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subroutine ONETO2(id, x, y)
implicit none
integer, intent(in) :: id
integer, intent(out) :: x, y
y = id / b
x = mod(id, b)
end subroutine ONETO2
function TWOtoONE(x, y) result(id)
implicit none
integer, intent(in) :: x, y
integer :: id
id = y * b + x
end function TWOtoONE
function get_neighbour_ids(p) result (neighbours)
integer, intent(in) :: p !> The sequential position
integer, allocatable, dimension(:) :: neighbours !> The list of neighbours
integer :: i,j,k
integer :: x_cell, y_cell, x_test, y_test
integer :: max_list(9)
!> Don't save the values between calls
k = 1
max_list = -1
call ONETO2(p,x_cell,y_cell)
max_list(k) = p
!print *, max_list
!> Start by just getting all of the neighbours
do i = -1,1
do j = -1,1
if(i == 0 .and. j == 0) cycle !> Skip the cell itself
!> The "test" coordinate
x_test = x_cell + i
y_test = y_cell + j
!> If the coordinates are real (within the expected range), add them to the list:
if((x_test .ge. 0 .and. x_test .lt. b) .and. (y_test .ge. 0 .and. y_test .lt. b)) then
!> Increment the number of correct coordinates
k = k + 1
!> Flip a zero to the new coordinate in the max list
max_list(k) = TWOtoONE(x_test, y_test)
end if
end do
end do
!> Return a vector of all non-zero elements
! neighbours = pack(max_list, max_list>= 0.0)
neighbours = max_list ! entries -1 must be skipped as they correspond to non-existent neighbours at the edge or corner
end function get_neighbour_ids
subroutine buildNBL()
integer :: sector
do sector=0,b*b-1
nbl(sector,:) = get_neighbour_ids(sector)
end do
end subroutine buildNBL
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