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Re: efficient partial sort in Python ?

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From Ian Kelly <ian.g.kelly@gmail.com>
Date Mon, 18 Aug 2014 12:48:04 -0600
Subject Re: efficient partial sort in Python ?
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On Mon, Aug 18, 2014 at 11:18 AM, Chiu Hsiang Hsu <wdv4758h@gmail.com> wrote:
> I know that Python use Timsort as default sorting algorithm and it is efficient,
> but I just wanna have a partial sorting (n-largest/smallest elements).
>
> In the current state, I can only find this kind of functions from heapq,
> but it's too slow for this problem,
> the pure c sorted function can easily beat heapq.nlargest even though it sort all the elements.
>
> I think it would be better if we have an effeicient partial sorting function,
> maybe it could be like this : partial_sorted(data, n), data.partial_sort(n)
>
> Does anyone have any more information for partial sorting ?
>
> Btw, C++ has a partial_sort function in <algorithm>, but I don't know what algorithm it really use.

According to http://www.sgi.com/tech/stl/partial_sort.html the STL
implementation also uses heapsort.

For better partial sorting algorithms, try Wikipedia:
http://en.wikipedia.org/wiki/Partial_sorting

However, I think you're still not likely to beat Timsort for smallish
data sets unless you also implement it in C.

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Thread

efficient partial sort in Python ? Chiu Hsiang Hsu <wdv4758h@gmail.com> - 2014-08-18 10:18 -0700
  Re: efficient partial sort in Python ? Ian Kelly <ian.g.kelly@gmail.com> - 2014-08-18 12:48 -0600
  Re: efficient partial sort in Python ? Dan Stromberg <drsalists@gmail.com> - 2014-08-18 14:42 -0700
    Re: efficient partial sort in Python ? Chiu Hsiang Hsu <wdv4758h@gmail.com> - 2014-08-19 12:37 -0700
      Re: efficient partial sort in Python ? Terry Reedy <tjreedy@udel.edu> - 2014-08-19 18:11 -0400
      Re: efficient partial sort in Python ? Dan Stromberg <drsalists@gmail.com> - 2014-08-19 16:05 -0700
      Re: efficient partial sort in Python ? Dan Stromberg <drsalists@gmail.com> - 2014-08-19 16:10 -0700
      Re: efficient partial sort in Python ? Dan Stromberg <drsalists@gmail.com> - 2014-08-19 16:22 -0700
      Re: efficient partial sort in Python ? Ian Kelly <ian.g.kelly@gmail.com> - 2014-08-19 18:00 -0600

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