Centre Blaise Pascal » Bench4GPU

/******************************************************************************

* FILE: Pi_Threads

* Pthreads based on Hello from Blaise Barney, LLNL Tutorial

* DESCRIPTION:

*   A Pi by Monte Carlo Pthreads program.  Demonstrates thread creation and

*   termination.

* AUTHOR: Emmanuel Quemener from Blaise Barney

* LAST REVISED: 2013-03-30

******************************************************************************/

#include <pthread.h>

#include <stdio.h>

#include <stdlib.h>

#include <math.h>

#include <stdio.h>

#define NUM_THREADS        1024

#define ITERATIONS 1000000000

#ifdef LONG

#define LENGTH unsigned long

#else

#define LENGTH unsigned int

#endif

struct thread_data

{

  int thread_id;

  unsigned int seed_w;

  unsigned int seed_z;

  LENGTH iterations;

  LENGTH inside;

};

struct thread_data thread_data_array[NUM_THREADS];

// Marsaglia RNG very simple implementation

#define znew  ((z=36969*(z&65535)+(z>>16))<<16)

#define wnew  ((w=18000*(w&65535)+(w>>16))&65535)

#define MWC   (znew+wnew)

#define SHR3  (jsr=(jsr=(jsr=jsr^(jsr<<17))^(jsr>>13))^(jsr<<5))

#define CONG  (jcong=69069*jcong+1234567)

#define KISS  ((MWC^CONG)+SHR3)

#define MWCfp MWC * 2.328306435454494e-10f

#define KISSfp KISS * 2.328306435454494e-10f

LENGTH MainLoopGlobal(LENGTH iterations,unsigned int seed_w,unsigned int seed_z)

{

  unsigned int z=seed_z;

  unsigned int w=seed_w;

  LENGTH total=0;

  for (LENGTH i=0;i<iterations;i++) {

    float x=MWCfp ;

    float y=MWCfp ;

    // Matching test

    LENGTH inside=((x*x+y*y) < 1.0f) ? 1:0;

    total+=inside;

   }

  return(total);

}

void *MainLoopThread(void *threadarg)

{

  int taskid;

  LENGTH iterations,total=0;

  unsigned int z,w;

  struct thread_data *my_data;

  my_data=(struct thread_data *) threadarg;

  taskid = my_data->thread_id;

  iterations = my_data->iterations;

  z = my_data->seed_z;

  w = my_data->seed_w;

  printf("\tThread #%i, with seeds (%u,%u) and %lu !\n",

         taskid,z,w,(unsigned long)iterations);

  for (LENGTH i=0;i<iterations;i++) {

    float x=MWCfp ;

    float y=MWCfp ;

    // Matching test

    LENGTH inside=((x*x+y*y) < 1.0f) ? 1:0;

    total+=inside;

  }

  my_data->inside=total;

  pthread_exit((void*) my_data);

}

int main(int argc, char *argv[])

{

  pthread_t threads[NUM_THREADS];

  pthread_attr_t attr;

  int rc, t;

  unsigned int num_threads;

  LENGTH iterations,inside=0;

  void *status;

  float pi;

  if (argc > 1) {

    iterations=(LENGTH)atol(argv[1]);

    num_threads=atoi(argv[2]);

  }

  else {

    iterations=ITERATIONS;

    num_threads=1;

    printf("\n\tPi : Estimate Pi with Monte Carlo exploration\n\n");

    printf("\t\t#1 : number of iterations (default 1 billion)\n");

    printf("\t\t#2 : number of threads (default 1)\n\n");

  }

  printf("\tNumber of threads defined to %u\n",num_threads);

  printf("\tNumber of iterations defined to %lu\n\n",(unsigned long)iterations);

  /* Initialize and set thread detached attribute */

  pthread_attr_init(&attr);

  pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

  for(t=0;t<num_threads;t++) {

    thread_data_array[t].thread_id = t;

    thread_data_array[t].iterations = iterations/num_threads;

    thread_data_array[t].seed_w = (t+1)<<4;

    thread_data_array[t].seed_z = (1048576*(t+1))>>4;

    thread_data_array[t].inside = 0;

    printf("\tCreating thread %d\n", t);

    rc = pthread_create(&threads[t], &attr, MainLoopThread, (void *) 

                        &thread_data_array[t]);

    if (rc) {

      printf("\tERROR; return code from pthread_create() is %d\n", rc);

      exit(-1);

    }

  }

  /* Free attribute and wait for the other threads */

  pthread_attr_destroy(&attr);

  for(t=0; t<num_threads; t++) {

    rc = pthread_join(threads[t], &status);

    if (rc) {

      printf("\tERROR; return code from pthread_join() is %d\n", rc);

      exit(-1);

    }

    printf("\tMain: completed join with thread %i having a status of %ld\n",

           t,(long)status);

  }

  for(t=0;t<num_threads;t++) {

    printf("\tReturn to main with %i thread, %lu inside\n", 

           t,(unsigned long)thread_data_array[t].inside);

    inside+=thread_data_array[t].inside;

  }

  printf("\tMain: program completed. Exiting.\n\n");

  pi=4.*(float)inside/(float)iterations;

  printf("\tPi=%f with error %f and %lu iterations\n\n",pi,

         fabs(pi-4*atan(1))/pi,(unsigned long)iterations);

  pthread_exit(NULL);

}