From cb9ad4b9f97b68c60dcebbb5ad2c331bd1802abe 2017-12-19 14:05:06
From: Alexandre Leroux <aleroux@itlink.fr>
Date: 2017-12-19 14:05:06
Subject: [PATCH] Adds weights to operations (1)

Modifies the algorithm for choosing a random element to add weights

---

diff --git a/plugins/amda/tests/FuzzingUtils.h b/plugins/amda/tests/FuzzingUtils.h
index adfe293..6ae89ea 100644
--- a/plugins/amda/tests/FuzzingUtils.h
+++ b/plugins/amda/tests/FuzzingUtils.h
@@ -1,6 +1,7 @@
 #ifndef SCIQLOP_FUZZINGUTILS_H
 #define SCIQLOP_FUZZINGUTILS_H
 
+#include <algorithm>
 #include <random>
 
 /**
@@ -16,10 +17,17 @@ public:
     /// Generates a random int between [min, max]
     int generateInt(int min, int max);
 
-    /// Returns a random element among the elements of a container. If the container is empty,
-    /// returns an element built by default
+    /**
+     * Returns a random element among the elements of a container. An item may be more likely to be
+     * selected if it has an associated weight greater than other items
+     * @param container the container from which to retrieve an element
+     * @param weights the weight associated to each element of the container. The vector must have
+     * the same size of the container for the weights to be effective
+     * @param nbDraws the number of random draws to perform
+     * @return the random element retrieved, an element built by default if the container is empty
+     */
     template <typename T, typename ValueType = typename T::value_type>
-    ValueType randomChoice(const T &container);
+    ValueType randomChoice(const T &container, const std::vector<double> &weights = {});
 
 private:
     std::mt19937 m_Mt;
@@ -28,14 +36,28 @@ private:
 };
 
 template <typename T, typename ValueType>
-ValueType RandomGenerator::randomChoice(const T &container)
+ValueType RandomGenerator::randomChoice(const T &container, const std::vector<double> &weights)
 {
     if (container.empty()) {
         return ValueType{};
     }
 
-    auto randomIndex = generateInt(0, container.size() - 1);
-    return container.at(randomIndex);
+    // Generates weights for each element: if the weights passed in parameter are malformed (the
+    // number of weights defined is inconsistent with the number of elements in the container, or
+    // all weights are zero), default weights are used
+    auto nbIndexes = container.size();
+    std::vector<double> indexWeights(nbIndexes);
+    if (weights.size() != nbIndexes || std::all_of(weights.cbegin(), weights.cend(),
+                                                   [](const auto &val) { return val == 0.; })) {
+        std::fill(indexWeights.begin(), indexWeights.end(), 1.);
+    }
+    else {
+        std::copy(weights.begin(), weights.end(), indexWeights.begin());
+    }
+
+    // Performs a draw to determine the index to return
+    std::discrete_distribution<> d{indexWeights.cbegin(), indexWeights.cend()};
+    return container.at(d(m_Mt));
 }
 
 #endif // SCIQLOP_FUZZINGUTILS