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- # Authors: Arnaud Joly
- #
- # License: BSD 3 clause
- cimport numpy as cnp
- ctypedef cnp.npy_uint32 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
- cpdef sample_without_replacement(cnp.int_t n_population,
- cnp.int_t n_samples,
- method=*,
- random_state=*)
- # 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)
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