On Fri, Feb 28, 2014 at 4:21 PM, Matthew Knepley <[email protected]> wrote:
> On Fri, Feb 28, 2014 at 1:16 PM, Xiangdong <[email protected]> wrote: > >> If I assembly the matrix with MatSetValuesStencil and use KspSetOpreators >> for Ksp, do I need to call KspSetDM first? >> > > No > > >> What is the key difference or advantage of using KspSetComputeOperators >> against KspSetOperators? >> > > With the later, you have to manage creating and preallocating the matrix. > If I use DMCreateMatrix and MatSetValuesStencil, I do not need to preallocate the matrix. Xiangdong > > Matt > > >> Thanks you. >> >> Xiangdong >> >> >> On Tue, Feb 25, 2014 at 4:24 PM, Jed Brown <[email protected]> wrote: >> >>> Xiangdong <[email protected]> writes: >>> > I am not clear about this. In this example, where is the format >>> declaration >>> > (e.g.,mpiaij) of Mat jac? Why is this mat jac always distributed in >>> > a compatible way as the DM vectors? >>> >>> src/ksp/ksp/examples/tutorials/ex25.c calls KSPSetDM and sets functions >>> to assemble the matrices and right hand side. Those objects are created >>> internally (you can use -dm_mat_type sbaij if you like) and the user >>> doesn't have to see them. >>> >> >> > > > -- > 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 >
