hello.c

/*
 * =====================================================================================
 *       Filename:  hello.c
 *         Author:  Raimon Grau Cuscó (rg), raimonster@gmail.com
 * =====================================================================================
 */

#include <omp.h>
#include <stdlib.h>

int main ()
{
        double start,end, r, sh;
        srand(8);
        //srand(time(0));
        sh=0;
        start = omp_get_wtime();
        printf("Total number of procs: %d\n", omp_get_num_procs());
        printf("Total number of max available threads: %d\n", omp_get_max_threads());
#pragma omp parallel shared(sh)
{
        printf("Hello world! %d\n", omp_get_thread_num());
        sh+=rand();
        printf("%f\n", sh);
}
        end = omp_get_wtime();
        printf("Elapsed time: %f\n", end - start);
        printf("acc rand: %f\n",sh);

        return 0;
}

matmul.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <math.h>
#include <omp.h>

#define MATSIZE 700

#define DEBUG

void init_mat (double M[MATSIZE][MATSIZE], double v)
{
   int i, j;

   #pragma omp for collapse(2)
   for (i=0; i<MATSIZE; i++) {
      for (j=0; j<MATSIZE; j++) {
         M[i][j] = sin((double) i);
      }
   }
}

void matmul (double C[MATSIZE][MATSIZE],
              double A[MATSIZE][MATSIZE], double B[MATSIZE][MATSIZE])
{
   int i, j, k;
   double aux;

   #pragma omp for private(j,k,aux)
   for (i=0; i<MATSIZE; i++) {
      for (j=0; j<MATSIZE; j++) {
         aux = 0;
         for (k=0; k<MATSIZE; k++) {
            aux += A[i][k] *B[k][j];
         }
        C[i][j] += aux;
      }
   }
}

int comp (double A[MATSIZE][MATSIZE], double B[MATSIZE][MATSIZE])
{
   int i, j, count = 0;

   for (i=0; i<MATSIZE; i++) {
      for (j=0; j<MATSIZE; j++) {
         if (abs (A[i][j]- B[i][j]) > 1e-10) count++;
      }
   }
   return count;
}

int main (int argc, char * argv[])
{
   double start, end;
   double A[MATSIZE][MATSIZE];
   double B[MATSIZE][MATSIZE];
   double C[MATSIZE][MATSIZE];

   init_mat (A, 0.1);
   init_mat (B, 0.1);
   init_mat (C, 0.0);

   start = omp_get_wtime();
   matmul (C, A, B);
   end = omp_get_wtime();
   printf ("matmul1 time: %f seconds\n", end-start);

#ifdef DEBUG
   double D[MATSIZE][MATSIZE];
   init_mat (D, 0.0);
   omp_set_num_threads(1);
   matmul (D,A,B);
   printf ("Comparing...\n");
   if (comp (C, D)) printf ("matmul unsuccessful\n");
   else  printf ("matmul ok\n");
#endif

}