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 read

This test case, test-parallel-read.c reads the variable SolData from the file created by a 2-processes run of test-nwrite.c. Each rank reads the data it wrote by querying Damsel for the handle container corresponding the tag named SolData. After getting the container with all handles, each rank creates a local container consisting of handles it wrote. There are 10 handles written in test-write.c. Rank 0 creates a local container of handles at index 0-4 and rank 1 does the same for 5-9.

These are the steps used to read in the data -

  1. Create a model - DMSLmodel_create
  2. Open the file for read and attach it to the model - DMSLmodel_attach
  3. Obtains the file-side tag handle for SolData - DMSLselect_tag_by_name
  4. Get a container of the file-side tage handle - DMSLselect_handles_with_values
  5. Create 5 local container handles for the desired read indices - DMSLcontainer_handle_at_position and DMSLcontainer_create_vector
  6. Map handles from the local container to the application-side handles - DMSLmodel_map_handles
  7. Execute read - DMSLmodel_transfer_async and DMSLmodel_wait
  8. Close model and all handles

The code for this use case is in test-parallel-read.c When data is read using test-parallel-read with 2 procs, rank 0 and 1 returns 0, 11, 22, 33, 44 and 1, 12, 23, 34, 45 respectively.

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