[petsc-users] Help with generalized eigenvalue problem

[Aulisa, Eugenio]

Can somebody help me figure it out the solver options for the attached generalized eigenvalue problem?

A x = lambda B x

where A and B have the same null space, with 5 zero eigenvalues.

The only non indefinite eigenvalue should be 41.1892

The problem is Hermite semi-positive so automatically slepc should purify it, but to be sure I added

EPSSetPurify(eps, PETSC_TRUE);

I guess with my non-solver-options slepc is still trying to do the inverse of the full
B matrix with an LU decomposition and gets zero pivot.

This is what I get as a PETSC error Message

 [0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
   [0]PETSC ERROR: Zero pivot in LU factorization: https://www.mcs.anl.gov/petsc/documentation/faq.html#zeropivot
   [0]PETSC ERROR: Bad LU factorization
   [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
   [0]PETSC ERROR: Petsc Development GIT revision: v3.11.3-2263-gce77f2ed1a  GIT Date: 2019-09-26 13:31:14 -0500
   [0]PETSC ERROR: Nitsche_ex4a on a arch-linux2-c-opt named linux-8biu by eaulisa Tue Jul  7 10:17:55 2020
   [0]PETSC ERROR: Configure options --with-debugging=0 --with-x=1 COPTFLAGS="-O3 -march=native -mtune=native" CXXOPTFLAGS="-O3 -march=native -mtune=native" FOPTFLAGS="-O3 -march=native -mtune=native" --download-openmpi=1 --download-fblaslapack=1 --download-hdf5=1 --download-metis=1 --download-parmetis=1 --with-shared-libraries=1 --download-blacs=1 --download-scalapack=1 --download-mumps=1 --download-suitesparse
   [0]PETSC ERROR: #1 MatLUFactor_SeqDense() line 633 in /home/eaulisa/software/petsc/src/mat/impls/dense/seq/dense.c
   [0]PETSC ERROR: #2 MatLUFactorNumeric_SeqDense() line 432 in /home/eaulisa/software/petsc/src/mat/impls/dense/seq/dense.c
   [0]PETSC ERROR: #3 MatLUFactorNumeric() line 3056 in /home/eaulisa/software/petsc/src/mat/interface/matrix.c
   [0]PETSC ERROR: #4 PCSetUp_LU() line 126 in /home/eaulisa/software/petsc/src/ksp/pc/impls/factor/lu/lu.c
   [0]PETSC ERROR: #5 PCSetUp() line 894 in /home/eaulisa/software/petsc/src/ksp/pc/interface/precon.c
   [0]PETSC ERROR: #6 KSPSetUp() line 377 in /home/eaulisa/software/petsc/src/ksp/ksp/interface/itfunc.c
   [0]PETSC ERROR: #7 STSetUp_Shift() line 119 in /home/eaulisa/software/slepc/src/sys/classes/st/impls/shift/shift.c
   [0]PETSC ERROR: #8 STSetUp() line 271 in /home/eaulisa/software/slepc/src/sys/classes/st/interface/stsolve.c
   [0]PETSC ERROR: #9 EPSSetUp() line 273 in /home/eaulisa/software/slepc/src/eps/interface/epssetup.c
   [0]PETSC ERROR: #10 EPSSolve() line 136 in /home/eaulisa/software/slepc/src/eps/interface/epssolve.c



Thanks
Eugenio




Eugenio Aulisa

Department of Mathematics and Statistics,
Texas Tech University
Lubbock TX, 79409-1042
room: 226
http://www.math.ttu.edu/~eaulisa/
phone: (806) 834-6684
fax: (806) 742-1112



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