I have a similar problem with H5Dread hanging for collective IO. Each MPI
process tries to read in a fraction of the dataset. If the dataset size is a
multiple of the number of processes (each process reads the same amount of
data) all is fine, otherwise the code below hangs in the H5Dread function.
Is it required for collective IO for all processes to read the same amount
of data?
Thanks.
//------------------- BEGINNING OF SOURCE CODE --------------------
MPI_Comm comm = MPI_COMM_WORLD;
MPI_Info info = MPI_INFO_NULL;
int mpi_size, mpi_rank;
MPI_Comm_size(comm, &mpi_size);
MPI_Comm_rank(comm, &mpi_rank);
herr_t status;
hid_t plist_id = H5Pcreate(H5P_FILE_ACCESS);
H5Pset_fapl_mpio(plist_id, comm, info);
hid_t file_id = H5Fopen(filename.c_str(), H5F_ACC_RDWR, plist_id);
CHECK_ERROR(file_id,"Error opening hdf5 file.");
H5Pclose(plist_id);
hid_t dataset_id;
#if H5Dopen_vers == 2
dataset_id = H5Dopen2(file_id, name.c_str(), H5P_DEFAULT);
#else
dataset_id = H5Dopen(file_id, name.c_str());
#endif
CHECK_ERROR(dataset_id,"Error opening dataset in file.");
hid_t space_id = H5Dget_space(dataset_id);
hsize_t dims[2];
H5Sget_simple_extent_dims(space_id, dims, NULL);
hsize_t count[2];
hsize_t offset[2];
hsize_t item_cnt = dims[0]/mpi_size+(dims[0]%mpi_size==0 ? 0 : 1);
hsize_t cnt = (mpi_rank<mpi_size-1 ? item_cnt :
dims[0]-item_cnt*(mpi_size-1));
count[0] = cnt;
count[1] = dims[1];
offset[0] = mpi_rank*item_cnt;
offset[1] = 0;
hid_t memspace_id = H5Screate_simple(2,count,NULL);
H5Sselect_hyperslab(space_id, H5S_SELECT_SET, offset, NULL, count,
NULL);
plist_id = H5Pcreate(H5P_DATASET_XFER);
H5Pset_dxpl_mpio(plist_id, H5FD_MPIO_COLLECTIVE);
status = H5Dread(dataset_id, get_hdf5_type<T>(), memspace_id, space_id,
plist_id, ptr);
//------------------- BEGINNING OF SOURCE CODE --------------------
--
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