Refactor sample to be out of main CMakeLists

sample/lib/mdlp/Metrics.cpp

@@ -0,0 +1,78 @@
+#include "Metrics.h"
+#include <set>
+#include <cmath>
+
+using namespace std;
+namespace mdlp {
+    Metrics::Metrics(labels_t& y_, indices_t& indices_): y(y_), indices(indices_),
+        numClasses(computeNumClasses(0, indices.size()))
+    {
+    }
+
+    int Metrics::computeNumClasses(size_t start, size_t end)
+    {
+        set<int> nClasses;
+        for (auto i = start; i < end; ++i) {
+            nClasses.insert(y[indices[i]]);
+        }
+        return static_cast<int>(nClasses.size());
+    }
+
+    void Metrics::setData(const labels_t& y_, const indices_t& indices_)
+    {
+        indices = indices_;
+        y = y_;
+        numClasses = computeNumClasses(0, indices.size());
+        entropyCache.clear();
+        igCache.clear();
+    }
+
+    precision_t Metrics::entropy(size_t start, size_t end)
+    {
+        precision_t p;
+        precision_t ventropy = 0;
+        int nElements = 0;
+        labels_t counts(numClasses + 1, 0);
+        if (end - start < 2)
+            return 0;
+        if (entropyCache.find({ start, end }) != entropyCache.end()) {
+            return entropyCache[{start, end}];
+        }
+        for (auto i = &indices[start]; i != &indices[end]; ++i) {
+            counts[y[*i]]++;
+            nElements++;
+        }
+        for (auto count : counts) {
+            if (count > 0) {
+                p = static_cast<precision_t>(count) / static_cast<precision_t>(nElements);
+                ventropy -= p * log2(p);
+            }
+        }
+        entropyCache[{start, end}] = ventropy;
+        return ventropy;
+    }
+
+    precision_t Metrics::informationGain(size_t start, size_t cut, size_t end)
+    {
+        precision_t iGain;
+        precision_t entropyInterval;
+        precision_t entropyLeft;
+        precision_t entropyRight;
+        size_t nElementsLeft = cut - start;
+        size_t nElementsRight = end - cut;
+        size_t nElements = end - start;
+        if (igCache.find(make_tuple(start, cut, end)) != igCache.end()) {
+            return igCache[make_tuple(start, cut, end)];
+        }
+        entropyInterval = entropy(start, end);
+        entropyLeft = entropy(start, cut);
+        entropyRight = entropy(cut, end);
+        iGain = entropyInterval -
+            (static_cast<precision_t>(nElementsLeft) * entropyLeft +
+                static_cast<precision_t>(nElementsRight) * entropyRight) /
+            static_cast<precision_t>(nElements);
+        igCache[make_tuple(start, cut, end)] = iGain;
+        return iGain;
+    }
+
+}