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<p style="margin-top:0;margin-bottom:0">My code (C/C++) uses PETSc to solve a linear system at each iteration in a time-stepping scheme. The PETSc routines are separated out because the scheme that uses them is optional in the larger code. </p>
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<p style="margin-top:0;margin-bottom:0">At each time step, the PETSc scheme calls a routine that includes:</p>
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<p style="margin-top:0;margin-bottom:0">{</p>
<p style="margin-top:0;margin-bottom:0"> Mat A;</p>
<p style="margin-top:0;margin-bottom:0"> Vec x,b;</p>
<p style="margin-top:0;margin-bottom:0"> KSP ksp;</p>
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<p style="margin-top:0;margin-bottom:0"> [Set up A,x,b]</p>
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<p style="margin-top:0;margin-bottom:0"> KSPCreate(PETSC_COMM_WORLD,&ksp);</p>
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<p style="margin-top:0;margin-bottom:0"> [Build A and b from simulation data]</p>
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<p style="margin-top:0;margin-bottom:0"> [Set nullspace of A with MatSetNullSpace]</p>
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<p style="margin-top:0;margin-bottom:0"> KSPSetOperators(ksp,A,A);</p>
<p style="margin-top:0;margin-bottom:0"> KSPSetFromOptions(ksp);</p>
<p style="margin-top:0;margin-bottom:0"> KSPSolve(ksp,b,x);</p>
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<p style="margin-top:0;margin-bottom:0"> [Write x into an instance of our array class, perform checks, etc.]</p>
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<p style="margin-top:0;margin-bottom:0"> KSPDestroy(&ksp);</p>
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<p style="margin-top:0;margin-bottom:0"> return(0);</p>
<p style="margin-top:0;margin-bottom:0">}</p>
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<p style="margin-top:0;margin-bottom:0">My question is: If I want to use superLU_DIST with the option -mat_superlu_dist_fact SamePattern (or SamePattern_SameRowPerm), should I move KSPCreate/Destroy outside of the time-step loop in the larger code?</p>
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<p style="margin-top:0;margin-bottom:0">Thanks.</p>
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<div>Matthew Young</div>
<div>PhD Candidate</div>
<div>Astronomy Department</div>
<div>Boston University</div>
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