PMI.md advertises a --with-pmilib value not documented in its synposis

[SomeoneSerge]

mpich/doc/wiki/design/PMI.md

Lines 57 to 59 in c2f04da

	As a special case, to build with a Slrum environment, use
	`--with-pmilib=slurm --with-slurm=[path]`. This is because Slurm installs its
	header file under `path/include/slurm/`, thus requires special handling.

...however:

mpich/configure.ac

Lines 1502 to 1506 in c2f04da

	AC_ARG_WITH(pmilib, [
	--with-pmilib=option - Specify whether to build and install libpmi.so.
	mpich - embed into libmpi (default)
	install - build and install libpmi.so
	],,with_pmilib=default)

• Should --with-pmilib be used this way?
• What exactly is the interpretation of --with-pmilib=slurm (i.e. as used with a name instead of mpich/install)?
• Is my understanding correct, that --with-pmi specifies the name of the interface, not (necessarily) an implementation?
• Does --with-pmi specify the interface to expose exclusively, or just the default? If so, how does one build mpich with the (optional) support for other interfaces? E.g. can one build mpich to use slurm's libpmi2 by default, but with an option to fallback to pmix?

This came up in relation to NixOS/nixpkgs#283071 (comment) and any general advice on the meaning and interaction of --with-pmi, --with-pmilib, and --with-pmix flags is welcome

Thanks!

[hzhou]

The slurm option was used as a transitional hack. Try --with-pmi2=[path to slurms libpmi2.so (above lib)].

[SomeoneSerge]

Just to clarify, do I get it right that --with-pmi{1,2,x} are declared at

mpich/configure.ac

Lines 1537 to 1539 in c2f04da

	PAC_CHECK_HEADER_LIB_EXPLICIT(pmi1, pmi.h, pmi, PMI_Init)
	PAC_CHECK_HEADER_LIB_EXPLICIT(pmi2, pmi2.h, pmi2, PMI2_Init)
	PAC_CHECK_HEADER_LIB_EXPLICIT(pmix, pmix.h, pmix, PMIx_Init)

...and also that instead of the autoconf-style --without-feature variants they implement --with-feature=no?

mpich/confdb/aclocal_libs.m4

Lines 165 to 167 in 1f055ee

	if test -n "${with_$1}" -a "${with_$1}" != "no" ; then
	PAC_CHECK_HEADER_LIB_OPTIONAL($1, $2, $3, $4)
	fi

[SomeoneSerge]

Getting configure: WARNING: unrecognized options: --with-pmi1, --with-pmi2

To be clear, --with-pmilib=slurm did work, I just wasn't sure if it's the right thing to do.

This is with mpich 4.1.2

EDIT: I see now that 4.1.2 did contain logic for --with-pmi={slurm,cray,pmix,...} and that --with-pmi{1,2} were introduced later. We'll have to wait for the release to use those, I guess. Otherwise, could you confirm if my understanding above was close to correct?

[hzhou]

The current state of PMI configure options are described in this PR: #6662