Author: Amaury Forgeot d'Arc <[email protected]>
Branch: py3k
Changeset: r48969:a72479c34dae
Date: 2011-11-08 20:12 +0100
http://bitbucket.org/pypy/pypy/changeset/a72479c34dae/
Log: A non quadratic implementation of random.getrandbits(), badly needed
by test_zlib
diff --git a/pypy/module/_random/interp_random.py
b/pypy/module/_random/interp_random.py
--- a/pypy/module/_random/interp_random.py
+++ b/pypy/module/_random/interp_random.py
@@ -2,8 +2,8 @@
from pypy.interpreter.typedef import TypeDef
from pypy.interpreter.gateway import NoneNotWrapped, interp2app, unwrap_spec
from pypy.interpreter.baseobjspace import Wrappable
-from pypy.rlib.rarithmetic import r_uint, intmask
-from pypy.rlib import rrandom
+from pypy.rlib.rarithmetic import r_uint, r_longlong, intmask
+from pypy.rlib import rbigint, rrandom
import time
@@ -83,31 +83,22 @@
n = space.int_w(w_n)
self._rnd.jumpahead(n)
+ assert rbigint.SHIFT <= 32
@unwrap_spec(k=int)
def getrandbits(self, space, k):
if k <= 0:
strerror = space.wrap("number of bits must be greater than zero")
raise OperationError(space.w_ValueError, strerror)
- bytes = ((k - 1) // 32 + 1) * 4
- bytesarray = [0] * bytes
- for i in range(0, bytes, 4):
- r = self._rnd.genrand32()
- if k < 32:
- r >>= (32 - k)
- bytesarray[i + 0] = r & r_uint(0xff)
- bytesarray[i + 1] = (r >> 8) & r_uint(0xff)
- bytesarray[i + 2] = (r >> 16) & r_uint(0xff)
- bytesarray[i + 3] = (r >> 24) & r_uint(0xff)
- k -= 32
-
- # XXX so far this is quadratic
- w_result = space.newint(0)
- w_eight = space.newint(8)
- for i in range(len(bytesarray) - 1, -1, -1):
- byte = bytesarray[i]
- w_result = space.or_(space.lshift(w_result, w_eight),
- space.newint(intmask(byte)))
- return w_result
+ needed = (k - 1) // rbigint.SHIFT + 1
+ result = rbigint.rbigint([rbigint.NULLDIGIT] * needed, 1)
+ for i in range(needed - 1):
+ # This loses some random digits, but not too many since SHIFT=31
+ value = self._rnd.genrand32()
+ if i < needed - 1:
+ result.setdigit(i, value & rbigint.MASK)
+ else:
+ result.setdigit(i, value >> ((needed * rbigint.SHIFT) - k))
+ return space.newlong_from_rbigint(result)
W_Random.typedef = TypeDef("Random",
diff --git a/pypy/module/_random/test/test_random.py
b/pypy/module/_random/test/test_random.py
--- a/pypy/module/_random/test/test_random.py
+++ b/pypy/module/_random/test/test_random.py
@@ -67,7 +67,7 @@
for arg in [None, 0, 0L, 1, 1L, -1, -1L, 10**20, -(10**20),
3.14, 1+2j, 'a', tuple('abc'), 0xffffffffffL]:
rnd.seed(arg)
- for arg in [range(3), dict(one=1)]:
+ for arg in [[1, 2, 3], dict(one=1)]:
raises(TypeError, rnd.seed, arg)
raises(TypeError, rnd.seed, 1, 2)
raises(TypeError, type(rnd), [])
@@ -92,7 +92,10 @@
def test_randbits(self):
import _random
rnd = _random.Random()
- for n in range(1, 10) + range(10, 1000, 15):
+ for n in range(1, 10):
+ k = rnd.getrandbits(n)
+ assert 0 <= k < 2 ** n
+ for n in range(10, 1000, 15):
k = rnd.getrandbits(n)
assert 0 <= k < 2 ** n
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