Prentice Bisbal wrote: > I hit send to early on my last reply, please forgive me... > > Jed Brown wrote: >> On Mon, 08 Feb 2010 13:54:10 -0500, Prentice Bisbal <prent...@ias.edu> wrote: >>> but I don't have that book handy >> The standard has lots of examples. >> >> http://www.mpi-forum.org/docs/docs.html > > Thanks, I'll check out those examples. >> You can do this, but for small structures, you're better off just >> packing buffers. For large structures containing variable-size fields, >> I think it is clearer to use MPI_BOTTOM instead of offsets from an >> arbitrary (instance-dependent) address. > > I'll give that a try, too. IMHO, MPI_Pack/Unpack looks easier and less > error prone, but Pacheco advocates using derived types over > MPI_Pack/Unpack. > >> [...] >> >>> if (rank == 0) { >>> a_point.index = 1; >>> a_point.coords = malloc(3 * sizeof(int)); >>> a_point.coords[0] = 3; >>> a_point.coords[1] = 6; >>> a_point.coords[2] = 9; >>> } >>> >>> block_lengths[0] = 1; >>> block_lengths[1] = 3; >>> >>> type_list[0] = MPI_INT; >>> type_list[1] = MPI_INT; >>> >>> displacements[0] = 0; >>> MPI_Address(&a_point.index, &start_address); >>> MPI_Address(a_point.coords, &address); >> ^^^^^^^^^^^^^^ >> >> Rank 1 has not allocated this yet. > > I'm glad you brought that up. I wanted to ask about that: > > In my situation, rank 0 is reading in a file containing all the coords. > So even if other ranks don't have the data, I still need to create the > structure on all the nodes, even if I don't populate it with data?
To clarify: I thought adding a similar structure, b_point in rank 1 would be adequate to receive the data from rank 0. -- Prentice
