[petsc-users] Floating point exception

[Matthew Knepley]

On Sat, Nov 30, 2019 at 3:56 PM baikadi pranay <pranayreddy865 at gmail.com>
wrote:

> Hello,
>
> The entire output is the following:
>

Okay, you are definitely getting an infinity in the output vector from the
LU solve, so you are giving it a singular matrix.
I am guessing this is B? How can you justify using a singular B?
Also, -st_pc_factor_shift_amount 1 is strange. You
would normally use a very small offset like 1.0e-10 or something.

  Thanks,

     Matt


> [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
>>> <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/
>> <http://www.cse.buffalo.edu/~knepley/>
>>
>

-- 
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/ <http://www.cse.buffalo.edu/~knepley/>
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