[petsc-users] Call to DMSetMatrixPreallocateSkip not changing allocation behavior

[Fackler, Philip]

I'm using the following sequence of functions related to the Jacobian matrix:

DMDACreate1d(..., &da);
DMSetFromOptions(da);
DMSetUp(da);
DMSetMatType(da, MATAIJKOKKOS);
DMSetMatrixPreallocateSkip(da, PETSC_TRUE);
Mat J;
DMCreateMatrix(da, &J);
MatSetPreallocationCOO(J, ...);

I recently added the call to DMSetMatrixPreallocateSkip, hoping the allocation would be delayed to MatSetPreallocationCOO, and that it would require less memory. The documentation<https://petsc.org/release/manualpages/DM/DMSetMatrixPreallocateSkip/> says that the data structures will not be preallocated. The following data from heaptrack shows that the allocation is still happening in the call to DMCreateMatrix.

[cid:bda9ef12-a46f-47b2-9b9b-a4b2808b6b13]

Can someone help me understand this?

Thanks,

Philip Fackler
Research Software Engineer, Application Engineering Group
Advanced Computing Systems Research Section
Computer Science and Mathematics Division
Oak Ridge National Laboratory
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