2 files changed, 20 insertions, 25 deletions
diff --git a/Swiften/Network/DomainNameServiceQuery.cpp b/Swiften/Network/DomainNameServiceQuery.cpp
index f7ffecc..da1e1ab 100644
--- a/Swiften/Network/DomainNameServiceQuery.cpp
+++ b/Swiften/Network/DomainNameServiceQuery.cpp
@@ -8,6 +8,8 @@
 
 #include <numeric>
 #include <cassert>
+#include <functional>
+#include <iterator>
 
 #include <Swiften/Base/RandomGenerator.h>
 #include <boost/numeric/conversion/cast.hpp>
@@ -21,19 +23,12 @@ namespace {
 		}
 	};
 
-	struct WeightAccumulator {
-			int operator()(int accumulator, const DomainNameServiceQuery::Result& result) {
-				return accumulator + result.weight;
-			}
-	};
+	struct GetWeight {
+			GetWeight() {}
 
-	struct WeightToProbability {
-			WeightToProbability(int total) : total(total) {}
-
-			double operator()(const DomainNameServiceQuery::Result& result) {
-				return result.weight / boost::numeric_cast<double>(total);
+			int operator()(const DomainNameServiceQuery::Result& result) {
+				return result.weight + 1 /* easy hack to account for '0' weights getting at least some weight */;
 			}
-			int total;
 	};
 }
 
@@ -50,15 +45,15 @@ void DomainNameServiceQuery::sortResults(std::vector<DomainNameServiceQuery::Res
 	while (i != queries.end()) {
 		std::vector<DomainNameServiceQuery::Result>::iterator next = std::upper_bound(i, queries.end(), *i, comparator);
 		if (std::distance(i, next) > 1) {
-			int weightSum = std::accumulate(i, next, 0, WeightAccumulator());
-			std::vector<double> probabilities;
-			std::transform(i, next, std::back_inserter(probabilities), WeightToProbability(weightSum > 0 ? weightSum : 1));
-
-			// Shuffling the result array and the probabilities in parallel
-			for (size_t j = 0; j < probabilities.size(); ++j) {
-				int selectedIndex = generator.generateWeighedRandomNumber(probabilities.begin() + j, probabilities.end());
+			std::vector<int> weights;
+			std::transform(i, next, std::back_inserter(weights), GetWeight());
+			for (size_t j = 0; j < weights.size() - 1; ++j) {
+				std::vector<int> cumulativeWeights;
+				std::partial_sum(weights.begin() + j, weights.end(), std::back_inserter(cumulativeWeights));
+				int randomNumber = generator.generateRandomInteger(cumulativeWeights.back());
+				int selectedIndex = std::lower_bound(cumulativeWeights.begin(), cumulativeWeights.end(), randomNumber) - cumulativeWeights.begin();
 				std::swap(i[j], i[j + selectedIndex]);
-				std::swap(probabilities.begin()[j], probabilities.begin()[j + selectedIndex]);
+				std::swap(weights.begin()[j], weights.begin()[j + selectedIndex]);
 			}
 		}
 		i = next;
diff --git a/Swiften/Network/UnitTest/DomainNameServiceQueryTest.cpp b/Swiften/Network/UnitTest/DomainNameServiceQueryTest.cpp
index aefd815..53b9413 100644
--- a/Swiften/Network/UnitTest/DomainNameServiceQueryTest.cpp
+++ b/Swiften/Network/UnitTest/DomainNameServiceQueryTest.cpp
@@ -16,14 +16,14 @@ using namespace Swift;
 
 namespace {
 	struct RandomGenerator1 : public RandomGenerator {
-		virtual int generateWeighedRandomNumber(std::vector<double>::const_iterator, std::vector<double>::const_iterator) {
+		virtual int generateRandomInteger(int) {
 			return 0;
 		}
 	};
 
 	struct RandomGenerator2 : public RandomGenerator {
-		virtual int generateWeighedRandomNumber(std::vector<double>::const_iterator probabilities_begin, std::vector<double>::const_iterator probabilities_end) {
-			return std::max_element(probabilities_begin, probabilities_end) - probabilities_begin;
+		virtual int generateRandomInteger(int i) {
+			return i;
 		}
 	};
 }
@@ -70,9 +70,9 @@ class DomainNameServiceQueryTest : public CppUnit::TestFixture {
 
 			CPPUNIT_ASSERT_EQUAL(std::string("server5.com"), results[0].hostname);
 			CPPUNIT_ASSERT_EQUAL(std::string("server7.com"), results[1].hostname);
-			CPPUNIT_ASSERT_EQUAL(std::string("server4.com"), results[2].hostname);
-			CPPUNIT_ASSERT_EQUAL(std::string("server6.com"), results[3].hostname);
-			CPPUNIT_ASSERT_EQUAL(std::string("server2.com"), results[4].hostname);
+			CPPUNIT_ASSERT_EQUAL(std::string("server2.com"), results[2].hostname);
+			CPPUNIT_ASSERT_EQUAL(std::string("server4.com"), results[3].hostname);
+			CPPUNIT_ASSERT_EQUAL(std::string("server6.com"), results[4].hostname);
 			CPPUNIT_ASSERT_EQUAL(std::string("server1.com"), results[5].hostname);
 			CPPUNIT_ASSERT_EQUAL(std::string("server3.com"), results[6].hostname);
 		}