From 345b6916a63cb79022342c2445d0f883ae0dfc5c Mon Sep 17 00:00:00 2001
From: Arnaud Giersch <arnaud.giersch@univ-fcomte.fr>
Date: Fri, 28 Jul 2017 11:07:28 +0200
Subject: [PATCH] Last replacement of qsort by std::sort.

Note that the rankmap array in replaced by a std::vector<std::pair<int, int>>,
and that the two elements of the pair are reversed in order to be correclty
ordered by std::sort.
---
 src/smpi/mpi/smpi_comm.cpp | 51 +++++++++++---------------------------
 1 file changed, 14 insertions(+), 37 deletions(-)

diff --git a/src/smpi/mpi/smpi_comm.cpp b/src/smpi/mpi/smpi_comm.cpp
index ed178f0802..b3dd93f9bc 100644
--- a/src/smpi/mpi/smpi_comm.cpp
+++ b/src/smpi/mpi/smpi_comm.cpp
@@ -16,6 +16,7 @@
 #include "src/simix/smx_private.h"
 #include <algorithm>
 #include <climits>
+#include <vector>
 
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(smpi_comm, smpi, "Logging specific to SMPI (comm)");
 
@@ -25,26 +26,6 @@ MPI_Comm MPI_COMM_UNINITIALIZED=&mpi_MPI_COMM_UNINITIALIZED;
 /* Support for cartesian topology was added, but there are 2 other types of topology, graph et dist graph. In order to
  * support them, we have to add a field SMPI_Topo_type, and replace the MPI_Topology field by an union. */
 
-static int smpi_compare_rankmap(const void *a, const void *b)
-{
-  const int* x = static_cast<const int*>(a);
-  const int* y = static_cast<const int*>(b);
-
-  if (x[1] < y[1]) {
-    return -1;
-  }
-  if (x[1] == y[1]) {
-    if (x[0] < y[0]) {
-      return -1;
-    }
-    if (x[0] == y[0]) {
-      return 0;
-    }
-    return 1;
-  }
-  return 1;
-}
-
 namespace simgrid{
 namespace smpi{
 
@@ -216,38 +197,35 @@ MPI_Comm Comm::split(int color, int key)
   /* Do the actual job */
   if(rank == 0) {
     MPI_Group* group_snd = xbt_new(MPI_Group, size);
-    int* rankmap         = xbt_new(int, 2 * size);
+    std::vector<std::pair<int, int>> rankmap;
+    rankmap.reserve(size);
     for (int i = 0; i < size; i++) {
       if (recvbuf[2 * i] != MPI_UNDEFINED) {
-        int count = 0;
+        rankmap.clear();
         for (int j = i + 1; j < size; j++) {
           if(recvbuf[2 * i] == recvbuf[2 * j]) {
             recvbuf[2 * j] = MPI_UNDEFINED;
-            rankmap[2 * count] = j;
-            rankmap[2 * count + 1] = recvbuf[2 * j + 1];
-            count++;
+            rankmap.push_back({recvbuf[2 * j + 1], j});
           }
         }
         /* Add self in the group */
         recvbuf[2 * i] = MPI_UNDEFINED;
-        rankmap[2 * count] = i;
-        rankmap[2 * count + 1] = recvbuf[2 * i + 1];
-        count++;
-        qsort(rankmap, count, 2 * sizeof(int), &smpi_compare_rankmap);
-        group_out = new  Group(count);
+        rankmap.push_back({recvbuf[2 * i + 1], i});
+        std::sort(begin(rankmap), end(rankmap));
+        group_out = new Group(rankmap.size());
         if (i == 0) {
           group_root = group_out; /* Save root's group */
         }
-        for (int j = 0; j < count; j++) {
-          int index = group->index(rankmap[2 * j]);
+        for (unsigned j = 0; j < rankmap.size(); j++) {
+          int index = group->index(rankmap[j].second);
           group_out->set_mapping(index, j);
         }
-        MPI_Request* requests = xbt_new(MPI_Request, count);
+        MPI_Request* requests = xbt_new(MPI_Request, rankmap.size());
         int reqs              = 0;
-        for (int j = 0; j < count; j++) {
-          if(rankmap[2 * j] != 0) {
+        for (const auto& rank : rankmap) {
+          if (rank.second != 0) {
             group_snd[reqs]=new  Group(group_out);
-            requests[reqs] = Request::isend(&(group_snd[reqs]), 1, MPI_PTR, rankmap[2 * j], system_tag, this);
+            requests[reqs] = Request::isend(&(group_snd[reqs]), 1, MPI_PTR, rank.second, system_tag, this);
             reqs++;
           }
         }
@@ -259,7 +237,6 @@ MPI_Comm Comm::split(int color, int key)
       }
     }
     xbt_free(recvbuf);
-    xbt_free(rankmap);
     xbt_free(group_snd);
     group_out = group_root; /* exit with root's group */
   } else {
-- 
2.20.1