distance_gradient.md

Calculation of a Distance Gradient

The aim of this code is to have a group of robots form a distance gradient from a source.

There is one robot that acts as the source; for simplicity here it is the robot with id 0. Every robot, including the source, emits its estimated distance from the source, and listens to other robots.

• The robots that can see the source directly emit the distance they sense;
• The robots that cannot see the source are in two categories:
  • Those who don't know any distance yet: these robots emit nil
  • Those who received a distance broadcast from one or more neighbors: these robots calculate their distance as the minimum among the received distances

This algorithm keeps running in the step() function, so it can adjust the distance gradient if the robots move around.

function init() {
  if (id == 0) {
    # Source robot
    my_dist = 0.0
  } else {
    # Other robots
    my_dist = 1000.0
    
    # Listen to other robots' distances
    neighbors.listen("dist_to_source",
      function(value_id, value, robot_id) {
        my_dist = math.min(my_dist, neighbors.get(robot_id).distance + value)
      })
  }
}

function step() {
  neighbors.broadcast("dist_to_source", my_dist)
}

function destroy() {
}