Child of Sandpile

;;关于沙堆模型：https://wiki.swarma.org/index.php?title=%E6%B2%99%E5%A0%86%E6%A8%A1%E5%9E%8B
;;改变沙子流动规则，严格按照四个方向流动
globals [
  N
  Ea
]

to setup
  clear-all
  set N [ ];;存储每加一粒沙子坍塌的次数
  set Ea [ ]
  setup-patches
  setup-turtles
  reset-ticks;;时间重置
end 

to setup-patches
  ask patches [ set pcolor yellow ];;
end 

to setup-turtles
  set-default-shape turtles "dot"
end 

to go
  if ticks > num_stop [ stop ];;程序停止标志
  updata-patches;;显示瓦片上的沙子数,一个沙子为绿色，二个为蓝色，三个为红色，
  add-turtles;;加沙子
  move-turtles;;沙子移动
  hide-turtles;;到达边界就隐藏
  tick;;要确保，tiks之前的命令都正常运行，ticks才能正常运行
  if ticks > num_stop [
    do-plots;;
  ]
end 

to add-turtles
  ;;ask patch random-xcor random-ycor [
  ask patch 0 0 [
    sprout 1  [ set color black ]
  ];;加沙子
end 

to hide-turtles
  ask turtles [
    if patch-at dx 0 = nobody
    [ hide-turtle ]
    if patch-at 0 dy = nobody
    [ hide-turtle ]
  ]
end 

to move-turtles
  let s 0
  let i 0;;控制只移动四个
;  ask turtles with [count turtles-here >= 4 ] [ ;;四个沙子进行四个方向的随机选择，而不是每一个方向有一个沙子的
;    set s s + 0.25
;    face one-of neighbors4              ;; face N, E, S, or W
;    forward 1                           ;; advance one step
;  ]
  while [ any? (patches with [count turtles-here >= 4 ])] [
    foreach sort (patches with [count turtles-here >= 4 ]) [ x -> ;;对由拥有四个沙子的瓦片组成的主体列表中的每一个瓦片进行操作
      set i 0;;控制只移动四个,其余的不用管，效果依旧很好，验证了沙子从那个瓦片开始流动的顺序是无关的
      (foreach sort ([turtles-at 0 0] of x) [ y -> ;;得到每一个瓦片上的四个沙子组成的主体列表，对每一只沙子进行转向移动操作
         if i < 4 [
          ask y [
            set heading (i * 90);;让沙子面向北东南西四个方向
            forward 1
          ]
        ]
        set i i + 1
      ])
      set s s + 1
    ]
  ]
  set N fput s N;;存放坍塌次数
  set Ea fput ticks Ea;;存放坍塌强度
  display
end 

to updata-patches
  ask patches with [ count turtles-here = 0 ] [
    set pcolor  yellow ]
  ask patches with [ count turtles-here = 1 ] [
    set pcolor  green ]
  ask patches with [ count turtles-here = 2 ] [
    set pcolor  blue ]
  ask patches with [ count turtles-here = 3 ] [
    set pcolor  red ]
  display
end 

to do-plots
  set N remove 0 N;;除去0.因为有0就不能取对数
  set N (map [ x -> ln x ] N)
  set-plot-pen-mode 1
  set-plot-pen-interval 1
  set-current-plot "N-E" ;;
  set-current-plot-pen "N" ;;
  histogram N ;;
end