Intel MPI Parameter to consider for Performance

Selection of best available communication fabrics

Suggestion 1:

 sock tcp  TCP/IP-enable network fabrics, such as Ethernet and Infiniband* (through IPoIB*)
 shm shm Shared-memory only
 ssm  shm:tcp  Shared-memory + TCP/IP
 rdma dapl  DAPL-capable network fabrics, such as Infiniband*, iWarp*, Dolphon*, and XPMEM* (through DAPK*)
 rdssm shm:dapl  Shared-Memory + DAPL + sockers
 ofa  OFA-capable network fabrics including Infiniband* (through OFED* verbs)
 tmi  TMI-capable network fabrics including Qlogic*, Myrinet* (through Tag Matching Interface)


Suggestion 2:

I_MPI_DAPL_UD Values Description
  • Connectionless feature works for DAPL fabrics only.
  • Works with OFED 1.4.2 and 2.0.24 or higher
  • Provides better scalability
  • Significant reduces memory requirements


Suggestion 3:

 I_MPI_PERHOST Values Remarks
 1  Make round-robin distirbution (Default value)
 all  Maps processes to all logical CPUs on a node
 allcores  Maps processes to all physical CPUs on a node


Suggestion 4:

I_MPI_SHM_BYPASS Values Remarks
 disable Set I_MPI_SHM_BYPASS* to ‘enable’ to turn on RDMA data exchange within single node that may outperform regular shared memory exchange. This is normally happens for large (350kb+) messages.


Suggestion 5:

 recursive doubling algorithm 1
 Rabenseifner’s algorithm 2
 Reduce + Bcast 3
Topology aware Reduce + Bcast algorithm 4  
 Binomial gather + scatter algorithm 5
 Topology Aware Binomial Gather + scatter algorithm 6
 Ring Algorithm 7


Suggesion 6:

I_MPI_WAIT_MODE Values Remarks
 1 Set I_MPI_WAIT_MODE ‘to enable’ to try wait mode of the progress engine. The processes that waits for receiving that waits for receiving messages without polling of the fabrics(d) can save CPU time.

Apply wait mode to oversubscribe jobs



  1. 23 Tips for Performance Tuning with the Intel Library (pdf)

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.