Third Assignment: Multi-agent Technologies

The third assignment of the Multi-agent Technologies, was implemented on top of the second assignment, more specifically the Brokering technique. The main goal of this assignment was to implement a combinatorial auction protocol between the agents and the broker (auctioneer). The combinatorial auction protocol is a type of auction in which bidders can place bids on combinations of items, or "packages," rather than just individual items. The protocol was implemented in the master branch.

Combinatorial Auction Protocol

The protocol is a two-phase protocol, where the first phase is the bidding phase and the second phase is the allocation of the winning bids to the agents. The broker is responsible for the management of the auction, and the agents are responsible for placing bids on the items.

Initially the broker checks in the system for items available for auction, and then it sends a message to all agents informing them of the items available for auction. The agents then place bids on the items, and the broker collects the bids. After the bidding phase is over, the broker then allocates the items to the agents based on the bids placed.

Bid Determination

Each participant in the auction submits bids for every potential combination of items. These bids correspond to the minimum costs associated with acquiring the specified set of items. For instance, in the case of agent 2, items A and B are considered complementary, while items B and D are deemed substitutes due to the disproportionate costs associated with acquiring them together (subadditivity principle). It's important to note that in this context, costs are represented as negative utilities, where higher values indicate worse outcomes.

XOR Bids

Participants make XOR bids, meaning that each participant can win at most one bundle. Additionally, there's an option for participants to bid zero for an empty bundle, signifying no cost.

Auctioneer's Role

The auctioneer is responsible for determining the solution that maximizes welfare and allocates one bundle (potentially an empty one) to each participant. In the provided example, the optimal solution is ({A,B},{C,D}) with a welfare value of C*=8. It's worth noting that the auctioneer acts as a dictator in this scenario, meaning that participants must accept the allocation. This setup allows for the implementation of various social choice mechanisms simply by adjusting the optimization criteria.

Practical Considerations

It's essential to acknowledge the practical challenges associated with solving this and similar problems. The computational complexity and communication overhead can be substantial. Specifically, as the number of tasks increases, so does the computational burden. Even computing a single bid, which involves planning optimal routes, can be highly complex for participants. While this might be more manageable in other problem domains, the auctioneer faces the most significant computational challenges, including filtering out dominated bids (a linear-time operation) and subsequently identifying the best allocation (an exponential-time task due to the power set of possible assignments). These factors contribute to the impracticality of certain approaches for addressing such problems.

Agents and Bids

Each agent is responsible for placing bids on the items. The bids are placed based on the distance of the agent to the pickup station and the capacity of the agent. Each bid is associated with a cost, which is the cost the system is being charged for the delivery of the item (or bundle of items). If an agent has capacity to carry more than one item, it can place bids on multiple items. The cost mechanism is based on the distance of the agent to the pickup station and agent's capacity. It costs more units if the agent has smaller capacity, as it is considered a quicker and more expensive delivery.

Selfish Agents & Non-selfish Agents

Agents can have different strategies when placing bids. Some agents can be selfish, meaning if new items are added to the system, they will place bids on the new items, even if they are already carrying an item. Other agents can be non-selfish, meaning they will not place bids on new items if they are already carrying an item.

Second Assignment: Multi-agent Technologies

Multi-agent Technologies

The repository is structured as follows:

• The master branch contains the implementation of the initial Basic technique.
• The brokering branch builds upon the main branch and implements the Brokering technique.
• The recommendation branch, also built upon the main branch, implements the Recommendation technique.

Techniques

Basic Technique

The Basic technique is a straightforward task allocation system where agents compete for tasks based on their availability and proximity to the task. The principle is First Come, First Serve. An agent moves towards the nearest pickup station and attempts to pick up an item. This technique serves as the foundational model for our study and is implemented in the main branch.

Brokering Technique

The Brokering technique represents a comprehensive brokering approach where a broker, having a full view of the grid, actively manages the task-sharing process by assigning tasks to agents. At every step, the broker checks for agents that are not currently carrying an item or moving towards a pickup station. When such agents are found, the broker assigns a specific item to the closest agent. This technique is implemented in the brokering branch.

Recommendation Technique

The Recommendation technique is a nuanced brokering approach where the broker recommends providers to the initiator, who then selects a provider to complete the task. In this case, the Pickup Station acts as the initiator, while the agents are the providers. When a new item is added, the pickup station contacts the broker, who then selects the top three nearest agents and recommends them to the pickup station. The pickup station then randomly selects one agent from the list and assigns the item to it. This technique is implemented in the recommendation branch.

Getting Started

To evaluate a specific technique, switch to the relevant branch by using the command git checkout <branch-name>. Replace <branch-name> with either master, brokering, or recommendation based on the technique you want to evaluate.

After switching to the desired branch, run the simulation using the command python main.py. Make sure you have all the necessary dependencies installed.

Running Experiments

Our codebase supports running different experiments by varying the initial setup for the environment. This is achieved by passing different JSON files as parameters to the main.py script.

The main.py script expects two parameters: rounds and a JSON file path. rounds represents the number of rounds the simulation will run, and the JSON file provides the initial setup for the environment.

We've provided several JSON files that represent different experimental setups by varying certain parameters. You can find these files in the experiments folder. Here are the available files:

• 10_pickup_stations.json
• 15_pickup_stations_experiment.json
• 16_obstacles_experiment.json
• 20_agent_experiment.json
• 30_agents_experiment.json
• experiment_1.json

You can choose to run the first experiment, which uses the main setup experiment_1.json, or different variations by specifying one of the other JSON files.

How to Run an Experiment

1. Navigate to the root directory of this repository on your local machine.
2. Run the main.py script with the desired number of rounds and the path to the chosen JSON file. For example, to run the main setup (experiment_1.json) for 400 rounds, you would use the following command:

python main.py rounds=400 experiments/experiment_1.json

Replace experiment_1.json with the name of the desired JSON file to run different variations.

By running different experiments, you can explore how changes in the initial setup affect the efficiency and effectiveness of the task-sharing strategies in the simulation.

Viewing Experiment Results

The results of the experiments can be viewed both in the console and in the log files generated by the simulation.

Console Output

While running the experiments, a significant amount of information is printed in the console. This includes:

• The number of ticks (simulation steps)
• The movements of the agents
• Actions of picking up and delivering items This real-time output provides a useful way to monitor the simulation as it progresses.

Log Files

For a more persistent record of the simulation data, we employ a logger package to log various actions and events during the simulation. This includes every move, intention, or action of each class, all logged into separate logger classes.

At the end of each simulation run, several log files are automatically generated in the main part of the repository. These files include:

• agent.log
• item.log
• environment.log

Each of these files contains valuable information about the actions taken during the simulation. For example, agent.log records the actions of the agents, item.log records details about the items being delivered, and environment.log keeps track of the overall state of the simulation environment.

These log files provide a comprehensive record of the entire simulation process, making them a valuable resource for in-depth analysis and evaluation of the task-sharing strategies. By examining these logs, you can gain insights into the behavior of the agents, the efficiency of item delivery, and the dynamics of the simulation environment under different initial setups.