prng.c

prng.c

// prng.c

#include <stdint.h>

/* *********************  */
/* *    XORSHIFT798    *  */
/* *      16-bit       *  */
/* *********************  */

static uint16_t x798_s = 0;

static inline void x798_init()
{
  while (!x798_s) {
    x798_s = __rdtsc();
  }
}

uint16_t x798_next(void)
{
  x798_s ^= x798_s << 7;
  x798_s ^= x798_s >> 9;
  x798_s ^= x798_s << 8;
  return x798_s;
}


/* **********************  */
/* *    XOSHIRO128++    *  */
/* *       32-bit       *  */
/* **********************  */

static uint32_t xs128_s[4] = { 0, 0, 0xC4FEB4B3, 0xDEADC0DE };

static inline void xs128_init()
{
  if (!xs128_s[0] && !xs128_s[1]) {
    uint32_t long tsc = __rdtsc();
    xs128_s[0] = ((uint32_t *)&tsc)[0];
    xs128_s[1] = ((uint32_t *)&tsc)[1];
  }
}

uint32_t xs128_next(void)
{
  const uint32_t result = (((xs128_s[0] + xs128_s[3]) << 7) | ((xs128_s[0] + xs128_s[3]) >> (32 - 7))) + xs128_s[0];
  const uint32_t t = xs128_s[1] << 9;
  xs128_s[2] ^= xs128_s[0];
  xs128_s[3] ^= xs128_s[1];
  xs128_s[1] ^= xs128_s[2];
  xs128_s[0] ^= xs128_s[3];
  xs128_s[2] ^= t;
  xs128_s[3] = ((xs128_s[3] << 11) | (xs128_s[3] >> (32 - 11)));

  return result;
}


/* **********************  */
/* *    XOSHIRO256++    *  */
/* *       64-bit       *  */
/* **********************  */

static uint64_t xs256_s[4] = { 0, 0xDEADBEEFC0DEF00D, 0xC4FEB4B3C0FFEEEE, 0xDEADDEADDEADC0DE };

static inline void xs256_init()
{
  if (!xs256_s[0]) {
    xs256_s[0] = __rdtsc();
  }
}

uint64_t xs256_next(void) {
  const uint64_t result = (((xs256_s[0] + xs256_s[3]) << 23) | ((xs256_s[0] + xs256_s[3]) >> (64 - 23))) + xs256_s[0];
  const uint64_t t = xs256_s[1] << 17;
  xs256_s[2] ^= xs256_s[0];
  xs256_s[3] ^= xs256_s[1];
  xs256_s[1] ^= xs256_s[2];
  xs256_s[0] ^= xs256_s[3];
  xs256_s[2] ^= t;
  xs256_s[3] = ((xs256_s[3] << 45) | (xs256_s[3] >> (64 - 45)));

  return result;
}