On Wed, Nov 16, 2011 at 03:52:05PM +0000, Kharche, Sanjay wrote: > > Dear All > > I am sure this issue has been discussed before on the forum, but I will > appreciate your comments. > > I have a package that tries to do parallel file output using MPI_File_Write: > > /* Write to file. */ > mpi_errno = MPI_File_write(file, New, 1, sourceType, MPI_STATUS_IGNORE); > > With an increasing number of processors, I see that this causes the file > output to take longer. Can someone suggest a solution?
Think a bit about what adding more processors will do. Each MPI process will write 1 sourceType to the file. More processors will write more data. I don't know how your program creates sourceType, nor do i know the file view (if any) it has placed on the output, so maybe you will need to show more code. I hope you are setting a file view here, or each processor will end up writing the same data to the same location in the file. If you duplicate the work identically to N processors then yeah, you will take N times longer. ==rob -- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA
