REF: Move entropy functions to standalone module

Move entropy to standalone module
Add fallback to entropy function
Add minimal test of entropy functions

Author: Sheppard, Kevin

randomstate/entropy.pyx

@@ -0,0 +1,77 @@
+cimport numpy as np
+import numpy as np
+
+from libc.stdint cimport uint32_t
+
+cdef extern from "src/common/entropy.h":
+    cdef bint entropy_getbytes(void* dest, size_t size)
+    cdef bint entropy_fallback_getbytes(void *dest, size_t size)
+
+cdef Py_ssize_t compute_numel(size):
+    cdef Py_ssize_t i, n = 1
+    if isinstance(size, tuple):
+        for i in range(len(size)):
+            n *= size[i]
+    else:
+        n = size
+    return n
+
+def random_entropy(size=None, source='system'):
+    """
+    random_entropy(size=None)
+
+    Read entropy from the system cryptographic provider
+
+    Parameters
+    ----------
+    size : int or tuple of ints, optional
+        Output shape.  If the given shape is, e.g., ``(m, n, k)``, then
+        ``m * n * k`` samples are drawn.  Default is None, in which case a
+        single value is returned.
+    source : str {'system', 'fallback'}
+        Source of entropy.  'system' uses system cryptographic pool.
+        'fallback' uses a has to the time and process id.
+
+    Returns
+    -------
+    entropy : scalar or ndarray
+        Entropy bits in 32-bit unsigned integers
+
+    Notes
+    -----
+    On Unix-like machines, reads from /dev/urandom. On Windows machines reads
+    from the RSA Full cryptographic service provider.
+
+    This function reads from the system entropy pool and so samples are
+    not reproducible.  In particular, it does *NOT* make use of a
+    RandomState, and so seed, get_state and set_state have no effect.
+
+    Raises RuntimeError if the command fails.
+    """
+    cdef bint success = True
+    cdef Py_ssize_t n = 0
+    cdef uint32_t random = 0
+    cdef uint32_t [:] randoms
+
+    if source not in ('system', 'fallback'):
+        raise ValueError('Unknown value in source.')
+
+    if size is None:
+        if source == 'system':
+            success = entropy_getbytes(<void *>&random, 4)
+        else:
+            success = entropy_fallback_getbytes(<void *>&random, 4)
+    else:
+        n = compute_numel(size)
+        randoms = np.zeros(n, dtype=np.uint32)
+        print(n)
+        if source == 'system':
+            success = entropy_getbytes(<void *>(&randoms[0]), 4 * n)
+        else:
+            success = entropy_fallback_getbytes(<void *>(&randoms[0]), 4 * n)
+    if not success:
+        raise RuntimeError('Unable to read from system cryptographic provider')
+
+    if n == 0:
+        return random
+    return np.asarray(randoms).reshape(size)

randomstate/interface.pyx

@@ -114,59 +114,11 @@ cdef extern from "distributions.h":
 
     cdef void entropy_fill(void *dest, size_t size)
     cdef bint entropy_getbytes(void* dest, size_t size)
+    cdef bint entropy_fallback_getbytes(void *dest, size_t size)
 
 include "array_utilities.pxi"
 include "bounded_integers.pxi"
 
-def random_entropy(size=None):
-    """
-    random_entropy(size=None)
-
-    Read entropy from the system cryptographic provider
-
-    Parameters
-    ----------
-    size : int or tuple of ints, optional
-        Output shape.  If the given shape is, e.g., ``(m, n, k)``, then
-        ``m * n * k`` samples are drawn.  Default is None, in which case a
-        single value is returned.
-
-    Returns
-    -------
-    entropy : scalar or ndarray
-        Entropy bits in 32-bit unsigned integers
-
-    Notes
-    -----
-    On Unix-like machines, reads from /dev/urandom. On Windows machines reads
-    from the RSA Full cryptographic service provider.
-
-    This function reads from the system entropy pool and so samples are
-    not reproducible.  In particular, it does *NOT* make use of a
-    RandomState, and so seed, get_state and set_state have no effect.
-
-    Raises RuntimeError if the command fails.
-    """
-    cdef bint success
-    cdef size_t n = 0
-    cdef uint32_t random = 0
-    cdef uint32_t [:] randoms
-
-    if size is None:
-        success = entropy_getbytes(<void *>&random, 4)
-    else:
-        n = compute_numel(size)
-        randoms = np.zeros(n, dtype=np.uint32)
-        print(n)
-        success = entropy_getbytes(<void *>(&randoms[0]), 4 * n)
-    if not success:
-        raise RuntimeError('Unable to read from system cryptographic provider')
-
-    if n == 0:
-        return random
-    return np.asarray(randoms).reshape(size)
-
-
 cdef double kahan_sum(double *darr, np.npy_intp n):
     cdef double c, y, t, sum
     cdef np.npy_intp i

randomstate/src/common/entropy.h

@@ -33,4 +33,6 @@ typedef int bool;
 
 extern void entropy_fill(void *dest, size_t size);
 
-extern bool entropy_getbytes(void* dest, size_t size);
+extern bool entropy_getbytes(void* dest, size_t size);
+
+extern bool entropy_fallback_getbytes(void *dest, size_t size);

randomstate/tests/test_smoke.py

@@ -7,6 +7,7 @@
 import os
 import unittest
 import numpy as np
+import randomstate.entropy as entropy
 from randomstate.prng.mlfg_1279_861 import mlfg_1279_861
 from randomstate.prng.mrg32k3a import mrg32k3a
 from randomstate.prng.mt19937 import mt19937
@@ -506,6 +507,20 @@ def setup_class(cls):
         cls.initial_state = cls.rs.get_state()
         cls._extra_setup()
 
+class TestEntropy(unittest.TestCase):
+    def test_entropy(self):
+        e1 = entropy.random_entropy()
+        e2 = entropy.random_entropy()
+        assert (e1 != e2)
+        e1 = entropy.random_entropy(source='fallback')
+        e2 = entropy.random_entropy(source='fallback')
+        assert (e1 != e2)
+        e1 = entropy.random_entropy(10)
+        e2 = entropy.random_entropy(10)
+        assert (e1 != e2).all()
+
+
+
 if __name__ == '__main__':
     import nose
     nose.run(argv=[__file__, '-vv'])

setup.py

@@ -120,8 +120,15 @@ def write_config(file_name, config):
 
     configs.append(config)
 
-extensions = []
 # Generate files and extensions
+extensions = cythonize([Extension('randomstate.entropy',
+                               sources=[join(mod_dir, 'entropy.pyx'),
+                                        join(mod_dir, 'src', 'common', 'entropy.c')],
+                               include_dirs=config['include_dirs'],
+                               define_macros=extra_defs,
+                               extra_compile_args=extra_compile_args,
+                               extra_link_args=extra_link_args)])
+
 for config in configs:
     config_file_name = mod_dir + '/' + config['file_name'] + '-config.pxi'
     # Rewrite core_rng to replace generic #include "config.pxi"