dummy in MyKSPConverged

[Klaij, Christiaan]

Matt,

Thanks for your answer!

dummy is defined as a PETSc integer inside MyKSPConverged, so why can't I set it to 0? I know it's not useful because it's just a dummy and nothing happens with it, but setting it shouldn't crash the code, right? Also, if setting it changes the basic definition of PETSC_NULL_OBJECT shouldn't you get a SEGV as well, or at least some kind of trouble? 

Chris



Message: 5
Date: Fri, 4 Sep 2009 10:49:25 -0500
From: Matthew Knepley <knepley at gmail.com>
Subject: Re: dummy in MyKSPConverged
To: PETSc users list <petsc-users at mcs.anl.gov>
Message-ID:
	<a9f269830909040849t7a8dd52dwc7fa33c6a0d313f7 at mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"

On Fri, Sep 4, 2009 at 10:35 AM, Klaij, Christiaan <C.Klaij at marin.nl> wrote:

>   Hello,
>
> With the new version 3.0.0-p8, if I assign a value to the dummy in
> MyKSPConverged at the end of src/ksp/ksp/examples/tutorials/ex2f.F, I get a
> segmentation fault (this didn't happen with version 2.3.3-p13). Any idea
> why?
>

1) I do not get a SEGV

2) You should not be setting this at all. You pass in PETSC_NULL_OBJECT,
which means you are changing the definition of that
    basic thing in PETSc. This can produce undefined results.

  Matt


> $ tail ex2f.F
>       else
>         flag = 0
>       endif
>       ierr = 0
>       dummy = 0
>
>       end
> $ ./ex2f -my_ksp_convergence
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation,
> probably memory access out of range
> [0]PETSC ERROR: Try option -start_in_debugger or -on_error_attach_debugger
> [0]PETSC ERROR: or see
> http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#Signal[0]PETSC
> ERROR: or try http://valgrind.org on linux or man libgmalloc on Apple 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] GMREScycle line 133 src/ksp/ksp/impls/gmres/gmres.c
> [0]PETSC ERROR: [0] KSPSolve_GMRES line 228 src/ksp/ksp/impls/gmres/gmres.c
> [0]PETSC ERROR: [0] KSPSolve line 308 src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Signal received!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
> [0]PETSC ERROR: Petsc Release Version 3.0.0, Patch 8, Fri Aug 21 14:02:12
> CDT 2009
> [0]PETSC ERROR: See docs/changes/index.html for recent updates.
> [0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
> [0]PETSC ERROR: See docs/index.html for manual pages.
> [0]PETSC ERROR:
> ------------------------------------------------------------------------

dr. ir. Christiaan Klaij
CFD Researcher
Research & Development
mailto:C.Klaij at marin.nl
T +31 317 49 33 44

MARIN
2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands
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