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Thanks for your reply. <br>
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For GMRES, I create a ghost vector and give it to KSPSolve. For Slepc, it only takes the shell matrix for EPSSetOperators. Suppose the shell matrix of the eigensolver defines MatMult(Mat m ,Vec x, Vec y), how does it know Vec x is a ghost vector and how many
ghost cells there are?</div>
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Thanks,</div>
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Feng<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Matthew Knepley <knepley@gmail.com><br>
<b>Sent:</b> 21 September 2022 11:58<br>
<b>To:</b> feng wang <snailsoar@hotmail.com><br>
<b>Cc:</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov><br>
<b>Subject:</b> Re: [petsc-users] Slepc, shell matrix, parallel, halo exchange</font>
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<div dir="ltr">On Wed, Sep 21, 2022 at 7:41 AM feng wang <<a href="mailto:snailsoar@hotmail.com">snailsoar@hotmail.com</a>> wrote:<br>
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Hello,</div>
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I am using Slepc with a shell matrix. The sequential version seems working and now I am trying to make it run in parallel.</div>
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The partition of the domain is done, I am not sure how to do the halo exchange in the shell matrix in Slepc. I have a parallel version of matrix-free GMRES in my code with Petsc. I was using VecCreateGhostBlock to create vector with ghost cells, and then used
VecGhostUpdateBegin/End for the halo exchange in the shell matrix, would this be the same for Slepc?</div>
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<div>That will be enough for the MatMult(). You would also have to use a SLEPc EPS that only needed MatMult().</div>
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<div> Thanks,</div>
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<div> Matt</div>
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Thanks,</div>
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Feng <br>
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-- <br>
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<div>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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<div><a href="http://www.cse.buffalo.edu/~knepley/" target="_blank">https://www.cse.buffalo.edu/~knepley/</a><br>
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