flux-pmi(1)

SYNOPSIS

[launcher] flux-pmi [-v] [--method=URI] barrier [--count=N]
[launcher] flux-pmi [-v] [--method=URI] exchange [--count=N]
[launcher] flux-pmi [-v] [--method=URI] get [--ranks=IDSET]

DESCRIPTION

flux pmi is a standalone Process Management Interface (PMI) client that embeds the same PMI client plugins as flux-broker(1). It can be used to test the PMI service offered by flux-shell(1) to parallel programs launched by Flux, or to probe the PMI services of an external launcher like Slurm or Hydra in isolation, without the complications of starting a Flux instance.

flux pmi tries a sequence of PMI plugins until one successfully initializes. Alternatively, the specific plugin can be forced with the --method option. Initialization is followed by a subcommand-specific sequence of PMI operations that mimics a common pattern, and then PMI finalization.

OPTIONS

-v, --verbose[=LEVEL]: Trace PMI operations. This is equivalent to setting FLUX_PMI_DEBUG in the broker environment.

-t, --timeout=FSD: Specify a timeout for the requested PMI operation(s) in RFC 23 Flux Standard Duration format, e.g. "0.1s" or "32m". If the timeout expires, the command exits with an error code. Default: no timeout.

--method=URI

Specify the PMI method to use, where the scheme portion of the URI specifies a plugin and the path portion specifies plugin-specific options. The builtin plugins are

simple: Use the simple PMI-1 wire protocol.
libpmi2[:PATH]: dlopen() libpmi2.so and use the PMI-2 API, optionally at a specific PATH.
libpmi[:PATH]: dlopen() libpmi.so and use the PMI-1 API, optionally at a specific PATH.
single: Become a singleton.

--libpmi-noflux: Fail if the libpmi or libpmi2 methods find the Flux libpmi.so.

--libpmi2-cray

Force the libpmi2 Cray workarounds to be enabled for testing. Normally they are enabled only if a heuristic detects that Cray libpmi2 is in use. The workarounds are

Encode all KVS values with base64.
Immediately fail an attempt to fetch any KVS with a flux. prefix.

COMMANDS

barrier

flux pmi barrier executes a PMI barrier and prints a message on rank 0 upon completion.

--test-timing: First execute a preliminary barrier to ensure all ranks enter the test barrier at the same time, then execute a test barrier and print the elapsed time for the test barrier on rank 0 stdout.

--test-count=N: Execute N barrier operations (default 1).

--test-abort=RANK: Instead of entering the barrier, arrange for RANK to call the PMI abort function. This option is intended for testing only.

exchange

flux pmi exchange does the following:

Execute PMI barrier

Put rank specific key to PMI KVS

Execute PMI barrier

Get rank specific key from PMI KVS for all other ranks

Execute PMI barrier

Print elapsed time of (2-5)