Rusty Snakes

Fast Battlesnake agents written in rust. This project has been developed as part of an AI games course at the Leibniz University Hannover.

Our Tree agent ("ich heisse marvin") reached second and first place in the global, dual, and royale arenas. In the Spring League 2021, we surpassed last year's best snake (Kreuzotter) from our university.

At the end of 2021, the new Flood agent reached second place in the Elite Division of the Winter Classic Invitational 2021.

Structure of this Repository

This repository contains a web server compatible with the Battlesnake API version 1 and abstractions for the data types (src/env.rs).

We developed multiple different agents (src/agents), from a simple random agent, a very fast area control agent, to a minimax tree search agent combining multiple heuristics to find the best possible moves. These heuristics are configurable, and the impact of specific variables and their influence over time can be specified on startup. This allows us to perform parameter optimization (Bayesian optimization) to improve the heuristic further.

We also developed a fast simulator to execute moves and analyze their outcomes. It is used to evaluate the heuristics and tune their parameters.

The hpo directory contains the code for automatically optimizing the agent's hyperparameters. It utilizes the simulator to simulate the generated configs and find the best-performing parameters. The current default configurations of the Flood, Tree, and Mobility agents are the results of several optimization campaigns.

Usage

Running the Server

First, the rust toolchain has to be installed (https://www.rust-lang.org/learn/get-started).

Starting the server:

cargo run --release -- [-h] [--host <ip:port>] [--config <json>]

There are additional options for --runtime and visual representation of the snake (--head, --tail, --color). Run cargo run --release -- -h to see all the commandline options.

config defines the agent to be used (Flood, Tree, Mobility, Random) and configures the agent's heuristic. The default config for the Flood agent is, for example:

{
  "Flood": {
    "health": 0.00044,
    "food_distance": 0.173,
    "space": 0.0026,
    "space_adv": 0.108,
    "size_adv": 7.049,
    "size_adv_decay": 0.041,
  }
}

If a config parameter (like health) is excluded the default value is used.

Simulating Configs

This tool can be used to simulate different configurations. These configurations specify the agent and its hyperparameters. If no parameters are provided, the default values for the agent are used. The number of simulated games can be specified with --game-count. Use -h for more information about other arguments to define the board size and game rules.

The example below simulates the Flood and Tree agents for 10 games:

cargo run --release --bin simulate -- '{"Flood":{"space":8.0}}' '{"Tree":{"centrality":0}}' --game-count 10

The last line of the standard output contains the number of wins of the first snake and the total number of games played:

Result: 3/10

Testing moves

The move program outputs the chosen move for a given game state and agent configuration. This can be useful for debugging situational bugs. The game input can be downloaded from the battlesnake with this Firefox extension.

cargo run --release --bin move -- [--config <json>] [--runtime] <json>

Running tests & benchmarks

There are multiple tests for the different modules that can be run, as shown below. For more information on unit testing in Rust, see https://doc.rust-lang.org/book/ch11-01-writing-tests.html.

cargo test -- [--nocapture] [testname]

Besides the functional tests, there are several performance benchmarks. They are executed with the release config with compiler and linker optimizations. The criterion benchmark runner tracks the execution times from previous runs and reports any improvements or degradations.

cargo bench -- [testname]