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

#define buffsize 650

int main(int argc, char* argv[])
{
	int taskid, ntasks;
	int *buff;
	double inittime, totaltime;

	MPI_Init(&argc, &argv);

	MPI_Comm_rank(MPI_COMM_WORLD, &taskid);
	MPI_Comm_size(MPI_COMM_WORLD, &ntasks);

	buff = (int *)malloc(sizeof(int)*buffsize);
	for (int i=0; i<buffsize; i++)
		buff[i] = i;

	printf("Task %d has started, ntasks = %d\n", taskid, ntasks);
	fflush(stdout);
	
	inittime = MPI_Wtime();

	if(taskid == 0) {
		buff[0] = 0;
		buff[1] = -1;
		printf("Task %d has started sending message, ntasks = %d\n", taskid, ntasks);
		fflush(stdout);
		MPI_Send(buff, buffsize, MPI_INT, 1, 0, MPI_COMM_WORLD);
	}

	MPI_Recv(buff, buffsize, MPI_INT, taskid, 0, MPI_COMM_WORLD, NULL);
	printf("Task %d has recieved the message, ntasks = %d\n", taskid, ntasks);
	fflush(stdout);

	if (taskid != 0) {
		for (int j = 0; j < buffsize; j++) {
			if(buff[j] == -1) {
				buff[j] = taskid;
				buff[j + 1] = -1;
				break;
			}
		}

		if (taskid != ntasks - 1) {
			MPI_Send(buff, buffsize, MPI_INT, 0, 0, MPI_COMM_WORLD);
		} else {
			MPI_Send(buff, buffsize, MPI_INT, taskid + 1, 0, MPI_COMM_WORLD);
		}
	}

	totaltime = MPI_Wtime() - inittime;
	
	if (taskid == 0) {
		printf("Cas prenosa: %f s, buffsize: %ld\n", totaltime, sizeof(int)*buffsize);
		for(int i = 0; i < buffsize; i++) {
			if(buff[i] == -1) {
				break;
			}
			printf("%d ", buff[i]);
		}
	}

	free(buff);
	MPI_Finalize();
	return 0;
}