<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div><br></div> Thanks for the bug report with reproducing example. I have a fix in <a href="https://gitlab.com/petsc/petsc/-/merge_requests/5797">https://gitlab.com/petsc/petsc/-/merge_requests/5797</a><div><br></div><div> Barry</div><div><br><div><br><blockquote type="cite"><div>On Nov 2, 2022, at 6:52 AM, Stephan Köhler <stephan.koehler@math.tu-freiberg.de> wrote:</div><br class="Apple-interchange-newline"><div><div>Dear PETSc/Tao team,<br><br>it seems to be that there is a bug in the LMVM matrix class:<br><br>In the function MatCreateVecs_LMVM, see, e.g., https://petsc.org/release/src/ksp/ksp/utils/lmvm/lmvmimpl.c.html at line 214.<br>it is not checked if the vectors *L, or *R are NULL. This is, in particular, a problem if this matrix class is combined with the Schur complement matrix class, since MatMult_SchurComplement<br>calls this function with NULL as *R, see, e.g. https://petsc.org/release/src/ksp/ksp/utils/schurm/schurm.c.html at line 66.<br><br>I attach a minimal example. You need to modify the paths to the PETSc installation in the makefile.<br><br>Best regards<br>Stephan Köhler<br><br>-- <br>Stephan Köhler<br>TU Bergakademie Freiberg<br>Institut für numerische Mathematik und Optimierung<br><br>Akademiestraße 6<br>09599 Freiberg<br>Gebäudeteil Mittelbau, Zimmer 2.07<br><br>Telefon: +49 (0)3731 39-3173 (Büro)<br><br><span id="cid:F9FF719B-D0B1-47D7-930E-57F579EECCD9"><Minimal_example_schur_lmvm.tar.gz></span><span id="cid:16A9CCB3-1F5F-47CE-BAE2-5794A97165A4"><OpenPGP_0xC9BF2C20DFE9F713.asc></span></div></div></blockquote></div><br></div></body></html>