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<p>Thank you, Mark. My question is if I have some node indices like [0, 1, 3, 8, 9] handled by the current processor, is that necessary to renumber these indices to something like 0 to 4? or is there any alternative?</p>
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<p>Dongyu<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Mark Adams <mfadams@lbl.gov><br>
<b>Sent:</b> Wednesday, July 3, 2019 3:54:49 PM<br>
<b>To:</b> Dongyu Liu - CITG<br>
<b>Cc:</b> petsc-users@mcs.anl.gov<br>
<b>Subject:</b> Re: [petsc-users] How to create a mapping of global to local indices?</font>
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<div dir="ltr">PETSc matrices and vectors are created with a local size n or global size N and PETSC_DECIDE instead of n. The global PETSc indices are ordered from 0 to n_0 - 1 where n_0 is the number of equations on process 0. This numbering continues for
all processes.
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<div>You can use:</div>
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<pre style="color:rgb(0,0,0)"><a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</a> <a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatGetOwnershipRange.html#MatGetOwnershipRange">MatGetOwnershipRange</a>(<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/Mat.html#Mat">Mat</a> mat,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</a> *m,<a href="https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</a> *n)</pre>
To see what your local global indices are (rows m to n-1 are on this process and so its the local indices are 0 to (n-m-1)).</div>
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<div>Mark</div>
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<div dir="ltr" class="gmail_attr">On Wed, Jul 3, 2019 at 9:11 AM Dongyu Liu - CITG via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov">petsc-users@mcs.anl.gov</a>> wrote:<br>
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<p>Hi,</p>
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<p>I am running a FEM program using PETSc. In the beginning, the mesh is partitioned in gmsh, and we read the partitioned mesh using our own reader.</p>
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<p>Now my question is: How can I get a global to local indices mapping? and do I need to renumber the indices after I read the partitioned mesh?</p>
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<p>From my understanding, the rows handled by each processor should be consecutive, but the indices of nodes which I directly read from a gmsh file are not. Is this an issue?</p>
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<p>Best,</p>
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<p>Dongyu<br>
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