Handout

kernel/utils/random.cc

@@ -0,0 +1,42 @@
+
+#include "./random.h"
+
+Random::Random(uint32_t seed) {
+	mt[0] = seed;
+
+	for (uint32_t i = 1; i < N; i++) {
+		mt[i] = (F * (mt[i - 1] ^ (mt[i - 1] >> 30)) + i);
+	}
+
+	index = N;
+}
+
+uint32_t Random::number() {
+	uint16_t v = index;
+
+	if (index >= N) {
+		// Twist
+		for (uint32_t i = 0; i < N; i++) {
+			uint32_t x = (mt[i] & MASK_UPPER) + (mt[(i + 1) % N] & MASK_LOWER);
+
+			uint32_t xA = x >> 1;
+
+			if ((x & 0x1) != 0) {
+				xA ^= A;
+			}
+
+			mt[i] = mt[(i + M) % N] ^ xA;
+		}
+		v = index = 0;
+	}
+
+	uint32_t y = mt[v];
+	index = v + 1;
+
+	y ^= (y >> U);
+	y ^= (y << S) & B;
+	y ^= (y << T) & C;
+	y ^= (y >> L);
+
+	return y;
+}