From 5218ec8afc077aee1cb4d6eec303af8eb57782cd Mon Sep 17 00:00:00 2001
From: Ryan Curtin <ryan@ratml.org>
Date: Wed, 9 May 2012 20:24:39 +0000
Subject: [PATCH] Save just a little time where we can.

---
 src/mlpack/core/tree/cover_tree_impl.hpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/mlpack/core/tree/cover_tree_impl.hpp b/src/mlpack/core/tree/cover_tree_impl.hpp
index f009dd31b7..3bf816c823 100644
--- a/src/mlpack/core/tree/cover_tree_impl.hpp
+++ b/src/mlpack/core/tree/cover_tree_impl.hpp
@@ -306,7 +306,9 @@ CoverTree<MetricType, RootPointPolicy, StatisticType>::CoverTree(
   // because all the points in the near set should be used up.
   farSetSize = childFarSetSize;
 
-  ComputeDistances(pointIndex, indices, distances, farSetSize);
+  // No need to rebuild the distances if we never modified them.
+  if (nearSet.n_elem != 0)
+    ComputeDistances(pointIndex, indices, distances, farSetSize);
 }
 
 template<typename MetricType, typename RootPointPolicy, typename StatisticType>