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Dear all,</div>
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[BugReport.c] is a sample code, [BugReportParallel.output] is the output when execute BugReport with mpiexec, [BugReportSerial.output] is the output in serial execution.</div>
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Best,</div>
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Changqing</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>发件人:</b> Dave May <dave.mayhem23@gmail.com><br>
<b>发送时间:</b> 2022年5月31日 22:55<br>
<b>收件人:</b> Ye Changqing <Ye_Changqing@outlook.com><br>
<b>抄送:</b> petsc-users@mcs.anl.gov <petsc-users@mcs.anl.gov><br>
<b>主题:</b> Re: [petsc-users] Mat created by DMStag cannot access ghost points</font>
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<div dir="ltr">On Tue 31. May 2022 at 16:28, Ye Changqing <<a href="mailto:Ye_Changqing@outlook.com" data-auth="NotApplicable">Ye_Changqing@outlook.com</a>> wrote:<br>
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Dear developers of PETSc,</div>
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I encountered a problem when using the DMStag module. The program could be executed perfectly in serial, while errors are thrown out in parallel (using mpiexec). Some rows in Mat cannot be accessed in local processes when looping all elements in DMStag. The
DM object I used only has one DOF in each element. Hence, I could switch to the DMDA module easily, and the program now is back to normal.</div>
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Some snippets are below.</div>
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Initialise a DMStag object:</div>
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PetscCall(DMStagCreate2d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, M, N, PETSC_DECIDE, PETSC_DECIDE, 0, 0, 1, DMSTAG_STENCIL_BOX, 1, NULL, NULL, &(s_ctx->dm_P)));<br>
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Created a Mat:</div>
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PetscCall(DMCreateMatrix(s_ctx->dm_P, A));<br>
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Loop:</div>
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PetscCall(DMStagGetCorners(s_ctx->dm_V, &startx, &starty, &startz, &nx, &ny, &nz, &extrax, &extray, &extraz));</div>
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<span style="color:rgb(0,0,0); font-family:Calibri,Helvetica,sans-serif; font-size:12pt">for (ey = starty; ey < starty + ny; ++ey)</span></div>
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<div>for (ex = startx; ex < startx + nx; ++ex)</div>
{<br>
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...</div>
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PetscCall(DMStagMatSetValuesStencil(s_ctx->dm_P, *A, 2, &row[0], 2, &col[0], &val_A[0][0], ADD_VALUES)); // The traceback shows the problem is in here.<br>
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}</div>
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<div dir="auto">In addition to the code or MWE, please forward us the complete stack trace / error thrown to stdout.</div>
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<div dir="auto">Thanks,</div>
<div dir="auto">Dave</div>
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Best,</div>
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Changqing</div>
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