Ultimatum Game - effect of carrying capacity

;; no age
;; children starts with wealth = 50

globals [ cycle
          cycle-rejected
          cycle-rejected%
        ]



turtles-own [ wealth
              offer%
              rejection%
              linked?
            ]

to setup
  ca
  crt 1000
      [ setxy random-xcor random-ycor
        set color red
        set wealth 50   ;; start off with 50. Each tick will minus 50 adjusted by carrying capacity. When wealth reaches 0, turtle dies
        set offer% random 100
        set rejection% random 100
        set linked? FALSE
      ]
  set cycle 0
  set cycle-rejected 0
  set cycle-rejected% 0

  reset-ticks
end 

to go
  link-turtles
  ask turtles [if linked?  [calculate-wealth]] ;; if the initiator's offer is higher than the receiver's rejection threshold
  ask turtles [ set linked? false ]
  clear-links
  ;; each tick, with each pair of agent/turtle, total amount of 100 units are added to the "world", or average of 50 to each,
  ;; in order to simulate evolutionary process, where less successful strategies are weeded out by the "death" or removal of thos
  ;; caarying out those strategy, certain amount of "wealth" has to be removed from each agent/turtle, and since with
  ;; each round, on average 50 is added to each agent/turtle, the base unit 50 is taken off. This is adjusted by the ratio of
  ;; population vs the carrying-capacity of the "world" or the society.
  ask turtles [ set wealth wealth - (50 * count turtles / carrying-capacity)
                reproduce
              ]
  ask turtles [ if wealth <= 0 [die]]

  tick
;  the commands below are meant to test the system when carrying-capacity is altered
;  if ticks >= 200 and ticks < 400 [set carrying-capacity 4000]
;  if ticks >= 400 and ticks < 600 [set carrying-capacity 1000]
;  if ticks >= 600 [stop]
end 

to link-turtles
  ask turtles [if (not linked?) and any? other turtles with [linked? = false]
                    [ create-link-with one-of other turtles with [linked? != true ]
                      set linked? true
                      ask link-neighbors [set linked? true ]

                    ]
  ]
end 

to calculate-wealth
  set cycle cycle + 1
  let t-offer% offer%
  let t-rejection% rejection%
  let t-wealth wealth
  let l-offer% 0
  let l-rejection% 0
  let l-wealth 0
  ask link-neighbors [ set l-offer% offer%
                       set l-rejection% rejection%
                       set l-wealth wealth]
  ;;print l-offer%
  ;;print [offer%] of link-neighbors
  ;;print l-rejection%
  ;;print [rejection%] of link-neighbors
  ;;print l-wealth
  ;;print [wealth] of link-neighbors
  ifelse t-offer% > l-rejection% [ set wealth wealth + ( 100 - offer%)
                               ask link-neighbors [ set wealth wealth + t-offer% ]
                                ]
                                 [set cycle-rejected cycle-rejected + 1]
  set cycle-rejected% cycle-rejected / cycle

  set linked? false
  ask link-neighbors [set linked? false]
end 

to reproduce
  let wealth-factor (wealth / 100 - 1) * 10 ;; verified. At 100 wealth, there is a 50% probability of reproduction.
                                            ;; 100 is used because each tick the total amount invoved is 100
  let q 1 / (1 + exp (- wealth-factor) )   ;; logistic function for probability of reproduction. Verified
  let p random-float 1
  if p <= q [hatch 1 [ set wealth 50 ;; offspring starts 50, same as all new turtles
                       set offer% (offer% + random 100) / 2
                       set rejection% (rejection% + random 100) / 2

;                       set offer% ([offer%] of myself + random 100) / 2  ;; add an element of randomness
;                       set rejection% ([rejection%] of myself + random 100) / 2  ;; add an element of randomness
                       setxy random-xcor random-ycor ] ;; move away from the parent
            ]
end