On Thu, Sep 20, 2018 at 12:09 PM Matthew Knepley <[email protected]> wrote:
> On Thu, Sep 20, 2018 at 1:26 PM Fande Kong <[email protected]> wrote: > >> Hi Developers, >> >> MATBAIJ actually assumes that the point-block is dense. It is fine if the >> block size is small for example less than 50, but we may suffer from a >> memory issue if the block is large such as 1000. The block is not necessary >> dense. In my application, neutron transport equations, the block is >> actually sparse (coming from direction and energy grids). Now I am using >> MATAIJ, but I want to take into consideration there are many variables on >> each spatial grid when doing some ILU(0). ILU(0) is used as a subdomain >> solver for ASM and BJACOBI. >> >> I would like to support point-block ILU(0) in MATAIJ (not MATBAIJ) >> because the block is sparse. Any comments? It is worthwhile to do that? I >> think we might reduce the symbolic factor time when considering the block. >> > > What optimization do you hope to take advantage of? > The inverse of sparse block can be approximated with the inverse of the block diagonal. Does it help reduce the compute time in symbolic factorization? Fande, > The main optimization in sparse LU is finding dense blocks, > and it should do a good job of that. I do not see what defining huge, > sparse blocks does for you. > > Thanks, > > Matt > > >> Thanks, >> >> Fande, >> > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > > https://www.cse.buffalo.edu/~knepley/ > <http://www.cse.buffalo.edu/~knepley/> >
