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! $Header$
! Take a mask where the boundary has been been marked.
! Return information about the normals in these locations.
#include "cctk.h"
#include "cctk_Parameters.h"
#include "maskvalues.h"
subroutine excision_findnormals (ierr, mask, dirx, diry, dirz, ni, nj, nk)
implicit none
DECLARE_CCTK_FUNCTIONS
DECLARE_CCTK_PARAMETERS
! Arguments
! out: zero for success, nonzero for error
integer :: ierr
! in: array sizes for grid functions
! (you can pass in cctk_lsh(:) for these)
integer :: ni,nj,nk
! in: mask
CCTK_REAL :: mask(ni,nj,nk)
! out: normal directions to use for interpolation
CCTK_REAL :: dirx(ni,nj,nk), diry(ni,nj,nk), dirz(ni,nj,nk)
! Extra variables.
integer i,j,k,ii,jj,kk
integer sx,sy,sz,smax
! Initialise direction arrays to zero.
dirx = 0
diry = 0
dirz = 0
! Loop over grid points.
do k=2,nk-1
do j=2,nj-1
do i=2,ni-1
! Check if the point is in the boundary.
if (mask(i,j,k)==MASK_BOUNDARY) then
! Initialise integer vector (sx,sy,sz) to zero.
sx = 0; sy = 0; sz = 0
! Loop around nearest neighbours.
do kk=-1,1
do jj=-1,1
do ii=-1,1
! If a neighbour is active, add its relative
! coordinates to (sx,sy,sz).
if (mask(i+ii,j+jj,k+kk)==MASK_ACTIVE) then
sx = sx + ii; sy = sy + jj; sz = sz + kk
end if
end do
end do
end do
! Find maximum component of (sx,sy,sz).
smax = max(abs(sx),abs(sy),abs(sz))
! Do an integer division of (sx,sy,sz) with smax.
! This ensures that we end up with a vector that
! has only 0 and +-1 as components.
sx = sx/smax
sy = sy/smax
sz = sz/smax
dirx(i,j,k) = sx
diry(i,j,k) = sy
dirz(i,j,k) = sz
! Sanity check.
if (mask(i+sx,j+sy,k+sz) /= MASK_ACTIVE) then
call CCTK_WARN (0, "Mask boundary layer is too thick")
end if
end if
end do
end do
end do
! Success
ierr = 0
end subroutine excision_findnormals
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