# Tag Info

11

This function will be rewritten in C for 10.0.2 and should come down to average-case complexity of $O(n)$ from its current $O(n \log(n))$. Note that the version most users will be bothered to write (and the way we advertized this before in the docpage for DeleteDuplicates) is $O(n^2)$, so most users are probably already winning. In the meantime, my advice ...

23

Summary We can look at the code of DeleteDuplicatesBy and it turns out it uses GroupBy. The test cases proposed by Mr.Wizard are all handled by some part of the code of DeleteDuplicatesBy. Other parts of this code also seem to have some issues. Most of the members of the *By family of functions seem to have side effects. How DeleteDuplicatesBy works It ...

16

Attempting to analyze the performance of this function in the manner that Taliesin Beynon did for PositionIndex I shall use the same tools. The old method that will be compared in all cases below: myDeDupeBy[x_, f_] := GatherBy[x, f][[All, 1]] Speed A BenchmarkPlot of DeleteDuplicatesBy versus myDeDupeBy: Needs["GeneralUtilities`"] BenchmarkPlot[ ...

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