MPI Library

The following are run-time configurable options for MPI programs which can be modified by environment variables:

Match list size

There are a finite number of match list entries that can be used. This number currently is directly related to the number of outstanding receives that can be posted, and the number of outstanding long protocol sends that can be posted. Default is 500.

setenv MPI_MATCH_LIST_SIZE 5000

Heap size

This option can be used to configure the size of the space allocated for receving unexpected messages. It is unrelated to the -heap argument to yod. Default is 500k.

setenv MPI_HEAP_SIZE 204800

Short protocol message size

This option can be used to configure the size of a short message in the two-level protocol. Default is 4k.

setenv MPI_SHORT_MSG_SIZE 10240

Collective work array size

This option can be used to increase the size of the work array used in collective operations, which may avoid allocating more memory as the program executes. Default is 10k.

setenv MPI_COLL_WORK_SIZE 102400

Collective operations

This option can be used to have the application use MPI point-to-point communications as the basis for all MPI collective operations instead of using Puma collective communications.

setenv MPI_DEFAULT_COLL_OPS

Context Ids

By default, context ids are not reused after they are freed. Should your application cycle through 8192 context ids, it will fail with a descriptive error message suggesting you set the environment variable, MPI_REUSE_CONTEXT_IDS. With this environment variable set, there will be a hopefully slight performance penalty, but the mpi library will search for freed context ids to reuse. (Available with TFLOPS OS R4.4.0 and beyond)

setenv MPI_REUSE_CONTEXT_IDS

MPI Debug Library

The following are run-time configurable options for MPI programs linked with the MPI Debug library (libmpi_dbg.a) which can be modified by environment variables:

Receive debugging information

This option will turn on receive debugging information. This is low-level information about how the MPICH Puma device is handling receipt of messages.

setenv MPI_DEBUG_RECV

Send debugging information

This option will turn on send debugging information. This is low-level information about how the MPICH Puma device is handling sending of messages.

setenv MPI_DEBUG_SEND

Debug configurable information

This option will cause the MPI application to print out information about which portals it is using and what its configuration values are.

setenv MPI_DEBUG_INFO

If you have any questions, email janus-help@sandia.gov

Updated: August 14, 2003
For information and feedback about these pages, please contact:
Robert K. Thomas -- rkthoma@sandia.gov