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Remove defunct parts of the random module
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Raymond Hettinger
parent
f7ec7a81a5
commit
28de64fd0f
6 changed files with 32 additions and 360 deletions
166
Lib/random.py
166
Lib/random.py
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@ -30,9 +30,6 @@
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* The period is 2**19937-1.
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* It is one of the most extensively tested generators in existence.
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* Without a direct way to compute N steps forward, the semantics of
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jumpahead(n) are weakened to simply jump to another distant state and rely
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on the large period to avoid overlapping sequences.
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* The random() method is implemented in C, executes in a single Python step,
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and is, therefore, threadsafe.
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@ -49,7 +46,7 @@
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"randrange","shuffle","normalvariate","lognormvariate",
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"expovariate","vonmisesvariate","gammavariate",
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"gauss","betavariate","paretovariate","weibullvariate",
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"getstate","setstate","jumpahead", "WichmannHill", "getrandbits",
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"getstate","setstate", "getrandbits",
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"SystemRandom"]
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NV_MAGICCONST = 4 * _exp(-0.5)/_sqrt(2.0)
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@ -70,14 +67,11 @@ class Random(_random.Random):
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"""Random number generator base class used by bound module functions.
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Used to instantiate instances of Random to get generators that don't
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share state. Especially useful for multi-threaded programs, creating
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a different instance of Random for each thread, and using the jumpahead()
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method to ensure that the generated sequences seen by each thread don't
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overlap.
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share state.
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Class Random can also be subclassed if you want to use a different basic
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generator of your own devising: in that case, override the following
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methods: random(), seed(), getstate(), setstate() and jumpahead().
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methods: random(), seed(), getstate(), and setstate().
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Optionally, implement a getrandombits() method so that randrange()
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can cover arbitrarily large ranges.
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@ -615,156 +609,6 @@ def weibullvariate(self, alpha, beta):
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u = 1.0 - self.random()
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return alpha * pow(-_log(u), 1.0/beta)
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## -------------------- Wichmann-Hill -------------------
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class WichmannHill(Random):
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VERSION = 1 # used by getstate/setstate
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def seed(self, a=None):
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"""Initialize internal state from hashable object.
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None or no argument seeds from current time or from an operating
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system specific randomness source if available.
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If a is not None or an int or long, hash(a) is used instead.
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If a is an int or long, a is used directly. Distinct values between
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0 and 27814431486575L inclusive are guaranteed to yield distinct
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internal states (this guarantee is specific to the default
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Wichmann-Hill generator).
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"""
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if a is None:
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try:
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a = int(_hexlify(_urandom(16)), 16)
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except NotImplementedError:
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import time
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a = int(time.time() * 256) # use fractional seconds
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if not isinstance(a, int):
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a = hash(a)
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a, x = divmod(a, 30268)
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a, y = divmod(a, 30306)
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a, z = divmod(a, 30322)
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self._seed = int(x)+1, int(y)+1, int(z)+1
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self.gauss_next = None
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def random(self):
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"""Get the next random number in the range [0.0, 1.0)."""
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# Wichman-Hill random number generator.
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#
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# Wichmann, B. A. & Hill, I. D. (1982)
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# Algorithm AS 183:
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# An efficient and portable pseudo-random number generator
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# Applied Statistics 31 (1982) 188-190
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#
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# see also:
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# Correction to Algorithm AS 183
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# Applied Statistics 33 (1984) 123
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#
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# McLeod, A. I. (1985)
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# A remark on Algorithm AS 183
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# Applied Statistics 34 (1985),198-200
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# This part is thread-unsafe:
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# BEGIN CRITICAL SECTION
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x, y, z = self._seed
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x = (171 * x) % 30269
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y = (172 * y) % 30307
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z = (170 * z) % 30323
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self._seed = x, y, z
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# END CRITICAL SECTION
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# Note: on a platform using IEEE-754 double arithmetic, this can
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# never return 0.0 (asserted by Tim; proof too long for a comment).
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return (x/30269.0 + y/30307.0 + z/30323.0) % 1.0
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def getstate(self):
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"""Return internal state; can be passed to setstate() later."""
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return self.VERSION, self._seed, self.gauss_next
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def setstate(self, state):
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"""Restore internal state from object returned by getstate()."""
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version = state[0]
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if version == 1:
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version, self._seed, self.gauss_next = state
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else:
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raise ValueError("state with version %s passed to "
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"Random.setstate() of version %s" %
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(version, self.VERSION))
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def jumpahead(self, n):
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"""Act as if n calls to random() were made, but quickly.
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n is an int, greater than or equal to 0.
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Example use: If you have 2 threads and know that each will
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consume no more than a million random numbers, create two Random
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objects r1 and r2, then do
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r2.setstate(r1.getstate())
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r2.jumpahead(1000000)
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Then r1 and r2 will use guaranteed-disjoint segments of the full
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period.
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"""
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if not n >= 0:
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raise ValueError("n must be >= 0")
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x, y, z = self._seed
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x = int(x * pow(171, n, 30269)) % 30269
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y = int(y * pow(172, n, 30307)) % 30307
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z = int(z * pow(170, n, 30323)) % 30323
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self._seed = x, y, z
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def __whseed(self, x=0, y=0, z=0):
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"""Set the Wichmann-Hill seed from (x, y, z).
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These must be integers in the range [0, 256).
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"""
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if not type(x) == type(y) == type(z) == int:
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raise TypeError('seeds must be integers')
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if not (0 <= x < 256 and 0 <= y < 256 and 0 <= z < 256):
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raise ValueError('seeds must be in range(0, 256)')
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if 0 == x == y == z:
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# Initialize from current time
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import time
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t = int(time.time() * 256)
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t = int((t&0xffffff) ^ (t>>24))
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t, x = divmod(t, 256)
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t, y = divmod(t, 256)
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t, z = divmod(t, 256)
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# Zero is a poor seed, so substitute 1
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self._seed = (x or 1, y or 1, z or 1)
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self.gauss_next = None
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def whseed(self, a=None):
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"""Seed from hashable object's hash code.
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None or no argument seeds from current time. It is not guaranteed
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that objects with distinct hash codes lead to distinct internal
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states.
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This is obsolete, provided for compatibility with the seed routine
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used prior to Python 2.1. Use the .seed() method instead.
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"""
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if a is None:
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self.__whseed()
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return
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a = hash(a)
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a, x = divmod(a, 256)
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a, y = divmod(a, 256)
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a, z = divmod(a, 256)
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x = (x + a) % 256 or 1
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y = (y + a) % 256 or 1
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z = (z + a) % 256 or 1
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self.__whseed(x, y, z)
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## --------------- Operating System Random Source ------------------
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class SystemRandom(Random):
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@ -789,10 +633,9 @@ def getrandbits(self, k):
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x = int(_hexlify(_urandom(bytes)), 16)
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return x >> (bytes * 8 - k) # trim excess bits
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def _stub(self, *args, **kwds):
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def seed(self, *args, **kwds):
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"Stub method. Not used for a system random number generator."
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return None
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seed = jumpahead = _stub
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def _notimplemented(self, *args, **kwds):
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"Method should not be called for a system random number generator."
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@ -866,7 +709,6 @@ def _test(N=2000):
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weibullvariate = _inst.weibullvariate
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getstate = _inst.getstate
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setstate = _inst.setstate
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jumpahead = _inst.jumpahead
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getrandbits = _inst.getrandbits
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if __name__ == '__main__':
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