Advanced tutorial: agents don't move in visualization

[yannickoswald]

I have two files to run the visualization of the MoneyModel. I think exactly according to the tutorial, however, the agents do not move at all while clicking on step in the browser visualization. I cannot find my mistake. I hope this is the right place to ask. Any ideas how to overcome this?

Like literally nothing happens when pressing start or step in the visualization. Also perhaps of interest: The server opens and automatically fills red agents as wanted. If reset is pressed, it actually goes blank. Exactly the reverse way of the tutorial description.

I have this file MoneyModel.py

import mesa
import mesa.time
import mesa.space
#import matplotlib.pyplot as plt
import numpy as np


def compute_gini(model):
    agent_wealths = [agent.wealth for agent in model.schedule.agents]
    x = sorted(agent_wealths)
    N = model.num_agents
    B = sum(xi * (N - i) for i, xi in enumerate(x)) / (N * sum(x))
    return 1 + (1 / N) - 2 * B


class MoneyAgent(mesa.Agent):
    """An agent with fixed initial wealth."""

    def __init__(self, unique_id, model):
        super().__init__(unique_id, model)
        self.wealth = 1

    def move(self):
        possible_steps = self.model.grid.get_neighborhood(
            self.pos, moore=True, include_center=False
        )
        new_position = self.random.choice(possible_steps)
        self.model.grid.move_agent(self, new_position)

    def give_money(self):
        cellmates = self.model.grid.get_cell_list_contents([self.pos])
        if len(cellmates) > 1:
            other = self.random.choice(cellmates)
            other.wealth += 1
            self.wealth -= 1

    def step(self):
        self.move()
        if self.wealth > 0:
            self.give_money()


class MoneyModel(mesa.Model):
    """A model with some number of agents."""

    def __init__(self, N, width, height):
        self.num_agents = N
        self.grid = mesa.space.MultiGrid(width, height, True)
        self.schedule = mesa.time.RandomActivation(self)

        # Create agents
        for i in range(self.num_agents):
            a = MoneyAgent(i, self)
            self.schedule.add(a)
            # Add the agent to a random grid cell
            x = self.random.randrange(self.grid.width)
            y = self.random.randrange(self.grid.height)
            self.grid.place_agent(a, (x, y))

        self.datacollector = mesa.DataCollector(
            model_reporters={"Gini": compute_gini}, agent_reporters={"Wealth": "wealth"}
        )

    def step(self):
        self.datacollector.collect(self)
        self.schedule.step()

and this file MoneyModel_viz

from MoneyModel import *
from mesa.visualization.modules import CanvasGrid
from mesa.visualization.ModularVisualization import ModularServer
import socket

import mesa


def agent_portrayal(agent):
    portrayal = {
        "Shape": "circle",
        "Filled": "true",
        "Layer": 0,
        "Color": "red",
        "r": 0.5,
    }
    return portrayal



grid = mesa.visualization.CanvasGrid(agent_portrayal, 10, 10, 500, 500)
server = mesa.visualization.ModularServer(
    MoneyModel, [grid], "Money Model", {"N": 100, "width": 10, "height": 10}
)

server = ModularServer(MoneyModel,
                       [grid],
                       "Money Model",
                       {"N":100, "width":10, "height":10})


server.port = 8521  # The default
server.launch()

[rht]

I found the cause. It's because in the model __init__, you didn't put self.running = True. This is a mistake that it is missin in the advanced tutorial.

[rht]

Ah, MoneyModel is defined in the intro tutorial. And the tutorial erroneously said that it is only needed for batch runner. I think the fix is to make self.running optional, so that we don't have to put extra explanation.

[yannickoswald]

Thanks a lot that works. although sometimes it does not work at all and reports an error that it does not find the module MoneyModel (even though it is all of course in the same directory etc.). Idk why.

I hope the tutorial will be updated at some point.