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What happens if you try to preallocate C matrix (in the same way as A and B) and use MatMatMult with MAT_REUSE_MATRIX?
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<div class="">Hong (Mr.)<br class="">
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<div class="">On Mar 5, 2019, at 6:19 PM, Marius Buerkle via petsc-users <<a href="mailto:petsc-users@mcs.anl.gov" class="">petsc-users@mcs.anl.gov</a>> wrote:</div>
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<p class=""><span style="font-size:11pt" class=""><span style="line-height:normal" class=""><span style="font-family:Calibri,sans-serif" class=""><span style="font-size:12.0pt" class=""><span style="font-family:"Times New Roman",serif" class="">Hi,</span></span></span></span></span></p>
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<p class=""><span style="font-size:11pt" class=""><span style="line-height:normal" class=""><span style="font-family:Calibri,sans-serif" class=""><span style="font-size:12.0pt" class=""><span style="font-family:"Times New Roman",serif" class="">I have a question
regarding MatMatMult for MPIDENSE matrices. I have two dense matrices A and B for which I set the number up the number of local rows each processor owns manually (same for A and B) when creating them with MatCreateDense (which is different from what PETSC_DECIDE
what do). When I calculate A*B=C using MatMatMult with MAT_INITIAL_MATRIX the resulting matrix C has a different distribution of the rows among the processes. Is this normal? I would have expected that C inherits the local row structure from A and B.
</span></span><span style="font-size:12.0pt" class=""><span style="font-family:"Yu Mincho",serif" class="">Later</span></span><span style="font-size:12.0pt" class=""><span style="font-family:"Times New Roman",serif" class=""> on, I want to multiply C let’s
say with A which gives then accordingly an error that the local size is not conform.
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<p class=""><span style="font-size:11pt" class=""><span style="line-height:normal" class=""><span style="font-family:Calibri,sans-serif" class=""><span style="font-size:12.0pt" class=""><span style="font-family:"Times New Roman",serif" class="">If on the other
hand A is MATMPIAIJ then C has the same local row structure.</span></span></span></span></span></p>
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<p class=""><span style="font-size:11pt" class=""><span style="line-height:normal" class=""><span style="font-family:Calibri,sans-serif" class=""><span style="font-size:12.0pt" class=""><span style="font-family:"Times New Roman",serif" class="">Best,</span></span></span></span></span></p>
<p class=""><span style="font-size:11pt" class=""><span style="line-height:normal" class=""><span style="font-family:Calibri,sans-serif" class=""><span style="font-size:12.0pt" class=""><span style="font-family:"Times New Roman",serif" class="">Marius</span></span></span></span></span></p>
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