From 409775bcbe46b293a886808c24d404e3f37f547b Mon Sep 17 00:00:00 2001
From: Remi Lehe <remi.lehe@normalesup.org>
Date: Sun, 21 Apr 2019 07:00:59 -0700
Subject: Apply shift factors

---
 .../SpectralSolver/SpectralFieldData.cpp           | 45 +++++++++++++++++-----
 1 file changed, 36 insertions(+), 9 deletions(-)

(limited to 'Source/FieldSolver/SpectralSolver/SpectralFieldData.cpp')

diff --git a/Source/FieldSolver/SpectralSolver/SpectralFieldData.cpp b/Source/FieldSolver/SpectralSolver/SpectralFieldData.cpp
index 3fd7177e5..7d712ba03 100644
--- a/Source/FieldSolver/SpectralSolver/SpectralFieldData.cpp
+++ b/Source/FieldSolver/SpectralSolver/SpectralFieldData.cpp
@@ -25,13 +25,18 @@ SpectralFieldData::SpectralFieldData( const BoxArray& realspace_ba,
     tmpRealField = SpectralField(realspace_ba, dm, 1, 0);
     tmpSpectralField = SpectralField(spectralspace_ba, dm, 1, 0);
 
-    // Allocate the vectors that allow to shift between nodal and cell-centered
-    for (int i_dim=0; i_dim<AMREX_SPACEDIM; i_dim++) {
-        shift_C2N[i_dim] = k_space.AllocateAndFillSpectralShiftFactor(
-                            dm, i_dim, ShiftType::CenteredToNodal );
-        shift_N2C[i_dim] = k_space.AllocateAndFillSpectralShiftFactor(
-                            dm, i_dim, ShiftType::NodalToCentered );
-    }
+    // Allocate the coefficients that allow to shift between nodal and cell-centered
+    xshift_C2N = k_space.getSpectralShiftFactor(dm, 0, ShiftType::CenteredToNodal);
+    xshift_N2C = k_space.getSpectralShiftFactor(dm, 0, ShiftType::NodalToCentered);
+#if (AMREX_SPACEDIM == 3)
+    yshift_C2N = k_space.getSpectralShiftFactor(dm, 1, ShiftType::CenteredToNodal);
+    yshift_N2C = k_space.getSpectralShiftFactor(dm, 1, ShiftType::NodalToCentered);
+    zshift_C2N = k_space.getSpectralShiftFactor(dm, 2, ShiftType::CenteredToNodal);
+    zshift_N2C = k_space.getSpectralShiftFactor(dm, 2, ShiftType::NodalToCentered);
+#else
+    zshift_C2N = k_space.getSpectralShiftFactor(dm, 1, ShiftType::CenteredToNodal);
+    zshift_N2C = k_space.getSpectralShiftFactor(dm, 1, ShiftType::NodalToCentered);
+#endif
 
     // Allocate and initialize the FFT plans
     forward_plan = FFTplans(spectralspace_ba, dm);
@@ -139,6 +144,15 @@ void
 SpectralFieldData::BackwardTransform( MultiFab& mf,
                                       const int field_index, const int i_comp )
 {
+    // Check field index type, in order to apply proper shift in spectral space
+    const bool is_nodal_x = mf.is_nodal(0);
+#if (AMREX_SPACEDIM == 3)
+    const bool is_nodal_y = mf.is_nodal(1);
+    const bool is_nodal_z = mf.is_nodal(2);
+#else
+    const bool is_nodal_z = mf.is_nodal(1);
+#endif
+
     // Loop over boxes
     for ( MFIter mfi(mf); mfi.isValid(); ++mfi ){
 
@@ -148,10 +162,22 @@ SpectralFieldData::BackwardTransform( MultiFab& mf,
             SpectralField& field = getSpectralField( field_index );
             Array4<const Complex> field_arr = field[mfi].array();
             Array4<Complex> tmp_arr = tmpSpectralField[mfi].array();
+            const Complex* xshift_C2N_arr = xshift_C2N[mfi].dataPtr();
+            const Complex* yshift_C2N_arr = yshift_C2N[mfi].dataPtr();
+            const Complex* zshift_C2N_arr = zshift_C2N[mfi].dataPtr();
+            // Loop over indices within one box
             const Box spectralspace_bx = tmpSpectralField[mfi].box();
             ParallelFor( spectralspace_bx,
             [=] AMREX_GPU_DEVICE(int i, int j, int k) noexcept {
-                tmp_arr(i,j,k) = field_arr(i,j,k);
+                Complex spectral_field_value = field_arr(i,j,k);
+                // Apply proper shift in each dimension
+                if (is_nodal_x==false) spectral_field_value *= xshift_C2N_arr[i];
+#if (AMREX_SPACEDIM == 3)
+                if (is_nodal_y==false) spectral_field_value *= yshift_C2N_arr[j];
+#endif
+                if (is_nodal_z==false) spectral_field_value *= zshift_C2N_arr[k];
+                // Copy field into temporary array
+                tmp_arr(i,j,k) = spectral_field_value;
             });
         }
 
@@ -170,7 +196,8 @@ SpectralFieldData::BackwardTransform( MultiFab& mf,
         // Normalize (divide by 1/N) since the FFT result in a factor N
         {
             Box bx = mf[mfi].box();
-            const Box realspace_bx = bx.enclosedCells(); // discards last point in each nodal direction
+            const Box realspace_bx = bx.enclosedCells();
+            // `enclosedells` discards last point in each nodal direction
             AMREX_ALWAYS_ASSERT( realspace_bx == tmpRealField[mfi].box() );
             Array4<Real> mf_arr = mf[mfi].array();
             Array4<const Complex> tmp_arr = tmpRealField[mfi].array();
-- 
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