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---

license: mit
library_name: stable-baselines3
pipeline_tag: reinforcement-learning
tags:
- 4d-snake
- 4d-snake-2x4
- snake
- reinforcement-learning
- deep-reinforcement-learning
- stable-baselines3
- sb3-contrib
- maskable-ppo
model-index:
- name: 4d-snake-exp02-ppo-2x4
  results:
  - task:
      type: reinforcement-learning
      name: reinforcement-learning
    dataset:
      name: 4d-snake-2x4
      type: 4d-snake-2x4
    metrics:
    - type: completion_rate
      name: completion rate (deterministic, 100 episodes x 3 seeds)
      value: 0.877 +/- 0.041
      verified: false
    - type: mean_reward
      name: mean episode return (deterministic)
      value: 23.41
      verified: false
    - type: fill
      name: mean final fill (deterministic)
      value: 0.987
      verified: false
    - type: steps_to_complete
      name: mean steps to complete (deterministic, won episodes)
      value: 34.4
      verified: false
---


# 4d-snake-exp02-ppo-2x4

A `512x512` MLP policy for **4-dimensional snake on the 2^4 board** (16 cells, 8 moves): MaskablePPO trained from scratch, no curriculum, 5,000,000 environment steps. From a length-1 start it completes the board in 87.7 % of deterministic episodes, evaluated with the protocol of [docs/evaluation.md](https://github.com/BurnyCoder/4d-snake-rl/blob/main/docs/evaluation.md) (100 episodes x 3 seeds, masked `evaluate_policy`).

## Results (`eval/summary.json`)

| mode | completion +- std | mean fill | steps to complete | won within 4C |
|---|---|---|---|---|
| deterministic (argmax) | 0.877 +- 0.041 | 0.987 | 34.4 | 0.877 |
| sampling | 0.853 +- 0.034 | 0.985 | 35.5 | 0.853 |

## How to use

The observation is this repository's `4*C + 2` float vector and the action space its `2*ndim` masked moves ([docs/game_rules.md](https://github.com/BurnyCoder/4d-snake-rl/blob/main/docs/game_rules.md)), so the checkpoint runs inside `snake4d`'s environment:

```bash

git clone https://github.com/BurnyCoder/4d-snake-rl.git && cd 4d-snake-rl && uv sync

hf download BurnyCoder/4d-snake-exp02-ppo-2x4 best_model.zip --local-dir weights

uv run snake4d evaluate --set model_path=weights/best_model.zip --set size=2 --set ndim=4

```

```python

# https://sb3-contrib.readthedocs.io/en/master/modules/ppo_mask.html

from sb3_contrib import MaskablePPO

from sb3_contrib.common.maskable.utils import get_action_masks

from snake4d.config import Config

from snake4d.vec_env import make_env



cfg = Config(size=2, ndim=4)

model = MaskablePPO.load("weights/best_model.zip", device="cpu")

env = make_env(cfg, 1, 0)  # one board; observation shape (1, 4*C + 2)

obs = env.reset()

masks = get_action_masks(env)  # the legal moves, one row per board

action, _ = model.predict(obs, action_masks=masks, deterministic=True)

```

## Training

- Phase `train`; experiment file `experiments/exp02_ppo_2x4.env`; write-up: https://github.com/BurnyCoder/4d-snake-rl/blob/main/reports/experiments/exp02_ppo_2x4.md.
- Resolved configuration (`config.json`):

```json

{

  "size": 2,

  "ndim": 4,

  "idle_mult": 4,

  "r_food": 1.0,

  "r_death": -1.0,

  "r_win": 10.0,

  "r_step": -0.001,

  "shaping_coef": 0.0,

  "n_envs": 1024,

  "total_timesteps": 5000000,

  "n_steps": 32,

  "batch_size": 4096,

  "n_epochs": 4,

  "gamma": 0.99,

  "gae_lambda": 0.95,

  "lr_start": 0.0003,

  "lr_end": 1e-05,

  "clip_start": 0.2,

  "clip_end": 0.05,

  "ent_coef": 0.01,

  "vf_coef": 0.5,

  "max_grad_norm": 0.5,

  "target_kl": 0.03,

  "net_width": 512,

  "device": "auto",

  "torch_threads": 8,

  "seed": 0,

  "curriculum": 0,

  "curriculum_window": 8,

  "curriculum_delta": 0,

  "curriculum_rho": 0.2,

  "curriculum_min_eps": 200,

  "p_true_start": 0.2,

  "eval_episodes": 100,

  "eval_every": 327680,

  "ckpt_every": 1310720,

  "eval_seeds": "0,1,2",

  "bench_steps": 200000,

  "runs_dir": "runs",

  "run_name": "exp02_ppo_2x4",

  "model_path": "",

  "policy": "route"

}

```

![exp02_ppo_2x4_curves.png](figures/exp02_ppo_2x4_curves.png)

![exp02_ppo_2x4_fill_hist.png](figures/exp02_ppo_2x4_fill_hist.png)

## Provenance

- Code: https://github.com/BurnyCoder/4d-snake-rl at commit `212b78092dfcae4aa3947fb1106e7c65cc969c7c`.
- Library versions (`versions.json`): torch 2.14.0+cu130, gymnasium 1.3.0, stable-baselines3 2.9.0, sb3-contrib 2.9.0, numpy 2.5.2, pygame-ce 2.5.8, cuda_device NVIDIA GeForce RTX 5070 Laptop GPU.

- `eval/summary.json` and `eval/eval_episodes.csv` are the files the repository's reports quote; every evaluated network is compared in [reports/networks.md](https://github.com/BurnyCoder/4d-snake-rl/blob/main/reports/networks.md).
- Collection: https://huggingface.co/collections/BurnyCoder/4d-snake-rl-all-evaluated-networks-6a9d0a0a66c7efcd101b7741

## Files

- `best_model.zip`: the evaluated checkpoint in Stable-Baselines3's save format (policy weights and optimizer state, https://stable-baselines3.readthedocs.io/en/master/guide/save_format.html).

- `config.json`, `versions.json`: the run's resolved configuration and environment.

- `eval/`: evaluation summary and one row per evaluation episode.

- `train/progress.csv`: the SB3 training log; `figures/`: the learning curves.



## Licence



MIT, like the repository.