From fa51efbe3c4c17ebf5e831ceee35c729ec520d47 Mon Sep 17 00:00:00 2001
From: Bruno <blais.bruno@gmail.com>
Date: Tue, 9 Feb 2021 22:20:08 -0500
Subject: [PATCH] Add recv and send data to particle cache

This adds teh recv and send data to the particle cache in order
to prevent dynamic reallocation of this vector, whose size is not
changing anyway. This can significantly (10%) increase performance
in some of our applications
---
 include/deal.II/particles/partitioner.h | 12 ++++++++++++
 source/particles/particle_handler.cc    | 12 +++++++-----
 2 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/include/deal.II/particles/partitioner.h b/include/deal.II/particles/partitioner.h
index 46ee1def56..f4361a3ae1 100644
--- a/include/deal.II/particles/partitioner.h
+++ b/include/deal.II/particles/partitioner.h
@@ -97,6 +97,18 @@ namespace Particles
       std::vector<typename std::multimap<internal::LevelInd,
                                          Particle<dim, spacedim>>::iterator>
         ghost_particles_iterators;
+
+      /**
+       * Vector of char that is used to organize the particle information to be
+       * sent to other processors
+       */
+      std::vector<char> send_data;
+
+      /**
+       * Vector of char that is used to organize the particle information to
+       * received from other processors
+       */
+      std::vector<char> recv_data;
     };
   } // namespace internal
 
diff --git a/source/particles/particle_handler.cc b/source/particles/particle_handler.cc
index b135d69a4a..4926f52ce3 100644
--- a/source/particles/particle_handler.cc
+++ b/source/particles/particle_handler.cc
@@ -1521,6 +1521,11 @@ namespace Particles
             n_recv_data[i] * individual_particle_data_size;
 
         ghost_particles_cache.neighbors = neighbors;
+
+        ghost_particles_cache.send_data.resize(
+          ghost_particles_cache.send_pointers.back());
+        ghost_particles_cache.recv_data.resize(
+          ghost_particles_cache.recv_pointers.back());
       }
 
     while (reinterpret_cast<std::size_t>(recv_data_it) -
@@ -1580,13 +1585,11 @@ namespace Particles
       ExcMessage(
         "This function is only implemented for parallel::TriangulationBase objects."));
 
-    std::vector<char> send_data;
+    std::vector<char> &send_data = ghost_particles_cache.send_data;
 
     // Fill data to send
     if (send_pointers.back() > 0)
       {
-        // Allocate space for sending particle data
-        send_data.resize(send_pointers.back());
         void *data = static_cast<void *>(&send_data.front());
 
         // Serialize the data sorted by receiving process
@@ -1599,8 +1602,7 @@ namespace Particles
             }
       }
 
-    // Set up the space for the received particle data
-    std::vector<char> recv_data(recv_pointers.back());
+    std::vector<char> &recv_data = ghost_particles_cache.recv_data;
 
     // Exchange the particle data between domains
     {
-- 
2.39.5