[petsc-users] Floating point exception

[Jose E. Roman]

If you have problems with PETSc's LU, I would suggest trying with an external package such as MUMPS. See section 3.4.1 of SLEPc's users manual.

On the other hand, if you know where the wanted eigenvalues are located (around a value s), use shift-and-invert: -st_type sinvert -eps_target s
This will factorize matrix (A-s*B) instead of B.

Jose


> El 30 nov 2019, a las 22:56, baikadi pranay <pranayreddy865 at gmail.com> escribió:
> 
> Hello, 
> 
> The entire output is the following:  
> 
> 
> [0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
> [0]PETSC ERROR: Floating point exception
> [0]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at end of function: Parameter number 3
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.11.1, Apr, 12, 2019
> [0]PETSC ERROR: ./a.out on a linux-gnu-c-debug named agave1.agave.rc.asu.edu by pbaikadi Sat Nov 30 14:54:31 2019
> [0]PETSC ERROR: Configure options
> [0]PETSC ERROR: #1 VecValidValues() line 28 in /packages/7x/petsc/3.11.1/petsc-3.11.1/src/vec/vec/interface/rvector.c
> [0]PETSC ERROR: #2 PCApply() line 464 in /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: #3 KSP_PCApply() line 281 in /packages/7x/petsc/3.11.1/petsc-3.11.1/include/petsc/private/kspimpl.h
> [0]PETSC ERROR: #4 KSPSolve_PREONLY() line 22 in /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/impls/preonly/preonly.c
> [0]PETSC ERROR: #5 KSPSolve() line 782 in /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: #6 STMatSolve() line 193 in /packages/7x/slepc/3.11.1/slepc-3.11.1/src/sys/classes/st/interface/stsles.c
> [0]PETSC ERROR: #7 STApply_Shift() line 25 in /packages/7x/slepc/3.11.1/slepc-3.11.1/src/sys/classes/st/impls/shift/shift.c
> [0]PETSC ERROR: #8 STApply() line 57 in /packages/7x/slepc/3.11.1/slepc-3.11.1/src/sys/classes/st/interface/stsolve.c
> [0]PETSC ERROR: #9 EPSGetStartVector() line 797 in /packages/7x/slepc/3.11.1/slepc-3.11.1/src/eps/interface/epssolve.c
> [0]PETSC ERROR: #10 EPSSolve_KrylovSchur_Symm() line 32 in /packages/7x/slepc/3.11.1/slepc-3.11.1/src/eps/impls/krylov/krylovschur/ks-symm.c
> [0]PETSC ERROR: #11 EPSSolve() line 149 in /packages/7x/slepc/3.11.1/slepc-3.11.1/src/eps/interface/epssolve.c
> 
> Regards,
> Pranay.
> 
> On Sat, Nov 30, 2019 at 2:46 PM Matthew Knepley <knepley at gmail.com> wrote:
> On Sat, Nov 30, 2019 at 3:19 PM baikadi pranay <pranayreddy865 at gmail.com> wrote:
> Hello PETSc users,
> 
> I am currently trying to build a 1-D Schrodinger solver. I have built my hamiltonian matrix (of size 121 x 121) and i'm trying to find the eigenvalues. I have the following lines of code for the solver: 
> 
> call EPSCreate(PETSC_COMM_WORLD,eps,ierr)
> call EPSSetOperators(eps,ham,S,ierr)
> call EPSSetProblemType(eps,EPS_GHEP,ierr)
> call EPSSetFromOptions(eps,ierr)
> call EPSSetDimensions(eps,10,PETSC_DEFAULT_INTEGER,PETSC_DEFAULT_INTEGER,ierr)
> call EPSSolve(eps,ierr)
> call EPSDestroy(eps,ierr)
> 
> At the EPSSolve line, i get the following error: 
> 
> [0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
> [0]PETSC ERROR: Floating point exception
> [0]PETSC ERROR: Vec entry at local location 0 is not-a-number or infinite at end of function: Parameter number 3
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.11.1, Apr, 12, 2019
> 
> You need to show the entire stack trace that is output here.
> 
>   Thanks,
> 
>      Matt
>  
> I am using the options -st_pc_factor_shift_type NONZERO -st_pc_factor_shift_amount 1     ( else I end up getting the "zero pivot in LU factorization" error ).
> 
> I outputted my matrix to matlab and confirmed that the null space is empty and the matrix is not singular. I am not sure why I'm getting this error. Could you provide me a hint as to how to solve this problem.
> 
> Sincerely,
> Pranay.
> 
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
> https://www.cse.buffalo.edu/~knepley/