[Numpy-discussion] np.dtype(int) 64bit

Christoph Gohlke cgohlke@uci....
Sun Oct 24 11:48:30 CDT 2010

On 10/24/2010 1:41 AM, Peter Butterworth wrote:
> thanks for the clarification.
> I haven't found any complete guide on the subject, but it does appear
> there are a some potential gotchas with using numpy 64bit on windows
> (result type is not what the user might expect).
>>>> np.shape([1, 5, 4])
> (3L,)

Correct and expected. Anyway, long integers and integer types have been 
unified in Python 3 (PEP 237).

> Is there a clear performance advantage for numpy 64bit over numpy
> 32bit on 64 bit windows ? I might be tempted to go back to 32bit
> python to

It depends. You would have to benchmark your code. 64 bit code can 
actually be slower. But meeting wrong user expectations is not a 
comprehensible reason to me.

> <quote author="Christoph Gohlke">
> Looks correct. CPython's 'int' is implemented as 'long' in C, which is
> 32 bit on Windows (LLP64 model) and 64 bit on other systems (LP64, etc).
> The function argmin() returns an index, which is implemented as
> 'Py_ssize_t' in C and is 64 bit on all 64 bit systems.
> --
> Christoph
> </quote>


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