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| author | John Högberg <[email protected]> | 2018-10-15 18:17:12 +0200 |
|---|---|---|
| committer | John Högberg <[email protected]> | 2018-10-29 08:10:55 +0100 |
| commit | eb9ee88f4cc640065f4902e270d834bfb596d5fc (patch) | |
| tree | a7ca57899b6d52417900eedd12995183f54f3bd5 /lib/stdlib/doc/src | |
| parent | 1056d2d1fd49f669a2001f03890e13c9cba76c1e (diff) | |
| download | otp-eb9ee88f4cc640065f4902e270d834bfb596d5fc.tar.gz otp-eb9ee88f4cc640065f4902e270d834bfb596d5fc.tar.bz2 otp-eb9ee88f4cc640065f4902e270d834bfb596d5fc.zip | |
Optimize operator '--' and yield on large inputs
The removal set now uses a red-black tree instead of an array on
large inputs, decreasing runtime complexity from `n*n` to
`n*log(n)`. It will also exit early when there are no more items
left in the removal set, drastically improving performance and
memory use when the items to be removed are present near the head
of the list.
This got a lot more complicated than before as the overhead of
always using a red-black tree was unacceptable when either of the
inputs were small, but this compromise has okay-to-decent
performance regardless of input size.
Co-authored-by: Dmytro Lytovchenko <[email protected]>
Diffstat (limited to 'lib/stdlib/doc/src')
| -rw-r--r-- | lib/stdlib/doc/src/lists.xml | 8 |
1 files changed, 0 insertions, 8 deletions
diff --git a/lib/stdlib/doc/src/lists.xml b/lib/stdlib/doc/src/lists.xml index c3d5d7e07a..e4215a5336 100644 --- a/lib/stdlib/doc/src/lists.xml +++ b/lib/stdlib/doc/src/lists.xml @@ -850,14 +850,6 @@ splitwith(Pred, List) -> > <input>lists:subtract("123212", "212").</input> "312".</pre> <p><c>lists:subtract(A, B)</c> is equivalent to <c>A -- B</c>.</p> - <warning> - <p>The complexity of <c>lists:subtract(A, B)</c> is proportional to - <c>length(A)*length(B)</c>, meaning that it is very slow if both - <c>A</c> and <c>B</c> are long lists. (If both lists are long, it - is a much better choice to use ordered lists and - <seealso marker="ordsets#subtract/2"> - <c>ordsets:subtract/2</c></seealso>.</p> - </warning> </desc> </func> |