add benchmark test

.gitignore

@@ -1,2 +1,3 @@
 *.out
+*.bin
 bin/

tests_benchmark/Makefile

@@ -0,0 +1,9 @@
+
+name := benchmark_hashtable
+include_dir := ../include
+
+all:
+	cc -lstdc++ -I${include_dir} ${name}.cpp -o ${name}.bin
+
+clean:
+	rm -f ${name}.bin

tests_benchmark/benchmark_hashtable.cpp

@@ -0,0 +1,65 @@
+// references:
+// https://github.com/tsoding/rust-hash-table/blob/main/src/main.rs
+// https://cplusplus.com/reference/unordered_map/unordered_map/find/
+
+#include <cstdint> // uint64_t
+#include <cstdlib> // rand, srand
+#include <ctime>
+#include <iostream>
+#include <unordered_map>
+
+extern "C" {
+#define PREFIX uint_ht
+#define KEY_TYPE uint64_t
+#define VALUE_TYPE uint64_t
+#include "fixed-containers/K_to_V_hashtable.h" // uint_ht
+
+void benchmark_uint_ht(size_t n, unsigned int seed) {
+    uint_ht_type* ht_p;
+    uint_ht_init(&ht_p, n);
+    srand(seed);
+    for (size_t i = 0; i < n; i++) {
+        uint64_t key = rand() & 1;
+        uint64_t* value_p = uint_ht_get_mut(ht_p, key);
+        if (value_p == NULL) {
+            uint_ht_set(ht_p, key, 1);
+        } else {
+            *value_p = *value_p + 1;
+        }
+    }
+}
+}
+
+void benchmark_std_unordered_map(size_t n, unsigned int seed) {
+    std::unordered_map<uint64_t, uint64_t> map;
+    srand(seed);
+    for (size_t i = 0; i < n; i++) {
+        uint64_t key = rand();
+        std::unordered_map<uint64_t, uint64_t>::iterator res_iterator = map.find(key);
+        if (res_iterator == map.end()) {
+            map.insert_or_assign(key, 1);
+        } else {
+            res_iterator->second = res_iterator->second + 1;
+        }
+    }
+}
+
+int main(void) {
+    const size_t N = 1000000;
+
+    for (size_t N = 10; N < 10000000; N *= 10) {
+        std::clock_t c_start1 = std::clock();
+        benchmark_uint_ht(N, N);
+        std::clock_t c_end1 = std::clock();
+
+        std::clock_t c_start2 = std::clock();
+        benchmark_std_unordered_map(N, N);
+        std::clock_t c_end2 = std::clock();
+
+        std::cout << "time elapsed for " << N << " elements:" << std::endl;
+        std::cout << " custom hashtable: " << (c_end1 - c_start1) / 1000.0 << "s" << std::endl;
+        std::cout << " c++ unordered map: " << (c_end2 - c_start2) / 1000.0 << "s" << std::endl;
+    }
+
+    return 0;
+}