Hi, I am a beginner and just try to use remote memory access, and I wrote a simple program to test it: #include "mpi.h" #include <stdio.h> #define SIZE 8 int main(int argc, char *argv[]) { int numtasks, rank, source=0, dest, tag=1, i; float a[64] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, 12.0, 13.0, 14.0, 15.0, 16.0, }; float b[SIZE]; MPI_Status stat; MPI_Init(&argc,&argv); MPI_Comm_rank(MPI_COMM_WORLD, &rank); MPI_Comm_size(MPI_COMM_WORLD, &numtasks); MPI_Win win; // check processor rank char processor_name[MPI_MAX_PROCESSOR_NAME]; int name_len; MPI_Get_processor_name(processor_name, &name_len); printf("-- processor %s, rank %d out of %d processors\n", processor_name, rank, numtasks); MPI_Barrier(MPI_COMM_WORLD); if (numtasks == 4) { if (rank == 0) { printf("create window \n"); MPI_Win_create(a, 8*sizeof(float), sizeof(float), MPI_INFO_NULL, MPI_COMM_WORLD, &win); } else { MPI_Win_create(MPI_BOTTOM, 0, sizeof(float), MPI_INFO_NULL, MPI_COMM_WORLD, &win); } MPI_Win_fence(0, win); if (rank == 1){ MPI_Get(b, SIZE, MPI_FLOAT, 0, 8, SIZE, MPI_FLOAT, win); MPI_Win_fence(0, win); } printf("rank= %d b= %3.1f %3.1f %3.1f %3.1f %3.1f %3.1f %3.1f %3.1f\n", rank,b[0],b[1],b[2],b[3],b[4],b[5],b[6],b[7]); } else printf("Must specify %d processors. Terminating.\n",SIZE); MPI_Win_free(&win); MPI_Finalize(); } However the terminal gives some odd results: rank= 0 b= 0.0 0.0 0.0 0.0 0.0 0.0 -71847793475452928.0 0.0 rank= 2 b= 0.0 0.0 0.0 0.0 0.0 0.0 222086852849451401216.0 0.0 rank= 3 b= 0.0 0.0 0.0 0.0 0.0 0.0 -74882.4 0.0 rank= 1 b= 9.0 10.0 11.0 12.0 13.0 14.0 15.0 16.0 the rank 1 is correct results, but others should be all zero. terminal also give some comments: "Assertion failed in file src/mpid/ch3/src/ch3u_rma_sync.c at line 5061: win_ptr->my_counter >= 0 internal ABORT - process 0" another question is if I use remote memory access. all process which does not create window for share must add additional line: MPI_Win_create(MPI_BOTTOM, 0, data_type, MPI_INFO_NULL, MPI_COMM_WORLD, &win); correct? Thanks a lot! -- Best Regards, Sufeng Niu ECASP lab, ECE department, Illinois Institute of Technology Tel: 312-731-7219