From 1c99519b3740d551e6c530cd94613f0893a6f848 Mon Sep 17 00:00:00 2001
From: Deepali Chourasia <deepali@us.ibm.com>
Date: Fri, 13 May 2016 04:57:23 -0500
Subject: [PATCH] Fix crash when pairing an odd number of devices without P2P
 (BVLC/github issue #3531,#3586)

---
 src/caffe/parallel.cpp | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/caffe/parallel.cpp b/src/caffe/parallel.cpp
index 34ad49edf8a..5d5e43a97d7 100644
--- a/src/caffe/parallel.cpp
+++ b/src/caffe/parallel.cpp
@@ -185,9 +185,8 @@ void DevicePair::compute(const vector<int> devices, vector<DevicePair>* pairs) {
   DLOG(INFO) << "GPUs paired by P2P access, remaining: " << s.str();
 
   // Group remaining
-  remaining_depth = ceil(log2(remaining.size()));
-  for (int d = 0; d < remaining_depth; ++d) {
-    for (int i = 0; i < remaining.size(); ++i) {
+  while (remaining.size() > 1) {
+    for (int i = 0; i+1 < remaining.size(); ++i) {
       pairs->push_back(DevicePair(remaining[i], remaining[i + 1]));
       DLOG(INFO) << "Remaining pair: " << remaining[i] << ":"
                  << remaining[i + 1];