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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>PETSc Users,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am doing a KSPPREONLY solution (of the heat transfer equation using FEA) and comparing several packages like PARDISO and MUMPS, and I am encountering a MatSolve() failure that I am having trouble diagnosing. The matrix inversion fails and I get “nan”. The failure only happens for certain input files, and its not (just) related to problem size. By making a slight change to the geometry of the problem I can get it to solve.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>The SuperLu solver is the only one that will give me any error message:<o:p></o:p></p><p class=MsoNormal>-ksp_type preonly -pc_type lu –pc_mat_solver_package superlu –info<o:p></o:p></p><p class=MsoNormal>I get the error message:<o:p></o:p></p><p class=MsoNormal>[0] MatSolve(): MatFactorError 2<o:p></o:p></p><p class=MsoNormal>Is that a PCFailedReason of PC_FACTOR_NUMERIC_ZEROPIVOT?<o:p></o:p></p><p class=MsoNormal>If so, is there a way to perturb the pivot in some way?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In another (non-PETSc) code which uses MKL PARDISO I am able to solve the exact same problem by the same approach without any issues, and that code gives PARDISO a pivot perturbation flag value.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Is there a better way to figure out what is happening? I have been running the code in TotalView with extreme memory checks and everything appears to be ok.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks,<o:p></o:p></p><p class=MsoNormal>Matt Overholt<o:p></o:p></p><p class=MsoNormal>CapeSym, Inc.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><o:p> </o:p></p></div><br />
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