diff options
Diffstat (limited to 'Lib/whrandom.py')
| -rw-r--r-- | Lib/whrandom.py | 190 |
1 files changed, 95 insertions, 95 deletions
diff --git a/Lib/whrandom.py b/Lib/whrandom.py index f43b2f9..a3a9bf7 100644 --- a/Lib/whrandom.py +++ b/Lib/whrandom.py @@ -1,21 +1,21 @@ """Wichman-Hill random number generator. Wichmann, B. A. & Hill, I. D. (1982) -Algorithm AS 183: +Algorithm AS 183: An efficient and portable pseudo-random number generator Applied Statistics 31 (1982) 188-190 -see also: +see also: Correction to Algorithm AS 183 - Applied Statistics 33 (1984) 123 + Applied Statistics 33 (1984) 123 McLeod, A. I. (1985) - A remark on Algorithm AS 183 + A remark on Algorithm AS 183 Applied Statistics 34 (1985),198-200 USE: -whrandom.random() yields double precision random numbers +whrandom.random() yields double precision random numbers uniformly distributed between 0 and 1. whrandom.seed(x, y, z) must be called before whrandom.random() @@ -38,96 +38,96 @@ down in the serial case by using a lock here.) class whrandom: - def __init__(self, x = 0, y = 0, z = 0): - """Initialize an instance. - Without arguments, initialize from current time. - With arguments (x, y, z), initialize from them.""" - self.seed(x, y, z) - - def seed(self, x = 0, y = 0, z = 0): - """Set the seed from (x, y, z). - These must be integers in the range [0, 256).""" - if not type(x) == type(y) == type(z) == type(0): - raise TypeError, 'seeds must be integers' - if not (0 <= x < 256 and 0 <= y < 256 and 0 <= z < 256): - raise ValueError, 'seeds must be in range(0, 256)' - if 0 == x == y == z: - # Initialize from current time - import time - t = long(time.time() * 256) - t = int((t&0xffffff) ^ (t>>24)) - t, x = divmod(t, 256) - t, y = divmod(t, 256) - t, z = divmod(t, 256) - # Zero is a poor seed, so substitute 1 - self._seed = (x or 1, y or 1, z or 1) - - def random(self): - """Get the next random number in the range [0.0, 1.0).""" - # This part is thread-unsafe: - # BEGIN CRITICAL SECTION - x, y, z = self._seed - # - x = (171 * x) % 30269 - y = (172 * y) % 30307 - z = (170 * z) % 30323 - # - self._seed = x, y, z - # END CRITICAL SECTION - # - return (x/30269.0 + y/30307.0 + z/30323.0) % 1.0 - - def uniform(self, a, b): - """Get a random number in the range [a, b).""" - return a + (b-a) * self.random() - - def randint(self, a, b): - """Get a random integer in the range [a, b] including - both end points. - - (Deprecated; use randrange below.)""" - return self.randrange(a, b+1) - - def choice(self, seq): - """Choose a random element from a non-empty sequence.""" - return seq[int(self.random() * len(seq))] - - def randrange(self, start, stop=None, step=1, int=int, default=None): - """Choose a random item from range(start, stop[, step]). - - This fixes the problem with randint() which includes the - endpoint; in Python this is usually not what you want. - Do not supply the 'int' and 'default' arguments.""" - # This code is a bit messy to make it fast for the - # common case while still doing adequate error checking - istart = int(start) - if istart != start: - raise ValueError, "non-integer arg 1 for randrange()" - if stop is default: - if istart > 0: - return int(self.random() * istart) - raise ValueError, "empty range for randrange()" - istop = int(stop) - if istop != stop: - raise ValueError, "non-integer stop for randrange()" - if step == 1: - if istart < istop: - return istart + int(self.random() * - (istop - istart)) - raise ValueError, "empty range for randrange()" - istep = int(step) - if istep != step: - raise ValueError, "non-integer step for randrange()" - if istep > 0: - n = (istop - istart + istep - 1) / istep - elif istep < 0: - n = (istop - istart + istep + 1) / istep - else: - raise ValueError, "zero step for randrange()" - - if n <= 0: - raise ValueError, "empty range for randrange()" - return istart + istep*int(self.random() * n) + def __init__(self, x = 0, y = 0, z = 0): + """Initialize an instance. + Without arguments, initialize from current time. + With arguments (x, y, z), initialize from them.""" + self.seed(x, y, z) + + def seed(self, x = 0, y = 0, z = 0): + """Set the seed from (x, y, z). + These must be integers in the range [0, 256).""" + if not type(x) == type(y) == type(z) == type(0): + raise TypeError, 'seeds must be integers' + if not (0 <= x < 256 and 0 <= y < 256 and 0 <= z < 256): + raise ValueError, 'seeds must be in range(0, 256)' + if 0 == x == y == z: + # Initialize from current time + import time + t = long(time.time() * 256) + t = int((t&0xffffff) ^ (t>>24)) + t, x = divmod(t, 256) + t, y = divmod(t, 256) + t, z = divmod(t, 256) + # Zero is a poor seed, so substitute 1 + self._seed = (x or 1, y or 1, z or 1) + + def random(self): + """Get the next random number in the range [0.0, 1.0).""" + # This part is thread-unsafe: + # BEGIN CRITICAL SECTION + x, y, z = self._seed + # + x = (171 * x) % 30269 + y = (172 * y) % 30307 + z = (170 * z) % 30323 + # + self._seed = x, y, z + # END CRITICAL SECTION + # + return (x/30269.0 + y/30307.0 + z/30323.0) % 1.0 + + def uniform(self, a, b): + """Get a random number in the range [a, b).""" + return a + (b-a) * self.random() + + def randint(self, a, b): + """Get a random integer in the range [a, b] including + both end points. + + (Deprecated; use randrange below.)""" + return self.randrange(a, b+1) + + def choice(self, seq): + """Choose a random element from a non-empty sequence.""" + return seq[int(self.random() * len(seq))] + + def randrange(self, start, stop=None, step=1, int=int, default=None): + """Choose a random item from range(start, stop[, step]). + + This fixes the problem with randint() which includes the + endpoint; in Python this is usually not what you want. + Do not supply the 'int' and 'default' arguments.""" + # This code is a bit messy to make it fast for the + # common case while still doing adequate error checking + istart = int(start) + if istart != start: + raise ValueError, "non-integer arg 1 for randrange()" + if stop is default: + if istart > 0: + return int(self.random() * istart) + raise ValueError, "empty range for randrange()" + istop = int(stop) + if istop != stop: + raise ValueError, "non-integer stop for randrange()" + if step == 1: + if istart < istop: + return istart + int(self.random() * + (istop - istart)) + raise ValueError, "empty range for randrange()" + istep = int(step) + if istep != step: + raise ValueError, "non-integer step for randrange()" + if istep > 0: + n = (istop - istart + istep - 1) / istep + elif istep < 0: + n = (istop - istart + istep + 1) / istep + else: + raise ValueError, "zero step for randrange()" + + if n <= 0: + raise ValueError, "empty range for randrange()" + return istart + istep*int(self.random() * n) # Initialize from the current time |