clojure - 如何在 Clojure 的 test.check 中对随机子序列进行采样？

Question

我正在尝试生成Subset Sum Problem的随机可解实例。Wikipedia 声明目标值应始终为零，但也可以指定目标值，这就是我在这里所做的。

所以这个想法是使用创建一个随机向量(gen/vector gen/int)，然后对一个随机子向量进行采样并对该向量求和以创建目标值。使用明显策略的问题gen/elements是它可能会重复采样相同的元素。
我的下一个最佳想法是创建一组随机索引并提取这些索引处的所有元素。有没有更简单的方法？

Answer 1

test.chuck 中的这个生成器通过为每个元素生成包含标志来满足您的要求。

Answer 2

这段代码是我认为您正在尝试做的事情的模型。它生成一个整数向量，每个整数都有一个标志来指示它是否属于子集（可以是无、一些或全部）。一个虚拟函数（代表子集和）决定测试是否通过。您将需要[tupelo "0.9.56"]在您的project.clj.

(ns tst.demo.core
  (:require
    [clojure.test.check :as tc]
    [clojure.test.check.generators :as tcgen]
    [clojure.test.check.properties :as tcprop]
    [tupelo.core :as t]
    [tupelo.test :as tt]
    [schema.core :as s]))

(def IntBoolTuple [ (s/one s/Int "x1") (s/one s/Bool "x2") ])

(s/defn is-sum-tuple? :- s/Bool
  [tuple :- IntBoolTuple]
  (let [[int-val bool-val] tuple]
    bool-val))

(s/defn tst-fn :- s/Bool
  "Dummy test function"
  [tuples :- [IntBoolTuple]]
  (let [all-ints      (mapv first tuples)
        flags         (mapv second tuples)
        tuples-to-add (vec (filter is-sum-tuple? tuples))
        ints-to-add   (mapv first tuples-to-add)
        int-sum       (apply + ints-to-add)]
    (< -20 int-sum))) ; dummy test: pass if not too negative

(tt/dospec 999
  (tcprop/for-all [tuples (tcgen/such-that
                            (fn st-fn [tuples] (pos? (count tuples))) ; ensure at least 1 tuple is present
                            (tcgen/vector ; 0 or more tuples, ex: [ [5 false] [2 true] ...]
                              (tcgen/tuple tcgen/int tcgen/boolean) ; a tuple like [5 false]
                              ))]
    (t/spyx tuples)   ; display
    (tst-fn tuples)))

上面的代码生成如下输出：

---------------------------------------
   Clojure 1.9.0-beta1    Java 9.0.1
---------------------------------------

Testing tst.demo.core
tuples => [[-1 false]]
tuples => [[1 true]]
tuples => [[-2 true] [-1 false]]
tuples => [[3 true] [-1 true]]
tuples => [[1 true]]
tuples => [[-1 true] [5 true] [-4 true] [5 false]]
tuples => [[5 true] [2 false] [3 false] [1 true] [0 true]]
tuples => [[2 false] [-4 false]]
tuples => [[2 false]]
tuples => [[2 false] [8 true] [9 true] [9 true] [3 true] [-7 true] [-9 true] [8 false] [-9 true]]
tuples => [[-9 true] [-1 true]]
tuples => [[4 false] [-6 true] [0 false] [10 true]]
tuples => [[-2 false] [7 true] [-12 false] [4 false] [4 false] [11 true] [6 false] [-5 false]]
tuples => [[-5 false] [6 true] [9 true] [-7 true] [1 false] [3 false] [-9 true] [-9 true] [-8 true] [-8 false] [-12 false]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-10 false] [1 false] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [5 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [-13 true]]
tuples => [[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false]]
tuples => [[8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-14 true] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-14 true] [-10 false] [1 false] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [5 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [-13 true]]
tuples => [[-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false]]
tuples => [[-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[8 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[8 false] [-1 false] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[8 false] [-1 false] [-14 true] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[8 false] [-1 false] [-14 true] [-10 false] [1 false] [5 false] [-13 true]]
tuples => [[8 false] [-1 false] [-14 true] [-10 false] [-8 true] [5 false] [-13 true]]
tuples => [[8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [-13 true]]
tuples => [[8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false]]
tuples => [[-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-1 false] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-1 false] [-14 true] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-1 false] [-14 true] [-10 false] [1 false] [5 false] [-13 true]]
tuples => [[-1 false] [-14 true] [-10 false] [-8 true] [5 false] [-13 true]]
tuples => [[-1 false] [-14 true] [-10 false] [-8 true] [1 false] [-13 true]]
tuples => [[-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false]]
tuples => [[-10 false] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 true] [-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-14 true] [-10 false] [1 false] [5 false] [-13 true]]
tuples => [[-14 true] [-10 false] [-8 true] [5 false] [-13 true]]
tuples => [[-14 true] [-10 false] [-8 true] [1 false] [-13 true]]
tuples => [[-14 true] [-10 false] [-8 true] [1 false] [5 false]]
tuples => [[-8 true] [1 false] [5 false] [-13 true]]
tuples => [[-10 false] [1 false] [5 false] [-13 true]]
tuples => [[-10 false] [-8 true] [5 false] [-13 true]]
tuples => [[-10 false] [-8 true] [1 false] [-13 true]]
tuples => [[-10 false] [-8 true] [1 false] [5 false]]
tuples => [[1 false] [5 false] [-13 true]]
tuples => [[-8 true] [5 false] [-13 true]]
tuples => [[-8 true] [1 false] [-13 true]]
tuples => [[-8 true] [1 false] [5 false]]
tuples => [[5 false] [-13 true]]
tuples => [[-8 true] [-13 true]]
tuples => [[-8 true] [5 false]]
tuples => [[-13 true]]
tuples => [[-8 true]]
tuples => [[0 true] [-13 true]]
tuples => [[-4 true] [-13 true]]
tuples => [[-6 true] [-13 true]]
tuples => [[-7 true] [-13 true]]
tuples => [[-8 false] [-13 true]]
tuples => [[-13 true]]
tuples => [[-7 true]]
tuples => [[0 true] [-13 true]]
tuples => [[-4 true] [-13 true]]
tuples => [[-6 true] [-13 true]]
tuples => [[-7 false] [-13 true]]
tuples => [[-7 true] [0 true]]
tuples => [[-7 true] [-7 true]]
tuples => [[-7 true] [-10 true]]
tuples => [[-7 true] [-12 true]]
tuples => [[-7 true] [-13 false]]
{:result false, :seed 1511919758351, :failing-size 14, :num-tests 15, :fail [[[-7 false] [-14 false] [8 false] [-1 false] [-14 true] [-10 false] [-8 true] [1 false] [5 false] [-13 true]]], :shrunk {:total-nodes-visited 27, :depth 9, :result false, :smallest [[[-7 true] [-13 true]]]}, :test-var "dospec-line-46"}

FAIL in (dospec-line-46) (clojure_test.cljc:21)
expected: result
  actual: false