On Tue, Oct 30, 2012 at 6:34 PM, TAY wee-beng <span dir="ltr"><<a href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</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">

  
    
  
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    <div>On 30/10/2012 1:44 PM, Matthew Knepley
      wrote:<br>
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    <blockquote type="cite">On Tue, Oct 30, 2012 at 7:41 AM, TAY wee-beng <span dir="ltr"><<a href="mailto:zonexo@gmail.com" target="_blank">zonexo@gmail.com</a>></span>
      wrote:<br>
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            <div>On 28/10/2012 2:17 PM, Jed Brown wrote:<br>
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              <p>Algebraic multigrid can be used directly, -pc_type gamg
                -pc_gamg_agg_nsmooths 1. Geometric either required that
                you use the PCMG interface to set interpolation (and
                provide a coarse operator for non-Galerkin) or use a DM
                that provides coarsening capability.</p>
              <p>What kind of problem are you solving?</p>
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            Hi, <br>
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            May I know if there is an example which explains using the
            geometric MG, either using PCMG or DM?<br>
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        <div>SNES ex5 and ex19 both use MG.</div>
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        <div>   Matt</div>
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    Are there examples which uses ksp and geometric MG? I want to solve
    a Poisson eqn which has been discretized to give a sys of linear
    eqns. <br></div></blockquote><div><br></div><div>This is geometric MG. Did you run any of the tutorial runs? For example, src/snes/examples/tutorials/makefile has</div><div><br></div><div><div>runex5:</div><div><span class="Apple-tab-span" style="white-space:pre">        </span>-@${MPIEXEC} -n 1 ./ex5 -pc_type mg -ksp_monitor_short  -snes_view -pc_mg_levels 3 -pc_mg_galerkin -da_grid_x 17 -da_grid_y 17 -mg_levels_ksp_monitor_short -mg_levels_ksp_norm_type unpreconditioned -snes_monitor_short -mg_levels_ksp_chebyshev_estimate_eigenvalues 0.5,1.1 -mg_levels_pc_type sor -pc_mg_type full > ex5_1.tmp 2>&1; \</div>
<div><span class="Apple-tab-span" style="white-space:pre">      </span>   if (${DIFF} output/ex5_1.out ex5_1.tmp) then true; \</div><div><span class="Apple-tab-span" style="white-space:pre">      </span>   else  echo  ${PWD} "\nPossible problem with with ex5, diffs above \n========================================="; fi; \</div>
<div><span class="Apple-tab-span" style="white-space:pre">      </span>   ${RM} -f ex5_1.tmp</div></div><div><br></div><div>and many more.</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">
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    I also found this thread :<br>
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<a href="http://lists.mcs.anl.gov/pipermail/petsc-users/2012-August/015073.html" target="_blank">http://lists.mcs.anl.gov/pipermail/petsc-users/2012-August/015073.html</a><br>
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    Is it using geometric MG to solve a sys of linear eqns?
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            <pre cols="72">Yours sincerely,

TAY wee-beng</pre>
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              <div class="gmail_quote">On Oct 28, 2012 6:09 AM,
                "w_ang_temp" <<a href="mailto:w_ang_temp@163.com" target="_blank">w_ang_temp@163.com</a>>

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                    <div>Hello,</div>
                    <div>   I want to use the multigrid as a
                      preconditioner. The introduction about it in the
                      manual is little.</div>
                    <div>So are there some typical examples or details
                      about multigrid? Is it used just like other
                      preconditioners</div>
                    <div>like jacobi, sor, which can be simply used in
                      the cammand line options?</div>
                    <div>   Thanks.</div>
                    <div>                                                                      

                      Jim</div>
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      <br clear="all"><span class="HOEnZb"><font color="#888888">
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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<br>
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</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>