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--></style></head><body lang=EN-CA link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>Dear All,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>Hope you are safe and healthy.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>I have a question regarding pretty different partition results of prism mesh. The partition in PETSc generates much more ghost nodes/cells than the partition in Gmsh, even though both use metis as partitioner. Attached please find the prism mesh in both vtk and exo format, the test code modified based on ex1f90 example. Similar problem are observed for larger dataset with more layers. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>For example, in Gmsh, I get partition results using two processors and four processors as shown below, which are pretty reasonable.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><img width=1243 height=629 style='width:12.9479in;height:6.552in' id="Picture_x0020_5" src="cid:image001.png@01D60D25.FEE686C0"></span><span lang=EN-US style='font-size:11.0pt'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><img width=1243 height=629 style='width:12.9479in;height:6.552in' id="Picture_x0020_6" src="cid:image002.png@01D60D25.FEE686C0"></span><span lang=EN-US style='font-size:11.0pt'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>However, in PETSc, the partition looks a bit weird. Looks like it takes layer partition first and then inside layer. If the number of nodes per layer is very large, this kind of partitioning results into much more ghost nodes/cells. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>Anybody know how to improve the partitioning in PETSc? I have tried parmetis and chaco. There is no big difference between them. <o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><img width=642 height=802 style='width:6.6875in;height:8.3541in' id="Picture_x0020_8" src="cid:image003.png@01D60D25.FEE686C0"></span><span lang=EN-US style='font-size:11.0pt'><o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>Thanks,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'>Danyang<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US style='font-size:11.0pt'><o:p> </o:p></span></p></div></body></html>