On Sun, May 10, 2020 at 4:18 AM Jeff Hammond <[email protected]> wrote:On Sat, May 9, 2020 at 10:10 AM hritikesh semwal via discuss <[email protected]> wrote:Hello,I have following two questions with MPI,1. Do I need to give a separate input file to each processor in a group or all of them can read the input from a single file? All data inside the file should be read by every processor.You can read the input file from every process but it isn't a good idea. Read the input file from rank 0 and broadcast the contents. This assumes that your input file is small. If your input file is huge, then you should consider designing it for parallel reading with MPI_File_* functions.Thanks for your response. I am reading two input files in my parallel CFD solver at different places of the code. The first input file has 7 integer values and second input file has 15 integer values. Is it large to read it through conventional C functions for file reading i.e. fscanf() and is broadcast good for this amount of data?
2. Can you please tell me what is the difference between MPI_Neighbor_alltoallw and MPI_Ineighbor_alltoallw? As I read in MPI 3.0 document that MPI_Neighbor_alltoallw also used non-blocking send and receive inside its execution.MPI_Neighbor_alltoallw is a blocking function while MPI_Ineighbor_alltoallw is not. Using non-blocking send and receive inside its execution does not mean that MPI_Neighbor_alltoallw doesn't block - if that is how it's implemented, then there will be the equivalent of a MPI_Waitall before the function returns. But in any case, just because the MPI document suggests a possible implementation does not mean that is how all implementations work.Yes, there is MPI_Waitall inside the MPI_Neighbor_alltoallw before it returns.JeffThank you._______________________________________________discuss mailing list [email protected]To manage subscription options or unsubscribe:--_______________________________________________discuss mailing list [email protected]To manage subscription options or unsubscribe: