[petsc-users] MatSetValuesCOO after MatDuplicate

Barry Smith bsmith at petsc.dev
Wed Apr 26 15:58:42 CDT 2023

   Yes, it looks like a bug since no one tested this situation.

   MatSetPreallocationCOO() is pretty heavy memory-wise. It essentially keeps a copy of all the coo_i, coo_j indices within the Mat as well as the usual matrix information. So in your scenario, you will have two copies of all this stuff; lots of memory. Is this really what you need?

> On Apr 26, 2023, at 4:07 PM, Maxime Bouyges <maxime.bouyges at gmail.com> wrote:
> Dear PETSc developers,
> I am trying to use the MatSetValuesCOO function (very appropriate and performant for my case) but I am encountering a problem when I use it on a Mat obtained with MatDuplicate. It seems that the non-zero pattern is preserved by MatDuplicate, but not the "COO information". Here are the few steps to reproduce the problem:
> MatCreate(comm, A)
> MatSetUp(A)
> MatSetPreallocationCOO(A, ncoo, coo_i, coo_j)
> MatSetValuesCOO(A, coo_v, INSERT_VALUES) # -> works ok
> MatDuplicate(A, MAT_DO_NOT_COPY_VALUES, B)
> MatSetValuesCOO(B, coo_v, INSERT_VALUES) # -> seg-fault
> Is this an expected behaviour? Of course if I call again MatSetPreallocationCOO on the duplicated matrix it's ok but the performance is lost in my case. Is there a way to fix it? Thank you in advance.
> Best regards,
> Maxime Bouyges

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