[petsc-users] Inconsistent PETSc MUMPS statistics

[Varun Hiremath]

Hi All,

I am using SLEPc to compute eigenvalues and MUMPS for factorization.

Please find attached:
1) A simple test program slepc_eps_mumps_test.cpp that reads a given PETSc
matrix and computes the smallest eigenvalues using MUMPS for factorization
2) An example PETSc matrix MatA of size 581343 rows (sending in .gz format
via Google drive link, please extract it "gunzip MatA.gz" before using).
You should be able to reproduce this issue with any other matrix of a
similar or bigger size.

I notice that when I run the attached test program in parallel with the
attached test matrix the MUMPS statistics printed (using the -eps_view
option in the command line) change with every run.

This is how I run the test:
*$ *mpiexec -n 24 ./slepc_eps_mumps_test.o -nev 5 -f MatA -eps_view
and for example, the output of this includes the following MUMPS stats
...
PC Object: (st_) 24 MPI processes
    type: lu
      out-of-place factorization
      tolerance for zero pivot 2.22045e-14
      matrix ordering: external
      factor fill ratio given 0., needed 0.
        Factored matrix follows:
          Mat Object: 24 MPI processes
            type: mumps
            rows=581343, cols=581343
            package used to perform factorization: mumps
            *total: nonzeros=348236349, allocated nonzeros=348236349*
              MUMPS run parameters:
                SYM (matrix type):                   0
...

I ran this test 10 times as follows and got a different number of nonzeros
(line highlighted above ) reported in each run. (If you save the full
output and compare, you will notice many other differences, but I wouldn't
have expected the nonzeros to change with every run.)

*$* for i in `seq 1 10`; do echo "run $i :-----"; mpiexec -n 24
./slepc_eps_mumps_test.o -nev 5 -f MatA -eps_view | grep -A 1
"factorization: mumps"; done

run 1 :-----
            package used to perform factorization: mumps
            total: nonzeros=354789915, allocated nonzeros=354789915
run 2 :-----
            package used to perform factorization: mumps
            total: nonzeros=359811101, allocated nonzeros=359811101
run 3 :-----
            package used to perform factorization: mumps
            total: nonzeros=354834871, allocated nonzeros=354834871
run 4 :-----
            package used to perform factorization: mumps
            total: nonzeros=354830397, allocated nonzeros=354830397
run 5 :-----
            package used to perform factorization: mumps
            total: nonzeros=353942929, allocated nonzeros=353942929
run 6 :-----
            package used to perform factorization: mumps
            total: nonzeros=354147241, allocated nonzeros=354147241
run 7 :-----
            package used to perform factorization: mumps
            total: nonzeros=354980083, allocated nonzeros=354980083
run 8 :-----
            package used to perform factorization: mumps
            total: nonzeros=354980083, allocated nonzeros=354980083
run 9 :-----
            package used to perform factorization: mumps
            total: nonzeros=354214219, allocated nonzeros=354214219
run 10 :-----
            package used to perform factorization: mumps
            total: nonzeros=355894047, allocated nonzeros=355894047

Can somebody please explain what causes these differences in MUMPS stats?

Thanks,
Varun
 MatA.gz
<https://drive.google.com/file/d/1gbi211awBK5nZtZ-dFiTmjBwStJQ_FKR/view?usp=drive_web>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20220116/99bd5e59/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: slepc_eps_mumps_test.cpp
Type: application/octet-stream
Size: 2255 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20220116/99bd5e59/attachment.obj>