I would like to avoid numpy, if possible. Even if it might be bundled
with PyPy (is it?) I still would like the code to run in CPython with
no dependencies.
On Mon, Apr 4, 2016 at 3:45 PM, Maciej Fijalkowski <fij...@gmail.com> wrote:
> so numpy64 will give you wrap-around arithmetics. What else are you
> looking for? :-)
>
> On Mon, Apr 4, 2016 at 3:38 PM, Tuom Larsen <tuom.lar...@gmail.com> wrote:
>> You mean I should first store the result into numpy's `int64`, and
>> then to `array.array`? Like:
>>
>> x = int64(2**63 << 1)
>> a[0] = x
>>
>> Or:
>>
>> x = int64(2**63)
>> x[0] = x << 1
>>
>> What the "real types" goes, is this the only option?
>>
>> Thanks in any case!
>>
>>
>> On Mon, Apr 4, 2016 at 3:32 PM, Maciej Fijalkowski <fij...@gmail.com> wrote:
>>> one option would be to use integers from _numpypy module:
>>>
>>> from numpy import int64 after installing numpy.
>>>
>>> There are obscure ways to get it without installing numpy. Another
>>> avenue would be to use __pypy__.intop.int_mul etc.
>>>
>>> Feel free to complain "no, I want real types that I can work with" :-)
>>>
>>> Cheers,
>>> fijal
>>>
>>> On Mon, Apr 4, 2016 at 3:10 PM, Tuom Larsen <tuom.lar...@gmail.com> wrote:
>>>> Hello!
>>>>
>>>> Suppose I'm on 64-bit machine and there is an `a = arrar.array('L',
>>>> [0])` (item size is 8 bytes). In Python, when an integer does not fit
>>>> machine width it gets promoted to "long" integer of arbitrary size. So
>>>> this will fail:
>>>>
>>>> a[0] = 2**63 << 1
>>>>
>>>> To fix this, one could instead write:
>>>>
>>>> a[0] = (2**63 << 1) & (2**64 - 1)
>>>>
>>>> My question is, when I know that the result will be stored in
>>>> `array.array` anyway, how to prevent the promotion to long integers?
>>>> What is the most performat way to perform such calculations? Is PyPy
>>>> able to optimize away that `& (2**64 - 1)` when I use `'L'` typecode?
>>>>
>>>> I mean, in C I wouldn't have to worry about it as everything above the
>>>> 63rd bit will be simply cut off. I would like to help PyPy to generate
>>>> the best possible code, does anyone have some suggestions please?
>>>>
>>>> Thanks!
>>>> _______________________________________________
>>>> pypy-dev mailing list
>>>> pypy-dev@python.org
>>>> https://mail.python.org/mailman/listinfo/pypy-dev
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