Greg: > OK, the difference is whether LU or Cholesky factorization is used. But I > would hope that neither one should give incorrect eigenvalues, and when I > run with the latter it does! > Are your matrices symmetric/Hermitian? Hong
> > On Thu, Sep 21, 2017 at 2:05 PM Hong <[email protected]> wrote: > >> Gregory : >> Use '-eps_view' for both runs to check the algorithms being used. >> Hong >> >> Hi all, >>> >>> I'm using shift-invert with EPS to solve for eigenvalues. I find that if >>> I do only >>> >>> ... >>> ierr = EPSGetST(eps,&st);CHKERRQ(ierr); >>> ierr = STSetType(st,STSINVERT);CHKERRQ(ierr); >>> ... >>> >>> in my code I get correct eigenvalues. But if I do >>> >>> ... >>> ierr = EPSGetST(eps,&st);CHKERRQ(ierr); >>> ierr = STSetType(st,STSINVERT);CHKERRQ(ierr); >>> ierr = STGetKSP(st,&ksp);CHKERRQ(ierr); >>> ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr); >>> ierr = KSPSetType(ksp,KSPPREONLY);CHKERRQ(ierr); >>> ierr = PCSetType(pc,PCCHOLESKY);CHKERRQ(ierr); >>> ... >>> >>> the eigenvalues found by EPS are completely wrong! Somehow I thought I >>> was supposed to do the latter, from the examples etc, but I guess that was >>> not correct? I attach the full piece of test code and a test matrix. >>> >>> Best, >>> Greg >>> >> >>
