<div dir="ltr">First, you probably want -ksp_type cg<div>ILU sucks, you can try 'gamg' and I would configure it with hypre and try that also.</div><div><br></div><div>Now, you are getting very little increase in flop rate on MatMult (8K -->8.6K). That is the problem</div><div>* You have a "bad" network</div><div>* Your problem is too small (with respect to your network) to get speedup after 16 porcs</div><div>* Bad partitioning</div><div>* You have a fair amount of load imbalance (<span style="color:rgb(0,0,0);font-family:Calibri,Arial,Helvetica,sans-serif;font-size:16px">MatMult 671 1.0 </span><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:16px;color:rgb(237,92,87)">4.7602e+01</span><span style="font-family:Calibri,Arial,Helvetica,sans-serif;font-size:16px"><font color="#000000"> </font><b style=""><font color="#ff00ff">2.0</font></b><font color="#000000"> </font></span>), and it gets worse at 32 procs. That can be from bad partitioning or a bad network.</div><div><br></div><div>With a decent network you probably want to keep at least 25K equations per processor. This depends on these other issues, but it is a start. With a good network you should be able to get down to 10K/proc</div><div><br></div><div>It is best to start with a simple model problem like a cube, with cube shaped subdomains is ideal, and isolate issues.</div><div><br></div><div>Mark</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Feb 27, 2022 at 9:51 AM Gong Yujie <<a href="mailto:yc17470@connect.um.edu.mo">yc17470@connect.um.edu.mo</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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Hi,</div>
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I'm using the GMRES with ASM preconditioner with sub-domain solver ILU(2) to solve an elasticity problem. First, I use 16 cores to test the computation time, then use 32 cores to run the same code with the same parameters. But I just get about 10% speed up.
From the log file I found that the computation time of KSPSolve() and MatSolve() just decrease a little bit. My PETSc version is 3.16.0 and use --with-debugging=0 when configure it. The matrix size is about 7*10^6. Some detail of the log is shown below:</div>
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16-cores:</div>
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<div>Event Count Time (sec) Flop --- Global --- --- Stage ---- Total</div>
<div> Max Ratio Max Ratio Max Ratio Mess AvgLen Reduct %T %F %M %L %R %T %F %M %L %R Mflop/s</div>
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MatMult 664 1.0 <span style="color:rgb(237,92,87)">5.0794e+01</span> 1.6 2.70e+10 1.1 7.1e+04 4.8e+04 1.0e+00 7 13 49 20 0 7 13 49 20 0 8010
<div>MatSolve 663 1.0 1.9868e+02 1.1 1.43e+11 1.1 0.0e+00 0.0e+00 0.0e+00 33 70 0 0 0 33 70 0 0 0 10932</div>
<div>MatLUFactorNum 1 1.0 6.1501e+00 1.1 1.40e+10 1.1 0.0e+00 0.0e+00 0.0e+00 1 7 0 0 0 1 7 0 0 0 35056</div>
<span>MatILUFactorSym 1 1.0 1.5566e+01 1.2 0.00e+00 0.0 0.0e+00 0.0e+00 0.0e+00 2 0 0 0 0 2 0 0 0 0 0</span><br>
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<span>KSPSetUp 2 1.0 5.9627e-03 1.9 0.00e+00 0.0 0.0e+00 0.0e+00 2.0e+00 0 0 0 0 0 0 0 0 0 0 0
<div>KSPSolve 1 1.0 <span style="color:rgb(12,136,42)">2.5168e+02</span> 1.0 1.90e+11 1.1 1.4e+05 4.8e+04 1.3e+03 44 93 98 40 89 44 93 98 40 90 11437</div>
<div>KSPGMRESOrthog 641 1.0 1.8980e+01 1.7 1.82e+10 1.1 0.0e+00 0.0e+00 6.4e+02 3 9 0 0 43 3 9 0 0 44 14578</div>
<div>PCSetUp 2 1.0 2.2480e+01 1.1 1.40e+10 1.1 5.3e+02 6.5e+05 7.0e+00 4 7 0 2 0 4 7 0 2 0 9591</div>
<div>PCSetUpOnBlocks 1 1.0 2.1555e+01 1.1 1.40e+10 1.1 0.0e+00 0.0e+00 0.0e+00 3 7 0 0 0 3 7 0 0 0 10002</div>
<div>PCApply 663 1.0 2.0296e+02 1.1 1.43e+11 1.1 7.0e+04 4.8e+04 1.0e+00 33 70 49 20 0 33 70 49 20 0 10701</div>
<span>PCApplyOnBlocks 663 1.0 1.9908e+02 1.1 1.43e+11 1.1 0.0e+00 0.0e+00 0.0e+00 33 70 0 0 0 33 70 0 0 0 10910</span><br>
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<span><span>32-cores:</span></span></div>
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<div>Event Count Time (sec) Flop --- Global --- --- Stage ---- Total</div>
<div> Max Ratio Max Ratio Max Ratio Mess AvgLen Reduct %T %F %M %L %R %T %F %M %L %R Mflop/s</div>
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<span><span>MatMult 671 1.0 </span><span style="color:rgb(237,92,87)">4.7602e+01</span><span> 2.0 1.39e+10 1.1 1.7e+05 2.8e+04 1.0e+00 7 13 49 23 0 7 13 49 23 0 8637
<div>MatSolve 670 1.0 1.7800e+02 1.1 7.56e+10 1.1 0.0e+00 0.0e+00 0.0e+00 33 71 0 0 0 33 71 0 0 0 12544</div>
<div>MatLUFactorNum 1 1.0 3.5714e+00 1.1 7.16e+09 1.1 0.0e+00 0.0e+00 0.0e+00 1 7 0 0 0 1 7 0 0 0 60743</div>
<span>MatILUFactorSym 1 1.0 8.4088e+00 1.2 0.00e+00 0.0 0.0e+00 0.0e+00 0.0e+00 2 0 0 0 0 2 0 0 0 0 0</span><br>
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<span><span><span>KSPSetUp 2 1.0 3.8060e-03 1.5 0.00e+00 0.0 0.0e+00 0.0e+00 2.0e+00 0 0 0 0 0 0 0 0 0 0 0
<div>KSPSolve 1 1.0 <span style="color:rgb(12,136,42)">2.1680e+02</span> 1.0 9.95e+10 1.1 3.5e+05 2.8e+04 1.3e+03 44 93 98 47 89 44 93 98 47 90 13592</div>
<div>KSPGMRESOrthog 648 1.0 1.6999e+01 2.0 9.39e+09 1.1 0.0e+00 0.0e+00 6.5e+02 2 9 0 0 43 2 9 0 0 44 16450</div>
<div>PCSetUp 2 1.0 1.2439e+01 1.1 7.16e+09 1.1 1.3e+03 3.7e+05 7.0e+00 2 7 0 2 0 2 7 0 2 0 17440</div>
<div>PCSetUpOnBlocks 1 1.0 1.1876e+01 1.1 7.16e+09 1.1 0.0e+00 0.0e+00 0.0e+00 2 7 0 0 0 2 7 0 0 0 18267</div>
<div>PCApply 670 1.0 1.8235e+02 1.1 7.56e+10 1.1 1.7e+05 2.7e+04 1.0e+00 34 71 49 23 0 34 71 49 23 0 12245</div>
<span>PCApplyOnBlocks 670 1.0 1.7838e+02 1.1 7.56e+10 1.1 0.0e+00 0.0e+00 0.0e+00 33 71 0 0 0 33 71 0 0 0 12517</span><br>
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<span><span><span>Hope you can help me!</span></span></span></div>
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Best Regards,
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Yujie</div>
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