You need to pass PETSC_NULL_MAT in those locations, you cannot just pass a Mat that has never been created (that is a different kind of NULL matrix :-). I have added clearer error checking in https://urldefense.us/v3/__https://gitlab.com/petsc/petsc/-/merge_requests/8526__;!!G_uCfscf7eWS!c7m-laUXAl00bSHNb-ohlO2tKeFMTPNbjzMWPv5thIWU9NSFKiyZzFTUJgVbOqSWRkgYoLYJVkqR6dtPIeyHqig$
Barry > On Jul 4, 2025, at 10:32 AM, Randall Mackie <rlmackie...@gmail.com> wrote: > > In the process of upgrading our code to version 3.23, we have run into > another issue, this time with nest matrices. > > In previous versions (well to at least 3.21) it was perfectly fine to pass in > null matrix blocks to create a nest matrix. There are situations where we > have, for example, only diagonal blocks. That should be allowed and was and > worked fine. > > In petsc 3.23, that no longer is true, or perhaps we do not know what is the > proper way to pass in a null matrix. > > The attached example reproduces this with the following error: > > [0]PETSC ERROR: Configure options: --force --with-clean=1 > --with-scalar-type=complex --with-debugging=1 --with-fortran=1 > --download-mpich=1 --with-cxx=0 > [0]PETSC ERROR: #1 PetscObjectReference() at > /home/rmackie/PETSc/petsc/src/sys/objects/inherit.c:620 > [0]PETSC ERROR: #2 MatNestSetSubMats_Nest() at > /home/rmackie/PETSc/petsc/src/mat/impls/nest/matnest.c:1407 > [0]PETSC ERROR: #3 MatNestSetSubMats() at > /home/rmackie/PETSc/petsc/src/mat/impls/nest/matnest.c:1518 > [0]PETSC ERROR: #4 MatCreateNest() at > /home/rmackie/PETSc/petsc/src/mat/impls/nest/matnest.c:1800 > [0]PETSC ERROR: #5 matnest_bug_reproducer.F90:48 > > > Thanks for helping with this, and thanks for all the work on the Fortran > interfaces - I’ve been playing around with your new branch and am excited by > all the work! > > Randy > <matnest_bug_reproducer.F90>
