Two improvements suggested by Tim Peters: speed up random() since we

gvanrossum · gvanrossum · commit d247812521c2 · 1997-07-10T15:14:50.000Z
know Python integers are at least 32 bits long; and avoid zeros in
initial seed value.
diff --git a/Lib/whrandom.py b/Lib/whrandom.py
@@ -54,20 +54,17 @@ def seed(self, x = 0, y = 0, z = 0):
 			t, x = divmod(t, 256)
 			t, y = divmod(t, 256)
 			t, z = divmod(t, 256)
-		self._seed = (x, y, z)
+		# Zero is a poor seed, so substitute 1
+		self._seed = (x or 1, y or 1, z or 1)
 	#
 	# Get the next random number in the range [0.0, 1.0).
 	#
 	def random(self):
 		x, y, z = self._seed
 		#
-		x1, x2 = divmod(x, 177)
-		y1, y2 = divmod(y, 176)
-		z1, z2 = divmod(z, 178)
-		#
-		x = (171 * x2 -  2 * x1) % 30269
-		y = (172 * y2 - 35 * y1) % 30307
-		z = (170 * z2 - 63 * z1) % 30323
+		x = (171 * x) % 30269
+		y = (172 * y) % 30307
+		z = (170 * z) % 30323
 		#
 		self._seed = x, y, z
 		#

Original file line number	Diff line number	Diff line change
`@@ -54,20 +54,17 @@ def seed(self, x = 0, y = 0, z = 0):`
`54`	`54`	`t, x = divmod(t, 256)`
`55`	`55`	`t, y = divmod(t, 256)`
`56`	`56`	`t, z = divmod(t, 256)`
`57`		`- self._seed = (x, y, z)`
	`57`	`+ # Zero is a poor seed, so substitute 1`
	`58`	`+ self._seed = (x or 1, y or 1, z or 1)`
`58`	`59`	`#`
`59`	`60`	`# Get the next random number in the range [0.0, 1.0).`
`60`	`61`	`#`
`61`	`62`	`def random(self):`
`62`	`63`	`x, y, z = self._seed`
`63`	`64`	`#`
`64`		`- x1, x2 = divmod(x, 177)`
`65`		`- y1, y2 = divmod(y, 176)`
`66`		`- z1, z2 = divmod(z, 178)`
`67`		`- #`
`68`		`- x = (171 * x2 - 2 * x1) % 30269`
`69`		`- y = (172 * y2 - 35 * y1) % 30307`
`70`		`- z = (170 * z2 - 63 * z1) % 30323`
	`65`	`+ x = (171 * x) % 30269`
	`66`	`+ y = (172 * y) % 30307`
	`67`	`+ z = (170 * z) % 30323`
`71`	`68`	`#`
`72`	`69`	`self._seed = x, y, z`
`73`	`70`	`#`