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Diffstat (limited to 'Swiften/Network/DomainNameServiceQuery.cpp')
-rw-r--r--Swiften/Network/DomainNameServiceQuery.cpp33
1 files changed, 14 insertions, 19 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;