Quicksort R benchmark is broken. #735
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…in place, do it like this.
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Thanks! |
JeffBezanson
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Quicksort R benchmark is broken.
KristofferC
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(cherry picked from commit 8e91d902458b9dbeab76fa7194ee58d1a6137334) (cherry picked from commit 909508ab4b4458b6f58c0a870bd3b7f896e5a818)
KristofferC
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(cherry picked from commit 8e91d902458b9dbeab76fa7194ee58d1a6137334) (cherry picked from commit 909508ab4b4458b6f58c0a870bd3b7f896e5a818) (cherry picked from commit a416c9f)
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(cherry picked from commit 8e91d902458b9dbeab76fa7194ee58d1a6137334) (cherry picked from commit 909508ab4b4458b6f58c0a870bd3b7f896e5a818) (cherry picked from commit a416c9f)
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The quicksort was written as though R passes mutable references, which it doesn't (R uses a copy-on-write scheme like Matlab/Octave). The recursive call to qsort_kernel did nothing, and produced an o(N^2) algorithm due to all the private copies of 'a' being made.
If you want to operate on an array in place, one way is to hold the array in an enclosing scope and use <<- operator.