[petsc-users] Error using MUMPS to solve large linear system

[Xiaoye S. Li]

Samar:
If you include the error message while crashing using superlu_dist, I
probably know the reason.  (better yet, include the printout before the
crash. )

Sherry


On Mon, Feb 24, 2014 at 9:56 AM, Hong Zhang <hzhang at mcs.anl.gov> wrote:

> Samar :
> There are limitations for direct solvers.
> Do not expect any solver can be used on arbitrarily large problems.
> Since superlu_dist also crashes, direct solvers may not be able to work on
> your application.
> This is why I suggest to increase size incrementally.
> You may have to experiment other type of solvers.
>
> Hong
>
>  Hi Hong and Jed,
>>
>>  Many thanks for replying. It would indeed be nice if the error messages
>> from MUMPS were less cryptic!
>>
>>  1) I have tried smaller matrices although given how my problem is set
>> up a jump is difficult to avoid. But a good idea
>> that I will try.
>>
>>  2) I did try various ordering but not the one you suggested.
>>
>>  3) Tracing the error through the MUMPS code suggest a rather abrupt
>> termination of the program (there should be more
>> error messages if, for example, memory was a problem). I therefore
>> thought it might be an interface problem rather than
>> one with mumps and turned to the petsc-users group first.
>>
>>  4) I've tried superlu_dist but it also crashes (also unclear as to why)
>> at which point I decided to try mumps. The fact that both
>> crash would again indicate a common (memory?) problem.
>>
>>  I'll try a few more things before asking the MUMPS developers.
>>
>>  Thanks again for your help!
>>
>>  Samar
>>
>>  On Feb 24, 2014, at 11:47 AM, Hong Zhang <hzhang at mcs.anl.gov> wrote:
>>
>>  Samar:
>> The crash occurs in
>>
>>> ...
>>> [161]PETSC ERROR: Error in external library!
>>> [161]PETSC ERROR: Error reported by MUMPS in numerical factorization
>>> phase: INFO(1)=-1, INFO(2)=48
>>
>>
>> for very large matrix, likely memory problem as you suspected.
>> I would suggest
>> 1. run problems with increased sizes (not jump from a small one to a very
>> large one) and observe memory usage using
>> '-ksp_view'.
>>    I see you use '-mat_mumps_icntl_14 1000', i.e., percentage of
>> estimated workspace increase. Is it too large?
>>    Anyway, this input should not cause the crash, I guess.
>> 2. experimenting with different matrix ordering -mat_mumps_icntl_7 <> (I
>> usually use sequential ordering 2)
>>     I see you use parallel ordering -mat_mumps_icntl_29 2.
>> 3. send bug report to mumps developers for their suggestion.
>>
>>  4. try other direct solvers, e.g., superlu_dist.
>>
>>
>>> ...
>>>
>>> etc etc. The above error I can tell has something to do with processor
>>> 48 (INFO(2)) and so forth but not the previous one.
>>>
>>> The full output enabled with -mat_mumps_icntl_4 3 looks as in the
>>> attached file. Any hints as to what could be giving this
>>> error would be very much appreciated.
>>>
>>
>> I do not know how to interpret this  output file. mumps developer would
>> give you better suggestion on it.
>> I would appreciate to learn as well :-)
>>
>>  Hong
>>
>>
>>
>
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