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Can somebody help me figure it out the solver options for the attached generalized eigenvalue problem?</div>
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A x = lambda B x <br>
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where A and B have the same null space, with 5 zero eigenvalues.</div>
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The only non indefinite eigenvalue should be 41.1892</div>
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The problem is Hermite semi-positive so automatically slepc should purify it, but to be sure I added</div>
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EPSSetPurify(eps, PETSC_TRUE);<br>
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I guess with my non-solver-options slepc is still trying to do the inverse of the full<br>
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B matrix with an LU decomposition and gets zero pivot.</div>
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This is what I get as a PETSC error Message<br>
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<span> [0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------<br>
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<div> [0]PETSC ERROR: Zero pivot in LU factorization: https://www.mcs.anl.gov/petsc/documentation/faq.html#zeropivot<br>
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<div> [0]PETSC ERROR: Bad LU factorization<br>
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<div> [0]PETSC ERROR: See https://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.<br>
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<div> [0]PETSC ERROR: Petsc Development GIT revision: v3.11.3-2263-gce77f2ed1a GIT Date: 2019-09-26 13:31:14 -0500<br>
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<div> [0]PETSC ERROR: Nitsche_ex4a on a arch-linux2-c-opt named linux-8biu by eaulisa Tue Jul 7 10:17:55 2020<br>
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<div> [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<br>
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<div> [0]PETSC ERROR: #1 MatLUFactor_SeqDense() line 633 in /home/eaulisa/software/petsc/src/mat/impls/dense/seq/dense.c<br>
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<div> [0]PETSC ERROR: #2 MatLUFactorNumeric_SeqDense() line 432 in /home/eaulisa/software/petsc/src/mat/impls/dense/seq/dense.c<br>
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<div> [0]PETSC ERROR: #3 MatLUFactorNumeric() line 3056 in /home/eaulisa/software/petsc/src/mat/interface/matrix.c<br>
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<div> [0]PETSC ERROR: #4 PCSetUp_LU() line 126 in /home/eaulisa/software/petsc/src/ksp/pc/impls/factor/lu/lu.c<br>
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<div> [0]PETSC ERROR: #5 PCSetUp() line 894 in /home/eaulisa/software/petsc/src/ksp/pc/interface/precon.c<br>
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<div> [0]PETSC ERROR: #6 KSPSetUp() line 377 in /home/eaulisa/software/petsc/src/ksp/ksp/interface/itfunc.c<br>
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<div> [0]PETSC ERROR: #7 STSetUp_Shift() line 119 in /home/eaulisa/software/slepc/src/sys/classes/st/impls/shift/shift.c<br>
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<div> [0]PETSC ERROR: #8 STSetUp() line 271 in /home/eaulisa/software/slepc/src/sys/classes/st/interface/stsolve.c<br>
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<div> [0]PETSC ERROR: #9 EPSSetUp() line 273 in /home/eaulisa/software/slepc/src/eps/interface/epssetup.c<br>
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<div> [0]PETSC ERROR: #10 EPSSolve() line 136 in /home/eaulisa/software/slepc/src/eps/interface/epssolve.c<br>
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Thanks</div>
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Eugenio<br>
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<div align="left"><font size="2">Eugenio Aulisa<br>
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Department of Mathematics and Statistics,<br>
Texas Tech University<br>
Lubbock TX, 79409-1042 <br>
room: 226<br>
http://www.math.ttu.edu/~eaulisa/<br>
phone: (806) 834-6684<br>
fax: (806) 742-1112 <br>
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