diff --git a/Lib/random.py b/Lib/random.py index 51ecb329954..1fa13773c92 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -6,6 +6,7 @@ # lognormal # negative exponential # gamma +# beta # # distributions on the circle (angles 0 to 2pi) # --------------------------------------------- @@ -15,7 +16,7 @@ # Translated from anonymously contributed C/C++ source. from whrandom import random, uniform, randint, choice # Also for export! -from math import log, exp, pi, e, sqrt, acos, cos +from math import log, exp, pi, e, sqrt, acos, cos, sin # Housekeeping function to verify that magic constants have been # computed correctly @@ -172,6 +173,37 @@ def stdgamma(alpha, ainv, bbb, ccc): break return x + +# -------------------- Gauss (faster alternative) -------------------- + +# When x and y are two variables from [0, 1), uniformly distributed, then +# +# cos(2*pi*x)*log(1-y) +# sin(2*pi*x)*log(1-y) +# +# are two *independent* variables with normal distribution (mu = 0, sigma = 1). +# (Lambert Meertens) + +gauss_next = None +def gauss(mu, sigma): + global gauss_next + if gauss_next != None: + z = gauss_next + gauss_next = None + else: + x2pi = random() * TWOPI + log1_y = log(1.0 - random()) + z = cos(x2pi) * log1_y + gauss_next = sin(x2pi) * log1_y + return mu + z*sigma + +# -------------------- beta -------------------- + +def betavariate(alpha, beta): + y = expovariate(alpha) + z = expovariate(1.0/beta) + return z/(y+z) + # -------------------- test program -------------------- def test(): @@ -179,7 +211,7 @@ def test(): print 'LOG4 =', LOG4 print 'NV_MAGICCONST =', NV_MAGICCONST print 'SG_MAGICCONST =', SG_MAGICCONST - N = 100 + N = 200 test_generator(N, 'random()') test_generator(N, 'normalvariate(0.0, 1.0)') test_generator(N, 'lognormvariate(0.0, 1.0)') @@ -192,21 +224,30 @@ def test(): test_generator(N, 'gammavariate(2.0, 1.0)') test_generator(N, 'gammavariate(20.0, 1.0)') test_generator(N, 'gammavariate(200.0, 1.0)') + test_generator(N, 'gauss(0.0, 1.0)') + test_generator(N, 'betavariate(3.0, 3.0)') def test_generator(n, funccall): - import sys - print '%d calls to %s:' % (n, funccall), - sys.stdout.flush() + import time + print n, 'times', funccall code = compile(funccall, funccall, 'eval') sum = 0.0 sqsum = 0.0 + smallest = 1e10 + largest = 1e-10 + t0 = time.time() for i in range(n): x = eval(code) sum = sum + x sqsum = sqsum + x*x + smallest = min(x, smallest) + largest = max(x, largest) + t1 = time.time() + print round(t1-t0, 3), 'sec,', avg = sum/n stddev = sqrt(sqsum/n - avg*avg) - print 'avg %g, stddev %g' % (avg, stddev) + print 'avg %g, stddev %g, min %g, max %g' % \ + (avg, stddev, smallest, largest) if __name__ == '__main__': test()