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

[Samar Khatiwala]

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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