[petsc-dev] broken stuff in next please fix

[Jed Brown]

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

>    I have switched back to using the
>    mpich-master-v3.0.4-106-g3adb59c.tar.gz I messed up and put that
>    change into a commit when I shouldn’t have. (I still miss the nice
>    bk gui that showed cleanly each change you were committing).

I never used the bk gui, but what is lacking in "git gui" or sourcetree?

>    But it is extremely worrisome that we need to use PARTICULAR
>    versions of MPI implementations to get clean compilers?!?!?!
>
>    1) Isn’t this fundamentally wrong? 

Like all dependencies, MPI implementations can have bugs.  This was a
bug and was fixed before it spent much time in the wild.  The memory bug
is more subtle and I have no idea why mpich-3.0.5 has not been released.

>    1.5) Do we want to be in the business of saying, “if you use
>    compiler XX version YY then you need to use MPICH implementation
>    version ZZ, otherwise it won’t work?

This is just a warning, but some MPI implementations have functions that
crash at runtime.  Others have space leaks (e.g., V1R2M0 on BG/Q).

>    2) Shouldn’t we be portable to all the various MPI implementations that are released at various times? 
>
>    3) Do we need a configure test to properly handle the “broken” MPI implementations? 

Lots of compilers have bugs too, including wrong code.  I don't think
it's maintainable to catalog all the bugs in all dependencies on all
architectures.  If something is buggy on a popular system, such that it
creates complaints, we can work around it.  Note that some packages like
ParMETIS have major open bugs that people hit all the time, and we
maintain patches that upstream inexplicably does not apply.

In the case of MPI type tags, the user encounters the same warnings if
they use MPI_2INT.


Public shaming for known bugs that intentionally cannot be detected at
configure time is one marginally-effective recourse.
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