jacobi_serial.c

#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <sys/time.h>
#include <time.h>

int main(int argc, char *argv[])
{

	struct timeval startTime, stopTime;

	int m;
	int n;
	double tol; // = 0.0001;

	long totalTime;

	int i, j, iter;

	m = atoi(argv[1]);
	n = atoi(argv[2]);
	tol = atof(argv[3]);

	double t[m + 2][n + 2], tnew[m + 1][n + 1], diff, difmax;

	int z;
	for (z = 0; z < 11; z++) //10 iterations

	{
		//printf("%d %d %lf\n",m,n, tol);

		gettimeofday(&startTime, NULL);
		// initialise temperature array
		for (i = 0; i <= m + 1; i++)
		{
			for (j = 0; j <= n + 1; j++)
			{
				t[i][j] = 30.0;
			}
		}

		// fix boundary conditions
		for (i = 1; i <= m; i++)
		{
			t[i][0] = 10.0;
			t[i][n + 1] = 140.0;
		}
		for (j = 1; j <= n; j++)
		{
			t[0][j] = 20.0;
			t[m + 1][j] = 100.0;
		}

		// main loop
		iter = 0;
		difmax = 1000000.0;
		while (difmax > tol)
		{
			iter++;

			// update temperature for next iteration
			for (i = 1; i <= m; i++)
			{
				for (j = 1; j <= n; j++)
				{
					tnew[i][j] = (t[i - 1][j] + t[i + 1][j] + t[i][j - 1] + t[i][j + 1]) / 4.0;
				}
			}

			// work out maximum difference between old and new temperatures
			difmax = 0.0;
			for (i = 1; i <= m; i++)
			{
				for (j = 1; j <= n; j++)
				{
					diff = fabs(tnew[i][j] - t[i][j]);
					if (diff > difmax)
					{
						difmax = diff;
					}
					// copy new to old temperatures
					t[i][j] = tnew[i][j];
				}
			}
		}
		gettimeofday(&stopTime, NULL);
		totalTime = (stopTime.tv_sec * 1000000 + stopTime.tv_usec) - (startTime.tv_sec * 1000000 + startTime.tv_usec);

		printf("%ld\n", totalTime);
	}

	/*
// print results
printf("iter = %d  difmax = %9.11lf", iter, difmax);
for (i=0; i <= m+1; i++) {
	printf("\n");
	for (j=0; j <= n+1; j++) {
		printf("%3.5lf ", t[i][j]);
	}
}
printf("\n");
*/
}