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<p>Thank you for your answer, Matt. In the MWE example attached
before, both Nest vectors (the r.h.s. of the system and the vector
of unknowns) are composed of the same number of blocks (2).
Indeed, PETSc is able to solve the system if KSPSetUp() is not
called, so the system/MatNest/MatVec's must not incompatible at
all. Therefore, I wonder if I have missed to called something
before this routine or if this is a KSPSetUp's bug.<br>
</p>
<p>Of course one can always directly define a single matrix and a
single vector, but I find it easier to work with Nest matrices and
vectors. Moreover, I think that the moment to use them is from the
beginning... once all the code is developed, it is very hard to
switch matrices types.<br>
</p>
<p>Regards,</p>
<p>Manuel</p>
<p>---</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 4/10/19 5:41 PM, Matthew Knepley
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAMYG4Gmnf2YdHBoXNo68sbcrBiF+s9i3=JU1b1kgUMSAwxUMyQ@mail.gmail.com">
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<div dir="ltr">On Wed, Apr 10, 2019 at 11:29 AM Manuel Colera
Rico via petsc-users <<a
href="mailto:petsc-users@mcs.anl.gov" moz-do-not-send="true">petsc-users@mcs.anl.gov</a>>
wrote:<br>
</div>
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Hello,<br>
<br>
I am trying to solve a system whose matrix is of type
MatNest. If I <br>
don't use KSPSetUp(), everything is fine. However, if I use
that <br>
routine, I get the following error:<br>
<br>
0]PETSC ERROR: --------------------- Error Message <br>
--------------------------------------------------------------<br>
[0]PETSC ERROR: Invalid argument<br>
[0]PETSC ERROR: Nest vector arguments 1 and 2 have different
numbers of <br>
blocks.<br>
</blockquote>
<div><br>
</div>
<div>This seems self-explanatory. Nest vectors must have the
same number of blocks to be compatible.</div>
<div><br>
</div>
<div>More broadly, there should be no reason to use Nest
vectors or matrices. It is an optimization to</div>
<div>be used at the very end, only after you have profiled the
code and seen that its important. You can</div>
<div>do everything you want to do without ever touching Nest,
and it looks like the Nest interface is a</div>
<div>problem for your code right now.</div>
<div><br>
</div>
<div> Thanks,</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
[0]PETSC ERROR: See <a
href="http://www.mcs.anl.gov/petsc/documentation/faq.html"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://www.mcs.anl.gov/petsc/documentation/faq.html</a>
<br>
for trouble shooting.<br>
[0]PETSC ERROR: Petsc Release Version 3.11.0, unknown<br>
[0]PETSC ERROR: <br>
/home/manu/Documents/FEM-fluids/C-codes/CLG2-ConvectionDiffusion/Debug/CLG2-ConvectionDiffusion
<br>
on a mcr_20190405 named mancolric by Unknown Wed Apr 10
17:20:16 2019<br>
[0]PETSC ERROR: Configure options --with-cc=gcc
--with-cxx=g++ <br>
--with-fc=gfortran COPTFLAGS="-O3 -march=native
-mtune=native" <br>
CXXOPTFLAGS="-O3 -march=native -mtune=native" FOPTFLAGS="-O3
<br>
-march=native -mtune=native" --with-debugging=0
--download-fblaslapack <br>
--download--f2cblaslapack --download-mpich --download--hypre
<br>
--download-scalapack --download-mumps --download-suitesparse
<br>
--download-ptscotch --download-pastix --with-matlab
--with-openmp<br>
[0]PETSC ERROR: #1 VecCopy_Nest() line 68 in <br>
/opt/PETSc_library/petsc-3.11.0/src/vec/vec/impls/nest/vecnest.c<br>
[0]PETSC ERROR: #2 VecCopy() line 1614 in <br>
/opt/PETSc_library/petsc-3.11.0/src/vec/vec/interface/vector.c<br>
[0]PETSC ERROR: #3 KSPInitialResidual() line 63 in <br>
/opt/PETSc_library/petsc-3.11.0/src/ksp/ksp/interface/itres.c<br>
[0]PETSC ERROR: #4 KSPSolve_GMRES() line 236 in <br>
/opt/PETSc_library/petsc-3.11.0/src/ksp/ksp/impls/gmres/gmres.c<br>
[0]PETSC ERROR: #5 KSPSolve() line 782 in <br>
/opt/PETSc_library/petsc-3.11.0/src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: #6 mwe() line 55 in ../Tests/tests.c<br>
<br>
Please find attached a MWE (it is a slight modification of
that of the <br>
post opened by Ce Qin, <br>
<a
href="https://lists.mcs.anl.gov/pipermail/petsc-users/2015-February/024230.html"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://lists.mcs.anl.gov/pipermail/petsc-users/2015-February/024230.html</a>,
<br>
whose answer I have not found).<br>
<br>
By the way, with the newest version of PETSc, Eclipse marks
as errors <br>
the commands PetscFree, CHKERRQ, PETSC_COMM_SELF,...
although it <br>
compiles and executes well. Perhaps it is a problem related
to Eclipse, <br>
but this did not happen with the older versions of PETSc.<br>
<br>
Thanks and regards,<br>
<br>
Manuel<br>
<br>
---<br>
<br>
</blockquote>
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-- <br>
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<div>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</div>
<div><br>
</div>
<div><a href="http://www.cse.buffalo.edu/~knepley/"
target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
</div>
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