Mailing List Archive: Python: Dev

Integer behaviour in Python 2.6.4

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sturla at molden

Nov 1, 2009, 7:22 PM

Post #1 of 3 (252 views)
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Integer behaviour in Python 2.6.4

Why does this happen?

>>> type(2**31-1)
<type 'long'>

It seems to have broken NumPy's RNG on Win32.

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curt at hagenlocher

Nov 1, 2009, 7:49 PM

Post #2 of 3 (236 views)
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Re: Integer behaviour in Python 2.6.4 [In reply to]

On Sun, Nov 1, 2009 at 8:22 PM, Sturla Molden <sturla [at] molden> wrote:
>
> Why does this happen?
>
> >>> type(2**31-1)
> <type 'long'>

Does that not happen on non-Windows platforms? 2**31 can't be
represented as a 32-bit signed integer, so it's automatically promoted
to a long.

--
Curt Hagenlocher
curt [at] hagenlocher
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sturla at molden

Nov 1, 2009, 8:21 PM

Post #3 of 3 (235 views)
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Re: Integer behaviour in Python 2.6.4 [In reply to]

Curt Hagenlocher skrev:
> Does that not happen on non-Windows platforms? 2**31 can't be
> represented as a 32-bit signed integer, so it's automatically promoted
> to a long.
>
>
Yes you are right.

I've now traced down the problem to an integer overflow in NumPy.

It seems to have this Pyrex code:

cdef long lo, hi, diff
[...]
diff = hi - lo - 1

:-D

Sturla

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