parallel.c

#include <stdio.h>
#include <unistd.h>
#include <sys/time.h>

#define CPU_NUM (104)
#define LOOP_NUM (100)
#define ARRAY_SIZE (CPU_NUM * LOOP_NUM)

double a[ARRAY_SIZE], b[ARRAY_SIZE], c[ARRAY_SIZE];

double mysecond(void)
{
	struct timeval tp;
	gettimeofday(&tp, NULL);

	return ( (double) tp.tv_sec + (double) tp.tv_usec * 1.e-6 );
}

void func(double a[ARRAY_SIZE], double b[ARRAY_SIZE], double c[ARRAY_SIZE], int index)
{
	for (int i = 0; i < 100000; i++)
	{
		c[index] = a[index];
		a[index] = c[index] * b[index];
		b[index] = c[index] / a[index];
	}
}
int main(void)
{
	for (size_t i = 0; i < ARRAY_SIZE; i++)
	{
		a[i] = 1.0;
		b[i] = 2.0;
	}

	for (int loop = 0; loop < 10; loop++)
	{
		double start = mysecond();
#if 1
		for (int i = 0; i < LOOP_NUM; i++)
		{
		#pragma omp parallel
			for (int j = 0; j < CPU_NUM; j++)
			{
				func(a, b, c, i * CPU_NUM + j);
			}
		}
#else
#pragma omp parallel
		for (int i = 0; i < ARRAY_SIZE; i++)
		{
			func(a, b, c, i);
		}
#endif
		printf("Time consumed is %.6f\n", mysecond() - start);
	}
	return 0;
}