Finding corresponding configurations from Intel MPI to open-mpi

[amroakmal]

Background information

What version of Open MPI are you using? (e.g., v4.1.6, v5.0.1, git branch name and hash, etc.)

v4.1.6

• Operating system/version: Linux

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Details of the problem

We are having a system that runs Intel MPI where use some environment variables/configs with it, and we would like to get the corresponding configurations in open-mpi. We tried looking into the open-mpi docs to find them, but we couldn't find that.

1. I_MPI_WAIT_MODE=1

Description: Control the Intel® MPI Library optimization for oversubscription mode.
Setting it to the value=1 for our program, we get:

Optimize MPI application to work in the oversubscription mode (multiple ranks on 1 CPU).

2. I_MPI_THREAD_YIELD=2

Description: Control the Intel® MPI Library thread yield customization during MPI busy wait time.
Do the shied_yield() system call for thread yield during the busy wait.

By looking more into the shied_yield() system call, the closest match I can found was the sched_yield(), from man pages:

sched_yield() causes the calling thread to relinquish the CPU.
       The thread is moved to the end of the queue for its static
       priority and a new thread gets to run.

Last question, do you recommend upgrading to more recent stable version?

Thank you so much.

[amroakmal]

@jsquyres : Any help on this issue, please?
Really appreciate your precious time

[bosilca]

The two MCA params you are looking for are mpi_yield_when_idle and, when using the pthread library, threads_pthreads_yield_strategy. The former controls if OMPI releases the core while during progress (oversubscription will automatically set this to true), and the latter which yield strategy shall be used, aka. sched_yield or nanosleep.