This web site is no longer maintained (but will remain online).
Please see The HDF Group's new Support Portal for the latest information.

HOME > HDF5 > TUTOR

Creating / Accessing a Dataset with PHDF5

The programming model for accessing a dataset with Parallel HDF5 is:

Create or open a Parallel HDF5 file with a collective call to:

Obtain a copy of the file transfer property list and set it to use collective or independent I/O.
Do this by first passing a data transfer property list class type to:

H5Pcreate (C) / h5pcreate_f (F90)

Then set the data transfer mode to either use independent I/O access or to use collective I/O, with a call to:

H5Pset_dxpl_mpio (C) / h5pset_dxpl_mpio_f (F90)

Following are the parameters required by this call:

C:
    herr_t H5Pset_dxpl_mpio (hid_t dxpl_id, H5FD_mpio_xfer_t  xfer_mode )
         dxpl_id    IN: Data transfer property list identifier
         xfer_mode  IN: Transfer mode:
                        H5FD_MPIO_INDEPENDENT - use independent I/O access
                                                (default)
                        H5FD_MPIO_COLLECTIVE  - use collective I/O access

F90:
   h5pset_dxpl_mpi_f (prp_id, data_xfer_mode, hdferr)
         prp_id         IN: Property List Identifer (INTEGER (HID_T))
         data_xfer_mode IN: Data transfer mode  (INTEGER)
                              H5FD_MPIO_INDEPENDENT_F (0)
                              H5FD_MPIO_COLLECTIVE_F (1)
         hdferr         IN: Error code  (INTEGER)

Access the dataset with the defined transfer property list.
All processes that have opened a dataset may do collective I/O. Each process may do an independent and arbitrary number of data I/O access calls, using:
If a dataset is unlimited, you can extend it with a collective call to:

The following code demonstrates a collective write using Parallel HDF5:

C:
    95      /*
    96       * Create property list for collective dataset write.
    97       */
    98      plist_id = H5Pcreate (H5P_DATASET_XFER);
    99      H5Pset_dxpl_mpio (plist_id, H5FD_MPIO_COLLECTIVE);
   100
   101      status = H5Dwrite (dset_id, H5T_NATIVE_INT, memspace, filespace,
   102                plist_id, data);

F90:
   108       ! Create property list for collective dataset write
   109       !
   110       CALL h5pcreate_f (H5P_DATASET_XFER_F, plist_id, error)
   111       CALL h5pset_dxpl_mpio_f (plist_id, H5FD_MPIO_COLLECTIVE_F, error)
   112
   113       !
   114       ! Write the dataset collectively.
   115       !
   116       CALL h5dwrite_f (dset_id, H5T_NATIVE_INTEGER, data, dimsfi, error, &
   117          file_space_id = filespace, mem_space_id = memspace, xfer_prp = plist_id)

The following example programs create a dataset in an HDF5 file using Parallel HDF5:

C Example

Dataset.c

FORTRAN90 Example

dataset.f90

- - Last modified: 21 December 2016