HP-MPI User's Guide (11th Edition)

Example applications
multi_par.f
Appendix A254
datatypes
integer ablen(:) ! array of block lengths
integer adisp(:) ! array of displacements
integer adtype(:) ! array of datatypes
allocatable
rbs,rbe,cbs,cbe,rdtype,cdtype,twdtype,ablen,adisp,
* adtype
integer rank ! rank iteration counter
integer comm_size ! number of MPI processes
integer comm_rank ! sequential ID of MPI
process
integer ierr ! MPI error code
integer mstat(mpi_status_size) ! MPI function status
integer src ! source rank
integer dest ! destination rank
integer dsize ! size of double
precision in bytes
double precision startt,endt,elapsed ! time keepers
external compcolumn,comprow ! subroutines execute in
threads
c
c MPI initialization
c
call mpi_init(ierr)
call mpi_comm_size(mpi_comm_world,comm_size,ierr)
call mpi_comm_rank(mpi_comm_world,comm_rank,ierr)
c
c Data initialization and start up
c
if (comm_rank.eq.0) then
write(6,*) 'Initializing',nrow,' x',ncol,' array...'
call getdata(nrow,ncol,array)
write(6,*) 'Start computation'
endif
call mpi_barrier(MPI_COMM_WORLD,ierr)
startt=mpi_wtime()
c
c Compose MPI datatypes for row/column send-receive
c
c Note that the numbers from rbs(i) to rbe(i) are the indices
c of the rows belonging to the i'th block of rows. These
indices
c specify a portion (the i'th portion) of a column and the
c datatype rdtype(i) is created as an MPI contiguous datatype
c to refer to the i'th portion of a column. Note this is a
c contiguous datatype because fortran arrays are stored
c column-wise.
c
c For a range of columns to specify portions of rows, the
situation
c is similar: the numbers from cbs(j) to cbe(j) are the
indices
c of the columns belonging to the j'th block of columns.
These