[petsc-users] segfault in MatAssemblyEnd() when using large matrices on multi-core MAC OS-X

[Ronald M. Caplan]

Attached is the code.  The original code which segfaults with more than one
core is the code I sent last week.

 - Ron C

On Mon, Jul 30, 2012 at 3:09 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Mon, Jul 30, 2012 at 3:04 PM, Ronald M. Caplan <caplanr at predsci.com>wrote:
>
>> I seem to have solved the problem.
>>
>> I was storing my entire matrix on node 0 and then calling MatAssembly
>> (begin and end) on all nodes (which should have worked...).
>>
>> Apparently I was using too much space for the buffering or the like,
>> because when I change the code so each node sets its own matrix values,
>> than the MatAssemblyEnd does not seg fault.
>>
>
> Can you send the test case. It shouldn't seg-fault unless the machine runs
> out of memory (and most desktop systems have overcommit, so the system will
> kill arbitrary processes, not necessarily the job that did the latest
> malloc.
>
> In practice, you should call MatAssemblyBegin(...,MAT_FLUSH_ASSEMBLY)
> periodically.
>
>
>>
>> Why should this be the case?   How many elements of a vector or matrix
>> can a single node "set" before Assembly to distribute over all nodes?
>>
>
>
>
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