[petsc-users] segv in VecSum when using nested vec

[Matthew Knepley]

On Wed, Mar 7, 2012 at 1:54 AM, Klaij, Christiaan <C.Klaij at marin.nl> wrote:

> > > >Could you get a stack trace with gdb? Also, I ran on petsc-dev.
> > >
> > > Breakpoint 1, vecsumsegv::vecsumsegv (this=0x7fffffffd310, m=3, n=4)
> > >    at vecsumsegv.cc:28
> > > 28        ierr = VecSum(x,&val);
> > > (gdb) next
> >
> >
> > This was fixed in petsc-dev.
> >
> > http://petsc.cs.iit.edu/petsc/petsc-dev/rev/3b9bc425b217
>
> Thanks, I'll switch to petsc-dev for this.
>
> >
> >
> > Why are you using VecNest? It causes more harm than good in all but some
> > very special circumstances.
>
> I'm using it to experiment with PETSc's block preconditioners. In
> short, I have a block matrix for the 2D Stokes eqs with the
> variables arranged as (u1,...,uN,v1,...,vN,p1,...pN). The matrix
> has the form A = [Q G, D 0]. I'm using VecCreateNest to assemble
> the vector x = [u p], just like I use MatCreateNest to assemble
> the matrix A from the blocks Q, G and D. The index sets are the
> ones you helped me with in a previous thread
> (
> https://lists.mcs.anl.gov/mailman/htdig/petsc-users/2012-February/012262.html
> )
>

This is just an optimization for block PCs, and for vectors I think it
makes almost
no difference.

  Matt


> dr. ir. Christiaan Klaij
> CFD Researcher
> Research & Development
> E mailto:C.Klaij at marin.nl
> T +31 317 49 33 44
>
> MARIN
> 2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands
> T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl
>
>


-- 
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