On Wed, Mar 7, 2012 at 1:54 AM, Klaij, Christiaan <span dir="ltr"><<a href="mailto:C.Klaij@marin.nl">C.Klaij@marin.nl</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
> > >Could you get a stack trace with gdb? Also, I ran on petsc-dev.<br>
> ><br>
> > Breakpoint 1, vecsumsegv::vecsumsegv (this=0x7fffffffd310, m=3, n=4)<br>
> > at vecsumsegv.cc:28<br>
> > 28 ierr = VecSum(x,&val);<br>
> > (gdb) next<br>
><br>
><br>
> This was fixed in petsc-dev.<br>
><br>
> <a href="http://petsc.cs.iit.edu/petsc/petsc-dev/rev/3b9bc425b217" target="_blank">http://petsc.cs.iit.edu/petsc/petsc-dev/rev/3b9bc425b217</a><br>
<br>
Thanks, I'll switch to petsc-dev for this.<br>
<br>
><br>
><br>
> Why are you using VecNest? It causes more harm than good in all but some<br>
> very special circumstances.<br>
<br>
I'm using it to experiment with PETSc's block preconditioners. In<br>
short, I have a block matrix for the 2D Stokes eqs with the<br>
variables arranged as (u1,...,uN,v1,...,vN,p1,...pN). The matrix<br>
has the form A = [Q G, D 0]. I'm using VecCreateNest to assemble<br>
the vector x = [u p], just like I use MatCreateNest to assemble<br>
the matrix A from the blocks Q, G and D. The index sets are the<br>
ones you helped me with in a previous thread<br>
(<a href="https://lists.mcs.anl.gov/mailman/htdig/petsc-users/2012-February/012262.html" target="_blank">https://lists.mcs.anl.gov/mailman/htdig/petsc-users/2012-February/012262.html</a>)<br></blockquote><div><br></div><div>
This is just an optimization for block PCs, and for vectors I think it makes almost</div><div>no difference.</div><div><br></div><div> Matt</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
dr. ir. Christiaan Klaij<br>
CFD Researcher<br>
Research & Development<br>
E mailto:<a href="mailto:C.Klaij@marin.nl">C.Klaij@marin.nl</a><br>
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<br>
MARIN<br>
2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands<br>
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<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br>What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br>
-- Norbert Wiener<br>