log(int(0), 2) hangs - Githubissues

katestange commented 1 week ago

Steps To Reproduce

In Sage 10.5.beta6 in Jupyter notebook, or on https://sagecell.sagemath.org/ (as of today), run:

for i in range(1):
    floor(log(i,2))

and the kernel appears to hang.

Expected Behavior

By contrast, the supposedly equivalent command

floor(log(0,2))

gives an error ValueError: Calling floor() on infinity or NaN which is the expected behaviour.

Actual Behavior

Kernel appears to hang. Becomes unresponsive, even to user interrupt. Must restart.

Additional Information

No response

Environment

OS: Ubuntu 24.04.1 LTS
Sage Version: SageMath 10.5.beta6 (from source) and also internet single cell server

Checklist

[X] I have searched the existing issues for a bug report that matches the one I want to file, without success.
[X] I have read the documentation and troubleshoot guide

DaveWitteMorris commented 1 week ago

Thanks for the bug report. I confirm the error (in 10.5.b9 on intel MacOS 14.8.1).

The two commands are not equivalent, because range returns python integers, whereas floor(log(0,2)) is preparsed to replace 0 with Integer(0) so it is taking the log of a sage integer, not a python integer. The equivalent command is floor(log(int(0), 2)) which does hang. For a for loop that does not hang (because it uses sage integers), change range to srange.

The minimal example seems to be log(int(0), 2), which puts sage into an uninterruptible hang.