp) return -1; else return 1; } } And here is my Test class to run the program. import java.util.Scanner; class PolyTest{ public static void main(String [] args) { Scanner kb = new Scanner(System.in); Polynomial r; Polynomial p = new Polynomial(); System.out.println("Enter first polynomial."); p.readPolynomial(kb); Polynomial q = new Polynomial(); System.out.println(); System.out.println("Enter second polynomial."); q.readPolynomial(kb); r = Polynomial.add(p,q); System.out.println(); System.out.print("The sum of "); p.display(); System.out.print(" and "); q.display(); System.out.print(" is "); r.display(); } }

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• Unexpected ArrayIndexOutOfBoundsException in JavaFX application, refering to no array

  - by Eugene

  I have the following code: public void setContent(Importer3D importer) { if (DEBUG) { System.out.println("Initialization of Mesh's arrays"); } coords = importer.getCoords(); texCoords = importer.getTexCoords(); faces = importer.getFaces(); if (DEBUG) { System.out.println("Applying Mesh's arrays"); } mesh = new TriangleMesh(); mesh.getPoints().setAll(coords); mesh.getTexCoords().setAll(texCoords); mesh.getFaces().setAll(faces); if (DEBUG) { System.out.println("Initialization of the material"); } initMaterial(); if (DEBUG) { System.out.println("Setting the MeshView"); } meshView.setMesh(mesh); meshView.setMaterial(material); meshView.setDrawMode(DrawMode.FILL); if (DEBUG) { System.out.println("Adding to 3D scene"); } root3d.getChildren().clear(); root3d.getChildren().add(meshView); if (DEBUG) { System.out.println("3D model is ready!"); } } The Imporeter3D class part: private void load(File file) { stlLoader = new STLLoader(file); } public float[] getCoords() { return stlLoader.getCoords(); } public float[] getTexCoords() { return stlLoader.getTexCoords(); } public int[] getFaces() { return stlLoader.getFaces(); } The STLLoader: public class STLLoader{ public STLLoader(File file) { stlFile = new STLFile(file); loadManager = stlFile.loadManager; pointsArray = new PointsArray(stlFile); texCoordsArray = new TexCoordsArray(); } public float[] getCoords() { return pointsArray.getPoints(); } public float[] getTexCoords() { return texCoordsArray.getTexCoords(); } public int[] getFaces() { return pointsArray.getFaces(); } private STLFile stlFile; private PointsArray pointsArray; private TexCoordsArray texCoordsArray; private FacesArray facesArray; public SimpleBooleanProperty finished = new SimpleBooleanProperty(false); public LoadManager loadManager;} PointsArray file: public class PointsArray { public PointsArray(STLFile stlFile) { this.stlFile = stlFile; initPoints(); } private void initPoints() { ArrayList<Double> pointsList = stlFile.getPoints(); ArrayList<Double> uPointsList = new ArrayList<>(); faces = new int[pointsList.size()*2]; int n = 0; for (Double d : pointsList) { if (uPointsList.indexOf(d) == -1) { uPointsList.add(d); } faces[n] = uPointsList.indexOf(d); faces[++n] = 0; n++; } int i = 0; points = new float[uPointsList.size()]; for (Double d : uPointsList) { points[i] = d.floatValue(); i++; } } public float[] getPoints() { return points; } public int[] getFaces() { return faces; } private float[] points; private int[] faces; private STLFile stlFile; public static boolean DEBUG = true; } And STLFile: ArrayList<Double> coords = new ArrayList<>(); double temp; private void readV(STLParser parser) { for (int n = 0; n < 3; n++) { if(!(parser.ttype==STLParser.TT_WORD && parser.sval.equals("vertex"))) { System.err.println("Format Error:expecting 'vertex' on line " + parser.lineno()); } else { if (parser.getNumber()) { temp = parser.nval; coords.add(temp); if(DEBUG) { System.out.println("Vertex:"); System.out.print("X=" + temp + " "); } if (parser.getNumber()) { temp = parser.nval; coords.add(temp); if(DEBUG) { System.out.print("Y=" + temp + " "); } if (parser.getNumber()) { temp = parser.nval; coords.add(temp); if(DEBUG) { System.out.println("Z=" + temp + " "); } readEOL(parser); } else System.err.println("Format Error: expecting coordinate on line " + parser.lineno()); } else System.err.println("Format Error: expecting coordinate on line " + parser.lineno()); } else System.err.println("Format Error: expecting coordinate on line " + parser.lineno()); } if (n < 2) { try { parser.nextToken(); } catch (IOException e) { System.err.println("IO Error on line " + parser.lineno() + ": " + e.getMessage()); } } } } public ArrayList<Double> getPoints() { return coords; } As a result of all of this code, I expected to get 3d model in MeshView. But the present result is very strange: everything works and in DEBUG mode I get 3d model is ready! from setContent(), and then unexpected ArrayIndexOutOfBoundsException: File readed Initialization of Mesh's arrays Applying Mesh's arrays Initialization of the material Setting the MeshView Adding to 3D scene 3D model is ready! java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 32252 at com.sun.javafx.collections.ObservableFloatArrayImpl.rangeCheck(ObservableFloatArrayImpl.java:276) at com.sun.javafx.collections.ObservableFloatArrayImpl.get(ObservableFloatArrayImpl.java:184) at javafx.scene.shape.TriangleMesh.computeBounds(TriangleMesh.java:262) at javafx.scene.shape.MeshView.impl_computeGeomBounds(MeshView.java:151) at javafx.scene.Node.updateGeomBounds(Node.java:3497) at javafx.scene.Node.getGeomBounds(Node.java:3450) at javafx.scene.Node.getLocalBounds(Node.java:3432) at javafx.scene.Node.updateTxBounds(Node.java:3510) at javafx.scene.Node.getTransformedBounds(Node.java:3350) at javafx.scene.Node.updateBounds(Node.java:516) at javafx.scene.Parent.updateBounds(Parent.java:1668) at javafx.scene.SubScene.updateBounds(SubScene.java:556) at javafx.scene.Parent.updateBounds(Parent.java:1668) at javafx.scene.Parent.updateBounds(Parent.java:1668) at javafx.scene.Parent.updateBounds(Parent.java:1668) at javafx.scene.Parent.updateBounds(Parent.java:1668) at javafx.scene.Parent.updateBounds(Parent.java:1668) at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2309) at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:329) at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:479) at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:459) at com.sun.javafx.tk.quantum.QuantumToolkit$13.run(QuantumToolkit.java:326) at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95) at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39) at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:101) at java.lang.Thread.run(Thread.java:724) Exception in thread "JavaFX Application Thread" java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 32252 at com.sun.javafx.collections.ObservableFloatArrayImpl.rangeCheck(ObservableFloatArrayImpl.java:276) at com.sun.javafx.collections.ObservableFloatArrayImpl.get(ObservableFloatArrayImpl.java:184) The stranger thing is that this stack doesn't stop until I close the program. And moreover it doesn't point to any my array. What is this? And why does it happen?

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• Incorrect output on changing sequence of declarations

  - by max

  Writing C++ code to implement Sutherland-Hodgeman polygon clipping. This order of declaration of these 2 statements gives correct output, reverse does not. int numberOfVertices = 5; Point pointList[] = { {50,50}, {200,300}, {310,110}, {130,90}, {70,40} }; I am passing the polygon vertex set to clippers in order - LEFT, RIGHT, TOP, BOTTOM. The exact error which comes when the declarations are reversed is that the bottom clipper, produces an empty set of vertices so no polygon is displayed after clipping. Correct: Incorrent: Confirmed by outputting the number of vertices produced after each pass: Correct: Incorrect: What is the reason for this error? Code: #include <iostream> #include <GL/glut.h> #define MAXVERTICES 10 #define LEFT 0 #define RIGHT 1 #define TOP 2 #define BOTTOM 3 using namespace std; /* Clipping window */ struct Window { double xmin; double xmax; double ymin; double ymax; }; struct Point { double x; double y; }; /* If I interchange these two lines, the code doesn't work. */ /**************/ int numberOfVertices = 5; Point pointList[] = { {50,50}, {200,300}, {310,110}, {130,90}, {70,40} }; /**************/ const Window w = { 100, 400, 60, 200 }; /* Checks whether a point is inside or outside a window side */ int isInside(Point p, int side) { switch(side) { case LEFT: return p.x >= w.xmin; case RIGHT: return p.x <= w.xmax; case TOP: return p.y <= w.ymax; case BOTTOM: return p.y >= w.ymin; } } /* Calculates intersection of a segment and a window side */ Point intersection(Point p1, Point p2, int side) { Point temp; double slope, intercept; bool infinite; /* Find slope and intercept of segment, taking care of inf slope */ if(p2.x - p1.x != 0) { slope = (p2.y - p1.y) / (p2.x - p1.x); infinite = false; } else { infinite = true; } intercept = p1.y - p1.x * slope; /* Calculate intersections */ switch(side) { case LEFT: temp.x = w.xmin; temp.y = temp.x * slope + intercept; break; case RIGHT: temp.x = w.xmax; temp.y = temp.x * slope + intercept; break; case TOP: temp.y = w.ymax; temp.x = infinite ? p1.x : (temp.y - intercept) / slope; break; case BOTTOM: temp.y = w.ymin; temp.x = infinite ? p1.x : (temp.y - intercept) / slope; break; } return temp; } /* Clips polygon against a side, updating the point list (called once for each side) */ void clipAgainstSide(int sideToClip) { int i, j=0; Point s,p; Point outputList[MAXVERTICES]; /* Main algorithm */ s = pointList[numberOfVertices-1]; for(i=0 ; i<numberOfVertices ; i++) { p = pointList[i]; if(isInside(p, sideToClip)) { /* p inside */ if(!isInside(s, sideToClip)) { /* p inside, s outside */ outputList[j] = intersection(p, s, sideToClip); j++; } outputList[j] = p; j++; } else if(isInside(s, sideToClip)) { /* s inside, p outside */ outputList[j] = intersection(s, p, sideToClip); j++; } s = p; } /* Updating number of points and point list */ numberOfVertices = j; /* ERROR: In last call with BOTTOM argument, numberOfVertices becomes 0 */ /* all earlier 3 calls have correct output */ cout<<numberOfVertices<<endl; for(i=0 ; i<numberOfVertices ; i++) { pointList[i] = outputList[i]; } } void SutherlandHodgemanPolygonClip() { clipAgainstSide(LEFT); clipAgainstSide(RIGHT); clipAgainstSide(TOP); clipAgainstSide(BOTTOM); } void init() { glClearColor(1,1,1,0); glMatrixMode(GL_PROJECTION); gluOrtho2D(0,1000,0,500); } void display() { glClear(GL_COLOR_BUFFER_BIT); /* Displaying ORIGINAL box and polygon */ glColor3f(0,0,1); glBegin(GL_LINE_LOOP); glVertex2i(w.xmin, w.ymin); glVertex2i(w.xmin, w.ymax); glVertex2i(w.xmax, w.ymax); glVertex2i(w.xmax, w.ymin); glEnd(); glColor3f(1,0,0); glBegin(GL_LINE_LOOP); for(int i=0 ; i<numberOfVertices ; i++) { glVertex2i(pointList[i].x, pointList[i].y); } glEnd(); /* Clipping */ SutherlandHodgemanPolygonClip(); /* Displaying CLIPPED box and polygon, 500px right */ glColor3f(0,0,1); glBegin(GL_LINE_LOOP); glVertex2i(w.xmin+500, w.ymin); glVertex2i(w.xmin+500, w.ymax); glVertex2i(w.xmax+500, w.ymax); glVertex2i(w.xmax+500, w.ymin); glEnd(); glColor3f(1,0,0); glBegin(GL_LINE_LOOP); for(int i=0 ; i<numberOfVertices ; i++) { glVertex2i(pointList[i].x+500, pointList[i].y); } glEnd(); glFlush(); } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowSize(1000,500); glutCreateWindow("Sutherland-Hodgeman polygon clipping"); init(); glutDisplayFunc(display); glutMainLoop(); return 0; }

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• Outlook 2007 - slow loading messages, etc

  - by studiohack

  Outlook 2007 is slow to load messages...Why is this, and what can I do to speed it up? Currently have about 850 messages in the Inbox folder, and the preview pane turned off, thus I view messages by double-clicking. This is where it gets slow, when I double click, it brings up a new window with everything but the actual message loaded. Solutions? Thanks! (running Windows 7)

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• Mac OS X: Finder view options?

  - by trolle3000

  Hi there. In OS X 10.6, Finder usually looks something like this: The Finder window looks like that when you double-click on most folders or drives. However, whenever I mount a Truecrypt Volume and double-click that, it looks like this: Is there any way to default to the first view option for all types of folders? I tried view options in Finder, but it didn't seem to work.

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• Problem with hp laser jet 1018

  - by dbf

  Hi! I'm using WinXP SP3 and HP LJ 1018. When I send 80 pages to pring as double side (directly or via FinePrint) only about 10 pages (at one side) are printed, I don't get any pages more and "Continue" button in double-side print dialog is disabled. Is it possible to fix it? Thanks!

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• Outlook 2007 - slow loading messages

  - by studiohack

  Outlook 2007 is slow to load messages...Why is this, and what can I do to speed it up? Currently have about 850 messages in the Inbox folder, and the preview pane turned off, thus I view messages by double-clicking. This is where it gets slow, when I double click, it brings up a new window with everything but the actual message loaded, which then takes several more seconds to appear. Solutions? Thanks! (running Windows 7)

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• Are there any video players for Windows that can play at different speeds?

  - by Nathan Fellman

  When I was an undergrad I used to watch videos of lectures on tape. The library had these cool videos that let you watch at double speed. The voice would be high pitched, but I was able to get through them a lot faster. These days are long gone because everything is digitized. Is there any way to watch videos at double speed, including the audio, on my Windows machine?

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• How can I make Finder always show the Side Bar when mounting a volume?

  - by trolle3000

  In OS X 10.6, Finder usually looks something like this: The Finder window looks like that when you double-click on most folders or drives. However, whenever I mount a Truecrypt Volume and double-click that, it looks like this: Is there any way to default to the first view option for all types of folders? I tried view options in Finder, but it didn't seem to work.

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• Adding default command line options when opening a particular filetype

  - by dbdkmezz

  I'd like to make it so that whenever I open a particular file type (by double clicking it in explorer) it always opens the associated program with particular command line options. So, for example, when double clicking a .tex file I want it to not only open it with emacs (which is easy to set up just by going into "Open With"), but run emacs with the command line option "-fs". What's the easiest way to do this? Thanks

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• MSFT Visio: How to make "documentation" field show in in a UML diagram?

  - by Rosarch

  I'm using Visio to make a UML diagram. When I double click on an object, it gives me a textbox labelled "Documentation". How can I make it so this text is displayed on the object itself in the diagram - so viewers don't have to double click it to see the text?

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• Synergy 1.5 crash (OSX 10.6.8)

  - by Oliver

  THANKS FOR TAKING THE TIME TO READ THIS I recently installed Synergy 1.5 r2278 (for Mac OSX 10.6.8) and was using it fine for most of the day, then it decided to stop working (the only thing I changed systemwise was the screensaver - and then after it started crashing disabled it - to see if it would resolve). When I start Synergy (on the Mac - Client) it says: after about 5 seconds (and successfully connecting to the Server) "synergyc quit unexpectedly" Here is the crash log (w/ binery info removed - too long for post requirements) Process: synergyc [1026] Path: /Applications/Synergy.app/Contents/MacOS/synergyc Identifier: synergy Version: ??? (???) Code Type: X86 (Native) Parent Process: Synergy [1023] Date/Time: 2014-05-28 15:36:17.746 +0930 OS Version: Mac OS X 10.6.8 (10K549) Report Version: 6 Interval Since Last Report: 2144189 sec Crashes Since Last Report: 23 Per-App Interval Since Last Report: 10242 sec Per-App Crashes Since Last Report: 9 Anonymous UUID: 86D5A57C-13D4-470E-AC72-48ACDDDE5EB0 Exception Type: EXC_CRASH (SIGABRT) Exception Codes: 0x0000000000000000, 0x0000000000000000 Crashed Thread: 5 Application Specific Information: abort() called Thread 0: Dispatch queue: com.apple.main-thread 0 libSystem.B.dylib 0x95cf3afa mach_msg_trap + 10 1 libSystem.B.dylib 0x95cf4267 mach_msg + 68 2 com.apple.CoreFoundation 0x95af02df __CFRunLoopRun + 2079 3 com.apple.CoreFoundation 0x95aef3c4 CFRunLoopRunSpecific + 452 4 com.apple.CoreFoundation 0x95aef1f1 CFRunLoopRunInMode + 97 5 com.apple.HIToolbox 0x93654e04 RunCurrentEventLoopInMode + 392 6 com.apple.HIToolbox 0x93654bb9 ReceiveNextEventCommon + 354 7 com.apple.HIToolbox 0x937dd137 ReceiveNextEvent + 83 8 synergyc 0x000356d0 COSXEventQueueBuffer::waitForEvent(double) + 48 9 synergyc 0x00010dd5 CEventQueue::getEvent(CEvent&, double) + 325 10 synergyc 0x00011fb0 CEventQueue::loop() + 272 11 synergyc 0x00044eb6 CClientApp::mainLoop() + 134 12 synergyc 0x0005c509 standardStartupStatic(int, char**) + 41 13 synergyc 0x000448a9 CClientApp::runInner(int, char**, ILogOutputter*, int (*)(int, char**)) + 137 14 synergyc 0x0005c4b0 CAppUtilUnix::run(int, char**) + 64 15 synergyc 0x000427df CApp::run(int, char**) + 63 16 synergyc 0x00006e65 main + 117 17 synergyc 0x00006dd9 start + 53 Thread 1: 0 libSystem.B.dylib 0x95d607da __sigwait + 10 1 libSystem.B.dylib 0x95d607b6 sigwait$UNIX2003 + 71 2 synergyc 0x00009583 CArchMultithreadPosix::threadSignalHandler(void*) + 67 3 libSystem.B.dylib 0x95d21259 _pthread_start + 345 4 libSystem.B.dylib 0x95d210de thread_start + 34 Thread 2: 0 libSystem.B.dylib 0x95d21aa2 __semwait_signal + 10 1 libSystem.B.dylib 0x95d2175e _pthread_cond_wait + 1191 2 libSystem.B.dylib 0x95d212b1 pthread_cond_timedwait$UNIX2003 + 72 3 synergyc 0x00009476 CArchMultithreadPosix::waitCondVar(CArchCondImpl*, CArchMutexImpl*, double) + 150 4 synergyc 0x0002b18f CCondVarBase::wait(double) const + 63 5 synergyc 0x0002ce68 CSocketMultiplexer::serviceThread(void*) + 136 6 synergyc 0x0002d698 TMethodJob<CSocketMultiplexer>::run() + 40 7 synergyc 0x0002b8f4 CThread::threadFunc(void*) + 132 8 synergyc 0x00008f30 CArchMultithreadPosix::doThreadFunc(CArchThreadImpl*) + 80 9 synergyc 0x0000902a CArchMultithreadPosix::threadFunc(void*) + 74 10 libSystem.B.dylib 0x95d21259 _pthread_start + 345 11 libSystem.B.dylib 0x95d210de thread_start + 34 Thread 3: Dispatch queue: com.apple.libdispatch-manager 0 libSystem.B.dylib 0x95d1a382 kevent + 10 1 libSystem.B.dylib 0x95d1aa9c _dispatch_mgr_invoke + 215 2 libSystem.B.dylib 0x95d19f59 _dispatch_queue_invoke + 163 3 libSystem.B.dylib 0x95d19cfe _dispatch_worker_thread2 + 240 4 libSystem.B.dylib 0x95d19781 _pthread_wqthread + 390 5 libSystem.B.dylib 0x95d195c6 start_wqthread + 30 Thread 4: 0 libSystem.B.dylib 0x95d19412 __workq_kernreturn + 10 1 libSystem.B.dylib 0x95d199a8 _pthread_wqthread + 941 2 libSystem.B.dylib 0x95d195c6 start_wqthread + 30 Thread 5 Crashed: 0 libSystem.B.dylib 0x95d610ee __semwait_signal_nocancel + 10 1 libSystem.B.dylib 0x95d60fd2 nanosleep$NOCANCEL$UNIX2003 + 166 2 libSystem.B.dylib 0x95ddbfb2 usleep$NOCANCEL$UNIX2003 + 61 3 libSystem.B.dylib 0x95dfd6f0 abort + 105 4 libSystem.B.dylib 0x95d79b1b _Unwind_Resume + 59 5 synergyc 0x00008fd1 CArchMultithreadPosix::doThreadFunc(CArchThreadImpl*) + 241 6 synergyc 0x0000902a CArchMultithreadPosix::threadFunc(void*) + 74 7 libSystem.B.dylib 0x95d21259 _pthread_start + 345 8 libSystem.B.dylib 0x95d210de thread_start + 34 Thread 5 crashed with X86 Thread State (32-bit): eax: 0x0000003c ebx: 0x95d60f39 ecx: 0xb0288a7c edx: 0x95d610ee edi: 0x00521950 esi: 0xb0288ad8 ebp: 0xb0288ab8 esp: 0xb0288a7c ss: 0x0000001f efl: 0x00000247 eip: 0x95d610ee cs: 0x00000007 ds: 0x0000001f es: 0x0000001f fs: 0x0000001f gs: 0x00000037 cr2: 0x002fe000 Model: MacBook2,1, BootROM MB21.00A5.B07, 2 processors, Intel Core 2 Duo, 2.16 GHz, 2 GB

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• Hashed pattern in bargraphs - MS excel

  - by user1189851

  I am drawing graphs for a paper that supports only black and white graphs. I need to show more than 3 histograms and want to have different patterns on them like hash, dotted, double hashed etc instead of different colors in the legend. I am using MS Excel 2007. I tried but dont find a way except for the option available in design tab that I find when I double click on the chart area( These are shades of grey color and I want patterns like hashing, dots etc). Thanks in advance,

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• MS Chart control with WPF C#

  - by Birgir Hrafn Sigurðsson

  Hello, Ive got a MS Chart control and it works just fine except that I can't figure out how to "format" the Y-Axis. I am adding a lot of double numbers into a Serie but when the double numb are actually whole numbers (20.000000.....) the Y-Axis on my chart shows 20. example: this serie : 12.32 11.00 10.13 would actually show up like this: 12.32 11 10.13 I have tried formatting the data as I insert it into the serie like this: serie.Points.AddXY(date.ToString(),double[i].ToString("##.##")); but that doesn't seem to work. I've tried to search for a place to format it in Chart.Series[0].* and Chart.ChartAreas[0].* but I didn't find it there. Thanks in advance, Regards, Birgir Hrafn

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• jQuery UI sortable('cancel') - this.helper is null

  - by Kerry

  I am trying to disable a sortable element from sorting when it has been double clicked. When I try to disable it, even without a condition, it gives me the error 'this.helper is null'. $('.roundedBox:first', division).sortable({ start: function( event, ui ) { if( true === true ) { $(this).sortable('cancel'); } $(this).parent().data( 'sorting', true ); }, stop: function() { $(this).parent().data( 'sorting', false ); }, items: '.department', update: function() {}, placeholder: 'department-placeholder' }) Any ideas on how I can do this? I don't need it to be this method. Literally anything thing that stops it will work. The problem is, sorting starts on a single click, but I have another action bound to double click. If it's double clicked, I don't want it to drag.

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• not so obvious pointers

  - by mike_hornbeck

  I have a class : class X{ public : void f ( int ) ; int a ; } ; And the task is "Inside the code provide declarations for : pointer to int variable of class X pointer to function void(int) defined inside class X pointer to double variable of class X" Ok so pointer to int a will be just int *x = &a, right ? If there is no double in X can I already create pointer to double inside this class ? And the biggest problem is the second task. How one declares pointer to function ?

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• Finding the distance between 2 points in Android using Cursor and the distanceTo() method

  - by LordSnoutimus

  Hello, I am trying to calculate the distance between the first GPS point stored in a SQLite database and the last GPs point stored. My code so far is this: private double Distance() { SQLiteDatabase db1 = waypoints.getWritableDatabase(); Cursor cursor = db1.query(TABLE_NAME, FROM, null, null, null, null,ORDER_BY); Cursor cursor1 = db1.query(TABLE_NAME, FROM, null, null, null, null,ORDER_BY); Double lat = cursor.getDouble(2); Double lon = cursor.getDouble(1); cursor.moveToFirst(); cursor.moveToLast(); cursor.close(); distance = cursor.distanceTo(cursor1); } I realise I need to return a value but the error I am receiving is for the distanceTo method "The method distanceTo(Cursor) is undefined for the type Cursor" Thanks.

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• Getting DataBinder Item's max value

  - by iTayb

  I'm working at the aspx page, and the following code is inserted in a Repeater control: <%# ((System.Collections.Generic.List<double>)DataBinder.Eval(Container.DataItem, "BookPrices")).Max() %> Brings up the following error: 'System.Collections.Generic.List<double>' does not contain a definition for 'Max' List does have an method of Max(), so I'm possibly messing up my code somehow. What is my problem? BookPrices is a list<double> object, which I'd like to print it's maximum value. P.S. You guys are great! I didn't find answers for many of my questions on the web. You really are life savers. Thank you very much! :)

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• Silverlight with using of DependencyProperty and ControlTemplate

  - by Taras

  Hello everyone, I'm starting to study Silverlight 3 and Visual Studio 2008. I've been trying to create Windows sidebar gadget with button controls that look like circles (I have couple of "roundish" png images). The behavior, I want, is the following: when the mouse hovers over the image it gets larger a bit. When we click on it, then it goes down and up. When we leave the button's image it becomes normal sized again. Cause I'm going to have couple of such controls I decided to implement custom control: like a button but with image and no content text. My problem is that I'm not able to set my custom properties in my template and style. What am I doing wrong? My teamplate control with three additional properties: namespace SilverlightGadgetDocked { public class ActionButton : Button { /// <summary> /// Gets or sets the image source of the button. /// </summary> public String ImageSource { get { return (String)GetValue(ImageSourceProperty); } set { SetValue(ImageSourceProperty, value); } } /// <summary> /// Gets or sets the ratio that is applied to the button's size /// when the mouse control is over the control. /// </summary> public Double ActiveRatio { get { return (Double)GetValue(ActiveRatioProperty); } set { SetValue(ActiveRatioProperty, value); } } /// <summary> /// Gets or sets the offset - the amount of pixels the button /// is shifted when the the mouse control is over the control. /// </summary> public Double ActiveOffset { get { return (Double)GetValue(ActiveOffsetProperty); } set { SetValue(ActiveOffsetProperty, value); } } public static readonly DependencyProperty ImageSourceProperty = DependencyProperty.Register("ImageSource", typeof(String), typeof(ActionButton), new PropertyMetadata(String.Empty)); public static readonly DependencyProperty ActiveRatioProperty = DependencyProperty.Register("ActiveRatio", typeof(Double), typeof(ActionButton), new PropertyMetadata(1.0)); public static readonly DependencyProperty ActiveOffsetProperty = DependencyProperty.Register("ActiveOffset", typeof(Double), typeof(ActionButton), new PropertyMetadata(0)); public ActionButton() { this.DefaultStyleKey = typeof(ActionButton); } } } And XAML with styles: <UserControl x:Class="SilverlightGadgetDocked.Page" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:SilverlightGadgetDocked="clr-namespace:SilverlightGadgetDocked" Width="130" Height="150" SizeChanged="UserControl_SizeChanged" MouseEnter="UserControl_MouseEnter" MouseLeave="UserControl_MouseLeave"> <Canvas> <Canvas.Resources> <Style x:Name="ActionButtonStyle" TargetType="SilverlightGadgetDocked:ActionButton"> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="SilverlightGadgetDocked:ActionButton"> <Grid> <Image Source="{TemplateBinding ImageSource}" Width="{TemplateBinding Width}" Height="{TemplateBinding Height}"/> </Grid> </ControlTemplate> </Setter.Value> </Setter> </Style> <Style x:Key="DockedActionButtonStyle" TargetType="SilverlightGadgetDocked:ActionButton" BasedOn="{StaticResource ActionButtonStyle}"> <Setter Property="Canvas.ZIndex" Value="2"/> <Setter Property="Canvas.Top" Value="10"/> <Setter Property="Width" Value="30"/> <Setter Property="Height" Value="30"/> <Setter Property="ActiveRatio" Value="1.15"/> <Setter Property="ActiveOffset" Value="5"/> </Style> <Style x:Key="InfoActionButtonStyle" TargetType="SilverlightGadgetDocked:ActionButton" BasedOn="{StaticResource DockedActionButtonStyle}"> <Setter Property="ImageSource" Value="images/action_button_info.png"/> </Style> <Style x:Key="ReadActionButtonStyle" TargetType="SilverlightGadgetDocked:ActionButton" BasedOn="{StaticResource DockedActionButtonStyle}"> <Setter Property="ImageSource" Value="images/action_button_read.png"/> </Style> <Style x:Key="WriteActionButtonStyle" TargetType="SilverlightGadgetDocked:ActionButton" BasedOn="{StaticResource DockedActionButtonStyle}"> <Setter Property="ImageSource" Value="images/action_button_write.png"/> </Style> </Canvas.Resources> <StackPanel> <Image Source="images/background_docked.png" Stretch="None"/> <TextBlock Foreground="White" MaxWidth="130" HorizontalAlignment="Right" VerticalAlignment="Top" Padding="0,0,5,0" Text="Name" FontSize="13"/> </StackPanel> <SilverlightGadgetDocked:ActionButton Canvas.Left="15" Style="{StaticResource InfoActionButtonStyle}" MouseLeftButtonDown="imgActionInfo_MouseLeftButtonDown"/> <SilverlightGadgetDocked:ActionButton Canvas.Left="45" Style="{StaticResource ReadActionButtonStyle}" MouseLeftButtonDown="imgActionRead_MouseLeftButtonDown"/> <SilverlightGadgetDocked:ActionButton Canvas.Left="75" Style="{StaticResource WriteAtionButtonStyle}" MouseLeftButtonDown="imgActionWrite_MouseLeftButtonDown"/> </Canvas> </UserControl> And Visual Studio reports that "Invalid attribute value ActiveRatio for property Property" in line 27 <Setter Property="ActiveRatio" Value="1.15"/> VERY BIG THANKS!!!

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• How to pass EventArgument information from view to view model in WPF?

  - by Ashish Ashu

  I have ListView control in my application which is binded to the collection of CustomObject List<CustomObject. The CustomObject has seperate view. This ListView has seperate view model. The collection List _customobject is containted in the ListView ViewModel class. My Query: I want to invoke a view that show properties of custom object, when user double click on any row of ListView. The ListView double click command is binded to the ListViewDoublClick Command in the view model. The CustomObject is in the event argument of listview double click command. To acheive this I have to pass the custom object ( or an unique id property of custom object through which I can retrieve the custom object from the collection) as command parameter. Please suggest me the solution!!

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• MS Chart control with WPF

  - by Birgir Hrafn Sigurðsson

  Ive got a MS Chart control and it works just fine except that I can't figure out how to "format" the Y-Axis. I am adding a lot of double numbers into a Serie but when the double numb are actually whole numbers (20.000000.....) the Y-Axis on my chart shows 20. example: this serie : 12.32 11.00 10.13 would actually show up like this: 12.32 11 10.13 I have tried formatting the data as I insert it into the serie like this: serie.Points.AddXY(date.ToString(),double[i].ToString("##.##")); but that doesn't seem to work. I've tried to search for a place to format it in Chart.Series[0].* and Chart.ChartAreas[0].* but I didn't find it there.

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