There are examples in the manpages, see for instance https://petsc.org/release/docs/manualpages/Mat/MatCreateAIJ/ https://petsc.org/release/docs/manualpages/Mat/MatMPIAIJSetPreallocation/
Jose > El 17 oct 2022, a las 10:12, fujisan <[email protected]> escribió: > > Can I preallocate space for a rectangular matrix using MatCreateAIJ() in > parallel? > It is not clear to me how I have to define d_nnz when the matrix is > rectangular? > > X * * * * > * X * * * > * * X * * > * * * X * > * * * * X > * * * * * > * * * * * > > The example shown is for an 8x8 matrix on 3 cpu > X * * > * X * > * * X > > On Mon, Oct 17, 2022 at 9:02 AM Jose E. Roman <[email protected]> wrote: > You have to preallocate, see > https://petsc.org/release/docs/manual/mat/#sec-matsparse > > > El 17 oct 2022, a las 8:37, fujisan <[email protected]> escribió: > > > > Hi everyone, > > > > I initialize a large sparse matrix (50000x20000) using MatCreate() and then > > filling it with MatSetValues() line by line > > but it takes a bit more than an hour on 80 cores to fill in the matrix. > > > > Is there a way to optimize this initialization? > > > > Fuji >
