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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Thank you Matt for answering, however even with that I don't think it works. For example, the command
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./ex70 -nx 32 -ny 48 -fieldsplit_1_type jacobi</p>
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<span style="font-family: Tahoma; font-size: 13px;">gives me the following output</span></p>
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</span></p>
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residual u = 2.6315e-05</p>
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residual p = 0.000229872</p>
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residual [u,p] = 0.000231373</p>
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discretization error u = 0.00633503</p>
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discretization error p = 0.121534</p>
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discretization error [u,p] = 0.121699</p>
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WARNING! There are options you set that were not used!</p>
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WARNING! could be spelling mistake, etc!</p>
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Option left: name:-fieldsplit_1_type value: jacobi</p>
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<p style="margin-right: 0px; margin-left: 0px;">Furthermore, if I look into the possible options with keyword fieldsplit involved by the command:</p>
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./ex70 -help | grep -A5 fieldsplit</p>
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</span></p>
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<span style="font-family: Tahoma; font-size: 13px;">I get this output:</span></p>
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eisenstat ilu icc cholesky asm gasm ksp composite redundant nn mat fieldsplit galerkin exotic hmpi asa cp lsc redistribute svd gamg tfs (PCSetType)</p>
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-pc_use_amat: <FALSE> use Amat (instead of Pmat) to define preconditioner in nested inner solves (PCSetUseAmat)</p>
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Krylov Method (KSP) options -------------------------------------------------</p>
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-ksp_type <gmres>: Krylov method (one of) cg groppcg pipecg cgne nash stcg gltr richardson</p>
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chebyshev gmres tcqmr bcgs ibcgs fbcgs fbcgsr bcgsl cgs tfqmr cr pipecr lsqr preonly qcg bicg fgmres minres symmlq lgmres lcd gcr pgmres specest dgmres (KSPSetType)</p>
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-ksp_max_it <10000>: Maximum number of iterations (KSPSetTolerances)</p>
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<span style="font-family: Tahoma; font-size: 13px;">So I don't see any option that's similar to -fieldsplit_1_type. </span></p>
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<span style="font-family: Tahoma; font-size: 13px;">Hui</span></p>
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<div id="divRpF622878" style="direction: ltr;"><font face="Tahoma" size="2" color="#000000"><b>From:</b> Matthew Knepley [knepley@gmail.com]<br>
<b>Sent:</b> Wednesday, July 16, 2014 2:16 PM<br>
<b>To:</b> Sun, Hui<br>
<b>Cc:</b> petsc-users@mcs.anl.gov<br>
<b>Subject:</b> Re: [petsc-users] why a certain option cannot be used<br>
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<div class="gmail_quote">On Wed, Jul 16, 2014 at 4:09 PM, Sun, Hui <span dir="ltr">
<<a href="mailto:hus003@ucsd.edu" target="_blank">hus003@ucsd.edu</a>></span> wrote:<br>
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<div style="direction:ltr; font-family:Tahoma; color:#000000; font-size:10pt">I want to solve Stokes equation using user defined schur complement preconditioner. So I'm reading and testing snes/examples/tutorial/ex55.c, and ex70.c. In these examples, there
are comments about the usage, for example:
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<div><span style="color:rgb(215,57,30); font-family:Menlo; font-size:11px">mpiexec -n 2 ./stokes -nx 32 -ny 48 -fieldsplit_1_user_pc. </span>
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<div><span style="font-size:10pt">However the option </span><span style="color:rgb(215,57,30); font-family:Menlo; font-size:11px">-fieldsplit_1_user_pc</span><span style="font-size:10pt"> is not recognized by the executable. The output of the above command
is:</span></div>
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<div>This ("user_pc") is just a mnemonic. What it means is that you can use any PC in this slot. What he should have written is</div>
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<div> -fieldsplit_1_pc_type <user pc></div>
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<div> Thanks,</div>
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<div> Matt</div>
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<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo"> residual u = 2.6315e-05</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo"> residual p = 0.000229872</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo"> residual [u,p] = 0.000231373</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo"> discretization error u = 0.00633503</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo"> discretization error p = 0.121534</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo"> discretization error [u,p] = 0.121699</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo">WARNING! There are options you set that were not used!</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo">WARNING! could be spelling mistake, etc!</p>
<p style="margin-right:0px; margin-left:0px; font-size:11px; font-family:Menlo">Option left: name:-fieldsplit_1_user_pc (no value)</p>
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<p style="margin-right:0px; margin-left:0px">I'm wondering what's going on. Is that because I need some specific options during my configuring of the package? By the way, the version of PETSc I'm using is 3.4.4. </p>
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<p style="margin-right:0px; margin-left:0px">Best,</p>
<p style="margin-right:0px; margin-left:0px">Hui</p>
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-- <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 </div>
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