map-invert应使用transients和reduce-kv代替reduce

Question

对clojure.set/map-invert的两次性能提升

1) 使用reduce-kv避免从输入map实例化mapentry
2) 使用transients创建输出map

*性能：*


(use 'criterium.core)
(require '[clojure.set :as set])
(def m1 (zipmap (range 1) (range 1)))
(def m10 (zipmap (range 10) (range 10)))
(def m100 (zipmap (range 100) (range 100)))
(def m1000 (zipmap (range 1000) (range 1000)))
(quick-bench (set/map-invert m1000))
(quick-bench (set/map-invert m100))
(quick-bench (set/map-invert m10))
(quick-bench (set/map-invert m1))

;; before:  138 ns  1.8 µs  20.6 µs  304 µs
;; after:   151 ns  1.3 µs   9.0 µs  126 µs


*补丁:* clj-1808-map-invert-should-use-reduce-kv-and-transient.patch

*审阅者:* Alex Miller

Answer 1

评论者：alexmiller

很希望看到比较前后时间的快速性能测试。

Answer 2

参考： https://clojure.atlassian.net/browse/CLJ-1808 (提交者：tonsky)