From 1f1b15b7b018c95025ce7afebd5e0b350d60f610 Mon Sep 17 00:00:00 2001
From: Edoardo Zoni <59625522+EZoni@users.noreply.github.com>
Date: Thu, 27 Jul 2023 13:18:06 -0700
Subject: Fix bug with MLMG solver, always pass ghost cells to `SumBoundary`
 (#4078)

* Must pass number of ghost cells to call `SumBoundary`

* Apply suggestions from #4093

* Add inline comments on possible performance optimization
---
 Source/Particles/MultiParticleContainer.cpp | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

(limited to 'Source/Particles/MultiParticleContainer.cpp')

diff --git a/Source/Particles/MultiParticleContainer.cpp b/Source/Particles/MultiParticleContainer.cpp
index 7bbb973bb..529a78c8e 100644
--- a/Source/Particles/MultiParticleContainer.cpp
+++ b/Source/Particles/MultiParticleContainer.cpp
@@ -613,7 +613,11 @@ MultiParticleContainer::GetChargeDensity (int lev, bool local)
     }
     if (!local) {
         const Geometry& gm = allcontainers[0]->Geom(lev);
-        ablastr::utils::communication::SumBoundary(*rho, WarpX::do_single_precision_comms, gm.periodicity());
+        // Possible performance optimization:
+        // pass less than `rho->nGrowVect()` in the fifth input variable `dst_ng`
+        ablastr::utils::communication::SumBoundary(
+            *rho, 0, rho->nComp(), rho->nGrowVect(), rho->nGrowVect(),
+            WarpX::do_single_precision_comms, gm.periodicity());
     }
 
     return rho;
-- 
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