Segregation Model - BehaviorSearch

globals [
  percent-similar  ;; on the average, what percent of a turtle's neighbors
                   ;; are the same color as that turtle?
  percent-unhappy  ;; what percent of the turtles are unhappy?
]

turtles-own [
  happy?       ;; for each turtle, indicates whether at least %-similar-wanted percent of
               ;; that turtles' neighbors are the same color as the turtle
  similar-nearby   ;; how many neighboring patches have a turtle with my color?
  other-nearby ;; how many have a turtle of another color?
  total-nearby  ;; sum of previous two variables
]

to setup
  clear-all
  if number > count patches
    [ user-message (word "This pond only has room for " count patches " turtles.")
      stop ]

  ;; create turtles on random patches.
  ask n-of number patches
    [ sprout 1
      [ set color red ] ]
  ;; turn half the turtles green
  ask n-of (number / 2) turtles
    [ set color green ]
  update-variables
  reset-ticks
end 

to go
  if all? turtles [happy?] [ stop ]
  move-unhappy-turtles
  update-variables
  tick
end 

to move-unhappy-turtles
  ask turtles with [ not happy? ]
    [ find-new-spot ]
end 

to find-new-spot
  rt random-float 360
  fd random-float 10
  if any? other turtles-here
    [ find-new-spot ]          ;; keep going until we find an unoccupied patch
  move-to patch-here  ;; move to center of patch
end 

to update-variables
  update-turtles
  update-globals
end 

to update-turtles
  ask turtles [
    ;; in next two lines, we use "neighbors" to test the eight patches
    ;; surrounding the current patch
    set similar-nearby count (turtles-on neighbors)
      with [color = [color] of myself]
    set other-nearby count (turtles-on neighbors)
      with [color != [color] of myself]
    set total-nearby similar-nearby + other-nearby
    set happy? similar-nearby >= ( pct-similar-wanted * total-nearby / 100 )
  ]
end 

to update-globals
  let similar-neighbors sum [similar-nearby] of turtles
  let total-neighbors sum [total-nearby] of turtles
  set percent-similar (similar-neighbors / total-neighbors) * 100
  set percent-unhappy (count turtles with [not happy?]) / (count turtles) * 100
end 


; Copyright 2006 Uri Wilensky.
; See Info tab for full copyright and license.