在 Clojure 中使用代理的多线程弹跳球程序答案

【问题标题】：Multithreaded bouncing balls program using agents in Clojure在 Clojure 中使用代理的多线程弹跳球程序
【发布时间】：2011-08-25 12:00:34
【问题描述】：

我在 clojure 中编写了一个多线程弹跳球程序。启动动画线程后，我做 -

(send-balls)

开始弹跳球线程。球不动，这会显示在控制台上 -

(#<Agent@5675b3ee FAILED: #<Ref@313d21d6: {:x 759, :y 629, :x-speed 3, :y-speed 1}>> #<Agent@22cf3539 FAILED: #<Ref@247881db: {:x 794, :y 258, :x-speed 2, :y-speed 3}>> #<Agent@51af4309 FAILED: #<Ref@445ead9d: {:x 831, :y 251, :x-speed 4, :y-speed 2}>>)

有人能指出这里发生了什么吗？

(import
 '(java.awt Color Graphics Dimension)
 '(java.awt.image BufferedImage)
 '(javax.swing JPanel JFrame))

(def width 1000)
(def height 1000)

(def number-of-balls 3)

(def rad 20)

(def origin-x 100)
(def origin-y 100)
(def box-height 500)
(def box-width 700)
(def max-x (+ origin-x box-width (* 4 rad)))
(def max-y (+ origin-y box-height (* 4 rad)))
(def min-x origin-x)
(def min-y origin-y)

(defn init-x
 []
 (+ (rand-int (- max-x min-x)) min-x))

(defn init-y
 []
  (+ (rand-int (- max-y min-y)) min-y))

(defstruct ball :x :y :x-speed :y-speed)

(def balls
 (apply vector (map (fn [_] (ref (struct ball (init-x) (init-y)
(rand-int 10) (rand-int 10))))
                 (range number-of-balls))))

(def ball-agents (apply vector (map agent balls)))

(defn get-ball
 [n]
 (balls n))


(defn set-new-x
 [ball]
 (let [x (@ball :x)
       x-speed (@ball :x-speed)
       new-x (+ x x-speed)]
   (dosync
     (if (and (>= new-x min-x) (<= new-x max-x))
      (ref-set ball (assoc @ball :x new-x))
            (ref-set ball (assoc @ball :x-speed (* -1 x-speed)))))
   (println "the new x is " @(ball :x)))
 @ball)

(defn set-new-y
 [ball]
 (let [y (@ball :y)
       y-speed (@ball :y-speed)
       new-y (+ y y-speed)]
   (dosync
     (if (and (>= new-y min-y) (<= new-y max-y))
             (ref-set ball (assoc @ball :y new-y))
             (ref-set ball (assoc @ball :y-speed (* -1 y-speed))))))
 @ball)

(defn paint-balls
 [bg x y]
 (doto bg
   (.setColor (. Color red))
   (.fillOval x y rad rad)))


(defn render
 [g]
 (let [img (new BufferedImage width height
                (. BufferedImage TYPE_INT_ARGB))
      bg (. img (getGraphics))]
  (doto bg
     (.setColor (. Color white))
     (.fillRect 0 0 (. img (getWidth)) (. img (getHeight)))
     (.setColor (. Color red))
     (.drawRect origin-x origin-y (+ origin-x box-width) (+ origin-y box-height)))
  (dorun
    (for [i (range number-of-balls)]
      (do
        (paint-balls bg (@(get-ball i) :x) (@(get-ball i) :y)))))
  (. g (drawImage img 0 0 nil))
  (. bg (dispose))))

(def panel (doto (proxy [JPanel] []
                       (paint [g] (render g)))
            (.setPreferredSize (new Dimension
                                    width
                                    height))))

(def frame (doto (new JFrame) (.add panel) .pack .show))

(def animator (agent nil))

(defn bounce
 [x]
 (while true
   (set-new-x @*agent*)
   (set-new-y @*agent*)
   (. Thread (sleep 100))
   (println "here in bounce " *agent*)))




(defn animation
 [x]
 (send-off *agent* animation)
 (. panel (repaint))
 (. Thread (sleep 100)))

(defn send-balls
 []
 (doall
   (for [i (range number-of-balls)]
     (do
       (send-off (ball-agents i) bounce)))))


(send-off animator animation)

【问题讨论】：

您的代理更新似乎失败 - 可能是由于退回功能中的异常。我怀疑一个问题是你做了太多的取消引用，即“@*agent*”实际上应该是“*agent*”。
@mikera - 我试过了，但不是这样......

标签： multithreading clojure agents

【解决方案1】：

我认为您不需要代理内部的参考。请参阅下面的仅包含代理的工作版本。您可以加载代码，例如。通过load-file 然后只需发出start。将弹出一个带有所需动画的帧。可以通过reset!将返回的原子发送到false 来停止它。您可以通过多次调用 start 来拥有任意数量的独立动画帧。

希望对您有所帮助。

(import
 '(java.awt Color Graphics Dimension)
 '(java.awt.image BufferedImage)
 '(javax.swing JPanel JFrame))

(def width 1000)
(def height 1000)

(def number-of-balls 3)

(def rad 20)

(def origin-x 100)
(def origin-y 100)
(def box-height 500)
(def box-width 700)
(def min-borders {:x origin-x
                  :y origin-y})
(def max-borders {:x (+ origin-x box-width (* 4 rad))
                  :y (+ origin-y box-height (* 4 rad))})

(defn init
 [coord]
 (+ (rand-int (- (get max-borders coord) (get min-borders coord)))
    (get min-borders coord)))

(defn init-balls
  []
  (->> (repeatedly number-of-balls
                   #(array-map :x (init :x) :y (init :y)
                               :x-speed (rand-int 10)
                               :y-speed (rand-int 10)))
    (map agent)
    vec))

(defn update-coordinate
  [ball coord-key speed-key]
  (let [coord (get ball coord-key)
        speed (get ball speed-key)
        new-c (+ coord speed)]
    (if (<= (get min-borders coord-key) new-c (get max-borders coord-key))
      (assoc ball coord-key new-c)
      (assoc ball speed-key (- speed)))))

(defn paint-ball
  [bg x y]
  (doto bg
    (.setColor Color/red)
    (.fillOval x y rad rad)))

(defn render
  [g balls]
  (let [img (BufferedImage. width height BufferedImage/TYPE_INT_ARGB)
        bg  (.getGraphics img)]
    (doto bg
      (.setColor Color/white)
      (.fillRect 0 0 (.getWidth img) (.getHeight img))
      (.setColor Color/red)
      (.drawRect origin-x origin-y
                 (+ origin-x box-width) (+ origin-y box-height)))
    (doseq [b balls]
      (let [ball @b]
        (paint-ball bg (:x ball) (:y ball))))
    (.drawImage g img 0 0 nil)))

(defn bounce
  [ball running?]
  (when @running?
    (send-off *agent* bounce running?))
  (Thread/sleep 100)
  (-> ball
    (update-coordinate :x :x-speed)
    (update-coordinate :y :y-speed)))

(defn animation
  [panel running?]
  (while @running?
    (javax.swing.SwingUtilities/invokeAndWait #(.repaint panel))
    (Thread/sleep 100)))

(defn start
  []
  (let [running? (atom true)
        balls    (init-balls)
        panel    (doto (proxy [JPanel] []
                         (paint [g] (render g balls)))
                   (.setPreferredSize (Dimension. width height)))
        frame    (doto (JFrame.) (.add panel) .pack .show)]
    (doseq [b balls]
      (send-off b bounce running?))
    (future (animation panel running?))
    running?))

【讨论】：

@pranav 哎呀。剪切粘贴故障。固定。

【解决方案2】：

正如我看到的主要问题 - 您发送给代理的功能不是与代理一起操作，而是与它的值（参考）一起操作。通过消除 set-new-x 和 set-new-y 函数中的 @ 可以使其工作。

(ns balls)

(import
  '(java.awt Color Graphics Dimension)
  '(java.awt.image BufferedImage)
  '(javax.swing JPanel JFrame))

(def width 1000)
(def height 1000)

(def number-of-balls 3)

(def rad 20)

(def origin-x 100)
(def origin-y 100)
(def box-height 500)
(def box-width 700)
(def max-x (+ origin-x box-width (* 4 rad)))
(def max-y (+ origin-y box-height (* 4 rad)))
(def min-x origin-x)
(def min-y origin-y)

(defn init-x
 []
 (+ (rand-int (- max-x min-x)) min-x))

(defn init-y
 []
  (+ (rand-int (- max-y min-y)) min-y))

(defstruct ball :x :y :x-speed :y-speed)

(def balls
 (apply vector (map (fn [_] (ref (struct ball (init-x) (init-y)
(rand-int 10) (rand-int 10))))
                 (range number-of-balls))))

(def ball-agents (apply vector (map agent balls)))

(defn get-ball
 [n]
 (balls n))


(defn set-new-x
  [ball]
  (let [x (ball :x)
        x-speed (ball :x-speed)
        new-x (+ x x-speed)]
    (dosync
      (if (and (>= new-x min-x) (<= new-x max-x))
        (alter ball assoc :x new-x)
        (alter ball assoc :x-speed (* -1 x-speed)))))
    ball)

(defn set-new-y
  [ball]
  (let [y (ball :y)
        y-speed (ball :y-speed)
        new-y (+ y y-speed)]
    (dosync
      (if (and (>= new-y min-y) (<= new-y max-y))
        (alter ball assoc :y new-y)
        (alter ball assoc :y-speed (* -1 y-speed))))
   ball))

(defn paint-balls
 [bg x y]
 (doto bg
   (.setColor (. Color red))
   (.fillOval x y rad rad)))


(defn render
 [g]
 (let [img (new BufferedImage width height
                (. BufferedImage TYPE_INT_ARGB))
      bg (. img (getGraphics))]
  (doto bg
     (.setColor (. Color white))
     (.fillRect 0 0 (. img (getWidth)) (. img (getHeight)))
     (.setColor (. Color red))
     (.drawRect origin-x origin-y (+ origin-x box-width) (+ origin-y box-height)))
  (dorun
    (for [i (range number-of-balls)]
      (do
        (paint-balls bg (@(get-ball i) :x) (@(get-ball i) :y)))))
  (. g (drawImage img 0 0 nil))
  (. bg (dispose))))

(def panel (doto (proxy [JPanel] []
                       (paint [g] (render g)))
            (.setPreferredSize (new Dimension
                                    width
                                    height))))

(def frame (doto (new JFrame) (.add panel) .pack .show))

(def animator (agent nil))

(defn bounce
 [ball_cur]
 (do
   (Thread/sleep 100)
   (send-off *agent* bounce)
   (set-new-x (set-new-y ball_cur))))

(defn animation
 [x]
 (send-off *agent* animation)
 (. panel (repaint))
 (. Thread (sleep 100)))

(defn send-balls
 []
 (doall
   (for [i (range number-of-balls)]
     (do
       (send-off (ball-agents i) bounce)))))


(send-off animator animation)
(send-balls)

【讨论】：

【解决方案3】：

代码有几个问题 -

正如 Maurits 所指出的，反弹不会返回代理的新状态。
弹跳函数中没有将弹跳再次添加到代理的操作队列的位置。这是需要的，因为需要一次又一次地计算新的协调。

【讨论】：

【解决方案4】：

您的发送（或发送）函数（在本例中为：退回）应返回代理的（新）状态。这在here 中有完整描述。

【讨论】：