[petsc-dev] BG hang still broken in petsc-maint!

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:

>   We’ve had this discussion before and wasted too much time on it. On
>   the BG just don’t allow the damn loading of options for files for
>   large runs, say greater than 128 nodes 

If we're going to ignore the files, we should generate a loud warning at
configure time and then *always* ignore the files.  Ignoring only on
large runs sets people up to do a small trial run and then launch their
expensive job, only to find that it ignored their options.

And what about -options_file?  It also uses MPI_Bcast and is vulnerable
to the same bugs.  What about DMDAGetLogicalCoordinate (an insane
function that should be deleted) or DMPlexDistribute, which also call
MPI_Bcast?

Alternative is to have configure detect BG/Q and warn loudly that the
user should set PAMID_COLLECTIVES=0 due to known bugs (all I really want
for Christmas is for IBM to have a public bug tracker we can reference)
and then have PetscInitialize check and warn again in case it is not
set.

>    We sure as hell shouldn’t have a product that for each new user on
>    BG requires them to try to use PETSc, have it fail, debug the
>    problem, like it is now!

Agreed, this is unacceptable.
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