Java Clojure中的快速随机字符串生成器

我想知道是否有一种方法可以在Clojure中生成固定长度的随机字符串

快速搜索的结果是：

查看VisualVM CPU配置文件数据后，我意识到is消耗了大量CPU：

我决定重写它，使其与我以前使用的Java函数类似：

(defn rand-str2-slow
  ^String [^Long len]
  (let [leftLimit 97
        rightLimit 122
        random (Random.)
        stringBuilder (StringBuilder. len)
        diff (- rightLimit leftLimit)]
    (dotimes [_ len]
      (let [ch (char (.intValue (+ leftLimit (* (.nextFloat random) (+ diff 1)))))]
        (.append stringBuilder ch)))
        (.toString stringBuilder)))

这导致了更慢的代码，但是堆栈跟踪的深度要小得多：

我注意到它有很多Reflector.getMethods。有没有办法键入提示函数以避免这种情况

更新1：

相关微基准：

兰德街

(with-progress-reporting (quick-bench (rand-str 5000) :verbose))

      Execution time sample mean : 1.483232 ms
             Execution time mean : 1.483547 ms
Execution time sample std-deviation : 31.161960 µs
    Execution time std-deviation : 31.651732 µs
   Execution time lower quantile : 1.441678 ms ( 2.5%)
   Execution time upper quantile : 1.531289 ms (97.5%)
                   Overhead used : 14.598226 ns

rand-str2-slow

(with-progress-reporting (quick-bench (rand-str2-slow 5000) :verbose))

      Execution time sample mean : 17.637256 ms
             Execution time mean : 17.647974 ms
Execution time sample std-deviation : 523.527242 µs
    Execution time std-deviation : 528.559280 µs
   Execution time lower quantile : 17.322583 ms ( 2.5%)
   Execution time upper quantile : 18.522246 ms (97.5%)
                   Overhead used : 14.598226 ns

rand-str2快速

(with-progress-reporting (quick-bench (rand-str2 5000) :verbose))

      Execution time sample mean : 84.362974 µs
             Execution time mean : 84.355379 µs
Execution time sample std-deviation : 3.496944 µs
    Execution time std-deviation : 3.674542 µs
   Execution time lower quantile : 80.911920 µs ( 2.5%)
   Execution time upper quantile : 89.264431 µs (97.5%)
                   Overhead used : 14.598226 ns

---

让我回答我自己的问题：

(defn rand-str2
  ^String [^Long len]
  (let [leftLimit 97
        rightLimit 122
        random (Random.)
        stringBuilder (StringBuilder. len)
        diff (- rightLimit leftLimit)]
    (dotimes [_ len]
      (let [ch (char (.intValue ^Double (+ leftLimit (* (.nextFloat ^Random random) (+ diff 1)))))]
        (.append ^StringBuilder stringBuilder ch)))
        (.toString ^StringBuilder stringBuilder)))

---

让我回答我自己的问题：

(defn rand-str2
  ^String [^Long len]
  (let [leftLimit 97
        rightLimit 122
        random (Random.)
        stringBuilder (StringBuilder. len)
        diff (- rightLimit leftLimit)]
    (dotimes [_ len]
      (let [ch (char (.intValue ^Double (+ leftLimit (* (.nextFloat ^Random random) (+ diff 1)))))]
        (.append ^StringBuilder stringBuilder ch)))
        (.toString ^StringBuilder stringBuilder)))

---

是的，避免装箱/拆箱和键入提示通常是一种方法。遗憾的是，第一个版本不能再优化了。是的，惯用的Clojure非常慢。这就是价格。是的，避免装箱/拆箱和键入提示通常是一种方法。遗憾的是，第一个版本不能再优化了。是的，惯用的Clojure非常慢。这就是价格。