crc32, JSHash, SDBMHash

?

'''

N = 2097152

0.0455327033996582

0.9995155334472656

0.9995260238647461

0.9997577667236328

起因是做推箱子游戏，想把箱子们的坐标hash下。如6个箱子，每个的x和y

都是0~31(一个字节有10位就好了)。上面的数越大，hash越接近perfect.

CRC32肯定慢。

'''

from random import randint

from zlib import crc32

 

N = 1 << 21; L = 12; s = [set(), set(), set(), set()]

 

def mine():

    h = v[0]

    for i in range(1, L): h ^= (v[i] << i)

    return h & 0x7FFFFFFF

 

def SDBMHash():

    h = 0

    # hash = 65599 * hash + *v++; 65599 = 65536 + 64 - 1

    for x in v: t = h << 6; h = (t << 10) + t - h + x

    return h & 0x7FFFFFFF

 

def JSHash():

    h = 1315423911 # nearly a prime. 1315423911 = 3 * 438474637

    for x in v: h ^= (h << 5) + x + (h >> 2)

    return h & 0x7FFFFFFF

     

v = L * [0]

for i in range(N):

    for j in range(L): v[j] = randint(1, 32)

    s[0].add(mine())

    s[1].add(SDBMHash())

    s[2].add(JSHash())

    s[3].add(crc32(bytes(v)))

     

print(f'{N = }')

for i in range(len(s)): print(len(s[i]) / N)