PPHPC - Predator-Prey for High-Performance Computing

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Default-person Nuno Fachada (Author)

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predator prey model 

Tagged by Nuno Fachada about 3 years ago

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globals [
  sheep-count     ;; how many sheep are there?
  wolves-count    ;; how many wolves are there?
  grass-alive     ;; how much alive grass there is
  sheep-energy    ;; mean sheep energy
  wolves-energy   ;; mean wolf energy
  grass-countdown ;; mean grass countdown
  maxwho          ;; youngest agent to date
]

;; Sheep and wolves are both breeds of turtle.
breed [sheep a-sheep]   ;; sheep is its own plural, so we use "a-sheep" as the singular.
breed [wolves wolf]
turtles-own [energy]    ;; both wolves and sheep have energy
patches-own [countdown] ;; patches have a countdown variable for grass

;; Initialization

to setup

  clear-all
  
  ;; Set random number generator seed
  random-seed rngseed
  
  ;; show-params

  ask patches [ 
    ifelse random 2 = 1 [
      set countdown 1 + random grass-regrowth-time ;; initialize grass grow clocks randomly
      set pcolor brown
    ] [
      set countdown 0
      set pcolor green 
    ]
  ]

  set-default-shape sheep "sheep"
  create-sheep initial-number-sheep  ;; create the sheep, then initialize their variables
  [
    set color white
    set size 1  ;; easier to see
    set label-color blue - 2
    set energy 1 + random (2 * sheep-gain-from-food)
    setxy random-pxcor random-pycor
  ]
  set-default-shape wolves "wolf"
  create-wolves initial-number-wolves  ;; create the wolves, then initialize their variables
  [
    set color black
    set size 1  ;; easier to see
    set energy 1 + random (2 * wolf-gain-from-food)
    setxy random-pxcor random-pycor
  ]

  gather-stats

  display-labels
  reset-ticks
end 

;; Simulation loop

to go

  ;; 1 - Agent movement
  ask turtles [
    move
    set energy energy - 1
    if energy < 1 [ die ] ;; if energy dips below zero, die
  ]
  
  ;; 2 - Grow food
  ask patches [ grow-grass ]
  
  ;; 3 - Act
  ask turtles [
    ifelse is-a-sheep? self [
      ;; is a sheep
      eat-grass
      reproduce sheep-reprod-thres sheep-reprod-prob
    ] [ 
      ;; is a wolf
      catch-sheep
      reproduce wolf-reprod-thres wolf-reprod-prob
    ]
  ]

  ;; 4 - Gather stats
  gather-stats
  display-labels
  
  ;; New iteration
  tick
  
  ;; Time to stop?
  if ticks = iterations [ stop ]
end 

to gather-stats
  set maxwho max [who] of sheep
  set sheep-count count sheep
  set wolves-count count wolves
  set grass-alive count patches with [countdown <= 0]
  if show-energy? [
    ifelse sheep-count > 0
      [ set sheep-energy mean [energy] of sheep ]
      [ set sheep-energy 0 ]
    ifelse wolves-count > 0
      [ set wolves-energy mean [energy] of wolves ]
      [ set wolves-energy 0 ]
    set grass-countdown mean [countdown] of patches
  ]
end 

to move  ;; turtle procedure
  let direction random 5
  if direction < 4 [
    set heading 90 * direction
    fd 1
  ]
end 

to eat-grass  ;; sheep procedure
  ;; sheep eat grass, turn the patch brown
  if pcolor = green [
    set pcolor brown
    ask patch-here [set countdown grass-regrowth-time]
    set energy energy + sheep-gain-from-food  ;; sheep gain energy by eating
  ]
end 

to reproduce [ reprod-thres reprod-prob ] ;; turtle procedure
  if energy > reprod-thres [
    if random 100 < reprod-prob [  ;; throw "dice" to see if you will reproduce
      let energy_offspring int (energy / 2)
      set energy energy - energy_offspring    ;; divide energy between parent and offspring
      hatch 1 [ ;; hatch an offspring which stays in the same place
        set energy energy_offspring  ] 
    ]
  ]
end 

to catch-sheep  ;; wolf procedure
  let prey one-of sheep-here with [ who <= maxwho ]  ;; grab a random sheep, cannot be a newly born sheep
  if prey != nobody                             ;; did we get one?  if so,
    [ ask prey [ die ]                          ;; kill it
      set energy energy + wolf-gain-from-food ] ;; get energy from eating
end 

to grow-grass  ;; patch procedure
  ;; countdown on brown patches: if reach 0, grow some grass
  if pcolor = brown [
    set countdown countdown - 1
    if countdown <= 0
      [ set pcolor green
        set countdown 0 ]
  ]
end 

to display-labels
  if show-energy? [
    ask wolves [ set label energy ]
    ask sheep [ set label energy ]
  ]
end 

to show-params
  print word "                INIT_SHEEP = " initial-number-sheep
  print word "      SHEEP_GAIN_FROM_FOOD = " sheep-gain-from-food
  print word " SHEEP_REPRODUCE_THRESHOLD = " sheep-reprod-thres
  print word "      SHEEP_REPRODUCE_PROB = " sheep-reprod-prob
  print word "               INIT_WOLVES = " initial-number-wolves
  print word "     WOLVES_GAIN_FROM_FOOD = " wolf-gain-from-food
  print word "WOLVES_REPRODUCE_THRESHOLD = " wolf-reprod-thres
  print word "     WOLVES_REPRODUCE_PROB = " wolf-reprod-prob
  print word "             GRASS_RESTART = " grass-regrowth-time
  print word "                    GRID_X = " world-width
  print word "                    GRID_Y = " world-height
  print word "                     ITERS = " iterations
end 

; Copyright 1997 Uri Wilensky. All rights reserved.
; Copyright 2015 Nuno Fachada. All rights reserved.
; The full copyright notice is in the Information tab.

There is only one version of this model, created about 3 years ago by Nuno Fachada.

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