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! Helper functions for all examples
module decomp
contains
! random integer from {minv, minv+1, ..., maxv}
! including minv and maxv
function get_random(minv, maxv) result(n)
implicit none
integer, intent(in) :: minv, maxv
real :: r
integer :: n
call random_number(r)
n = minv + FLOOR((maxv+1-minv)*r)
end function get_random
! gather the local sizes of arrays and sum them up
! so that each process knows the global shape
! and its own offset in the global space
subroutine gather_decomp_1d(mysize, myshape, myoffset)
use mpivars
implicit none
integer*8, intent(in) :: mysize
integer*8, intent(out) :: myshape, myoffset
integer*8, dimension(:), allocatable :: sizes
allocate(sizes(nproc))
call MPI_Allgather( mysize, 1, MPI_LONG_LONG, &
sizes, 1, MPI_LONG_LONG, &
app_comm, ierr)
myshape = sum(sizes)
myoffset = sum(sizes(1:rank))
deallocate(sizes)
end subroutine gather_decomp_1d
subroutine decompose_1d(globalsize, myoffset, mysize)
use mpivars
implicit none
integer*8, intent(in) :: globalsize
integer*8, intent(out) :: myoffset, mysize
integer*8 :: rem
mysize = globalsize/nproc
rem = globalsize-(nproc*mysize)
if (rank < rem) then
mysize = mysize + 1
myoffset = rank*mysize
else
myoffset = rank*mysize + rem
endif
end subroutine decompose_1d
end module decomp
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