From 9991fa404afccbad6bc1dfb68366c78d76195045 Mon Sep 17 00:00:00 2001
From: Arnaud Giersch <arnaud.giersch@univ-fcomte.fr>
Date: Wed, 1 Nov 2017 15:13:39 +0100
Subject: [PATCH 1/1] Use a vector for index_to_rank_map_ too.

---
 src/smpi/include/smpi_group.hpp |  3 ++-
 src/smpi/mpi/smpi_group.cpp     | 37 ++++++++++++++++-----------------
 2 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/src/smpi/include/smpi_group.hpp b/src/smpi/include/smpi_group.hpp
index ca6ad345d8..a76354814c 100644
--- a/src/smpi/include/smpi_group.hpp
+++ b/src/smpi/include/smpi_group.hpp
@@ -9,6 +9,7 @@
 
 #include "smpi_f2c.hpp"
 #include <smpi/smpi.h>
+#include <vector>
 
 namespace simgrid{
 namespace smpi{
@@ -21,7 +22,7 @@ class Group : public F2C{
      * 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_;
+    std::vector<int> index_to_rank_map_;
     int refcount_;
   public:
     explicit Group();
diff --git a/src/smpi/mpi/smpi_group.cpp b/src/smpi/mpi/smpi_group.cpp
index 23c4809e80..bd774248ec 100644
--- a/src/smpi/mpi/smpi_group.cpp
+++ b/src/smpi/mpi/smpi_group.cpp
@@ -22,11 +22,9 @@ Group::Group()
   refcount_          = 1;       /* refcount_: start > 0 so that this group never gets freed */
 }
 
-Group::Group(int n) : size_(n), rank_to_index_map_(size_)
+Group::Group(int n) : size_(n), rank_to_index_map_(size_, MPI_UNDEFINED)
 {
   refcount_ = 1;
-  for (int i              = 0; i < size_; i++)
-    rank_to_index_map_[i] = MPI_UNDEFINED;
 }
 
 Group::Group(MPI_Group origin)
@@ -35,43 +33,44 @@ Group::Group(MPI_Group origin)
     size_              = origin->size();
     refcount_          = 1;
     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});
-    }
+    index_to_rank_map_ = origin->index_to_rank_map_;
   }
 }
 
 Group::~Group()
 {
-  rank_to_index_map_.clear();
 }
 
 void Group::set_mapping(int index, int rank)
 {
-  if (rank < size_) {
+  if (0 <= rank && rank < size_) {
     rank_to_index_map_[rank] = index;
-    if (index != MPI_UNDEFINED)
-      index_to_rank_map_.insert({index, rank});
+    if (index != MPI_UNDEFINED) {
+      if ((unsigned)index >= index_to_rank_map_.size())
+        index_to_rank_map_.resize(index + 1, MPI_UNDEFINED);
+      index_to_rank_map_[index] = rank;
+    }
   }
 }
 
 int Group::index(int rank)
 {
-  int index = MPI_UNDEFINED;
-
-  if (0 <= rank && rank < size_) {
+  int index;
+  if (0 <= rank && rank < size_)
     index = rank_to_index_map_[rank];
-  }
+  else
+    index = MPI_UNDEFINED;
   return index;
 }
 
 int Group::rank(int index)
 {
-  if (this == MPI_GROUP_EMPTY)
-    return MPI_UNDEFINED;
-  auto rank = index_to_rank_map_.find(index);
-  return rank == index_to_rank_map_.end() ? MPI_UNDEFINED : rank->second;
+  int rank;
+  if (0 <= index && (unsigned)index < index_to_rank_map_.size())
+    rank = index_to_rank_map_[index];
+  else
+    rank = MPI_UNDEFINED;
+  return rank;
 }
 
 void Group::ref()
-- 
2.20.1