/*
 * C program to compute the value of pi using Monte Carlo
 *
 * command-line arguments:  number_of_samples, seed
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>   /* has M_PI, fabs() */
#include "timer.h"  /* has get_time() */

/* main program */

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

    int num_samples;
    int seed;
    double start_time, end_time;
    int count = 0;
    double x, y;
    int i;
    double pi;

    /* process command-line arguments */
    if (argc != 3)  {
        fprintf(stderr, "usage:  %s number_of_samples seed\n", argv[0]);
        exit(EXIT_FAILURE);
    }
    num_samples = atoi(argv[1]);
    seed = atoi(argv[2]);
    if ((num_samples <= 0) || (seed <= 0)) {
        fprintf(stderr, "usage:  %s number_of_samples seed\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    /* record start time */
    start_time = get_time();

    /* do calculation */ 
    srandom((unsigned int) seed);
    for (i = 0; i < num_samples; ++i) {
        x = (double) random() / (double) (RAND_MAX);
        y = (double) random() / (double) (RAND_MAX);
        if ((x*x + y*y) <= 1.0)
            ++count;
    }
    pi = 4.0 * (double) count / (double) num_samples;

    /* record end time and print results */
    end_time = get_time();
    printf("sequential C program results:\n");
    printf("number of samples = %d, seed = %d\n", num_samples, seed);
    printf("estimated pi = %12.10f\n", pi);
    printf("difference between estimated pi and math.h M_PI = %12.10f\n", 
            fabs(pi - M_PI));
    printf("time to compute = %g seconds\n", end_time - start_time);

    /* clean up and return */
    return EXIT_SUCCESS;
}