将定制的随机生成器从 JS 移植到 Python 3

Question

伙计们。

我发现 here 一个非常基本的随机生成器，具有播种功能。还将代码作为片段附上。

var m_w = 123456789;
var m_z = 987654321;
var mask = 0xffffffff;

// Takes any integer
function seed(i) {
    m_w = (123456789 + i) & mask;
    m_z = (987654321 - i) & mask;
}

// Returns number between 0 (inclusive) and 1.0 (exclusive),
// just like Math.random().
function random()
{


    m_z = (36969 * (m_z & 65535) + (m_z >> 16)) & mask;
    m_w = (18000 * (m_w & 65535) + (m_w >> 16)) & mask;

    var result = ((m_z << 16) + (m_w & 65535)) >>> 0;
    result /= 4294967296;
    return result;
}

seed(1);

console.log(random())
console.log(random())
console.log(random())
console.log(random())
console.log(random())

我正在尝试将其移植到 Python 3 并意识到按位运算存在差异，因为 JS 和 Python 对长整数的行为不同。

目前的Python代码是：

#!/usr/bin/python
import ctypes

m_w = 123456789
m_z = 987654321
mask = 0xFFFFFF

#JS returns 123456790, 987654320
def bespokeSeed(seed_):

    global m_w, m_z, mask

    m_w = m_w + seed_
    m_z = m_z - seed_

def bespokeRandom():

    global m_w, m_z, mask

    #JS returns 990784270, 945037883
    m_z = (36969 * (m_z & 65535 & (2**53-1)) + (m_z >> 16) & (2**53-1))
    m_w = (18000 * (m_w & 65535 & (2**53-1)) + (m_w >> 16) & (2**53-1))
    #JS returns 722346555
    result = ((ctypes.c_int(m_z << 16 ^ 0).value + ctypes.c_int(m_w & 65535 ^ 0).value) >> 0) / 4294967296
    return result

bespokeSeed(1)
print(bespokeRandom())
print(bespokeRandom())
print(bespokeRandom())
print(bespokeRandom())
print(bespokeRandom())

JS代码（调用5次random()）returns

0.16818441334180534
0.7648323038592935
0.1521853597369045
0.22241602488793433
0.4391189150046557

而 Python 得到

0.16818441334180534
-0.23516769614070654
0.1521853597369045
0.22241602488793433
0.4391189150046557

如您所见，它部分有效，但在返回负数时存在一些问题。关于如何修复它有什么想法吗？

Answer 1

我完全不明白为什么你有 ctypes。问题是 Javascript 整数限制为 32 位，而 Python 具有无限精度。这就是你想要的：

import ctypes

m_w = 123456789
m_z = 987654321
mask = 0xFFFFFFFF

def bespokeSeed(seed_):

    global m_w, m_z

    m_w = m_w + seed_
    m_z = m_z - seed_

def bespokeRandom():

    global m_w, m_z

    #JS returns 990784270, 945037883
    m_z = (36969 * (m_z & 65535) + (m_z >> 16)) & mask
    m_w = (18000 * (m_w & 65535) + (m_w >> 16)) & mask 
    result = ((m_z << 16 & mask) + (m_w & 65535)) / 4294967296
    return result

bespokeSeed(1)
print(bespokeRandom())
print(bespokeRandom())
print(bespokeRandom())
print(bespokeRandom())
print(bespokeRandom())

将定制的随机生成器从 JS 移植到 Python 3

Porting bespoke random generator from JS to Python 3

javascript

python

porting

bitwise-operators

random-seed