From 03b2fe60ff49748aaff8402824ea0457eef24d5c Mon Sep 17 00:00:00 2001
From: Edoardo Zoni <59625522+EZoni@users.noreply.github.com>
Date: Wed, 8 Mar 2023 20:52:56 -0800
Subject: New user input for grid type (collocated, staggered, hybrid) (#3683)

* Introduce `warpx.grid_type` parameter

* Replace `or` with `||`

* Update examples with new user input syntax

* Fix `if` condition

* Improve error message

* Fix `if` condition

* Fix bugs

* Fix warning

* Fix RZ

* Debugging

* Fix RZ

* Fix bug

* Clean up

* More changes:

- set default algo parameters with hybrid grid
- all hybrid input parameters under warpx name

* Set default field gathering algo for hybrid grids

* Update documentation
---
 Source/FieldSolver/SpectralSolver/SpectralKSpace.cpp | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

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

diff --git a/Source/FieldSolver/SpectralSolver/SpectralKSpace.cpp b/Source/FieldSolver/SpectralSolver/SpectralKSpace.cpp
index b9afc63b4..8330b645e 100644
--- a/Source/FieldSolver/SpectralSolver/SpectralKSpace.cpp
+++ b/Source/FieldSolver/SpectralSolver/SpectralKSpace.cpp
@@ -141,7 +141,7 @@ SpectralKSpace::getKComponent( const DistributionMapping& dm,
  * corresponding correcting "shift" factor, along the dimension
  * specified by `i_dim`.
  *
- * (By default, we assume the FFT is done from/to a nodal grid in real space
+ * (By default, we assume the FFT is done from/to a collocated grid in real space
  * It the FFT is performed from/to a cell-centered grid in real space,
  * a correcting "shift" factor must be applied in spectral space.)
  */
@@ -190,14 +190,13 @@ SpectralKSpace::getSpectralShiftFactor( const DistributionMapping& dm,
  *
  * \param n_order Order of accuracy of the stencil, in discretizing
  *                a spatial derivative
- * \param nodal Whether the stencil is to be applied to a nodal or
-                staggered set of fields
+ * \param grid_type type of grid (collocated or not)
  */
 KVectorComponent
 SpectralKSpace::getModifiedKComponent( const DistributionMapping& dm,
                                        const int i_dim,
                                        const int n_order,
-                                       const bool nodal ) const
+                                       const short grid_type ) const
 {
     // Initialize an empty DeviceVector in each box
     KVectorComponent modified_k_comp(spectralspace_ba, dm);
@@ -217,7 +216,7 @@ SpectralKSpace::getModifiedKComponent( const DistributionMapping& dm,
     } else {
 
         // Compute real-space stencil coefficients
-        Vector<Real> h_stencil_coef = WarpX::getFornbergStencilCoefficients(n_order, nodal);
+        Vector<Real> h_stencil_coef = WarpX::getFornbergStencilCoefficients(n_order, grid_type);
         Gpu::DeviceVector<Real> d_stencil_coef(h_stencil_coef.size());
         Gpu::copyAsync(Gpu::hostToDevice, h_stencil_coef.begin(), h_stencil_coef.end(),
                        d_stencil_coef.begin());
@@ -243,7 +242,7 @@ SpectralKSpace::getModifiedKComponent( const DistributionMapping& dm,
             {
                 p_modified_k[i] = 0;
                 for (int n=0; n<nstencil; n++){
-                    if (nodal){
+                    if (grid_type == GridType::Collocated){
                         p_modified_k[i] += p_stencil_coef[n]*
                             std::sin( p_k[i]*(n+1)*delta_x )/( (n+1)*delta_x );
                     } else {
@@ -252,12 +251,12 @@ SpectralKSpace::getModifiedKComponent( const DistributionMapping& dm,
                     }
                 }
 
-                // By construction, at finite order and for a nodal grid,
+                // By construction, at finite order and for a collocated grid,
                 // the *modified* k corresponding to the Nyquist frequency
                 // (i.e. highest *real* k) is 0. However, the above calculation
                 // based on stencil coefficients does not give 0 to machine precision.
                 // Therefore, we need to enforce the fact that the modified k be 0 here.
-                if (nodal){
+                if (grid_type == GridType::Collocated){
                     if (i_dim == 0){
                         // Because of the real-to-complex FFTs, the first axis (idim=0)
                         // contains only the positive k, and the Nyquist frequency is
-- 
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