+/* Copyright (c) 2019. Jonathan Borne.
+*/
+/* Copyright (c) 2009-2019. The SimGrid Team.
+ * All rights reserved. */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <mpi.h>
+
+#define DIM 2
+#define Q 2
+/* Where DIM is the dimension of the Grid (2D) */
+/* and Q is the number of processes per dimension */
+#define N 3
+/* Local matrices size N*N */
+
+int main(int argc, char **argv){
+ /* Nb of nodes in the grid:
+ initialized by MPI_Comm_size according to commandline -np value */
+ int nbNodes;
+
+ /* Communicators */
+ MPI_Comm gridComm, lineComm;
+ /* Current process ranks */
+ int rank, gridSize, myGridRank, myLineRank, myColRank;
+ /* coords: used to get myLineRank and myColRank
+ initialized by MPI_Cart_coords
+ */
+ int coords[DIM];
+ /* dims: Integer array of size ndims specifying the number
+ of processes in each dimension.
+ if init value is 0 it is reset by MPI_Dims_create.
+ */
+ int dims[DIM];
+ for(int i=0; i<DIM; i++){
+ dims[i] = Q;
+ }
+ /* periods:
+ Logical array of size ndims specifying whether the grid is
+ periodic (true) or not (false) in each dimension. */
+ int periods[DIM];
+ for(int i=0; i<DIM; i++){
+ periods[i] = 1;
+ }
+ /* reorder: do not allows rank reordering when creating the grid comm */
+ int reorder = 0;
+ /* remainDims[]: used to set which dimension is kept in subcommunicators */
+ int remainDim[DIM];
+
+ /* Local Matrix */
+ int *A = (int *)malloc(N * N * sizeof(int));
+
+ /* Init */
+ MPI_Init(&argc, &argv);
+ MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+ MPI_Comm_size(MPI_COMM_WORLD, &nbNodes);
+
+ printf("rank %d: Alive \n", rank);
+
+ MPI_Barrier(MPI_COMM_WORLD);
+
+ /* Set dims[] values to descibe a grid of nbNodes and DIM dimensions*/
+ MPI_Cart_create(MPI_COMM_WORLD, DIM, dims, periods, reorder,
+ &gridComm);
+
+ if(gridComm == MPI_COMM_NULL) printf("error grid NULLCOMM \n");
+
+ MPI_Comm_rank(gridComm, &myGridRank);
+ MPI_Comm_size(gridComm, &gridSize);
+ MPI_Cart_coords(gridComm, myGridRank, DIM, coords);
+ myLineRank = coords[0];
+ myColRank = coords[1];
+
+ MPI_Barrier(MPI_COMM_WORLD);
+
+ /* Create a line communicator for current process */
+ remainDim[0] = 0;
+ remainDim[1] = 1;
+ MPI_Cart_sub(gridComm, remainDim , &lineComm);
+
+ /* Check if lineComm was initialized */
+ if(lineComm == MPI_COMM_NULL) printf("(%d,%d): ERR (lineComm == NULLCOMM)\n",
+ myLineRank, myColRank);
+
+ /* A Initialization */
+ for(int i=0; i<N; i++){
+ for(int j=0; j<N; j++){
+ *(A + (i*N) + j) = i==j?rank:0;
+ }
+ }
+
+ MPI_Barrier(MPI_COMM_WORLD);
+
+ /* Broadcast */
+ int root = 0;
+ MPI_Bcast(A, N*N, MPI_INT, root, lineComm);
+
+ /* Print A */
+ printf("process:(%d,%d) \n", myLineRank,
+ myColRank);
+
+ printf("-------------------\n");
+ for(int i=0; i<N; i++){
+ for(int j=0; j<N; j++){
+ printf("%d ", *(A + (i*N) + j));
+ }
+ printf("\n");
+ }
+ printf("-------------------\n");
+ free(A);
+ MPI_Barrier (MPI_COMM_WORLD);
+ MPI_Finalize();
+ return 0;
+}