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

[Hong Zhang]

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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