Dear All,
In my large parallel simulation, I need to precompute eigenvalues (or at
least the largest one) of smallish simple matrix (from 4x4 up to maybe
50x50, tridiagonal and symmetric). Computation time here is not
important and I thought to do it for each processor independently in
serial. I thought to use petsc for this as I already use petsc for
everything else. However, simple solution seems not to work:
Mat M;
MatCreateSeqDense(PETSC_COMM_SELF,n,n,NULL,&M);
... insering some values
MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);
MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);
KSP ksp;
KSPCreate(PETSC_COMM_WORLD,&ksp);
KSPSetOperators(ksp,M,M);
PetscReal r[n], c[n];
KSPComputeEigenvaluesExplicitly(ksp,n,r,c);
which produces the error:
[0]PETSC ERROR: --------------------- Error Message
--------------------------------------------------------------
[0]PETSC ERROR: Null argument, when expecting valid pointer
[0]PETSC ERROR: Null Object: Parameter # 1
[0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html
for trouble shooting.
[0]PETSC ERROR: Petsc Release Version 3.9.2, May, 20, 2018
[0]PETSC ERROR: ./eigtest on a arch-linux2-c-debug named koshlaptop by
kosh Mon Jul 23 19:25:29 2018
[0]PETSC ERROR: Configure options --with-hdf5-dir=/home/kosh/.local/hdf5
[0]PETSC ERROR: #1 VecDuplicate() line 372 in
/home/kosh/.local/petsc-3.9.2/src/vec/vec/interface/vector.c
[0]PETSC ERROR: #2 KSPComputeExplicitOperator() line 47 in
/home/kosh/.local/petsc-3.9.2/src/ksp/ksp/interface/eige.c
[0]PETSC ERROR: #3 KSPComputeEigenvaluesExplicitly() line 140 in
/home/kosh/.local/petsc-3.9.2/src/ksp/ksp/interface/eige.c
Is it possible to use petsc for this simple task? or KSP will not work
with dense serial matrix?
Thank you in advance and best regards,
Alex.
