Ant-Based Stochastic Search-and-Reset Strategy

patches-own [
  chemical             ;; amount of chemical on this patch
  food                 ;; amount of food on this patch (0, 1, or 2)
  nest?                ;; true on nest patches, false elsewhere
  nest-scent           ;; number that is higher closer to the nest
  food-source-number   ;; number (1, 2, or 3) to identify the food sources
  xc                   ;; unwrapped xcor
  yc                   ;; unwrapped ycor
  dist                 ;; turtle distance from origin

]

globals [
  total-time           ;; total number of ticks since initiation
  nest-mark            ;; marks the nest
]

;;;;;;;;;;;;;;;;;;;;;;;;
;;; Setup procedures ;;;
;;;;;;;;;;;;;;;;;;;;;;;;

to setup
  clear-all
  set-default-shape turtles "bug"
  create-turtles population
  [ set size 1         ;; easier to see
    set color red  ]   ;; red = not carrying food
  setup-patches
  reset-ticks
end 

to setup-patches
  ask patches
  [ setup-nest
    setup-food
    recolor-patch ]
end 

to setup-nest  ;; patch procedure
  ;; set nest? variable to true inside the nest, false elsewhere
  set nest? (distancexy 0 0) < 1
  ;; spread a nest-scent over the whole world -- stronger near the nest
  ;set nest-scent 200 - distancexy 0 0
end 

to setup-food  ;; patch procedure
  ;; setup food source one
  if (distancexy food-x-coordinate food-y-coordinate) < 1
  [ set food-source-number 1 ]
  ;; setup food source two on the lower-left
  ;if (distancexy (-0.6 * max-pxcor) (-0.6 * max-pycor)) < 1
  ;[ set food-source-number 2 ]
  ;; setup food source three on the upper-left
  ;if (distancexy (-0.8 * max-pxcor) (0.8 * max-pycor)) < 1
  ;[ set food-source-number 3 ]
  ;; set "food" at sources to either 1 or 2, randomly
  if food-source-number > 0
  [ set food 1 ]
end 

to recolor-patch  ;; patch procedure
  ;; give color to nest and food sources
  ifelse nest?
  [ set pcolor violet ]
  [ ifelse food > 0
    [ if food-source-number = 1 [ set pcolor green ]
      if food-source-number = 2 [ set pcolor green + 3  ]
      if food-source-number = 3 [ set pcolor green - 3 ] ]
    ;; scale color to show chemical concentration
    [ set pcolor scale-color green chemical 0.1 5 ] ]
end 

;;;;;;;;;;;;;;;;;;;;;
;;; Go procedures ;;;
;;;;;;;;;;;;;;;;;;;;;

to go  ;; forever button
  ifelse ticks < reset-time ;; if time is less than reset time
   [ ask turtles
     [ if food > 0;; stop tracking ants that find food
        [ set nest-mark 1 ;; mark nest
          die ]
     wiggle
     fd 1]] ;; move
  [ ask turtles ;; time is more than reset time
     [ setxy 0 0 ;; send turtles back to origin
       if nest-mark > 0 ;; if nest is marked, stop tracking ants
         [ die ]]
    reset-ticks ] ;; reset ticks
   if count turtles = 0
    [stop] ;; stop when all ants have found food
  set total-time total-time + 1 ;; time increment
  tick
  ;diffuse chemical (diffusion-rate / 100)
  ;ask patches
  ;[ set chemical chemical * (100 - evaporation-rate) / 100  ;; slowly evaporate chemical
  ;  recolor-patch ]
end 

to look-for-food  ;; turtle procedure
  if food > 0
   [set nest-mark 1
        die ]
  ;[ set color orange + 1     ;; pick up food
  ;  rt 180                   ;; and turn around
  ;  stop ]
  ;; go in the direction where the chemical smell is strongest
  ;if (chemical >= 0.05) and (chemical < 2)
  ;[ uphill-chemical ]
end 

to return-to-nest  ;; turtle procedure
  ;; drop food and head out again
  ;  set color red
  ;  rt 180 ]
  ;[ set chemical chemical + 60  ;; drop some chemical
  ; uphill-nest-scent ]         ;; head toward the greatest value of nest-scent
end 

;; sniff left and right, and go where the strongest smell is

to uphill-chemical  ;; turtle procedure
  ;let scent-ahead chemical-scent-at-angle   0
  ;let scent-right chemical-scent-at-angle  45
  ;let scent-left  chemical-scent-at-angle -45
  ;if (scent-right > scent-ahead) or (scent-left > scent-ahead)
  ;[ ifelse scent-right > scent-left
  ;  [ rt 45 ]
  ;  [ lt 45 ] ]
end 

;; sniff left and right, and go where the strongest smell is

to uphill-nest-scent  ;; turtle procedure
  ;let scent-ahead nest-scent-at-angle   0
  ;let scent-right nest-scent-at-angle  45
  ;let scent-left  nest-scent-at-angle -45
  ;if (scent-right > scent-ahead) or (scent-left > scent-ahead)
  ;[ ifelse scent-right > scent-left
  ;  [ rt 45 ]
  ;  [ lt 45 ] ]
end 

to wiggle  ;; turtle procedure
  rt random-float 360
  lt random-float 360
  ifelse not can-move? 1
    [ hide-turtle ]
    [ show-turtle ]
  set dist xcor * xcor + ycor * ycor
end 

to-report nest-scent-at-angle [angle]
  ;let p patch-right-and-ahead angle 1
  ;if p = nobody [ report 0 ]
  ;report [nest-scent] of p
end 

to-report chemical-scent-at-angle [angle]
  ;let p patch-right-and-ahead angle 1
  ;if p = nobody [ report 0 ]
  ;report [chemical] of p
end 

to-report replace-all [target replacement str] ;; screeshot button setup
  let acc str
  while [position target acc != false] [
    set acc (replace-item (position target acc) acc replacement)
  ]
  report acc
end 


; Copyright 1997 Uri Wilensky.
; See Info tab for full copyright and license.