gistfile1.h

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#define ENTROPY 1000

void usage(const char* name)
{	printf("Usage:\n");
	printf("%s [xxxx] [-vh]\n", name);
	printf("xxxx\tuse xxxx random numbers to calculate pi, default 1000\n");
	printf("-v\tshow progress\n");
	printf("-h\tshow this message\n");
	exit(1);
}

int main(int argc, char* argv[])
{	srand(time(0));
	long entropy = ENTROPY;
	char verbose = 0;
	
	while (argc-- > 1)
	{	if (!strcmp(argv[argc], "-v"))
			verbose = 1;
		else if (!strcmp(argv[argc], "-h"))
			usage(argv[0]);
		else
			entropy = atoi(argv[argc]);		
	}
		
	long hit = 0, total = 0;
	if (verbose)
		printf("Gathering entropy, please wait...\n");
	for (; total != entropy - 1; total++)
	{	long double x = (1.00 * rand()) / (RAND_MAX);
		long double y = (1.00 * rand()) / (RAND_MAX);
		if ((x*x) + (y*y) <= 1) hit++;
		if (verbose)
			printf("\r%.3f%% %ld (%ld) / %ld",((1.00 * total) / entropy) * (100.00), total,hit, entropy);
	}
	long double pi = ((1.00 * hit) / (1.00 * total + 1)) * 4;
	if (verbose)
		printf("\napprox. value of pi: %.50Lf\n",pi);
	else
		printf("%.50Lf\n",pi);
	return 0;
}