import hashlib
import os
import struct
import numpy as np
from six import integer_types
# from gym import error
[docs]def np_random(seed=None):
if seed is not None and not (isinstance(seed, integer_types) and 0 <= seed):
# raise error.Error('Seed must be a non-negative integer or omitted, not {}'.format(seed))
raise TypeError('Seed must be a non-negative integer or omitted, not {}'.format(seed))
seed = create_seed(seed)
rng = np.random.RandomState()
rng.seed(_int_list_from_bigint(hash_seed(seed)))
return rng, seed
[docs]def hash_seed(seed=None, max_bytes=8):
"""Any given evaluation is likely to have many PRNG's active at
once. (Most commonly, because the environment is running in
multiple processes.) There's literature indicating that having
linear correlations between seeds of multiple PRNG's can correlate
the outputs:
http://blogs.unity3d.com/2015/01/07/a-primer-on-repeatable-random-numbers/
http://stackoverflow.com/questions/1554958/how-different-do-random-seeds-need-to-be
http://dl.acm.org/citation.cfm?id=1276928
Thus, for sanity we hash the seeds before using them. (This scheme
is likely not crypto-strength, but it should be good enough to get
rid of simple correlations.)
Args:
seed (Optional[int]): None seeds from an operating system specific randomness source.
max_bytes: Maximum number of bytes to use in the hashed seed.
"""
if seed is None:
seed = create_seed(max_bytes=max_bytes)
hash = hashlib.sha512(str(seed).encode('utf8')).digest()
return _bigint_from_bytes(hash[:max_bytes])
[docs]def create_seed(a=None, max_bytes=8):
"""Create a strong random seed. Otherwise, Python 2 would seed using
the system time, which might be non-robust especially in the
presence of concurrency.
Args:
a (Optional[int, str]): None seeds from an operating system specific randomness source.
max_bytes: Maximum number of bytes to use in the seed.
"""
# Adapted from https://svn.python.org/projects/python/tags/r32/Lib/random.py
if a is None:
a = _bigint_from_bytes(os.urandom(max_bytes))
elif isinstance(a, str):
a = a.encode('utf8')
a += hashlib.sha512(a).digest()
a = _bigint_from_bytes(a[:max_bytes])
elif isinstance(a, integer_types):
a = a % 2**(8 * max_bytes)
else:
raise TypeError('Invalid type for seed: {} ({})'.format(type(a), a))
return a
# TODO: don't hardcode sizeof_int here
def _bigint_from_bytes(bytes):
sizeof_int = 4
padding = sizeof_int - len(bytes) % sizeof_int
bytes += b'\0' * padding
int_count = int(len(bytes) / sizeof_int)
unpacked = struct.unpack("{}I".format(int_count), bytes)
accum = 0
for i, val in enumerate(unpacked):
accum += 2 ** (sizeof_int * 8 * i) * val
return accum
def _int_list_from_bigint(bigint):
# Special case 0
if bigint < 0:
raise TypeError('Seed must be non-negative, not {}'.format(bigint))
elif bigint == 0:
return [0]
ints = []
while bigint > 0:
bigint, mod = divmod(bigint, 2 ** 32)
ints.append(mod)
return ints