added random number generation algorithms

src/random/xoshiro/32bitValue/xoshiro128plus.c

@@ -0,0 +1,58 @@
+/*  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 "../../krandom.h"
+
+/* This is xoshiro128+ 1.0, our best and fastest 32-bit generator for 32-bit
+   floating-point numbers. We suggest to use its upper bits for
+   floating-point generation, as it is slightly faster than xoshiro128**.
+   It passes all tests we are aware of except for
+   linearity tests, as the lowest four bits have low linear complexity, so
+   if low linear complexity is not considered an issue (as it is usually
+   the case) it can be used to generate 32-bit outputs, too.
+
+   We suggest to use a sign test to extract a random Boolean value, and
+   right shifts to extract subsets of bits.
+
+   The state must be seeded so that it is not everywhere zero. */
+
+
+static inline uint32 rotl(const uint32 x, int k) {
+    return (x << k) | (x >> (32 - k));
+}
+
+typedef union {
+    uint64 merged[2];
+    uint32 s[4];
+} _state_t;
+
+uint32 xoshiro128plus_next(void* _state){    
+    _state_t* state=_state;
+    const uint32 result = state->s[0] + state->s[3];
+
+    const uint32 t = state->s[1] << 9;
+
+    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], 11);
+
+    return result;
+}
+
+void* xoshiro128plus_init(uint64 seed){
+    _state_t* state=malloc(sizeof(_state_t));
+    splitmix64_state splitmix=splitmix64_init(seed);
+    state->merged[0]=splitmix64_next(splitmix);
+    state->merged[1]=splitmix64_next(splitmix);
+    return state;
+}