如何使用rand-int生成可重复的随机序列 [英] How to generate repeatable random sequences with rand-int

问题描述

我希望能够使用Clojure中的 rand 生成可重复的数字。 （具体来说，我希望调用 rand-nth 或Incanter的 sample 的结果可重复，而这些调用 rand-int 依次称为 rand ）。

I want to be able to generate repeatable numbers using rand in Clojure. (Specifically, I want results of calls to rand-nth or Incanter's sample to be repeatable, and these call rand-int which in turn calls rand).

I从这个问题中找出来如果我使用clojure.data.generators，则可以重置随机状态：

I figured out from this question that if I use clojure.data.generators, I can reset the random state:

(require '[clojure.data.generators :as gen])
(alter-var-root #'gen/*rnd* (constantly (java.util.Random. 437)))
(gen/reservoir-sample 5 (range 1000)) ; => [940 591 636 12 755]
(gen/reservoir-sample 5 (range 1000)) ; => [376 540 827 307 463]
; reset random state:
(alter-var-root #'gen/*rnd* (constantly (java.util.Random. 437)))
; now the same results are generated again:
(gen/reservoir-sample 5 (range 1000)) ; => [940 591 636 12 755]
(gen/reservoir-sample 5 (range 1000)) ; => [376 540 827 307 463]

但是，该方法似乎只影响clojure.data中的函数。生成器，这并不奇怪：

However, that method only seems to affect functions in clojure.data.generators, which isn't surprising:

(alter-var-root #'gen/*rnd* (constantly (java.util.Random. 437)))
(rand) ; => 0.9372552374760151
(rand) ; => 0.2712729314667742
; reset random state:
(alter-var-root #'gen/*rnd* (constantly (java.util.Random. 437)))
; not same results as before:
(rand) ; => 0.630238593767316
(rand) ; => 0.426744420572015

如何恢复随机状态，例如从<$ c中获得可重复的结果$ c> rand ？到目前为止，我还没有找到任何相关文档。

How can I restore the random state in such as way as to get repeatable results from rand? So far I haven't found any documentation about this.

（另一个问题听起来好像是同一问题，但它询问的是完全不同的东西。）

(Another question sounds as if it might be the same issue, but it's asking about something completely different.)

推荐答案

可能不是最干净的方法，但您可以通过重新定义 clojure.core / rand ：

Probably not the cleanest way, but you can make it work by redefining clojure.core/rand:

(ns clojure.core)

(def r (java.util.Random. 1))

(defn rand
  ([] (.nextDouble r))
  ([n] (.nextInt r n)))

(take 10 (repeatedly #(rand-int 10)))

每次运行它都会产生（5 8 7 3 4 4 4 6 6 8 8）。

This produces (5 8 7 3 4 4 4 6 8 8) every time I run it.

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