added random number generation algorithms

src/random/xoshiro/64bitValue/xoshiro256plusplus.c

@@ -0,0 +1,51 @@
+/*  Written in 2019 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 "../../krandom.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 rotl(const uint64 x, int k) {
+    return (x << k) | (x>>(64 - k));
+}
+
+typedef union {
+    uint64 s[4];
+} _state_t;
+
+uint64 xoshiro256plusplus_next(void* _state) {
+    _state_t* state=_state;
+    const uint64 result=rotl(state->s[0] + state->s[3], 23) + state->s[0];
+    const uint64 t=state->s[1] << 17;
+    state->s[2] ^= state->s[0];
+    state->s[3] ^= state->s[1];
+    state->s[1] ^= state->s[2];
+    state->s[0] ^= state->s[3];
+    state->s[2] ^= t;
+    state->s[3]=rotl(state->s[3], 45);
+    return result;
+}
+
+void* xoshiro256plusplus_init(uint64 seed){
+    _state_t* state=malloc(sizeof(_state_t));
+    splitmix64_state splitmix=splitmix64_init(seed);
+    state->s[0]=splitmix64_next(splitmix);
+    state->s[1]=splitmix64_next(splitmix);
+    state->s[2]=splitmix64_next(splitmix);
+    state->s[3]=splitmix64_next(splitmix);
+    return state;
+}