Specify MPI Options

The MPIOptions section provides a set of options that control MPI communication behavior in ways that are likely to affect message-passing performance. It contains two templates with predefined option settings. These templates are shown in Example 3-5 and are discussed below.

General-Purpose, Multiuser Template - The first template in the MPIOptions section is designed for general-purpose use at times when multiple message-passing jobs will be running concurrently.

Performance Template - The second template is designed to maximize the performance of message-passing jobs when only one job is allowed to run at a time.

The first line of each template contains the phrase "Queue=xxxx." This is because the queue-based LSF workload manager runtime environment also uses this hpc.conf file.

The options in the general-purpose template are the same as the default settings for the Sun MPI library. In other words, you do not have to uncomment the general-purpose template to have its option values be in effect. This template is provided in the MPIOptions section so you can see what options are most beneficial when operating in a multiuser mode.

Example 3-5 MPIOptions Section Example

# Following is an example of the options that affect the runtime
# environment of the MPI library. The listings below are identical
# to the default settings of the library. The "queue=hpc" phrase
# makes it an LSF-specific entry, and only for the queue named hpc.
# These options are a good choice for a multiuser queue. To be
# recognized by CRE, the "Queue=hpc" needs to be removed.
#
# Begin MPIOptions queue=hpc
# coscheduling  avail
# pbind         avail
# spindtimeout   1000
# progressadjust   on
# spin            off
#
# shm_numpostbox       16
# shm_shortmsgsize    256
# rsm_numpostbox       15
# rsm_shortmsgsize    401
# rsm_maxstripe         2
# End MPIOptions

# The listing below is a good choice when trying to get maximum
# performance out of MPI jobs that are running in a queue that
# allows only one job to run at a time.
#
# Begin MPIOptions Queue=performance
# coscheduling             off
# spin                      on
# End MPIOptions

If you want to use the performance template, do the following:

• Delete the "Queue=performance" phrase from the Begin MPIOptions line.

• Delete the comment character (#) from the beginning of each line of the performance template, including the Begin MPIOptions and End MPIOptions lines.

The resulting template should appear as follows:

Begin MPIOptions
coscheduling			off
spin			on
End MPIOptions