[mpich-discuss] Extent of support for MPI_T_... interface?

Alexander Rast alex.rast.technical at gmail.com
Mon Jun 19 10:27:26 CDT 2017

I have to comment that clearly the documentation needs improvement. It's
always the last on the priority list, I realise, but this is really very
obscure. I'd read through configure --help multiple times and not noticed
this option, and even now the description is highly non-obvious if you
didn't already know what you were looking for and what it meant. The line

'--enable-mpit-pvars=list - selectively enable MPI_T performance variable
                             modules. list is a comma-separated module
                              including (Default is "none"):
          none     - No performance info recorded
          recvq    - All message queue-related
          nem      - All nemesis-related
          rma       - All rma-related
          all         - All variables above'

which requires a very close read to interpret the implications. It's not
the kind of thing you're going to spot immediately even ex post facto
without significant prior knowledge. It's not documented or mentioned
anywhere else.

I also think this would more appropriately be a run-time option for mpiexec
rather than a build-time option for the toolchain itself. There are
numerous situations where I'd want to have performance monitoring enabled
for some runs but not others. It doesn't seem to me to be an obvious choice
to make it a build-time option, and it would be awkward to have 2 separate
builds. In addition there are the MPICH binary installs available for many
OS's which ought to have these options available in some form - it would be
a surprise I suspect to a user who'd installed from a binary image to find
support disabled for certain features that they'd not even been given the
option to select.

By the way, just looking through the configure --help output again I notice
that at least one option: --enable-error-messages-level, doesn't document
what the default setting actually is. There may be others.
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