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sort: Fast path for already sorted data #29675

Merged
merged 2 commits into from
Nov 13, 2015
Merged

sort: Fast path for already sorted data #29675

merged 2 commits into from
Nov 13, 2015

Commits on Nov 7, 2015

  1. sort: Fast path for already sorted data 

    When merging two sorted blocks `left` and `right` if the last element in
`left` is <= the first in `right`, the blocks are already sorted.

Add this as an additional fast path by simply copying the whole left
block into the output and advancing the left pointer. The right block is
then treated the same way by the already present logic in the merge
loop.

Reduces runtime of .sort() to less than 50% of the previous, if the data
was already perfectly sorted. Sorted data with a few swaps are also
sorted quicker than before. The overhead of one comparison per merge
seems to be negligible.
    @bluss
    bluss committed Nov 7, 2015
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  2. sort: Guard the fast path by length check 

    The right part must not be empty.
    @bluss
    bluss committed Nov 7, 2015
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