NetLogo hatch and die

Question

I want to make turtles move around and look for a partner (a turtle that is not already partnered that is on the same patch) , and when they found one I want them to hatch a certain number of turtles and then die. But what happens is that when I start the simulation, all turtles die at the first tick. What am I doing wrong?

to go
  ask turtles [
    partner-up
  ]
  birth
  death
  tick
end


to partner-up
  if (not partnered?) [
    rt (random-float 90 - random-float 90) fd 1
    set partner one-of (turtles-at 0 0) with [ not partnered? ]
    if partner != nobody [
      set partnered? true
      ask partner [
        set partnered? true
        set partner myself
      ]
    ]
  ]
end

to birth
  let partnered-turtles turtles with [ partnered? ]
  ask partnered-turtles [
    calculate-score
    hatch (score + 1)
  ]
end

to death
  let partnered-turtles turtles with [ partnered? ]
  ask partnered-turtles [
    die
  ]
end

user_5593066 · Answer

Two things stand out- one is the call to one-of (turtles-at 0 0) with [ not partnered? ]. This includes ALL turtles on the patch that you indicate (equivalent to turtles-here), which means including the turtle executing the command. I think you want other turtles-here or (other turtles-at 0 0).

Next, your 'baby turtles' are inheriting all the attributes of their parents, including values in their partnered? and partner variables. So, the turtles are being hatched with partnered? = true, and so when the call to death occurs in your go procedure, they qualify as partnered-turtles and therefore die. To correct this, you can explicitly set the variables for your hatched turtles- for example:

to birth
  let partnered-turtles turtles with [ partnered? ]
  ask partnered-turtles [
    let score 1
    hatch (score + 1) [
      set partnered? false
      set partner nobody
    ]
  ]
end

Also, not sure if this is intentional but wanted to point out that both 'partners' will hatch an offspring. If you want a more standard biological model you may want only one of the parents to hatch.

Revised toy model:

turtles-own [ partnered? partner]

to setup
  ca
  reset-ticks
  ask n-of 10 patches [
    sprout 1 [
      set partnered? false
      set partner nobody
    ]
  ]
end

to go
  ask turtles [
    partner-up
  ]
  birth
  death
  tick
end


to partner-up
  if (not partnered?) [
    rt (random-float 90 - random-float 90) fd 1
    set partner one-of (other turtles-at 0 0) with [ not partnered? ]
    if partner != nobody [
      set partnered? true
      ask partner [
        set partnered? true
        set partner myself
      ]
    ]
  ]
end

to birth
  let partnered-turtles turtles with [ partnered? ]
  ask partnered-turtles [
    let score one-of [ 0 1 ]
    hatch (score + 1) [
      set partnered? false
      set partner nobody
    ]
  ]
end

to death
  let partnered-turtles turtles with [ partnered? ]
  ask partnered-turtles [
    die
  ]
end

NetLogo hatch and die

1 Answers