image_parts_gather.c
787b716cd37dstudents-2019

image_parts_gather.c
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			#include <stdio.h>
			#include <mpi.h>

			#define image_size 1024

			int main(int argc, char *argv[]) {
			int myrank, mysize;
			int * imgPart;
			int * buf;
			int i;
			int partSize;
			int count;

			MPI_Request request;
			MPI_Status status;
			MPI_Status s;

			MPI_Init(&argc, &argv);
			MPI_Comm_rank(MPI_COMM_WORLD, &myrank);
			MPI_Comm_size(MPI_COMM_WORLD, &mysize);

			imgPart = (int)malloc(image_size/mysize sizeof(int));

			/* Generate image parts */
			for (i=0; i < (image_size/mysize) ; i++){
			imgPart[i] = myrank * 1;
			}
			partSize = image_size/mysize;

			/* Process 0 is the root of the collective, i.e. the receiver of all parts */
			if (myrank == 0) /* Only the root must allocate buf */
			buf = (int)malloc(image_size sizeof(int));

			MPI_Gather(imgPart, partSize, MPI_INT, buf, partSize, MPI_INT, 0, MPI_COMM_WORLD);

			free(imgPart);
			if (myrank==0) free(buf);

			MPI_Finalize();
			}