[GitHub] incubator-beam pull request #741: Top improvements

[robertwb <gi...@git.apache.org>]

GitHub user robertwb opened a pull request:

    https://github.com/apache/incubator-beam/pull/741

    Top improvements

    Be sure to do all of the following to help us incorporate your contribution
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    ---


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/robertwb/incubator-beam top

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/incubator-beam/pull/741.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #741
    
----
commit 9151fcf861704c550c21f411a9047f955f179ec4
Author: Robert Bradshaw <ro...@gmail.com>
Date:   2016-07-27T17:09:49Z

    Better top implementation.
    
    When selecting the top k of n, it is common that k << n.
    Using a heap is O(n log k) while select algorithms can
    achieve O(n + k log k).
    
    This also avoids the ugliness that heapq does not take the
    comparator as an argument, resulting in _HeapItem classes that
    were cumbersome and expensive to serialize.

commit e38d6f60f18bf6ad61f2d387c67efa2012af2e14
Author: Robert Bradshaw <ro...@gmail.com>
Date:   2016-07-27T19:23:02Z

    Allow Top operations to take key argument rather than compare, and order
    by the natural ordering if neither is specified.

----


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[GitHub] incubator-beam pull request #741: Top improvements

[robertwb <gi...@git.apache.org>]

Github user robertwb closed the pull request at:

    https://github.com/apache/incubator-beam/pull/741


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