[Libmesh-users] Reduced Basis: Petsc Matrix Ignore Zero Entries

[Nikhil V. <nik...@gm...>]

Hi,

I am using reduced basis for my work. The number of Aq matrices in my
problem is very large (~250). Because of this, the memory requirements of
my program are ~200 times the mesh-file size. I did some memory usage study
and found out that the allocate_data_structures() function in
RBConstruction is responsible for most of the memory usage.

I think this might be due to the large number of Petsc sparse matrices
being constructed. Each Aq matrix is known to have non-zero entries
corresponding to only a small sub-domain of the geometry. All these
sub-domains are separate blocks in the mesh. I get the feeling that for
each sparse matrix memory is being allocated even for the zero entries. I
saw that Petsc has an option MAT_IGNORE_ZERO_ENTRIES. How does one pass
this in libMesh? Please note that I am not using libMesh directly. My code
is a MOOSE app, and I am using the RB functionality of the underlying
libmesh code.

Best regards,
Nikhil