Thanks Barry - this is a very helpful clarification. Randy
> On Jul 6, 2025, at 9:59 AM, Barry Smith <bsm...@petsc.dev> wrote: > > > Yes, they are automatically initialized to something ((void*)-2 actually). > They are NOT automatically initialized to PETSC_NULL_XXX > > #define PetscObjectIsNull(obj) (obj%v == 0 .or. obj%v == -2 .or. obj%v == > -3) > > PETSc Fortran has multiple representations of NULL objects. When you want > to pass in the meaning "I am a null" you pass PETSC_NULL_XXX. Not the other > representations. > > > Barry > > Why? Well, if variables were initialized to 0 and then got passed into a > routine, the routine would see the 0 and think: Oh, the person does not want > to set this variable (because passing x would be the same as passing > PETSC_NULL_XXX). > > > > > > >> On Jul 4, 2025, at 9:59 PM, Randall Mackie <rlmackie...@gmail.com> wrote: >> >> Thanks Barry >> >> We were confused because the online manual says: >> >> PETSc objects are always automatically initialized when declared so you do >> not need to (and should not) do >> >> type(tXXX) x = PETSC_NULL_XXX >> XXX x = PETSC_NULL_XXX >> >> Randy >> >> >>> On Jul 4, 2025, at 6:56 PM, Barry Smith <bsm...@petsc.dev> wrote: >>> >>> >>> 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!cuhCwQPErEmmFpD3ik1xLziqtbh4SbXqQViT4PDY_DgSHIm0dkes0boQKPJnZkhSqaayUh78IUoqo7i2dMIPbibEsw$ >>> >>> >>> 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> >>> >> >
