From 6269c20a6c42037c85efd76bfa9ed162a312df96 Mon Sep 17 00:00:00 2001
From: Edoardo Zoni <59625522+EZoni@users.noreply.github.com>
Date: Thu, 8 Jul 2021 02:05:26 -0700
Subject: Do Not Fill Guard Cells with Inverse FFTs, Unless for Field Damping
 (#2045)

* Do Not Always Fill Guard Cells with Inverse FFTs

* Query psatd.fill_guards from Inputs

* Clean Up and Reduce Style Changes

* Fix Bug for Periodic Single Box

* Clean Up and Reduce Style Changes

* Fix Bug for RZ PSATD

* Remove Input Parameter, Default 0 Unless Damping

* Fix CI Tests (2D)

* Fix CI Tests (3D)
---
 Source/WarpX.cpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

(limited to 'Source/WarpX.cpp')

diff --git a/Source/WarpX.cpp b/Source/WarpX.cpp
index 0745b0941..3c5604a8b 100644
--- a/Source/WarpX.cpp
+++ b/Source/WarpX.cpp
@@ -99,6 +99,8 @@ Real WarpX::moving_window_v = std::numeric_limits<amrex::Real>::max();
 
 bool WarpX::fft_do_time_averaging = false;
 
+amrex::IntVect WarpX::fill_guards = amrex::IntVect(0);
+
 Real WarpX::quantum_xi_c2 = PhysConst::xi_c2;
 Real WarpX::gamma_boost = 1._rt;
 Real WarpX::beta_boost = 0._rt;
@@ -1089,6 +1091,18 @@ WarpX::ReadParameters ()
                 "field boundary in both lo and hi must be set to Damped for PSATD"
             );
         }
+
+        // Whether to fill the guard cells with inverse FFTs:
+        // WarpX::fill_guards = amrex::IntVect(0) by default,
+        // except for non-periodic directions with damping.
+        for (int dir = 0; dir < AMREX_SPACEDIM; dir++)
+        {
+            if (WarpX::field_boundary_lo[dir] == FieldBoundaryType::Damped ||
+                WarpX::field_boundary_hi[dir] == FieldBoundaryType::Damped)
+            {
+                WarpX::fill_guards[dir] = 1;
+            }
+        }
     }
 
     if (maxwell_solver_id != MaxwellSolverAlgo::PSATD ) {
@@ -1846,6 +1860,7 @@ void WarpX::AllocLevelSpectralSolver (amrex::Vector<std::unique_ptr<SpectralSolv
                                                 noy_fft,
                                                 noz_fft,
                                                 do_nodal,
+                                                WarpX::fill_guards,
                                                 m_v_galilean,
                                                 m_v_comoving,
                                                 dx_vect,
-- 
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