[ ]Example array file layout

[ ]Example local array filetype for process 1 Assume we are writing out a 100x100 2D array of double precision floating point numbers that is distributed among 4 processes such that each process has a block of 25 columns (e.g., process 0 has columns 0-24, process 1 has columns 25-49, etc.; see Figure 16 ). To create the filetypes for each process one could use the following C program:

Or, equivalently in Fortran:double subarray[100][25]; MPI_Datatype filetype; int sizes[2], subsizes[2], starts[2]; int rank; MPI_Comm_rank(MPI_COMM_WORLD, &rank); sizes[0]=100; sizes[1]=100; subsizes[0]=100; subsizes[1]=25; starts[0]=0; starts[1]=rank*subsizes[1]; MPI_Type_create_subarray(2, sizes, subsizes, starts, MPI_ORDER_C, MPI_DOUBLE, &filetype);

The generated filetype will then describe the portion of the file contained within the process's subarray with holes for the space taken by the other processes. Figure 17 shows the filetype created for process 1.double precision subarray(100,25) integer filetype, rank, ierror integer sizes(2), subsizes(2), starts(2) call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierror) sizes(1)=100 sizes(2)=100 subsizes(1)=100 subsizes(2)=25 starts(1)=0 starts(2)=rank*subsizes(2) call MPI_TYPE_CREATE_SUBARRAY(2, sizes, subsizes, starts, & MPI_ORDER_FORTRAN, MPI_DOUBLE_PRECISION, & filetype, ierror)

Return to MPI-2 Standard Index

Return to MPI 1.1 Standard Index

Return to MPI Forum Home Page

MPI-2.0 of July 18, 1997

HTML Generated on September 10, 2001