Hello, Thanks for your response.
@David Reducing the number of Aq matrices is not really ideal for my application. I would like to try and see if I can reduce the memory requirement in some other way. @Paul Indeed PetscMatrix is used for Reduced Basis also. I went through the PetscMatrix class documentation, and tried to insert the flag MAT_IGNORE_ZERO_ENTRIES in the MatSetOption function. It turns out that that flag does not work if the matrix is pre-allocated. Since pre-allocation of the matrix is necessary for good performance, I do not want to disable it. Is it possible to construct a sparsity pattern only for a particular subdomain of the mesh and then attach it to a sparse matrix? If this works, I think it will solve my problem. Best regards, Nikhil On Thu, Apr 23, 2020 at 3:22 PM Paul T. Bauman <ptbau...@gmail.com> wrote: > Hi Nikhil, > > Typically, you would grab the "raw" underlying Mat object and do the PETSc > call yourself. This would be accessible from the libMesh::PetscMatrix > object. Typically the ImplicitSystem has the system matrix, but I'm not > familiar with where these matrices would be cached on the RB side of > things. I would use the Oxygen documentation as a starting point: > libmesh.github.io (although it seems GitHub is misbehaving ATM). I hope > that helps. > > Best, > > Paul > > On Thu, Apr 23, 2020 at 12:06 AM Nikhil Vaidya <nikhilvaidy...@gmail.com> > wrote: > >> 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 >> >> _______________________________________________ >> Libmesh-users mailing list >> Libmesh-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/libmesh-users >> > _______________________________________________ Libmesh-users mailing list Libmesh-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/libmesh-users
