File size: 1,250 Bytes
7885a28 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 |
# Authors: The scikit-learn developers
# SPDX-License-Identifier: BSD-3-Clause
from ._typedefs cimport uint32_t
cdef inline uint32_t DEFAULT_SEED = 1
cdef enum:
# Max value for our rand_r replacement (near the bottom).
# We don't use RAND_MAX because it's different across platforms and
# particularly tiny on Windows/MSVC.
# It corresponds to the maximum representable value for
# 32-bit signed integers (i.e. 2^31 - 1).
RAND_R_MAX = 2147483647
# rand_r replacement using a 32bit XorShift generator
# See http://www.jstatsoft.org/v08/i14/paper for details
cdef inline uint32_t our_rand_r(uint32_t* seed) nogil:
"""Generate a pseudo-random np.uint32 from a np.uint32 seed"""
# seed shouldn't ever be 0.
if (seed[0] == 0):
seed[0] = DEFAULT_SEED
seed[0] ^= <uint32_t>(seed[0] << 13)
seed[0] ^= <uint32_t>(seed[0] >> 17)
seed[0] ^= <uint32_t>(seed[0] << 5)
# Use the modulo to make sure that we don't return a values greater than the
# maximum representable value for signed 32bit integers (i.e. 2^31 - 1).
# Note that the parenthesis are needed to avoid overflow: here
# RAND_R_MAX is cast to uint32_t before 1 is added.
return seed[0] % ((<uint32_t>RAND_R_MAX) + 1)
|