[SciPy-user] Dealing with Large Data Sets

Anne Archibald peridot.faceted@gmail....
Sat May 10 15:39:04 CDT 2008


2008/5/10 Damian Eads <eads@soe.ucsc.edu>:
> Damian Eads wrote:
>
>> which perform the operations in an in-place fashion. If data.sum(axis =
>> 2) is large, preallocate an array to store the sum,
>>
>>    # for summing over columns
>>    sum_result = numpy.zeros(data.shape[0:2])
>
> I meant to include
>
>    data **= 2
>    np.sum(data, axis=2, out=sum_result)
>
> which does an in-place, element-wise exponentiate, sums over the
> columns, and stores the result in sum_result.

What is the advantage to preallocating the result rather than letting
sum() do the allocation?

Ane


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