Python 0.9.1 as posted in alt.sources

1 files changed, 74 insertions, 0 deletions

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+# WICHMANN-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() must be called before whrandom.random()
+# to seed the generator
+
+
+# Translated by Guido van Rossum from C source provided by
+# Adrian Baddeley.
+
+
+# The seed
+#
+_seed = [0, 0, 0]
+
+
+# Set the seed
+#
+def seed(x, y, z):
+ _seed[:] = [x, y, z]
+
+
+# Return the next random number in the range [0.0 .. 1.0)
+#
+def random():
+ from math import floor # floor() function
+ #
+ [x, y, z] = _seed
+ x = 171 * (x % 177) - 2 * (x/177)
+ y = 172 * (y % 176) - 35 * (y/176)
+ z = 170 * (z % 178) - 63 * (z/178)
+ #
+ if x < 0: x = x + 30269
+ if y < 0: y = y + 30307
+ if z < 0: z = z + 30323
+ #
+ _seed[:] = [x, y, z]
+ #
+ term = float(x)/30269.0 + float(y)/30307.0 + float(z)/30323.0
+ rand = term - floor(term)
+ #
+ if rand >= 1.0: rand = 0.0 # floor() inaccuracy?
+ #
+ return rand
+
+
+# Initialize from the current time
+#
+def init():
+ import time
+ t = time.time()
+ seed(t%256, t/256%256, t/65536%256)
+
+
+# Make sure the generator is preset to a nonzero value
+#
+init()