James Henderson <ja***@logicalprogression.net> wrote in message news:<ma*************************************@pyth on.org>...
As I said before, I don't think the particular code you posted would have
worked at all before 2.3.
No, indeed. I tried to make a small program that demonstrates the
problem.
But since you are interested, I have made another more accurate
demonstration of my problem.
Willem
--------------------demonstration---------------------------
# we want to read lots of 32 bit CRC values form a text file
# the numbers are hexadecimal ASCII-strings and have to be
# converted to 32-bit signed integers (which happens to be
# the output of zlib.crc32)
import warnings
from time import clock
# be compatible with Python 2.2 for integer overflow
warnings.filterwarnings ('error', category=OverflowWarning)
# my original 8char-hex to 32bit-int conversion in Python 2.2
# it runs much faster for positive numbers than for negative ones
# but is on average faster then an if-based version
a = -158933416 # an example number, make it positive to see quite
# different results
b = '%08x' % a # the hex ascii string
print a, b
t1 = clock()
for i in range (10000):
try: c = int (b, 16)
except: c = - int (0x100000000 - long (b, 16))
t2 = clock()
print t2 - t1, c, type (c)
# straight forward adaptation to Python 2.3: replace try by if.
# first we set warnings to the default
# (this version does not work in Python 2.2)
warnings.filterwarnings ('ignore', category=OverflowWarning)
t1 = clock()
for i in range (10000):
c = int (b, 16)
if c > 0x7fffffff: c = - int (0x100000000 - c)
t2 = clock()
print t2 - t1, c, type (c)
# this adaptation runs 10 times faster then the previous version
# in Python 2.3, but is on average slower than the first version
# in Python 2.2. This is certainly not an obvious adaptation.
# Nobody would expect a long conversion to be, on average, faster
# than an int conversion for 32 bit numbers ...
t1 = clock()
for i in range (10000):
c = long (b, 16)
if c > 0x7fffffff: c = - int (0x100000000 - c)
else: c = int(c)
t2 = clock()
print t2 - t1, c, type (c)
