turtle not moving to next position in a list when list is updated


6 days ago


4 time


I have a netlogo gis model. The model consists of a road network and on the roads I have created vertices (nodes). I have placed two types of agents, red and blue. The blue agents are stationary while the red agents find the closest blue agents (using in-radius), go to them and collect them (red agents are able to collect a maximum of 2 blue agents). The way the red agents travel, is by travelling from node to node till they reach the node with the blue agents. I have done this through using nw:turtles-on-weighted-path-to function which finds a list of nodes between the red and blue agents. i.e vertex-1 (red agent position) vertex-2 vertex-3 vertex-4(1st-blue-agent-position)

The next step is once they collect their first blue agent, they need to find the 2nd closest blue agent from that point, then similarly travel to that position and collect. This is where i get problems. My list gets appended with the location of the 2nd blue-agent but the red-agent doesn't travel that location. i.e

vertex-1 vertex-2 vertex-3 vertex-4(red-agent-position (blue-collected)) vertex-5 vertex-6 vertex-7 (2nd-blue-agent -position)

Any ideas how to solve?

connect-find: variable consisting the closest agent (i.e blue-agent 2)

breed [red-agents red-agent]
breed [blue-agents blue-agent]
globals [current-node-red]
red-agents-own [current-node next-node vertex-blue-agents-at connect-find
blue-agents-own [current-node-red node-blue red-agent-pos

ask red-agents[
set connect-find min-one-of blue-agents in-radius 9 [distance myself]

ask connect-find[
set connect-vertex min-one-of vertices in-radius 1 [distance myself] 
set vertex-blue-agents-at connect-vertex

;;Assigning Destination
ask red-agents [
set initial-node min-one-of vertices in-radius 1 [distance myself]
set collected-agents 0
set current-node initial-node
set previous-node current-node
set next-node current-node

let end-location vertex-blue-agents-at
let path []
ask initial-node [set path nw:turtles-on-weighted-path-to end-location 
set commute-path path    

ask red-agents [

let route-length (length commute-path)
let next-pos ((position (current-node) commute-path) + 1)
if next-pos < route-length [set next-node item (next-pos) commute-path]

;global variable holding red-agent position
set current-node-red current-node

;red-agent position passed on to blue-agent-own
ask blue-agents [set red-agent-pos current-node-red]

;To make turtles move from one node to another 
 set current-node next-node
 move-to current-node

;To kill blue-agents when red-agent reaches destination
 ask blue-agents[
   if red-agent-pos = node-blue [die]]

;To update blue-agents collected
if current-node = vertex-blue-agents-at and connect-find = nobody[set 
collected-agents (collected-agents + 1)] 

;To find next blue agent (2nd)
 if current-node = vertex-blue-agents-at [
  set connect-find (min-one-of blue-agents in-radius 9 [distance myself]) 
  ;finds the 2nd closest agent
  ask connect-find [
  set connect-vertex min-one-of vertices in-radius 0.0001 [distance 
  myself] ;closest agent find the vertex they are on

;Assigns red agents the vertex location of the closest blue-agent
  set vertex-blue-agents-at connect-vertex

;set the path to the new agent
  let path []
  let end-location vertex-blue-agents-at
  set initial-node current-node

  ask initial-node [set path nw:turtles-on-weighted-path-to end-location 
  foreach path[ 
  i ->
  set commute-path lput i commute-path

0 answers