[petsc-users] Memory Usage in Matrix Assembly.

[Pantelis Moschopoulos]

Hi everyone,

I am a new Petsc user that incorporates Petsc for FEM in a Fortran code.
My question concerns the sudden increase of the memory that Petsc needs during the assembly of the jacobian matrix. After this point, memory is freed. It seems to me like Petsc performs memory allocations and the deallocations during assembly.
I have used the following commands with no success:
CALL MatSetOption(petsc_A, MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE,ier)
CALL MatSetOption(petsc_A, MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE,ier)
CALL MatSetOption(petsc_A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_TRUE,ier).
CALL MatSetOption(petsc_A, MAT_KEEP_NONZERO_PATTERN,PETSC_TRUE,ier)

The structure of the matrix does not change during my simulation, just the values. I am expecting this behavior the first time that I create this matrix because the preallocation instructions that I use are not very accurate but this continues every time I assemble the matrix.
What I am missing here?

Thank you very much,
Pantelis
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