Sponsor:

Advanced Scientific Computing Research (ASCR) under the U.S. Department of Energy Office of Science (Office of Science)

Project Team Members:

Northwestern University

The HDF Group

Argonne National Laboratory

North Carolina State University





Northwestern University - EECS Dept.


Damsel API Usecase - parallel write

test-nwrite.c is a illustrative example that writes data values of 10 vertex entities from two ranks in parallel. Each rank defines 5 vertex entities, a tag named SolData, and tags it to the 5 vertex entities. In this example, data values written by rank 0 are {0, 11, 22, 33, 44} and rank 1 {1, 12, 23, 34, 45}, each value corresponding to a vertex entity. The steps used to write data on each rank are as follows.

  1. Initialize Damsel environment - DMSLlib_init
  2. Create a Damsel model - DMSLmodel_create
  3. Create a container with 5 Damsel handles in it - DMSLcontainer_create_vector or DMSLcontainer_create_sequence
  4. Use this container to define 5 vertex entities - DMSLentity_define
  5. Create a tag named SolData of short integer type - DMSLtag_define
  6. Map the tag and the I/O buffer of 5 integers to the container - DMSL_model_map_tag
  7. Create a file using the model created in Step 2 - DMSLmodel_attach
  8. Invent the file-side handle for the container - DMSLmodel_map_handles_inventing_file_handles
  9. Invent the file-side handle for the tag - DMSLmodel_map_single_handle_inventing_file_handle
  10. Execute write - DMSLmodel_transfer_async and DMSLmodel_wait
  11. Close all the handles and model - DMSLmodel_close
  12. Exit Damsel environment - DMSLlib_finalize

The result in the h5 file after both rank 0 and rank 1 execute the above steps looks like

GROUP "/" {

DATASET SolData-200001395 {

DATATYPE H5T_STD_I16LE DATASPACE SIMPLE { ( 5 ) / ( 5 ) } DATA { (0): 0, 11, 22, 33, 44 }

} DATASET SolData-300001395 {

DATATYPE H5T_STD_I16LE DATASPACE SIMPLE { ( 5 ) / ( 5 ) } DATA { (0): 1, 12, 23, 34, 45 }

}

.....

Note that none of the vertex handles, tag handles, or data is shared among the ranks. However, the tag name used by the two ranks is the same.

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Last Updated: $LastChangedDate: 2016-11-06 13:53:06 -0600 (Sun, 06 Nov 2016) $