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Hi Barry,</div>
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Thanks! That answers my question.</div>
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Cheers,</div>
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Jasper</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Barry Smith <bsmith@petsc.dev><br>
<b>Sent:</b> Thursday, August 21, 2025 5:31 PM<br>
<b>To:</b> Jasper Hatton <jasper.hatton@mail.utoronto.ca><br>
<b>Cc:</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov><br>
<b>Subject:</b> Re: [petsc-users] Suggestions for single process setup code</font>
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As you note, the MPI linear solver server is for matrices whose entries are explicitly provided (so xAIJ sparse and dense) it doesn't have code that would help with shell matrices.
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<div> You should write a parallel code, but have rank 0 do most of the work initially. You can have rank 0, for example, do the MatSetValues() calls. </div>
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<div> Any specific questions, feel free to ask.</div>
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<div> Barry<br id="x_lineBreakAtBeginningOfMessage">
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<div>On Aug 21, 2025, at 3:42 PM, Jasper Hatton via petsc-users <petsc-users@mcs.anl.gov> wrote:</div>
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Hi,</div>
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I am looking for advice on using PETSc in a situation where I don't want the initial setup part of my application to run on multiple processes. The solution stage is taking up most of the time, so I would like to avoid making the setup stage a fully parallel
code for now.</div>
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My solution stage takes a shell matrix, which includes an FFT as well as multiple sparse mat-vec products. So I was planning to use the rank zero process to setup the distributed FFT and put values into the distributed matrices, then execute KSPSolve on all
ranks.</div>
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However, I see there is also the MPI linear solver server option. It seems mostly useful for cases where the input to KSPSolve is a sparse/dense matrix rather than a shell code. Is it something I should consider for my case?</div>
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This is meant to be an first step which can at least run well on a 2-socket node with many cores available, and eventually could be made a fully distributed code in the future.</div>
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Any advice would be apreciated!</div>
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Thanks,</div>
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Jasper</div>
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