Implement nodal solver

4 files changed, 129 insertions, 14 deletions

diff --git a/Source/FieldSolver/FiniteDifferenceSolver/EvolveB.cpp b/Source/FieldSolver/FiniteDifferenceSolver/EvolveB.cpp
index 72d3a1135..7a3f5aa9b 100644
--- a/Source/FieldSolver/FiniteDifferenceSolver/EvolveB.cpp
+++ b/Source/FieldSolver/FiniteDifferenceSolver/EvolveB.cpp
@@ -5,6 +5,7 @@
 #else
     #include "FiniteDifferenceAlgorithms/YeeAlgorithm.H"
     #include "FiniteDifferenceAlgorithms/CKCAlgorithm.H"
+    #include "FiniteDifferenceAlgorithms/NodalAlgorithm.H"
 #endif
 #include <AMReX_Gpu.H>
 
@@ -20,7 +21,9 @@ void FiniteDifferenceSolver::EvolveB ( VectorField& Bfield,
     if (m_fdtd_algo == MaxwellSolverAlgo::Yee){
         EvolveBCylindrical <CylindricalYeeAlgorithm> ( Bfield, Efield, dt );
 #else
-    if (m_fdtd_algo == MaxwellSolverAlgo::Yee){
+    if (m_do_nodal) {
+        EvolveBCartesian <NodalAlgorithm> ( Bfield, Efield, dt );
+    } else if (m_fdtd_algo == MaxwellSolverAlgo::Yee) {
         EvolveBCartesian <YeeAlgorithm> ( Bfield, Efield, dt );
     } else if (m_fdtd_algo == MaxwellSolverAlgo::CKC) {
         EvolveBCartesian <CKCAlgorithm> ( Bfield, Efield, dt );
diff --git a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/NodalAlgorithm.H b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/NodalAlgorithm.H
new file mode 100644
index 000000000..8ffd23b79
--- /dev/null
+++ b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceAlgorithms/NodalAlgorithm.H
@@ -0,0 +1,103 @@
+#ifndef WARPX_FINITE_DIFFERENCE_ALGORITHM_NODAL_H_
+#define WARPX_FINITE_DIFFERENCE_ALGORITHM_NODAL_H_
+
+#include <AMReX_REAL.H>
+#include <AMReX_Array4.H>
+#include <AMReX_Gpu.H>
+
+struct NodalAlgorithm {
+
+    static void InitializeStencilCoefficients(
+        std::array<amrex::Real,3>& cell_size,
+        amrex::Gpu::ManagedVector<amrex::Real>& stencil_coefs_x,
+        amrex::Gpu::ManagedVector<amrex::Real>& stencil_coefs_y,
+        amrex::Gpu::ManagedVector<amrex::Real>& stencil_coefs_z ) {
+
+        // Store the inverse cell size along each direction in the coefficients
+        stencil_coefs_x.resize(1);
+        stencil_coefs_x[0] = 1./cell_size[0];
+        stencil_coefs_y.resize(1);
+        stencil_coefs_y[0] = 1./cell_size[1];
+        stencil_coefs_z.resize(1);
+        stencil_coefs_z[0] = 1./cell_size[2];
+    }
+
+    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+    static amrex::Real UpwardDx(
+        amrex::Array4<amrex::Real> const& F,
+        amrex::Real const* coefs_x, int const n_coefs_x,
+        int const i, int const j, int const k ) {
+
+        amrex::Real inv_dx = coefs_x[0];
+        return 0.5*inv_dx*( F(i+1,j,k) - F(i-1,j,k) );
+    };
+
+    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+    static amrex::Real DownwardDx(
+        amrex::Array4<amrex::Real> const& F,
+        amrex::Real const* coefs_x, int const n_coefs_x,
+        int const i, int const j, int const k ) {
+
+        amrex::Real inv_dx = coefs_x[0];
+        return 0.5*inv_dx*( F(i+1,j,k) - F(i-1,j,k) );
+    };
+
+    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+    static amrex::Real UpwardDy(
+        amrex::Array4<amrex::Real> const& F,
+        amrex::Real const* coefs_y, int const n_coefs_y,
+        int const i, int const j, int const k ) {
+
+        #if defined WARPX_DIM_3D
+            amrex::Real inv_dy = coefs_y[0];
+            return 0.5*inv_dy*( F(i,j+1,k) - F(i,j-1,k) );
+        #elif (defined WARPX_DIM_XZ)
+            return 0; // 2D Cartesian: derivative along y is 0
+        #endif
+    };
+
+    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+    static amrex::Real DownwardDy(
+        amrex::Array4<amrex::Real> const& F,
+        amrex::Real const* coefs_y, int const n_coefs_y,
+        int const i, int const j, int const k ) {
+
+        #if defined WARPX_DIM_3D
+            amrex::Real inv_dy = coefs_y[0];
+            return 0.5*inv_dy*( F(i,j+1,k) - F(i,j-1,k) );
+        #elif (defined WARPX_DIM_XZ)
+            return 0; // 2D Cartesian: derivative along y is 0
+        #endif
+    };
+
+    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+    static amrex::Real UpwardDz(
+        amrex::Array4<amrex::Real> const& F,
+        amrex::Real const* coefs_z, int const n_coefs_z,
+        int const i, int const j, int const k ) {
+
+        amrex::Real inv_dz = coefs_z[0];
+        #if defined WARPX_DIM_3D
+            return 0.5*inv_dz*( F(i,j,k+1) - F(i,j,k-1) );
+        #elif (defined WARPX_DIM_XZ)
+            return 0.5*inv_dz*( F(i,j+1,k) - F(i,j-1,k) );
+        #endif
+    };
+
+    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
+    static amrex::Real DownwardDz(
+        amrex::Array4<amrex::Real> const& F,
+        amrex::Real const* coefs_z, int const n_coefs_z,
+        int const i, int const j, int const k ) {
+
+        amrex::Real inv_dz = coefs_z[0];
+        #if defined WARPX_DIM_3D
+            return 0.5*inv_dz*( F(i,j,k+1) - F(i,j,k-1) );
+        #elif (defined WARPX_DIM_XZ)
+            return 0.5*inv_dz*( F(i,j+1,k) - F(i,j-1,k) );
+        #endif
+    };
+
+};
+
+#endif // WARPX_FINITE_DIFFERENCE_ALGORITHM_NODAL_H_
diff --git a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.H b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.H
index 9ce910e3d..0673befca 100644
--- a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.H
+++ b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.H
@@ -1,13 +1,6 @@
 #ifndef WARPX_FINITE_DIFFERENCE_SOLVER_H_
 #define WARPX_FINITE_DIFFERENCE_SOLVER_H_
 
-#include "WarpXAlgorithmSelection.H"
-#ifdef WARPX_DIM_RZ
-    #include "FiniteDifferenceAlgorithms/CylindricalYeeAlgorithm.H"
-#else
-    #include "FiniteDifferenceAlgorithms/YeeAlgorithm.H"
-    #include "FiniteDifferenceAlgorithms/CKCAlgorithm.H"
-#endif
 #include <AMReX_MultiFab.H>
 
 /**
@@ -22,8 +15,10 @@ class FiniteDifferenceSolver
         using VectorField = std::array< std::unique_ptr<amrex::MultiFab>, 3 >;
 
         // Constructor
-        FiniteDifferenceSolver ( int const fdtd_algo,
-            std::array<amrex::Real,3> cell_size );
+        FiniteDifferenceSolver (
+            int const fdtd_algo,
+            std::array<amrex::Real,3> cell_size,
+            int const do_nodal );
 
         void EvolveB ( VectorField& Bfield,
                        VectorField const& Efield,
@@ -31,6 +26,7 @@ class FiniteDifferenceSolver
     private:
 
         int m_fdtd_algo;
+        int m_do_nodal;
 
 #ifdef WARPX_DIM_RZ
         amrex::Real m_dr, m_rmin;
diff --git a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.cpp b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.cpp
index d89e6e9d3..94499200a 100644
--- a/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.cpp
+++ b/Source/FieldSolver/FiniteDifferenceSolver/FiniteDifferenceSolver.cpp
@@ -1,9 +1,19 @@
+#include "WarpXAlgorithmSelection.H"
+#ifdef WARPX_DIM_RZ
+    #include "FiniteDifferenceAlgorithms/CylindricalYeeAlgorithm.H"
+#else
+    #include "FiniteDifferenceAlgorithms/YeeAlgorithm.H"
+    #include "FiniteDifferenceAlgorithms/CKCAlgorithm.H"
+    #include "FiniteDifferenceAlgorithms/NodalAlgorithm.H"
+#endif
 #include "FiniteDifferenceSolver.H"
 #include "WarpX.H"
 
 // Constructor
-FiniteDifferenceSolver::FiniteDifferenceSolver ( int const fdtd_algo,
-    std::array<amrex::Real,3> cell_size ) {
+FiniteDifferenceSolver::FiniteDifferenceSolver (
+    int const fdtd_algo,
+    std::array<amrex::Real,3> cell_size,
+    int do_nodal ) {
 
     // Register the type of finite-difference algorithm
     m_fdtd_algo = fdtd_algo;
@@ -13,11 +23,14 @@ FiniteDifferenceSolver::FiniteDifferenceSolver ( int const fdtd_algo,
     m_dr = cell_size[0];
     m_nmodes = WarpX::GetInstance().n_rz_azimuthal_modes;
     m_rmin = WarpX::GetInstance().Geom(0).ProbLo(0);
-    if (fdtd_algo == MaxwellSolverAlgo::Yee){
+    if (fdtd_algo == MaxwellSolverAlgo::Yee) {
         CylindricalYeeAlgorithm::InitializeStencilCoefficients( cell_size,
             stencil_coefs_r, stencil_coefs_z );
 #else
-    if (fdtd_algo == MaxwellSolverAlgo::Yee){
+    if (do_nodal) {
+        NodalAlgorithm::InitializeStencilCoefficients( cell_size,
+            stencil_coefs_x, stencil_coefs_y, stencil_coefs_z );
+    } else if (fdtd_algo == MaxwellSolverAlgo::Yee) {
         YeeAlgorithm::InitializeStencilCoefficients( cell_size,
             stencil_coefs_x, stencil_coefs_y, stencil_coefs_z );
     } else if (fdtd_algo == MaxwellSolverAlgo::CKC) {