<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /></head><body style='font-size: 10pt; font-family: Verdana,Geneva,sans-serif'>
<p>It would be possible in the case I showed you but in mine that would actually be quite complicated, isn't there any other workaround ? I precise that I am not entitled to utilizing the MATNEST format, it's just that I think the other ones wouldn't work.</p>
<div>---<br />
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">Clément BERGER<br /> ENS de Lyon</div>
</div>
<p><br /></p>
<p>Le 2023-03-17 15:48, Barry Smith a écrit :</p>
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0"><!-- html ignored --><!-- head ignored --><!-- meta ignored -->
<div> </div>
You may be able to mimic what you want by not using PETSC_DECIDE but instead computing up front how many rows of each matrix you want stored on each MPI process. You can use 0 for on certain MPI processes for certain matrices if you don't want any rows of that particular matrix stored on that particular MPI process.
<div> </div>
<div> Barry</div>
<div><br />
<div><br />
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">
<div>On Mar 17, 2023, at 10:10 AM, Berger Clement <clement.berger@ens-lyon.fr> wrote:</div>
<div>
<div style="font-size: 10pt; font-family: Verdana,Geneva,sans-serif;">
<p>Dear all,</p>
<p>I want to construct a matrix by blocs, each block having different sizes and partially stored by multiple processors. If I am not mistaken, the right way to do so is by using the MATNEST type. However, the following code</p>
<p>Call MatCreateConstantDiagonal(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,4,4,2.0E0_wp,A,ierr)<br />Call MatCreateConstantDiagonal(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,4,4,1.0E0_wp,B,ierr)<br />Call MatCreateNest(PETSC_COMM_WORLD,2,PETSC_NULL_INTEGER,2,PETSC_NULL_INTEGER,(/A,PETSC_NULL_MAT,PETSC_NULL_MAT,B/),C,ierr)</p>
<p>does not generate the same matrix depending on the number of processors. It seems that it starts by everything owned by the first proc for A and B, then goes on to the second proc and so on (I hope I am being clear).</p>
<p>Is it possible to change that ?</p>
<p>Note that I am coding in fortran if that has ay consequence.</p>
<p>Thank you,</p>
<p>Sincerely,</p>
<div>-- <br />
<div class="pre" style="margin: 0; padding: 0; font-family: monospace;">Clément BERGER<br /> ENS de Lyon</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
</blockquote>
</body></html>