For the benefit of historians . . .

Lib/lib-old/whrandom.py

@@ -0,0 +1,144 @@
+"""Wichman-Hill random number generator.
+
+Wichmann, B. A. & Hill, I. D. (1982)
+Algorithm AS 183:
+An efficient and portable pseudo-random number generator
+Applied Statistics 31 (1982) 188-190
+
+see also:
+        Correction to Algorithm AS 183
+        Applied Statistics 33 (1984) 123
+
+        McLeod, A. I. (1985)
+        A remark on Algorithm AS 183
+        Applied Statistics 34 (1985),198-200
+
+
+USE:
+whrandom.random()       yields double precision random numbers
+                        uniformly distributed between 0 and 1.
+
+whrandom.seed(x, y, z)  must be called before whrandom.random()
+                        to seed the generator
+
+There is also an interface to create multiple independent
+random generators, and to choose from other ranges.
+
+
+
+Multi-threading note: the random number generator used here is not
+thread-safe; it is possible that nearly simultaneous calls in
+different theads return the same random value.  To avoid this, you
+have to use a lock around all calls.  (I didn't want to slow this
+down in the serial case by using a lock here.)
+"""
+
+import warnings
+warnings.warn("the whrandom module is deprecated; please use the random module",
+              DeprecationWarning)
+
+# Translated by Guido van Rossum from C source provided by
+# Adrian Baddeley.
+
+
+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)
+
+
+# Initialize from the current time
+_inst = whrandom()
+seed = _inst.seed
+random = _inst.random
+uniform = _inst.uniform
+randint = _inst.randint
+choice = _inst.choice
+randrange = _inst.randrange