Author: Armin Rigo <ar...@tunes.org>
Branch:
Changeset: r45944:70d00af8294e
Date: 2011-07-24 18:46 +0200
http://bitbucket.org/pypy/pypy/changeset/70d00af8294e/
Log: Test and -er- fix, by commenting out the buggy code.
diff --git a/pypy/rlib/rbigint.py b/pypy/rlib/rbigint.py
--- a/pypy/rlib/rbigint.py
+++ b/pypy/rlib/rbigint.py
@@ -40,7 +40,7 @@
# In that case, do 5 bits at a time. The potential drawback is that
# a table of 2**5 intermediate results is computed.
-FIVEARY_CUTOFF = 8
+## FIVEARY_CUTOFF = 8 disabled for now
def _mask_digit(x):
@@ -456,7 +456,7 @@
# python adaptation: moved macros REDUCE(X) and MULT(X, Y, result)
# into helper function result = _help_mult(x, y, c)
- if b.numdigits() <= FIVEARY_CUTOFF:
+ if 1: ## b.numdigits() <= FIVEARY_CUTOFF:
# Left-to-right binary exponentiation (HAC Algorithm 14.79)
# http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf
i = b.numdigits() - 1
@@ -469,26 +469,30 @@
z = _help_mult(z, a, c)
j >>= 1
i -= 1
- else:
- # Left-to-right 5-ary exponentiation (HAC Algorithm 14.82)
- # This is only useful in the case where c != None.
- # z still holds 1L
- table = [z] * 32
- table[0] = z
- for i in range(1, 32):
- table[i] = _help_mult(table[i-1], a, c)
- i = b.numdigits() - 1
- while i >= 0:
- bi = b.digit(i)
- j = SHIFT - 5
- while j >= 0:
- index = (bi >> j) & 0x1f
- for k in range(5):
- z = _help_mult(z, z, c)
- if index:
- z = _help_mult(z, table[index], c)
- j -= 5
- i -= 1
+## else:
+## This code is disabled for now, because it assumes that
+## SHIFT is a multiple of 5. It could be fixed but it looks
+## like it's more troubles than benefits...
+##
+## # Left-to-right 5-ary exponentiation (HAC Algorithm 14.82)
+## # This is only useful in the case where c != None.
+## # z still holds 1L
+## table = [z] * 32
+## table[0] = z
+## for i in range(1, 32):
+## table[i] = _help_mult(table[i-1], a, c)
+## i = b.numdigits() - 1
+## while i >= 0:
+## bi = b.digit(i)
+## j = SHIFT - 5
+## while j >= 0:
+## index = (bi >> j) & 0x1f
+## for k in range(5):
+## z = _help_mult(z, z, c)
+## if index:
+## z = _help_mult(z, table[index], c)
+## j -= 5
+## i -= 1
if negativeOutput and z.sign != 0:
z = z.sub(c)
diff --git a/pypy/rlib/test/test_rbigint.py b/pypy/rlib/test/test_rbigint.py
--- a/pypy/rlib/test/test_rbigint.py
+++ b/pypy/rlib/test/test_rbigint.py
@@ -373,6 +373,13 @@
print '--->', v
assert v.tolong() == pow(x, y, z)
+ def test_pow_lll_bug(self):
+ two = rbigint.fromint(2)
+ t =
rbigint.fromlong(2655689964083835493447941032762343136647965588635159615997220691002017799304)
+ for n, expected in [(37, 9), (1291, 931), (67889, 39464)]:
+ v = two.pow(t, rbigint.fromint(n))
+ assert v.toint() == expected
+
def test_pow_lln(self):
x = 10L
y = 2L
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