Alexander Schmolck wrote:
Gary Herron <[EMAIL PROTECTED]> writes:But... It's not!A simple test shows that. I've attached a tiny test program that shows this extremely clearly. Please run it and watch it fail.In [7]: run ~/tmp/t.py final count: 2000000 should be: 2000000 (I took the liberty to correct your test to actually do what I said, namely use a numpy.array; just replace ``count = 0`` with ``import numpy; count = numpy.array(0)``).
The test was meant to simulate the OP's problem, but even with your suggestion of using numpy, it *still* fails! Just start increasing the number of increments by a factor of 2, 4, 10 until it fails:
final count: 1999998 should be: 2000000 final count: 5999997 should be: 6000000 final count: 5995068 should be: 6000000(Surprisingly, using numpy makes this test *much* slower, meaning the increment executes many more instructions, which implies hitting a thread context switch at exactly the critical point is much less common. But it can happen if you run the test long enough.)
I am running this on a Core2 Duo CPU, but the GIL should prevent that from affecting the result of the run.
I've reattached the file with the numpy change (and a larger loop counter) for others to try.
Gary Herron
'as p.s. please don't send me copies to on-list replies, at least not without explicitly mentioning the fact -- I've got better things to do then guessing whether something was meant to be off-list or not.
My apologies.
-- http://mail.python.org/mailman/listinfo/python-list
t.py
Description: application/python
-- http://mail.python.org/mailman/listinfo/python-list
