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multiproc/A1/omp_hello.c
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omp_hello.c
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/******************************************************************************
* FILE: omp_hello.c
* DESCRIPTION:
* OpenMP Example - Hello World - C/C++ Version
* In this simple example, the master thread forks a parallel region.
* All threads in the team obtain their unique thread number and
* a random number and print them. Only the master thread prints the
* total number of threads. Two OpenMP library routines are used to
* obtain the number of threads and each thread's number. set_clock
* and elapsed_time functions are used to measure the time. The three
* *_rand functions are used to manage the random number generator.
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include "utility.h"
#define NTHREADS 8
void hello_world(int nthreads){
int tid;
/* Fork a team of threads giving them their own copies of variables */
#pragma omp parallel private(nthreads, tid)
{
rand_gen gen = init_rand();
double rand_number = next_rand(gen);
/* Obtain thread number */
tid = omp_get_thread_num();
printf("Hello World from thread = %d, this is my random number: %f\n", tid, rand_number);
/* Only master thread does this */
if (tid == 0) {
printf("Master thread: Number of threads = %d\n", nthreads);
}
free_rand(gen);
} /* All threads join master thread and disband */
}
int main (int argc, char *argv[]) {
int nthreads = NTHREADS;
omp_set_num_threads(nthreads);
set_clock();
hello_world(nthreads);
printf("- Using %d threads: Hello World took %.4gs.\n", nthreads, elapsed_time());
return 0;
}
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