[petsc-users] MPI-IO

[Jed Brown]

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

>> but it would be nice to have a common way to
>> address other viewer implementations.
>
>    What do you mean by this?

That we should be able to tell the VTK viewer to use MPI-IO in the same
way we tell the Binary viewer or any other viewer capable of using MPI-IO.

>>>> PETSc devs, do you suppose MPI-IO support is stable enough that we could
>>>> make this a default?
>>> 
>>>     It is not so much a question of stability, it is more a question
>>>     of (I believe) MPI IO is just loads slower for what might normal
>>>     PETSc users use, it only pays off for large numbers of nodes.
>> 
>> Do we have current data demonstrating that this is still the case?  It's
>> really a failure of the implementations if they can't fall back to the
>> dumbest mechanism when it's faster.
>
>    Oh, actually I just remembered what always drove me crazy with MPI
>    IO is that it saves it in native format meaning it is not portable
>    to all systems (which have different endian). Portability before
>    performance :-)

Uh, MPI_Pack_external and MPI_Unpack_external?
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