[mpich-discuss] Deadlock in MPI_Ibarrier over ch3:sock

[Jed Brown]

As we've discussed here several times before, PETSc's --download-mpich
option uses ch3:sock by default because this issue

http://trac.mpich.org/projects/mpich/ticket/79

makes nemesis unusable when oversubscribed. We're also checking for
MPI_Ibarrier and using Torsten's "nonblocking consensus" algorithm when
possible. Unfortunately, MPI_Ibarrier deadlocks when run over ch3:sock.
(Both procs have posted the Ibarrier, but the requests never complete.) I
can prepare a reduced test case if you'd like. Are you still supporting
ch3:sock?

Is there some test we can do to check whether ch3:sock is being used so
that we can choose a safe algorithm?
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