tooru honda <[EMAIL PROTECTED]> wrote:
> At the end, I think it is worthwhile to implement my own shuffle and
> random methods based on os.urandom. Not only does the resulting code
> gets rid of the minuscule bias, but the program also runs much faster.
>
> When using random.SystemRandom.shuffle, posix.open and posix.close from
> calling os.urandom account for almost half of the total execution time
> for my program. By implementing my own random and getting a much larger
> chunk of random bytes from os.urandom each time, I am able to reduce the
> total execution time by half.
If I were in your shoes, I would optimize by subclassing
random.SystemRandom and overriding the random method to use os.urandom
with some large block size and then parcel it out, instead of the
_urandom(7) that it now uses. E.g., something like:
class SystemBlockRandom(random.SystemRandom):
def __init__(self):
random.SystemRandom.__init__(self)
def rand7():
while True:
randata = os.urandom(7*1024)
for i in xrange(0, 7*1024, 7):
yield long(binascii.hexlify(randata[i:i+7]),16)
self.rand7 = rand7().next
def random(self):
"""Get the next random number in the range [0.0, 1.0)."""
return (self.rand7() >> 3) * random.RECIP_BPF
(untested code). No need to reimplement anything else, it seems to me.
Alex
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