So... what do I need to do, please? Why am I getting wrong results when solving the linear system if the matrix is filled in with MatSetPreallocationCOO and MatSetValuesCOO?
Em ter., 20 de jun. de 2023 às 14:56, Jed Brown <j...@jedbrown.org> escreveu: > Matthew Knepley <knep...@gmail.com> writes: > > >> The matrix entries are multiplied by 2, that is, the number of processes > >> used to execute the code. > >> > > > > No. This was mostly intended for GPUs, where there is 1 process. If you > > want to use multiple MPI processes, then each process can only introduce > > some disjoint subset of the values. This is also how MatSetValues() > works, > > but it might not be as obvious. > > They need not be disjoint, just sum to the expected values. This interface > is very convenient for FE and FV methods. MatSetValues with ADD_VALUES has > similar semantics without the intermediate storage, but it forces you to > submit one element matrix at a time. Classic parallelism granularity versus > memory use tradeoff with MatSetValuesCOO being a clear win on GPUs and more > nuanced for CPUs. >
