get_local_grid_info Subroutine

public subroutine get_local_grid_info(domainDecomp, rank, global_nrows, global_ncols, nrows_per_rank, ncols_per_rank, coords, row_start, col_start, local_nrows, local_ncols)

Subroutine to get local grid information for a rank

Arguments

Type IntentOptional Attributes Name
type(DomainDecomposition), intent(inout) :: domainDecomp

The MPI communication domain decomposition object
integer, intent(in) :: rank

The rank of the current process
integer, intent(in) :: global_nrows

The number of columns in the global board
integer, intent(in) :: global_ncols

The number of rows in the global board
integer, intent(out) :: nrows_per_rank

The number of columns per rank
integer, intent(out) :: ncols_per_rank

The number of rows per rank
integer, intent(out) :: coords(2)

The coordinates of the current rank in the Cartesian grid
integer, intent(out) :: row_start

The starting column index for the local grid
integer, intent(out) :: col_start

The starting row index for the local grid
integer, intent(out) :: local_nrows

The number of columns in the local grid
integer, intent(out) :: local_ncols

The number of rows in the local grid

Calls

proc~~get_local_grid_info~~CallsGraph proc~get_local_grid_info get_local_grid_info mpi_cart_coords mpi_cart_coords proc~get_local_grid_info->mpi_cart_coords mpi_cart_shift mpi_cart_shift proc~get_local_grid_info->mpi_cart_shift

Called by

proc~~get_local_grid_info~~CalledByGraph proc~get_local_grid_info get_local_grid_info proc~find_steady_state find_steady_state proc~find_steady_state->proc~get_local_grid_info program~main main program~main->proc~find_steady_state

Source Code

    subroutine get_local_grid_info(domainDecomp, rank, global_nrows, global_ncols, nrows_per_rank, ncols_per_rank, coords, &
                                row_start, col_start, local_nrows, local_ncols)
        !> The MPI communication domain decomposition object
        type(DomainDecomposition), intent(inout) :: domainDecomp
        !> The rank of the current process
        integer, intent(in) :: rank
        !> The number of columns in the global board
        integer, intent(in) :: global_nrows
        !> The number of rows in the global board
        integer, intent(in) :: global_ncols
        !> The number of columns per rank
        integer, intent(out) :: nrows_per_rank
        !> The number of rows per rank
        integer, intent(out) :: ncols_per_rank
        !> The coordinates of the current rank in the Cartesian grid
        integer, intent(out) :: coords(2)
        !> The starting column index for the local grid
        integer, intent(out) :: row_start
        !> The starting row index for the local grid
        integer, intent(out) :: col_start
        !> The number of columns in the local grid
        integer, intent(out) :: local_nrows
        !> The number of rows in the local grid
        integer, intent(out) :: local_ncols

        integer :: mpierr, num_ranks_col, num_ranks_row

        call MPI_Cart_coords(domainDecomp%communicator, rank, 2, coords, mpierr)
        call MPI_Cart_shift(domainDecomp%communicator, 0, 1, domainDecomp%neighbours(DOWN), domainDecomp%neighbours(UP), mpierr)
        call MPI_Cart_shift(domainDecomp%communicator, 1, 1, domainDecomp%neighbours(LEFT), domainDecomp%neighbours(RIGHT), mpierr)

        nrows_per_rank = global_nrows / domainDecomp%dims(1)
        ncols_per_rank = global_ncols / domainDecomp%dims(2)

        row_start = coords(1)*nrows_per_rank + 1
        col_start = coords(2)*ncols_per_rank + 1

        num_ranks_row = domainDecomp%dims(1)
        num_ranks_col = domainDecomp%dims(2)

        ! Add remainders if on the top or right of the grid
        local_ncols = ncols_per_rank
        local_nrows = nrows_per_rank
        if (domainDecomp%neighbours(RIGHT) == MPI_PROC_NULL) local_ncols = local_ncols + modulo(global_ncols, ncols_per_rank)
        if (domainDecomp%neighbours(UP) == MPI_PROC_NULL) local_nrows = local_nrows + modulo(global_nrows, nrows_per_rank)
    end subroutine get_local_grid_info