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<div class="moz-cite-prefix">On 09/06/2013 06:16 PM, Matthew Knepley
wrote:<br>
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<div>1) Forget about MatNest. It is completely orthogonal to
FieldSplit. Its just an optimization.</div>
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Hi Matt,<br>
<br>
Thanks, slowly getting there.<br>
<br>
Ok I built up a simple matrix in MATLAB and interfaced it to PETSc
what I would like to try to try with PETSc at the end is a similar
system with a similar operator like <br>
<br>
A =<br>
A C1<br>
C2 B<br>
<br>
as mentioned in my previous mail. I also found out your tutorial <br>
<br>
<cite><a class="moz-txt-link-abbreviated" href="http://www.mcs.anl.gov/">www.mcs.anl.gov/</a><b>petsc</b>/.../<b>ACTS</b>Tutorial2012.pdf</cite><br>
<br>
and there are some examples on the usage of Stokes problems. That is
exactly what I want to try for my problems, setting different
preconditioners and solvers for different blocks(I guess these are
denoted as splits, correct me if I am wrong).<br>
<br>
I investigated that presentation but I still have a problem
somewhere. The simple code is also attached with a simple matrix and
the right hand side vector. I have a problem on the field numbers. <br>
<br>
What I defined was the row index sets to set the fields but
apparently the error I get is telling me that I still have a single
field when I try to run <br>
<br>
./ex2 -pc_type fieldsplit > simple_log<br>
<br>
And the output is <br>
<br>
[0]PETSC ERROR: --------------------- Error Message
------------------------------------<br>
[0]PETSC ERROR: Petsc has generated inconsistent data!<br>
[0]PETSC ERROR: Unhandled case, must have at least two fields, not
1!<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: Petsc Release Version 3.4.2, Jul, 02, 2013 <br>
[0]PETSC ERROR: See docs/changes/index.html for recent updates.<br>
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.<br>
[0]PETSC ERROR: See docs/index.html for manual pages.<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: ./ex2 on a linux-gnu-c-debug named hp8570w by utabak
Sat Sep 7 11:58:25 2013<br>
[0]PETSC ERROR: Libraries linked from
/home/utabak/external_libraries/petsc-3.4.2/linux-gnu-c-debug/lib<br>
[0]PETSC ERROR: Configure run at Fri Sep 6 14:18:08 2013<br>
[0]PETSC ERROR: Configure options --with-cc=gcc --with-fc=gfortran
--with-cxx=g++ --download-f-blas-lapack=1 --with-mpi=1
--with-clanguage=cxx --download-mumps=1 --download-scalapack=1
--download-blacs=1 --download-superlu=1 --download-spooles=1
--download-umfpack=1 --download-mpich=1 --download-metis=1
--download-parmetis=1 -download-hypre=1 COPTFLAGS=-O3<br>
[0]PETSC ERROR:
------------------------------------------------------------------------<br>
[0]PETSC ERROR: PCFieldSplitSetDefaults() line 440 in
/home/utabak/external_libraries/petsc-3.4.2/src/ksp/pc/impls/fieldsplit/fieldsplit.c<br>
[0]PETSC ERROR: PCSetUp_FieldSplit() line 458 in
/home/utabak/external_libraries/petsc-3.4.2/src/ksp/pc/impls/fieldsplit/fieldsplit.c<br>
[0]PETSC ERROR: PCSetUp() line 890 in
/home/utabak/external_libraries/petsc-3.4.2/src/ksp/pc/interface/precon.c<br>
[0]PETSC ERROR: KSPSetUp() line 278 in
/home/utabak/external_libraries/petsc-3.4.2/src/ksp/ksp/interface/itfunc.c<br>
[0]PETSC ERROR: KSPSolve() line 399 in
/home/utabak/external_libraries/petsc-3.4.2/src/ksp/ksp/interface/itfunc.c<br>
<br>
How can I correct this error?<br>
<br>
Could you please help me at this point?<br>
<br>
Best,<br>
Umut<br>
<br>
<br>
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cite="mid:CAMYG4GmWQahAqg+UKjt-8hvDe=H9a6nhzT5uDNV5MdC-NQR15Q@mail.gmail.com"
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<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">but
I could not understand really the following steps on how
to associate a KSP object with Field split properties to
use different conditioners on different blocks? In the
mean time, continue on reading. If you can outline the
basic steps on how to construct this scheme and submit
analysis with basic command line options, that would of
great help.<br>
</blockquote>
<div><br>
</div>
<div>2) If you have the ISes to make a MatNest, just use
them to make the FS:</div>
<div><br>
</div>
<div> <a moz-do-not-send="true"
href="http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCFieldSplitSetIS.html">http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCFieldSplitSetIS.html</a></div>
<div><br>
</div>
<div>so you have</div>
<div><br>
</div>
<div> PCFieldSplitSetIS(pc, "1", is1);</div>
<div> PCFieldSplitSetIS(pc, "2", is2);</div>
<div><br>
</div>
<div>Now you can use all the fieldsplit options. There are
many examples in PETSc, see</div>
<div><br>
</div>
<div> src/snes/examples/tutorials/makefile</div>
<div><br>
</div>
<div>and ex19 for instance.</div>
<div><br>
</div>
<div> Matt</div>
<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">By
the way, is not possible to output blockA that is
assembled above on the standard output?<br>
<br>
Best regards,<br>
Umut<br>
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<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
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