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

* OpenMP Example - Matrix-vector multiplication - C/C++ Version

* FILE: omp_matvec.c

* DESCRIPTION:

*   This example multiplies all row i elements of matrix A with vector

*   element b(i) and stores the summed products in vector c(i).  A total is

*   maintained for the entire matrix.  Performed by using the OpenMP loop

*   work-sharing construct.  The update of the shared global total is

*   serialized by using the OpenMP critical directive.

* SOURCE: Blaise Barney  5/99

* LAST REVISED:

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

#include <omp.h>

#include <stdio.h>

#define SIZE 10

main ()

{

float A[SIZE][SIZE], b[SIZE], c[SIZE], total;

int i, j, tid;

/* Initializations */

total = 0.0;

for (i=0; i < SIZE; i++)

  {

  for (j=0; j < SIZE; j++)

    A[i][j] = (j+1) * 1.0;

  b[i] = 1.0 * (i+1);

  c[i] = 0.0;

  }

printf("\nStarting values of matrix A and vector b:\n");

for (i=0; i < SIZE; i++)

  {

  printf("  A[%d]= ",i);

  for (j=0; j < SIZE; j++)

    printf("%.1f ",A[i][j]);

  printf("  b[%d]= %.1f\n",i,b[i]);

  }

printf("\nResults by thread/row:\n");

/* Create a team of threads and scope variables */

#pragma omp parallel shared(A,b,c,total) private(tid,i)

  {

  tid = omp_get_thread_num();

/* Loop work-sharing construct - distribute rows of matrix */

#pragma omp for private(j)

  for (i=0; i < SIZE; i++)

    {

    for (j=0; j < SIZE; j++)

      c[i] += (A[i][j] * b[i]);

    /* Update and display of running total must be serialized */

    #pragma omp critical

      {

      total = total + c[i];

      printf("  thread %d did row %d\t c[%d]=%.2f\t",tid,i,i,c[i]);

      printf("Running total= %.2f\n",total);

      }

    }   /* end of parallel i loop */

  } /* end of parallel construct */

printf("\nMatrix-vector total - sum of all c[] = %.2f\n\n",total);

  return 0;

}