DOC: Clean up examples of low-level random access

Test examples on Linux and Windows
Correct bug in Cython example
Improve building instructions for numba examples

3 files changed, 23 insertions, 13 deletions

diff --git a/numpy/random/_examples/cython/extending.pyx b/numpy/random/_examples/cython/extending.pyx
index 2a866648d..d12c0b919 100644
--- a/numpy/random/_examples/cython/extending.pyx
+++ b/numpy/random/_examples/cython/extending.pyx
@@ -39,7 +39,7 @@ def uniform_mean(Py_ssize_t n):
     return randoms.mean()
 
 
-# This function is declated nogil so it can be used without the GIL below
+# This function is declared nogil so it can be used without the GIL below
 cdef uint32_t bounded_uint(uint32_t lb, uint32_t ub, bitgen_t *rng) nogil:
     cdef uint32_t mask, delta, val
     mask = delta = ub - lb
diff --git a/numpy/random/_examples/cython/extending_distributions.pyx b/numpy/random/_examples/cython/extending_distributions.pyx
index d17da45c1..3f342c475 100644
--- a/numpy/random/_examples/cython/extending_distributions.pyx
+++ b/numpy/random/_examples/cython/extending_distributions.pyx
@@ -7,14 +7,17 @@ import numpy as np
 cimport numpy as np
 cimport cython
 from cpython.pycapsule cimport PyCapsule_IsValid, PyCapsule_GetPointer
+from libc.stdint cimport uint16_t, uint64_t
 from numpy.random._bit_generator cimport bitgen_t
+
 from numpy.random import PCG64
 
 
 @cython.boundscheck(False)
 @cython.wraparound(False)
 def uniforms(Py_ssize_t n):
-    """ Create an array of `n` uniformly distributed doubles.
+    """
+    Create an array of `n` uniformly distributed doubles.
     A 'real' distribution would want to process the values into
     some non-uniform distribution
     """
@@ -40,24 +43,32 @@ def uniforms(Py_ssize_t n):
     return randoms
  
 # cython example 2
-
 @cython.boundscheck(False)
 @cython.wraparound(False)
-def uint16_uniforms(Py_ssize_t n):
+def uint10_uniforms(Py_ssize_t n):
+    """Uniform 10 bit integers stored as 16-bit unsigned integers"""
     cdef Py_ssize_t i
     cdef bitgen_t *rng
     cdef const char *capsule_name = "BitGenerator"
-    cdef double[::1] random_values
+    cdef uint16_t[::1] random_values
+    cdef int bits_remaining
+    cdef int width = 10
+    cdef uint64_t buff, mask = 0x3FF
 
     x = PCG64()
     capsule = x.capsule
     if not PyCapsule_IsValid(capsule, capsule_name):
         raise ValueError("Invalid pointer to anon_func_state")
     rng = <bitgen_t *> PyCapsule_GetPointer(capsule, capsule_name)
-    random_values = np.empty(n, dtype='uint32')
+    random_values = np.empty(n, dtype='uint16')
     # Best practice is to release GIL and acquire the lock
+    bits_remaining = 0
     with x.lock, nogil:
         for i in range(n):
-            random_values[i] = rng.next_uint32(rng.state)
+            if bits_remaining < width:
+                buff = rng.next_uint64(rng.state)
+            random_values[i] = buff & mask
+            buff >>= width
+
     randoms = np.asarray(random_values)
     return randoms
diff --git a/numpy/random/_examples/cython/setup.py b/numpy/random/_examples/cython/setup.py
index 315527a2d..19f045fc0 100644
--- a/numpy/random/_examples/cython/setup.py
+++ b/numpy/random/_examples/cython/setup.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 """
-Build the demos
+Build the Cython demonstrations of low-level access to NumPy random
 
 Usage: python setup.py build_ext -i
 """
@@ -11,18 +11,17 @@ from Cython.Build import cythonize
 from setuptools.extension import Extension
 from os.path import join, abspath, dirname
 
-curpath = abspath(dirname(__file__))
+path = abspath(dirname(__file__))
 
 extending = Extension("extending",
-                      sources=[join(curpath, 'extending.pyx')],
+                      sources=[join(path, 'extending.pyx')],
                       include_dirs=[
                             np.get_include(),
-                            join(curpath, '..', '..')
+                            join(path, '..', '..')
                         ],
                       )
 distributions = Extension("extending_distributions",
-                          sources=[join(curpath, 'extending_distributions.pyx'),
-                                  ],
+                          sources=[join(path, 'extending_distributions.pyx')],
                           include_dirs=[np.get_include()])
 
 extensions = [extending, distributions]