mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-01 03:53:33 +00:00
29bf8b1a30
- Make rand64() thread safe - Introduce lemur64 lcg prng - Improve strace on New Technology - Improve msync() on New Technology
45 lines
2.7 KiB
C
45 lines
2.7 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
|
│ Copyright 2022 Justine Alexandra Roberts Tunney │
|
|
│ │
|
|
│ Permission to use, copy, modify, and/or distribute this software for │
|
|
│ any purpose with or without fee is hereby granted, provided that the │
|
|
│ above copyright notice and this permission notice appear in all copies. │
|
|
│ │
|
|
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
|
|
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
|
|
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
|
|
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
|
|
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
|
|
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
|
|
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
|
|
│ PERFORMANCE OF THIS SOFTWARE. │
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
|
#include "libc/rand/rand.h"
|
|
|
|
/**
|
|
* Returns linear congruential deterministic pseudorandom data, e.g.
|
|
*
|
|
* uint64_t x = lemur64();
|
|
*
|
|
* You can generate different types of numbers as follows:
|
|
*
|
|
* int64_t x = lemur64() >> 1; // make positive signed integer
|
|
* double x = _real1(lemur64()); // make float on [0,1]-interval
|
|
*
|
|
* If you want a fast pseudorandom number generator that seeds itself
|
|
* automatically on startup and fork() then consider rand64(). If you
|
|
* want true random data then consider rdseed, rdrand, and getrandom.
|
|
*
|
|
* @return 64 bits of pseudorandom data
|
|
* @note this is Lemire's Lehmer generator
|
|
* @note this function takes at minimum 1 cycle
|
|
* @note this function passes bigcrush and practrand
|
|
* @note this function is not intended for cryptography
|
|
* @see rand64(), rngset(), _real1(), _real2(), _real3()
|
|
*/
|
|
uint64_t lemur64(void) {
|
|
static uint128_t s = 2131259787901769494;
|
|
return (s *= 15750249268501108917ull) >> 64;
|
|
}
|