On Wed, Dec 15, 2021 at 6:21 PM Guido van Rossum <gu...@python.org> wrote:
> On Wed, Dec 15, 2021 at 2:57 PM Guido van Rossum <gu...@python.org> wrote: > >> >> I don't know how long that would take, but I suspect that a program that >> just increments the refcount relentlessly would have to run for hours >> before hitting this range. On a 64-bit machine the same approach would >> require years to run before a refcount would exceed the maximum allowable >> imbalance. (These estimates are from Mark Shannon.) >> > > Hm, not quite. I modified a fast builtin to incref its argument, and then > I called it in a `while True` loop, interrupted, and timed it. This did > ~24,000,000 INCREFs/second. This would hit 0x_2000_0000 in about 9 minutes. > And I wasn't even trying that hard -- I could have written the loop in C. > (I did comment out an audit call though. :-) The same loop on 64-bit would > take 1700 years to reach the limit, so we're safe there. > Similar 32-bit vs 64-bit overflow estimates were made by Victor Stinner in the dict version tag PEP 509 https://www.python.org/dev/peps/pep-0509/#integer-overflow tldr 4sec on 32-bit and 584 years on 64-bit Granted, the risk there is only for *exactly* `2 ** (Nbits)` increments. > > -- > --Guido van Rossum (python.org/~guido) > *Pronouns: he/him **(why is my pronoun here?)* > <http://feministing.com/2015/02/03/how-using-they-as-a-singular-pronoun-can-change-the-world/> > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/2PQVABDBGJEKRBGVLOQEFY72KZO66W3J/ > Code of Conduct: http://python.org/psf/codeofconduct/ >
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