SAC HalfCheetah-v5

This is a Stable Baselines3 SAC policy trained locally on Gymnasium HalfCheetah-v5.

The environment uses a small anti-flip reward guard. It penalizes extreme torso plane angle and low torso height, then terminates clear fall or belly-slide exploit postures.

Files

  • sac_half_cheetah.zip: Stable Baselines3 SAC checkpoint.
  • videos/initial.mp4: random policy before training.
  • videos/final.mp4: trained policy rollout.
  • sac_cheetah/: minimal training, environment, check, and video code.
  • pyproject.toml: Python dependency setup.

Training

  • Algorithm: Soft Actor-Critic
  • Implementation: Stable Baselines3
  • Policy: MlpPolicy
  • Environment: HalfCheetah-v5
  • Timesteps: 300000
  • Seed: 7
  • Device: Quadro P520 with torch==2.7.1+cu118

Evaluation

Single deterministic rollout with seed 8.

Metric Value
Steps 1000
Return 7031.927
Mean reward 7.032
Mean x velocity 7.465
Final x position 373.190
Minimum torso height 0.534
Maximum absolute root angle 0.269
Fell false

These numbers are a local smoke evaluation, not a benchmark sweep.

Load

from stable_baselines3 import SAC

model = SAC.load("sac_half_cheetah.zip", device="auto")

Use the wrapper in sac_cheetah.envs if you want evaluation to match this model card.

from sac_cheetah.config import TrainConfig
from sac_cheetah.envs import make_env

cfg = TrainConfig()
env = make_env(cfg.env_id, cfg.seed + 1, render_mode="rgb_array")

Limitations

This policy is only tested on Gymnasium HalfCheetah-v5 with the included anti-flip wrapper. It is not meant for real robots, safety-critical systems, or transfer to other MuJoCo tasks without retraining.

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