[hashes] murmur hash の分布を調べるコードを追加

Author: nojima

hash-functions/hashes.cpp

@@ -0,0 +1,35 @@
+#include <cstdio>
+#include <cstdint>
+#include <cmath>
+
+uint32_t murmur_hash_11(uint32_t src) {
+    const uint32_t M = 0x5bd1e995u;
+    uint32_t h = 1190494759u;
+    src *= M; src ^= src>>24; src *= M;
+    h *= M; h ^= src;
+    h ^= h>>13; h *= M; h ^= h>>15;
+    return h;
+}
+
+float sine_based_hash(float src) {
+    float i;
+    float f = modf(sin(src * 12.9898) * 43758.5453123, &i);
+    if (f < 0.0) f += 1.0;
+    return f;
+}
+
+int main() {
+    std::puts("hashes");
+    int loop_count = 100000;
+    for (int i = 0; i < loop_count; ++i) {
+        union {
+            float f;
+            uint32_t u;
+        } hash;
+        hash.u = (murmur_hash_11(i) & 0x007fffffu) | 0x3f800000u;
+        std::printf("%.9f\n", hash.f - 1.0);
+        /*
+        std::printf("%.9f\n", sine_based_hash((float)i / loop_count));
+        */
+    }
+}