From 8adc09758d857a4964013fa30184c9eec770f2bf Mon Sep 17 00:00:00 2001
From: Christian Heinrich <franz-christian.heinrich@inria.fr>
Date: Tue, 24 Oct 2017 11:29:47 +0200
Subject: [PATCH 1/1] [SMPI] Move a map in smpi::Group from array to
 std::vector

See the source code comment why I'm not using std::map.
---
 src/smpi/include/smpi_group.hpp |  6 +++++-
 src/smpi/mpi/smpi_group.cpp     | 11 +++--------
 2 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/smpi/include/smpi_group.hpp b/src/smpi/include/smpi_group.hpp
index 4637dea46f..ca6ad345d8 100644
--- a/src/smpi/include/smpi_group.hpp
+++ b/src/smpi/include/smpi_group.hpp
@@ -16,7 +16,11 @@ namespace smpi{
 class Group : public F2C{
   private:
     int size_;
-    int *rank_to_index_map_;
+    /* This is actually a map from int to int. We could use
+     * std::map here, but looking up a value there costs O(log(n)).
+     * For a vector, this costs O(1). We hence go with the vector.
+     */
+    std::vector<int> rank_to_index_map_;
     std::unordered_map<int, int> index_to_rank_map_;
     int refcount_;
   public:
diff --git a/src/smpi/mpi/smpi_group.cpp b/src/smpi/mpi/smpi_group.cpp
index 6f837af73e..23c4809e80 100644
--- a/src/smpi/mpi/smpi_group.cpp
+++ b/src/smpi/mpi/smpi_group.cpp
@@ -19,13 +19,11 @@ namespace smpi{
 Group::Group()
 {
   size_              = 0;       /* size */
-  rank_to_index_map_ = nullptr; /* rank_to_index_map_ */
   refcount_          = 1;       /* refcount_: start > 0 so that this group never gets freed */
 }
 
-Group::Group(int n) : size_(n)
+Group::Group(int n) : size_(n), rank_to_index_map_(size_)
 {
-  rank_to_index_map_ = new int[size_];
   refcount_ = 1;
   for (int i              = 0; i < size_; i++)
     rank_to_index_map_[i] = MPI_UNDEFINED;
@@ -35,11 +33,8 @@ Group::Group(MPI_Group origin)
 {
   if (origin != MPI_GROUP_NULL && origin != MPI_GROUP_EMPTY) {
     size_              = origin->size();
-    rank_to_index_map_ = new int[size_];
     refcount_          = 1;
-    for (int i = 0; i < size_; i++) {
-      rank_to_index_map_[i] = origin->rank_to_index_map_[i];
-    }
+    rank_to_index_map_ = origin->rank_to_index_map_;
 
     for (auto const& elm : origin->index_to_rank_map_) {
       index_to_rank_map_.insert({elm.first, elm.second});
@@ -49,7 +44,7 @@ Group::Group(MPI_Group origin)
 
 Group::~Group()
 {
-  delete[] rank_to_index_map_;
+  rank_to_index_map_.clear();
 }
 
 void Group::set_mapping(int index, int rank)
-- 
2.20.1