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/*
* naive parallel matrix multiplication
* A matrix is represented by a nested array.
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#define DIM (2*3*5*7*8) /* dividable by 1 - 8 */
static double **matrix1;
static double **matrix2;
static double **result;
static unsigned int nthreads;
static double **
alloc_matrix(double init)
{
unsigned int i, j;
double **matrix;
matrix = malloc(sizeof(double*) * DIM);
if (matrix == NULL) abort();
for (i = 0; i < DIM; i++) {
matrix[i] = malloc(sizeof(double) * DIM);
if (matrix[i] == NULL) abort();
for (j = 0; j < DIM; j++) matrix[i][j] = init;
}
return matrix;
}
static void *
calc(void *arg)
{
unsigned int start = (unsigned int)arg;
unsigned int i, j, k;
for (i = start; i < start + DIM / nthreads; i++) {
for (j = 0; j < DIM; j++) {
double d = 0.0;
for (k = 0; k < DIM; k++)
d += matrix1[i][k] * matrix2[k][j];
result[i][j] = d;
}
}
return NULL;
}
int
main(int argc, char **argv)
{
unsigned int i, start;
int err;
pthread_t *th;
nthreads = 1;
if (argc == 2)
nthreads = atoi(argv[1]);
th = malloc(sizeof(pthread_t) * nthreads);
if (th == NULL) abort();
matrix1 = alloc_matrix(1.2345678);
matrix2 = alloc_matrix(1.2345678);
result = alloc_matrix(0.0);
for (i = 1; i < nthreads; i++) {
start = i * DIM / nthreads;
err = pthread_create(&th[i], NULL, calc, (void*)start);
if (err != 0) abort();
}
calc((void*)0);
for (i = 1; i < nthreads; i++) {
err = pthread_join(th[i], NULL);
if (err != 0) abort();
}
return 0;
}
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