On Thursday, August 3, 2017 at 7:58:50 PM UTC+2, Travis Scrimshaw wrote:
>
> Hey all,
> I think I have come across a possible Cython bug, but I am not sure. I
> am using 8.1beta0. Here is as small of a working example as I can currently
> get.
>
> sage: %%cython
> ....: def foo(F, int i):
> ....: return F[i]
> ....: def foo2(F, int i):
> ....: return F._dictionary[i]
> ....:
> sage: F = Family({-1:0})
> sage: foo2(F, int(-1)) # This works
> 0
> sage: foo(F, int(-1))
> KeyError: 0
> sage: F._dictionary
> {-1: 0}
> sage: foo(F, int(2)) # Expected failure, but the input matches
> ---------------------------------------------------------------------------
> KeyError Traceback (most recent call last
> )
> ...
> KeyError: 2
>
> It seems to have to do with a __getitem__. I do not understand what
> precisely the situation is that makes this fail; when I try to go to
> smaller examples, it works.
>
> Indication of what might be happening: with your example upstairs I get
>
sage: foo(F,-2)
0
sage: foo(F,-3)
KeyError: -2
sage: foo(F,3)
KeyError: 3
sage: foo(F,2**31)
OverflowError: value too large to convert to int
sage: foo(F,2**31-1)
KeyError: 2147483647
sage: foo(F,-2**31)
KeyError: -2147483647
so it looks like with "foo" something goes wrong with the conversion of
signed ints. The boundary cases perhaps give an indication where this goes
wrong. I'd think this is indeed a bug.
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