> El 3 abr 2016, a las 20:47, Manav Bhatia <bhatiama...@gmail.com> escribió: > > Hi, > > I am using slepc to solve for the natural frequencies of a > small-disturbance modal eigensolution of a plate with compressive stresses. > > M x = (1/omega^2) K(lambda) x > > lambda is the loading parameter. I first solve for the nonlinear static > solution for a given load, which gives K (after linearization), which is used > here. > > Note that I am solving for 1/omega^2, instead of omega^2, since the mass > matrix may have zero entries related to some dofs, while the stiffness matrix > of the constrained structure has no zero eigenvalues (except, perhaps in the > nonlinear region at the bifurcation point). > > As lambda increases, the structure crosses into the post-buckled region, > so a bifurcation point is crossed at some lambda. The fundamental natural > frequency with this tangent stiffness matrix is expected to reduce to zero, > and then increase after the bifurcation point. > > I am calling slepc without any command line options, except that I specify > LU-decomposition as the linear solver. > > The challenge that I am facing is that I am able to get eigensolutions > till the lowest natural frequency drops to 0, and then the solver quits with > the following error message: > > [0]PETSC ERROR: --------------------- Error Message > -------------------------------------------------------------- > [0]PETSC ERROR: Error in external library > [0]PETSC ERROR: Error in Lapack xHSEQR 100 > [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for > trouble shooting. > [0]PETSC ERROR: Petsc Release Version 3.6.3, Dec, 03, 2015 > [0]PETSC ERROR: /Users/manav/Documents/codes/MAST/build/opt/example_driver on > a arch-darwin-cxx-opt named Dhcp-90-243.HPC.MsState.Edu by manav Sun Apr 3 > 13:31:08 2016 > [0]PETSC ERROR: Configure options > --prefix=/Users/manav/Documents/codes/numerical_lib/petsc/petsc-3.6.3/../ > --CC=mpicc --CXX=mpicxx --FC=mpif90 --with-clanguage=c++ --with-fortran=0 > --with-mpiexec=/opt/ > local/bin/mpiexec --with-shared-libraries=1 --with-x=1 --with-x-dir=/opt/X11 > --with-debugging=0 --with-lapack-lib=/usr/lib/liblapack.dylib > --with-blas-lib=/usr/lib/libblas.dylib --download-superlu=yes - > -download-superlu_dist=yes --download-suitesparse=yes --download-mumps=yes > --download-scalapack=yes --download-parmetis=yes --download-parmetis-shared=1 > --download-metis=yes --download-metis-shared=1 -- > download-hypre=yes --download-hypre-shared=1 --download-ml=yes > --download-ml-shared=1 --download-sundials=yes --download-sundials-shared=1 > [0]PETSC ERROR: #1 DSSolve_NHEP() line 622 in > /Users/manav/Documents/codes/numerical_lib/slepc/slepc-3.6.2/src/sys/classes/ds/impls/nhep/dsnhep.c > [0]PETSC ERROR: #2 DSSolve() line 543 in > /Users/manav/Documents/codes/numerical_lib/slepc/slepc-3.6.2/src/sys/classes/ds/interface/dsops.c > [0]PETSC ERROR: #3 EPSSolve_Arnoldi() line 124 in > /Users/manav/Documents/codes/numerical_lib/slepc/slepc-3.6.2/src/eps/impls/krylov/arnoldi/arnoldi.c > [0]PETSC ERROR: #4 EPSSolve() line 101 in > /Users/manav/Documents/codes/numerical_lib/slepc/slepc-3.6.2/src/eps/interface/epssolve.c > > > Is this related to the loss of positive-definite nature of the stiffness > matrix? Is there a way I can still get solution form slepc? > > I would greatly appreciate any advice. > > Regards, > Manav >
You are using the Arnoldi solver, I would strongly recommend the default solver (Krylov-Schur) - although it may not be relevant for this problem. I assume you are using MUMPS for the linear solves. For a better diagnostic I would need to have access to your matrices. Is it possible? Send an email to slepc-maint. Jose
