//============================================================================
// Name        : parallel_pi_calc.c
// Author      : Morteza Zakeri
// Version     : 1.0.0
// Copyright   : All right received.
// Description : SERIAL PI CACULATION in C, Ansi-style
//============================================================================

#include <mpi.h>

#include <stdio.h>
#include <stdlib.h> // include rand function

#define sqr(x)	((x)*(x))

double cal_pi(int darts)
{
	double x_coord, /* x coordinate, between -1 and 1  */
	y_coord, 	/* y coordinate, between -1 and 1  */
	pi, 		/* value of pi  */
	r; 		/* random number scaled between 0 and 1  */

	int score, /* number of darts that hit circle */
	n;

	score = 0;

	for (n = 1; n <= darts; n++)
	{
		/* generate random numbers for x and y coordinates */
		r = (double) rand() / (double) RAND_MAX;
		x_coord = (2.0 * r) - 1.0;

		r = (double) rand() / (double) RAND_MAX;
		y_coord = (2.0 * r) - 1.0;

		/* if dart lands in circle, increment score */
		if ((sqr(x_coord) + sqr(y_coord)) <= 1.0)
			score++;
	}

	/* calculate pi */
	pi = 4.0 * (double) score / (double) darts;
	return (pi);
}



#define DARTS 100000     /* number of throws at dartboard */
#define ROUNDS 100      /* number of times "darts" is iterated */
#define MASTER 0        /* master process ID  */

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

	double home_pi, /* value of pi calculated by current task */
	pi, /* average of pi after "darts" is thrown */
	avepi, /* average pi value for all iterations */
	pirecv, /* pi received from worker */
	pisum; /* sum of workers pi values */

	int taskid, /* process ID or task ID */
	numtasks, /* number of process */
	source, /* source of incoming message */
	mtype, /* message type */
	rc, /* return code */
	i, n;

	MPI_Status status;

	/* Obtain number of tasks and task ID */
	MPI_Init(&argc, &argv);
	MPI_Comm_size(MPI_COMM_WORLD, &numtasks);
	MPI_Comm_rank(MPI_COMM_WORLD, &taskid);
	
	printf("MPI task %d has started \n", taskid);

	/* Set seed for random number generator equal to task ID */
	srandom(taskid);

	avepi = 0;
	for (i = 0; i < ROUNDS; i++)
	{
		/* All proccess calculate pi using dartboard algorithm */
		home_pi = cal_pi(DARTS);

		/* Workers send homepi to master */
		/* - Message type will be set to the iteration count */
		if (taskid != MASTER)
		{
			//do in slaves
			mtype = i;
			rc = MPI_Send(&home_pi, 1, MPI_DOUBLE, MASTER, mtype,MPI_COMM_WORLD);
			
			if (rc != MPI_SUCCESS)
			{
				printf("%d: Send failure on round %d\n", taskid, mtype);
			}
		}
		else
		{
			//do in master
			mtype = i;
			pisum = 0;
			for (n = 1; n < numtasks; n++)
			{
				rc = MPI_Recv(&pirecv, 1, MPI_DOUBLE, MPI_ANY_SOURCE, mtype,MPI_COMM_WORLD, &status);
				
				if (rc != MPI_SUCCESS)
					printf("%d: Receive failure on round %d\n", taskid, mtype);
				
				/* keep running total of pi */
				pisum = pisum + pirecv;
			}

			/* Master calculates the average value of pi for this iteration */
			pi = (pisum + home_pi) / numtasks;
			/* Master calculates the average value of pi over all iterations */
			avepi = ((avepi * i) + pi) / (i + 1);
			printf("   After %4d rounds, average value of PI is: %10.8f\n", ((i + 1)), avepi);
		}
	}

	if (taskid == MASTER)
		printf("Real value of PI: 3.1415926535897 \n");

	MPI_Finalize();
	return 0;

}