adding the robin hood code

lectures/optimization/robin_hood/robin_hood_test.cpp

@@ -0,0 +1,58 @@
+#include <iostream>
+#include <unordered_map>
+#include <chrono>
+#include <string>
+#include "robin_hood.h"
+
+constexpr size_t NUM_ELEMENTS = 2'000'000;
+
+void benchmark_std() {
+    std::unordered_map<std::string, int> map;
+    auto start = std::chrono::high_resolution_clock::now();
+
+    // Insert
+    for (size_t i = 0; i < NUM_ELEMENTS; ++i) {
+        map["key" + std::to_string(i)] = i;
+    }
+
+    // Lookup
+    int sum = 0;
+    for (size_t i = 0; i < NUM_ELEMENTS; ++i) {
+        sum += map["key" + std::to_string(i)];
+    }
+
+    auto end = std::chrono::high_resolution_clock::now();
+    std::cout << "[std::unordered_map] Time: "
+              << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
+              << " ms. Sum: " << sum << "\n";
+}
+
+void benchmark_robin() {
+    robin_hood::unordered_map<std::string, int> map;
+    auto start = std::chrono::high_resolution_clock::now();
+
+    // Insert
+    for (size_t i = 0; i < NUM_ELEMENTS; ++i) {
+        map["key" + std::to_string(i)] = i;
+    }
+
+    // Lookup
+    int sum = 0;
+    for (size_t i = 0; i < NUM_ELEMENTS; ++i) {
+        sum += map["key" + std::to_string(i)];
+    }
+
+    auto end = std::chrono::high_resolution_clock::now();
+    std::cout << "[robin_hood::unordered_map] Time: "
+              << std::chrono::duration_cast<std::chrono::milliseconds>(end - start).count()
+              << " ms. Sum: " << sum << "\n";
+}
+
+int main() {
+    benchmark_std();
+    benchmark_robin();
+    benchmark_robin();
+    benchmark_std();
+    return 0;
+}
+