#include <mpi.h>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>

#define TRIALS          20
#define ARRAY_SIZE      10000

int main (int argc, char *argv[])
{
	int myid, numprocs;
	double startwtime, endwtime;
	int namelen;
	int* numbers = new int[ARRAY_SIZE];
	int i, j, max;
	int s, s0, startIndex, endIndex;
	double totalTime;
	MPI_Status stat;

	char processor_name[MPI_MAX_PROCESSOR_NAME];

	MPI_Init(&argc, &argv);
	MPI_Comm_size(MPI_COMM_WORLD, &numprocs);
	MPI_Comm_rank(MPI_COMM_WORLD, &myid);
	MPI_Get_processor_name(processor_name, &namelen);

	fprintf(stderr, "Process %d on $s\n", myid, processor_name);
	fflush(stderr);

	if (myid == 0)
	{
		s = (int) floor(ARRAY_SIZE/numprocs);
		s0 = s + ARRAY_SIZE%numprocs;
		max = 0;

		for (i = 0; i < ARRAY_SIZE; i++)
		{
			numbers[i] = i;
		}
	}

	MPI_Send(&numbers, ARRAY_SIZE, MPI_INT, 0, 1, MPI_COMM_WORLD);
	MPI_Send(&s, ARRAY_SIZE, MPI_INT, 0, 2, MPI_COMM_WORLD);
	MPI_Send(&s0, ARRAY_SIZE, MPI_INT, 0, 3, MPI_COMM_WORLD);
	MPI_Send(&max, ARRAY_SIZE, MPI_INT, 0, 4, MPI_COMM_WORLD);

	startIndex = s0 + (myid - 1)*s;
	endIndex = startIndex + s;

	totalTime = 0;

	for (j = 1; j <= TRIALS; j++)
	{
		if (myid == 0)
		{
			for (i = 0; i < s0; i++)
			{
				if (max < numbers[i])
				{
					max = numbers[i];
				}
			}
		}
		else
		{
			for (i = startIndex; i < endIndex; i++)
			{
				if (max < numbers[i])
				{
					max = numbers[i];
				}
			}
		}

		MPI_Recv(&numbers, ARRAY_SIZE, MPI_INT, i,  1, MPI_COMM_WORLD, &stat);
		MPI_Recv(&s, ARRAY_SIZE, MPI_INT, i, 2, MPI_COMM_WORLD, &stat);
		MPI_Recv(&s0, ARRAY_SIZE, MPI_INT, i, 3, MPI_COMM_WORLD, &stat);
		MPI_Recv(&max, ARRAY_SIZE, MPI_INT, i, 4, MPI_COMM_WORLD, &stat);

		if (myid == 0)
		{
			double runTime;
			endwtime = MPI_Wtime();
			runTime = endwtime - startwtime;

			printf("Trial %d : Execution time (sec) = %f\n", j, runTime);
			printf("Max = %d \n", max);
			totalTime += runTime;
		}
	}

	MPI_Finalize();

	if (myid == 0)
		printf("Average time efor %d trials = %f\n", TRIALS, totalTime/TRIALS);
}