fix offset in spectral space

src/omp/kernels/spectral_processing.f90

@@ -4,15 +4,15 @@ module m_omp_spectral
 
 contains
   subroutine process_spectral_div_u( &
-    div_u, waves, nx_spec, ny_spec, nz_spec, y_sp_st, z_sp_st, &
+    div_u, waves, nx_spec, ny_spec, nz_spec, x_sp_st, y_sp_st, z_sp_st, &
     nx, ny, nz, ax, bx, ay, by, az, bz &
     )
 
     complex(dp), intent(inout), dimension(:, :, :) :: div_u
     complex(dp), intent(in), dimension(:, :, :) :: waves
     real(dp), intent(in), dimension(:) :: ax, bx, ay, by, az, bz
     integer, intent(in) :: nx_spec, ny_spec, nz_spec
-    integer, intent(in) :: y_sp_st, z_sp_st
+    integer, intent(in) :: x_sp_st, y_sp_st, z_sp_st
     integer, intent(in) :: nx, ny, nz
 
     integer :: i, j, k, ix, iy, iz
@@ -25,7 +25,7 @@ subroutine process_spectral_div_u( &
           div_r = real(div_u(i, j, k), kind=dp)/nx/ny/nz
           div_c = aimag(div_u(i, j, k))/nx/ny/nz
 
-          ix = i
+          ix = i + x_sp_st
           iy = j + y_sp_st
           iz = k + z_sp_st
 

src/omp/poisson_fft.f90

@@ -45,6 +45,8 @@ function init(mesh, xdirps, ydirps, zdirps) result(poisson_fft)
 
     call decomp_2d_fft_init(PHYSICAL_IN_X)
     call decomp_2d_fft_get_size(istart, iend, isize)
+    ! Converts a start position into an offset
+    istart(:) = istart(:) - 1
     call poisson_fft%spec_init(mesh, xdirps, ydirps, zdirps, isize, istart)
 
     allocate (poisson_fft%c_x(poisson_fft%nx_spec, poisson_fft%ny_spec, &
@@ -78,7 +80,7 @@ subroutine fft_postprocess_omp(self)
     class(omp_poisson_fft_t) :: self
 
     call process_spectral_div_u( &
-      self%c_x, self%waves, self%nx_spec, self%ny_spec, self%nz_spec, &
+      self%c_x, self%waves, self%nx_spec, self%ny_spec, self%nz_spec, self%x_sp_st, &
       self%y_sp_st, self%z_sp_st, self%nx_glob, self%ny_glob, self%nz_glob, &
       self%ax, self%bx, self%ay, self%by, self%az, self%bz &
       )

src/poisson_fft.f90

@@ -17,7 +17,7 @@ module m_poisson_fft
     !> Local dimensions in the permuted slabs in spectral space
     integer :: nx_spec, ny_spec, nz_spec
     !> Offset in y and z directions in the permuted slabs in spectral space
-    integer :: y_sp_st, z_sp_st
+    integer :: x_sp_st, y_sp_st, z_sp_st
     !> Local domain sized array storing the spectral equivalence constants
     complex(dp), allocatable, dimension(:, :, :) :: waves
     !> Wave numbers in x, y, and z
@@ -89,12 +89,13 @@ subroutine spec_init(self, mesh, xdirps, ydirps, zdirps, n_spec, n_sp_st)
     type(mesh_t), intent(in) :: mesh
     type(dirps_t), intent(in) :: xdirps, ydirps, zdirps
     integer, dimension(3), intent(in) :: n_spec ! Size of the spectral pencil
-    integer, dimension(3), intent(in) :: n_sp_st ! Start of the spectral pencil (=offset)
+    integer, dimension(3), intent(in) :: n_sp_st ! Offset of the spectral pencil
 
     self%nx_spec = n_spec(1)
     self%ny_spec = n_spec(2)
     self%nz_spec = n_spec(3)
 
+    self%x_sp_st = n_sp_st(1)
     self%y_sp_st = n_sp_st(2)
     self%z_sp_st = n_sp_st(3)
 
@@ -209,7 +210,7 @@ subroutine waves_set(self, geo, xdirps, ydirps, zdirps)
     do k = 1, self%nz_spec
       do j = 1, self%ny_spec
         do i = 1, self%nx_spec
-          ix = i; iy = j + self%y_sp_st; iz = k + self%z_sp_st
+          ix = i + self%x_sp_st; iy = j + self%y_sp_st; iz = k + self%z_sp_st
           rlexs = real(exs(ix), kind=dp)*geo%d(1)
           rleys = real(eys(iy), kind=dp)*geo%d(2)
           rlezs = real(ezs(iz), kind=dp)*geo%d(3)