[content] train_dynamics.py (python)
    # Logging
    log: bool = False
    entity: str = ""
    project: str = ""
    name: str = "train_dynamics"
    tags: list[str] = field(default_factory=lambda: ["dynamics"])
    log_interval: int = 5
    log_image_interval: int = 250
    ckpt_dir: str = ""
    log_checkpoint_interval: int = 25000
    log_checkpoint_keep_period: int = 20000
    log_gradients: bool = False


args = tyro.cli(Args)


def dynamics_loss_fn(params, state, inputs):
    """Compute masked dynamics loss"""
    inputs["videos"] = inputs["videos"].astype(args.dtype) / 255.0
    outputs = state.apply_fn(
        params,
        inputs,
        training=True,
        rngs={"params": inputs["rng"], "dropout": inputs["dropout_rng"]},
    )
    mask = outputs["mask"]
    outputs["token_logits"] = outputs["token_logits"].astype(jnp.float32)
    ce_loss = optax.softmax_cross_entropy_with_integer_labels(
        outputs["token_logits"], outputs["video_tokens"]
    )
    ce_loss = (mask * ce_loss).sum() / mask.sum()
    acc = outputs["token_logits"].argmax(-1) == outputs["video_tokens"]
    acc = (mask * acc).sum() / mask.sum()
    select_probs = jax.nn.softmax(outputs["token_logits"])
    metrics = dict(
        cross_entropy_loss=ce_loss,
        masked_token_accuracy=acc,
        select_logit=outputs["token_logits"].max(-1).mean(),
        select_p=select_probs.max(-1).mean(),
        entropy=jax.scipy.special.entr(select_probs).sum(-1).mean(),
    )
    return ce_loss, (outputs["recon"], metrics)


@jax.jit
def train_step(state, inputs):
    """Update state and compute metrics"""
    grad_fn = jax.value_and_grad(dynamics_loss_fn, has_aux=True, allow_int=True)
    (loss, (recon, metrics)), grads = grad_fn(state.params, state, inputs)
    state = state.apply_gradients(grads=grads)
    if args.log_gradients:
        metrics["gradients_std/"] = jax.tree.map(
            lambda x: x.std(), grads["params"]["dynamics"]
        )
    return state, loss, recon, metrics


if __name__ == "__main__":
    jax.distributed.initialize()
    num_devices = jax.device_count()
    if num_devices == 0:
        raise ValueError("No JAX devices found.")
    print(f"Running on {num_devices} devices.")

    if args.batch_size % num_devices != 0:
        raise ValueError(
            f"Global batch size {args.batch_size} must be divisible by "
            f"number of devices {num_devices}."
        )

    per_device_batch_size_for_init = args.batch_size // num_devices

    rng = jax.random.PRNGKey(args.seed)

    # --- Initialize model ---
    genie = Genie(
        # Tokenizer
        in_dim=args.image_channels,
        tokenizer_dim=args.tokenizer_dim,
        latent_patch_dim=args.latent_patch_dim,
        num_patch_latents=args.num_patch_latents,
        patch_size=args.patch_size,
        tokenizer_num_blocks=args.tokenizer_num_blocks,
        tokenizer_num_heads=args.tokenizer_num_heads,
        # LAM
        lam_dim=args.lam_dim,
        latent_action_dim=args.latent_action_dim,
        num_latent_actions=args.num_latent_actions,
        lam_patch_size=args.lam_patch_size,
        lam_num_blocks=args.lam_num_blocks,
        lam_num_heads=args.lam_num_heads,
        lam_co_train=not args.lam_checkpoint,
        # Dynamics
        dyna_dim=args.dyna_dim,
        dyna_num_blocks=args.dyna_num_blocks,
        dyna_num_heads=args.dyna_num_heads,
        dropout=args.dropout,
        mask_limit=args.mask_limit,
        param_dtype=args.param_dtype,
        dtype=args.dtype,