[petsc-users] MUMPS error

[David Knezevic]

On Sat, May 16, 2015 at 8:08 AM, venkatesh g <venkateshgk.j at gmail.com>
wrote:

> Hi,
> I am trying to solving AX=lambda BX eigenvalue problem.
>
> A and B are of sizes 3600x3600
>
> I run with this command :
>
> 'mpiexec -np 4 ./ex7 -f1 a2 -f2 b2 -eps_nev 1 -st_type sinvert -eps_max_it
> 5000 -st_ksp_type preonly -st_pc_type lu -st_pc_factor_mat_solver_package
> mumps'
>
> I get this error: (I get result only when I give 1 or 2 processors)
> Reading COMPLEX matrices from binary files...
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Error in external library!
> [0]PETSC ERROR: Error reported by MUMPS in numerical factorization phase:
> INFO(1)=-9, INFO(2)=2024
>


The MUMPS error types are described in Chapter 7 of the MUMPS manual. In
this case you have INFO(1)=-9, which is explained in the manual as:

"–9 Main internal real/complex workarray S too small. If INFO(2) is
positive, then the number of entries that are missing in S at the moment
when the error is raised is available in INFO(2). If INFO(2) is negative,
then its absolute value should be multiplied by 1 million. If an error –9
occurs, the user should increase the value of ICNTL(14) before calling the
factorization (JOB=2) again, except if ICNTL(23) is provided, in which case
ICNTL(23) should be increased."

This says that you should use ICTNL(14) to increase the working space size:

"ICNTL(14) is accessed by the host both during the analysis and the
factorization phases. It corresponds to the percentage increase in the
estimated working space. When significant extra fill-in is caused by
numerical pivoting, increasing ICNTL(14) may help. Except in special cases,
the default value is 20 (which corresponds to a 20 % increase)."

So, for example, you can avoid this error via the following command line
argument to PETSc: "-mat_mumps_icntl_14 30", where 30 indicates that we
allow a 30% increase in the workspace instead of the default 20%.

David
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