X-Git-Url: https://git.draconx.ca/gitweb/rrace.git/blobdiff_plain/e9ab90141032c23a97fa82a723a7a751658bce66..30f49b9152dcf5ce7baefa9287b0ec627155fba9:/t/xos256ss.c

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+/*  Written in 2018 by David Blackman and Sebastiano Vigna (vigna@acm.org)
+
+To the extent possible under law, the author has dedicated all copyright
+and related and neighboring rights to this software to the public domain
+worldwide. This software is distributed without any warranty.
+
+See <http://creativecommons.org/publicdomain/zero/1.0/>. */
+
+#include <stdint.h>
+
+/* This is xoshiro256** 1.0, one of our all-purpose, rock-solid
+   generators. It has excellent (sub-ns) speed, a state (256 bits) that is
+   large enough for any parallel application, and it passes all tests we
+   are aware of.
+
+   For generating just floating-point numbers, xoshiro256+ is even faster.
+
+   The state must be seeded so that it is not everywhere zero. If you have
+   a 64-bit seed, we suggest to seed a splitmix64 generator and use its
+   output to fill s. */
+
+static inline uint64_t rotl(const uint64_t x, int k) {
+	return (x << k) | (x >> (64 - k));
+}
+
+
+static uint64_t s[4];
+
+uint64_t next(void) {
+	const uint64_t result = rotl(s[1] * 5, 7) * 9;
+
+	const uint64_t t = s[1] << 17;
+
+	s[2] ^= s[0];
+	s[3] ^= s[1];
+	s[1] ^= s[2];
+	s[0] ^= s[3];
+
+	s[2] ^= t;
+
+	s[3] = rotl(s[3], 45);
+
+	return result;
+}
+
+
+/* This is the jump function for the generator. It is equivalent
+   to 2^128 calls to next(); it can be used to generate 2^128
+   non-overlapping subsequences for parallel computations. */
+
+void jump(void) {
+	static const uint64_t JUMP[] = { 0x180ec6d33cfd0aba, 0xd5a61266f0c9392c, 0xa9582618e03fc9aa, 0x39abdc4529b1661c };
+
+	uint64_t s0 = 0;
+	uint64_t s1 = 0;
+	uint64_t s2 = 0;
+	uint64_t s3 = 0;
+	for(int i = 0; i < sizeof JUMP / sizeof *JUMP; i++)
+		for(int b = 0; b < 64; b++) {
+			if (JUMP[i] & UINT64_C(1) << b) {
+				s0 ^= s[0];
+				s1 ^= s[1];
+				s2 ^= s[2];
+				s3 ^= s[3];
+			}
+			next();
+		}
+
+	s[0] = s0;
+	s[1] = s1;
+	s[2] = s2;
+	s[3] = s3;
+}
+
+
+
+/* This is the long-jump function for the generator. It is equivalent to
+   2^192 calls to next(); it can be used to generate 2^64 starting points,
+   from each of which jump() will generate 2^64 non-overlapping
+   subsequences for parallel distributed computations. */
+
+void long_jump(void) {
+	static const uint64_t LONG_JUMP[] = { 0x76e15d3efefdcbbf, 0xc5004e441c522fb3, 0x77710069854ee241, 0x39109bb02acbe635 };
+
+	uint64_t s0 = 0;
+	uint64_t s1 = 0;
+	uint64_t s2 = 0;
+	uint64_t s3 = 0;
+	for(int i = 0; i < sizeof LONG_JUMP / sizeof *LONG_JUMP; i++)
+		for(int b = 0; b < 64; b++) {
+			if (LONG_JUMP[i] & UINT64_C(1) << b) {
+				s0 ^= s[0];
+				s1 ^= s[1];
+				s2 ^= s[2];
+				s3 ^= s[3];
+			}
+			next();
+		}
+
+	s[0] = s0;
+	s[1] = s1;
+	s[2] = s2;
+	s[3] = s3;
+}