[petsc-users] FPE when trying to find the condition number

[Matthew Knepley]

On Thu, Oct 22, 2020 at 3:13 PM baikadi pranay <pranayreddy865 at gmail.com>
wrote:

> Hello,
>
> I am trying to find the condition number of the A matrix for a linear
> system I am solving. I have used the following commands.
>
> *./a.out -ksp_monitor_singular_value -ksp_type gmres -ksp_gmres_restart
> 1000 -pc_type none*However, the execution comes to a halt after a few
> iterations with the following error.
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Caught signal number 8 FPE: Floating Point
> Exception,probably divide by zero
> [0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
> [0]PETSC ERROR: or see
> http://www.mcs.anl.gov/petsc/documentation/faq.html#valgrind
> [0]PETSC ERROR: or try http://valgrind.org on GNU/linux and Apple Mac OS
> X to find memory corruption errors
> [0]PETSC ERROR: likely location of problem given in stack below
> [0]PETSC ERROR: ---------------------  Stack Frames
> ------------------------------------
> [0]PETSC ERROR: Note: The EXACT line numbers in the stack are not
> available,
> [0]PETSC ERROR:       INSTEAD the line number of the start of the function
> [0]PETSC ERROR:       is given.
> [0]PETSC ERROR: [0] LAPACKgesvd line 40
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/impls/gmres/gmreig.c
> [0]PETSC ERROR: [0] KSPComputeExtremeSingularValues_GMRES line 22
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/impls/gmres/gmreig.c
> [0]PETSC ERROR: [0] KSPComputeExtremeSingularValues line 59
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: [0] KSPMonitorSingularValue line 130
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/interface/iterativ.c
> [0]PETSC ERROR: [0] KSPMonitor line 1765
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: [0] KSPGMRESCycle line 122
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/impls/gmres/gmres.c
> [0]PETSC ERROR: [0] KSPSolve_GMRES line 225
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/impls/gmres/gmres.c
> [0]PETSC ERROR: [0] KSPSolve line 678
> /packages/7x/petsc/3.11.1/petsc-3.11.1/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> [0]PETSC ERROR: Signal received
> [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
> cg17-9.agave.rc.asu.edu by pbaikadi Thu Oct 22 12:07:11 2020
> [0]PETSC ERROR: Configure options
> [0]PETSC ERROR: #1 User provided function() line 0 in  unknown file
> --------------------------------------------------------------------------
> MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
> with errorcode 59.
>
> NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
> You may or may not see output from other processes, depending on
> exactly when Open MPI kills them.
> --------------------------------------------------------------------------
> Is the error because the A matrix is singular (causing the max/min to be
> undefined)? Please let me know.
>

No. It is more likely that there is an invalid value, like an Inf or NaN.

  Thanks,

     Matt


> Thank you,
> Sincerely,
> Pranay.
> ᐧ
>


-- 
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/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20201022/d3254e23/attachment-0001.html>