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<font face="Ubuntu">Barry,<br>
<br>
thank you. I will have to go with option 1) since with 2) the
number of iterations is almost the double (I tried with ex34).<br>
I am testing the piecewise constant interpolation for periodic BCs
we discussed about in a previous conversation: in case I am
successful, how do I submit the fix?<br>
<br>
Michele<br>
<br>
</font>
<div class="moz-cite-prefix">On 11/14/2013 06:11 PM, Barry Smith
wrote:<br>
</div>
<blockquote
cite="mid:BE83A799-EB4B-43FD-9FCA-1A037E681B7B@mcs.anl.gov"
type="cite">
<pre wrap="">
Since you set the DM inactive the PCSetUp_MG() has no code to compute the coarser grid operators. You need to either
1) provide a DMKSPSetComputeOperators () function that will compute the operator for all levels or
2) run with -pc_mg_galerkin to have the coarse grid operators computed by multiplying the fine grid operator by the restriction/interpolation.
Barry
On Nov 14, 2013, at 7:49 PM, Michele Rosso <a class="moz-txt-link-rfc2396E" href="mailto:mrosso@uci.edu"><mrosso@uci.edu></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
I am solving a Poisson equation (cell-centered discretization) with multigrid.
I am using a 2D version of ksp/ksp/examples/tutorials/ex34.c as a reference.
The following code performs the same calculations as ex34:
call PetscInitialize(PETSC_NULL_CHARACTER,ierr)
call DMDACreate2d(PETSC_COMM_WORLD, DMDA_BOUNDARY_NONE, DMDA_BOUNDARY_NONE,&
& DMDA_STENCIL_STAR, 16, 16, PETSC_DECIDE, PETSC_DECIDE, &
& 1, 1, PETSC_NULL_INTEGER, PETSC_NULL_INTEGER,da,ierr)
call DMDASetInterpolationType(da, DMDA_Q0, ierr);
call DMCreateGlobalVector(da,b,ierr)
call create_rhs(da,b)
call DMCreateMatrix(da,'aij',A,ierr)
call create_matrix(da,A)
call VecDuplicate(b,x,ierr)
! Create solver
call KSPCreate(PETSC_COMM_WORLD,solver,ierr)
call KSPSetDM(solver,da,ierr)
call KSPSetDMActive(solver,PETSC_FALSE,ierr)
call KSPSetOperators(solver,A,A,SAME_NONZERO_PATTERN,ierr)
call KSPSetType(solver,'cg',ierr)
call KSPSetNormType(solver,KSP_NORM_UNPRECONDITIONED,ierr)
call KSPSetFromOptions(solver,ierr)
call KSPSolve(solver,b,x,ierr)
rerr = error(da,x)
call PetscFinalize(ierr)
Both ex34 and my code produce exactly the same results except when I run with
-ksp_view -ksp_monitor_true_residual -ksp_converged_reason -ksp_type cg -pc_type mg -pc_mg_levels 4
In this case my code results in the following error, despite KSPSetDMActive is used after KSPSetDM:
[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Object is in wrong state!
[0]PETSC ERROR: You called KSPSetDM() but did not use DMKSPSetComputeOperators() or KSPSetDMActive(dm,PETSC_FALSE);!
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.4.3, Oct, 15, 2013
[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: ------------------------------------------------------------------------
[0]PETSC ERROR: ./test on a linux-gnu-dbg named enterprise-A by mic Thu Nov 14 17:38:23 2013
[0]PETSC ERROR: Libraries linked from /opt/petsc/petsc-3.4.3/linux-gnu-dbg/lib
[0]PETSC ERROR: Configure run at Tue Oct 29 22:43:45 2013
[0]PETSC ERROR: Configure options --known-mpi-shared="0 " --known-memcmp-ok --with-debugging="1 " --with-fortran-datatypes --with-shared-libraries=0 --with-dynamic-loading=0 --with-mpi-compilers="1 " --download-blacs="1 " --download-superlu_dist="1 " --download-metis="1 " --download-parmetis="1 " --download-ml=1 PETSC_ARCH=linux-gnu-dbg
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: KSPSetUp() line 230 in /opt/petsc/petsc-3.4.3/src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCSetUp_MG() line 730 in /opt/petsc/petsc-3.4.3/src/ksp/pc/impls/mg/mg.c
[0]PETSC ERROR: PCSetUp() line 890 in /opt/petsc/petsc-3.4.3/src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSetUp() line 278 in /opt/petsc/petsc-3.4.3/src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: KSPSolve() line 399 in /opt/petsc/petsc-3.4.3/src/ksp/ksp/interface/itfunc.c
Am I missing anything?
Thank you,
Michele
</pre>
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