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Dear mailing list, I have a question regarding memory usage in SLEPc. Specifically, I am running out of memory when solving a generalized eigenvalue problem Ax = alpha Mx. Here M is singular so we set the problem type as GNHEP and solve with
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<div dir="ltr"><div dir="ltr"><div>Dear mailing list, <br></div><div><br></div><div>I have a question regarding memory usage in SLEPc. Specifically, I am running out of memory when solving a generalized </div><div>eigenvalue problem Ax = alpha Mx. Here M is singular so we set the problem type as GNHEP and solve with Krylov-Schur </div><div>method and shift-and-invert spectral transform. The matrix A come from Stokes like problem so the transform is set to use </div><div>a block diagonal preconditioner B where each of the blocks (through fieldsplit) uses hypre. The solver works nicely on smaller </div><div>problems in 3d (with about 100K dofs). However, upon further refinement the system size gets to millions of dofs and we run </div><div>out of memory (>150GB). I find it surprising because KSP(A, B) on the same machine works without issues. When running <br></div><div>with "-log_trace -info" I see that the memory requests before the job is killed come from the preconditioner setup<br></div><div><br></div><i>[0] PCSetUp(): Setting up PC for first time<br>[0] MatConvert(): Check superclass seqhypre mpiaij -> 0<br>[0] MatConvert(): Check superclass mpihypre mpiaij -> 0<br>[0] MatConvert(): Check specialized (1) MatConvert_mpiaij_seqhypre_C (mpiaij) -> 0<br>[0] MatConvert(): Check specialized (1) MatConvert_mpiaij_mpihypre_C (mpiaij) -> 0<br></i><div><i>[0] MatConvert(): Check specialized (1) MatConvert_mpiaij_hypre_C (mpiaij) -> 1</i></div><div><i><br></i></div><div>Interestingly,
when solving just the problem Ax = b with B as preconditioner I don't
see any calls like the above. We can get access </div><div>to a larger machine but I am curious if our setup/solution strategy can be improved/optimized. Do you have any advice on how to<br><div>reduce the memory footprint? <br></div><br><div>Thanks and best regards, Miro</div></div></div></div>