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Code Issues 1 Releases Wiki Activity

Tweak sort: use insertion sort for small arrays

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This commit is contained in:
Felix Riedel 2020-12-28 16:06:48 +00:00
parent 0d46352ff4
commit 0ea77cabfb
1 changed files with 32 additions and 21 deletions
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35
src/boot/boot.janet
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@ -795,11 +795,27 @@
a
(if (not= (> b a) (> b c)) b c)))
(defn sort-help [a lo hi by]
(defn- insertion-sort [a lo hi by]
(for i (+ lo 1) (+ hi 1)
(def temp (in a i))
(var j (- i 1))
(while (and (>= j lo) (by temp (in a j)))
(set (a (+ j 1)) (in a j))
(-- j))
(set (a (+ j 1)) temp))
a)
(defn sort
"Sort an array in-place. Uses quick-sort and is not a stable sort."
[a &opt by]
(default by <)
(def stack @[[0 (- (length a) 1)]])
(while (not (empty? stack))
(def [lo hi] (array/pop stack))
(when (< lo hi)
(def pivot
(median-of-three (in a hi) (in a lo)
(in a (math/floor (/ (+ lo hi) 2)))))
(when (< (- hi lo) 32) (insertion-sort a lo hi by) (break))
(def pivot (median-of-three (in a hi) (in a lo) (in a (math/floor (/ (+ lo hi) 2)))))
(var left lo)
(var right hi)
(while true
@ -812,17 +828,12 @@
(++ left)
(-- right))
(if (>= left right) (break)))
(sort-help a lo right by)
(sort-help a left hi by))
(array/push stack [lo right])
(array/push stack [left hi])))
a)
(defn sort
"Sort an array in-place. Uses quick-sort and is not a stable sort."
[a &opt by]
(sort-help a 0 (- (length a) 1) (or by <)))
(undef median-of-three)
(undef sort-help)
(undef insertion-sort)
(defn sort-by
`Returns a new sorted array that compares elements by invoking