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Hello Matt,
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<div class="">Thanks for the information.</div>
<div class="">After using -log_summary to print out for both cases, I found both of them(openMpi and Mvapich2) give same performance.</div>
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<div class="">On the other hand, I still cannot get clear ideas how to get the returned subKsps by the function of getASMSubKSP.</div>
<div class="">It seems the return subKsp are saved in a list of KSP objects.</div>
<div class="">So I used :</div>
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<div class="">subksp = pc.getASMSubKsp()</div>
<div class="">subksp[0].setType(‘richardson')</div>
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<div class="">subksp[1].setType(‘richardson’)</div>
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<div class="">with 2 processors.</div>
<div class="">But it showed "list index out of range”.</div>
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<div class="">As you said on each rank, I can get the local KSPs.</div>
<div class="">Would you mind telling me how to get them?</div>
<div class="">Thanks very much.</div>
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<div class="">Best,</div>
<div class="">Chih-Hao</div>
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<div class="">On Mar 14, 2016, at 3:02 PM, Matthew Knepley <<a href="mailto:knepley@gmail.com" class="">knepley@gmail.com</a>> wrote:</div>
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<div class="gmail_quote">On Mon, Mar 14, 2016 at 12:58 PM, Chih-Hao Chen<span class="Apple-converted-space"> </span><span dir="ltr" class=""><<a href="mailto:chih-hao.chen2@mail.mcgill.ca" target="_blank" class="">chih-hao.chen2@mail.mcgill.ca</a>></span><span class="Apple-converted-space"> </span>wrote:<br class="">
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<div style="word-wrap: break-word;" class="">Hell Matt,
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<div class="">Thanks for the information.</div>
<div class="">I am still trying it now.</div>
<div class="">But I observed an interesting thing about the performance difference when running ex8.c about the ASM.</div>
<div class="">When using Mvapich2 for mph, its convergence speed is much faster than OpenMPI.</div>
<div class="">Is it becasue the ASM function has been optimized based on Mvapich2?</div>
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<div class="">No, it is probably because you have a different partition on the two cases. For performance questions, we</div>
<div class="">need to see the output of -log_summary for each case.</div>
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<div class=""> Thanks,</div>
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<div class=""> Matt</div>
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<div class="">Thanks very much.</div>
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<div class="">Best,</div>
<div class="">Chih-Hao<br class="">
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<div class="">On Mar 10, 2016, at 4:28 PM, Matthew Knepley <<a href="mailto:knepley@gmail.com" target="_blank" class="">knepley@gmail.com</a>> wrote:</div>
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<div class="gmail_quote">On Thu, Mar 10, 2016 at 3:23 PM, Chih-Hao Chen<span class=""> </span><span dir="ltr" class=""><<a href="mailto:chih-hao.chen2@mail.mcgill.ca" target="_blank" class="">chih-hao.chen2@mail.mcgill.ca</a>></span><span class=""> </span>wrote:<br class="">
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<div style="word-wrap: break-word;" class=""><span style="font-size: 14px;" class="">Hello PETSc members,</span>
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<div class=""><span style="font-size: 14px;" class="">Sorry for asking for help about the ASM in petsc4py.</span></div>
<div class=""><span style="font-size: 14px;" class="">Currently I am using your ASM as my preconditioned in my solver.</span></div>
<div class=""><span style="font-size: 14px;" class="">I know how to setup the PCASM based on the ex8.c in the following link.</span></div>
<div class=""><span style="font-size: 14px;" class=""><a href="http://www.mcs.anl.gov/petsc/petsc-3.4/src/ksp/ksp/examples/tutorials/ex8.c" target="_blank" class="">http://www.mcs.anl.gov/petsc/petsc-3.4/src/ksp/ksp/examples/tutorials/ex8.c</a></span></div>
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<div class=""><span style="font-size: 14px;" class="">But when using the function “getASMSubKSP” in petsc4py, </span></div>
<div class=""><span style="font-size: 14px;" class="">I have tried several methods, but still cannot get the subksp from each mpi.</span></div>
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<div class="">The subKSPs do not have to do with MPI. On each rank, you get the local KSPs.</div>
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<div class=""><span style="font-size: 14px;" class="">Here is the snippet of the code of the function.</span></div>
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<pre class=""><span style="font-size: 14px;" class="">def getASMSubKSP(self):
<a name="1027171775_-9334186_l-266" class=""></a> cdef PetscInt i = 0, n = 0
<a name="1027171775_-9334186_l-267" class=""></a> cdef PetscKSP *p = NULL
<a name="1027171775_-9334186_l-268" class=""></a> CHKERR( PCASMGetSubKSP(self.pc, <span class="">&</span>n, NULL, <span class="">&</span>p) )
<a name="1027171775_-9334186_l-269" class=""></a> return <span class="">[</span><span class="">ref_KSP</span><span class="">(</span><span class="">p</span><span class="">[</span><span class="">i</span><span class="">]</span>) for i from 0 <span class=""><</span>= i <span class=""><n</span><span class="">]</span></span></pre>
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<div class=""><span style="font-size: 14px;" class="">In ex8.c, we could use a “FOR” loop to access the indiivdual subksp.</span></div>
<div class=""><span style="font-size: 14px;" class="">But in python, could I use “FOR” loop to get all the subksps with:</span></div>
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<div class=""><span style="font-size: 14px;" class="">subksp[i] = pc.getASMSubKSP[i] </span></div>
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<div class="">I do not understand this, but I think the answer is no.</div>
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<div class=""><span style="font-size: 14px;" class="">Another question is in ex8.c, it seems I don’t need to do any setup to decompose the RHS vector.</span></div>
<div class=""><span style="font-size: 14px;" class="">But do I need to decompose the RHS vector with any settings if I don’t use PETSc solvers but with your preconditioners?</span></div>
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<div class="">I do not understand what you mean by "decompose the RHS vector".</div>
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<div class=""> Thanks,</div>
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<div class=""> Matt</div>
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<div class=""><span style="font-size: 14px;" class="">Thanks very much.</span></div>
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<div class=""><span style="font-size: 14px;" class="">Best,</span></div>
<div class=""><span style="font-size: 14px;" class="">Chih-Hao</span></div>
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<div class="">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br class="">
-- Norbert Wiener</div>
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<div class="gmail_signature">What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.<br class="">
-- Norbert Wiener</div>
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