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</o:shapelayout></xml><![endif]--></head><body lang=EN-GB link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Hi,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I’ve been using PETSc for a conventional full parallel implicit solver, currently in MPIBAIJ format. However, I’d like to understand the performance verse memory and speed trade-offs of just having a block diagonal system. In this case I do not scatter to the off diagonal blocks. Each block is 7x7 in size and fully dense. In my view this should be a point implicit solution of the system. I am looking for the best way to solve this in PETSc, clearly because of the lack of coupling between neighbouring cells by only having a block diagonal it’s actually a 7x7 dense linear solve, but to test my theory at present I’d prefer to just not scatter to off diagonals, and use:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>MATBDIAG with my current ksp solver and take it from there. BDIAG seems to have been removed as off 3.0:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><a href="http://www.mcs.anl.gov/petsc/documentation/changes/300.html">http://www.mcs.anl.gov/petsc/documentation/changes/300.html</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Can anybody help me with this, your thoughts on the above and what I should use to solve this reduced system would be appreciated??<o:p></o:p></p><p class=MsoNormal><br>Cheers,<o:p></o:p></p><p class=MsoNormal>Andy<o:p></o:p></p></div> <br>
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