[content] jasmine/train_dynamics.py (python)
    param_dtype = jnp.float32
    dtype = jnp.bfloat16
    use_flash_attention: bool = True
    use_gt_actions: bool = False
    # 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
    val_data_dir: str = ""
    val_interval: int = 20_000
    val_steps: int = 50
    eval_full_frame: bool = False
    val_maskgit_steps: int = 25
    val_temperature: float = 1
    val_sample_argmax: bool = False
    wandb_id: str = ""


def build_model(args: Args, rng: jax.Array) -> tuple[Genie, jax.Array]:
    rng, _rng = jax.random.split(rng)
    rngs = nnx.Rngs(_rng)
    genie = Genie(
        # Tokenizer
        in_dim=args.image_channels,
        tokenizer_dim=args.tokenizer_dim,
        tokenizer_ffn_dim=args.tokenizer_ffn_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,
        lam_ffn_dim=args.lam_ffn_dim,
        latent_action_dim=args.latent_action_dim,
        num_actions=args.num_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,
        use_gt_actions=args.use_gt_actions,
        # Dynamics
        dyna_type=args.dyna_type,
        dyna_dim=args.dyna_dim,
        dyna_ffn_dim=args.dyna_ffn_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,
        use_flash_attention=args.use_flash_attention,
        decode=False,
        rngs=rngs,
    )
    if args.use_gt_actions:
        assert (
            not args.lam_checkpoint
        ), "Cannot use LAM when using ground-truth actions."
    else:
        assert genie.lam is not None
        del genie.lam.decoder
    return genie, rng


def build_optimizer(genie: Genie, args: Args) -> nnx.ModelAndOptimizer:
    lr_schedule = get_lr_schedule(
        args.lr_schedule,
        args.init_lr,
        args.max_lr,
        args.decay_end,
        args.num_steps,
        args.warmup_steps,
        args.wsd_decay_steps,
    )
    tx = optax.adamw(
        learning_rate=lr_schedule,
        b1=0.9,
        b2=0.9,
        weight_decay=1e-4,
        mu_dtype=args.param_dtype,  # moments in full precision
    )
    optimizer = nnx.ModelAndOptimizer(genie, tx)
    return optimizer


def build_mesh_and_sharding(
    num_devices: int,
) -> tuple[Mesh, NamedSharding, NamedSharding, NamedSharding]:
    device_mesh_arr = create_device_mesh((num_devices,))
    mesh = Mesh(devices=device_mesh_arr, axis_names=("data",))
    replicated_sharding = NamedSharding(mesh, PartitionSpec())
    videos_sharding = NamedSharding(mesh, PartitionSpec("data", None, None, None, None))
    actions_sharding = NamedSharding(mesh, PartitionSpec("data", None))
    return mesh, replicated_sharding, videos_sharding, actions_sharding


def shard_optimizer_states(
    optimizer: nnx.ModelAndOptimizer, replicated_sharding: NamedSharding
) -> None:
    model_state = nnx.state(optimizer.model)
    model_sharded_state = jax.lax.with_sharding_constraint(
        model_state, replicated_sharding
    )
    nnx.update(optimizer.model, model_sharded_state)
    optimizer_state = nnx.state(optimizer, nnx.optimizer.OptState)
    optimizer_sharded_state = jax.lax.with_sharding_constraint(
        optimizer_state, replicated_sharding
    )
    nnx.update(optimizer, optimizer_sharded_state)


def build_dataloader(args: Args, data_dir: str) -> grain.DataLoaderIterator:
    image_shape = (args.image_height, args.image_width, args.image_channels)
    array_record_files = [
        os.path.join(data_dir, x)
        for x in os.listdir(data_dir)
        if x.endswith(".array_record")
    ]
    grain_dataloader = get_dataloader(
        array_record_files,
        args.seq_len,
        # NOTE: We deliberately pass the global batch size
        # The dataloader shards the dataset across all processes
        args.batch_size,
        *image_shape,
        num_workers=8,
        prefetch_buffer_size=1,
        seed=args.seed,
    )
    initial_state = grain_dataloader._create_initial_state()
    grain_iterator = grain.DataLoaderIterator(grain_dataloader, initial_state)
    return grain_iterator


def build_checkpoint_manager(args: Args) -> Optional[ocp.CheckpointManager]:
    if args.restore_ckpt or args.save_ckpt:
        handler_registry = ocp.handlers.DefaultCheckpointHandlerRegistry()
        handler_registry.add(
            "model_state", ocp.args.PyTreeSave, ocp.handlers.PyTreeCheckpointHandler
        )
        handler_registry.add(
            "model_state", ocp.args.PyTreeRestore, ocp.handlers.PyTreeCheckpointHandler
        )
        handler_registry.add(
            "train_dataloader_state",
            grain.checkpoint.CheckpointSave,
            cast(ocp.handlers.CheckpointHandler, grain.checkpoint.CheckpointHandler),
        )
        handler_registry.add(
            "train_dataloader_state",
            grain.checkpoint.CheckpointRestore,
            cast(ocp.handlers.CheckpointHandler, grain.checkpoint.CheckpointHandler),
        )
        if args.val_data_dir:
            handler_registry.add(
                "val_dataloader_state",
                grain.checkpoint.CheckpointSave,
                cast(
                    ocp.handlers.CheckpointHandler, grain.checkpoint.CheckpointHandler
                ),
            )
            handler_registry.add(
                "val_dataloader_state",
                grain.checkpoint.CheckpointRestore,
                cast(
                    ocp.handlers.CheckpointHandler, grain.checkpoint.CheckpointHandler
                ),
            )
        checkpoint_options = ocp.CheckpointManagerOptions(
            save_interval_steps=args.log_checkpoint_interval,
            max_to_keep=3,
            keep_period=args.log_checkpoint_keep_period,
            step_format_fixed_length=6,
            cleanup_tmp_directories=True,
        )
        checkpoint_manager = ocp.CheckpointManager(
            args.ckpt_dir,
            options=checkpoint_options,
            handler_registry=handler_registry,
        )
        return checkpoint_manager
    else:
        return None


def restore_or_initialize_components(
    args: Args,
    checkpoint_manager: Optional[ocp.CheckpointManager],
    optimizer: nnx.ModelAndOptimizer,
    train_iterator: grain.DataLoaderIterator,
    rng: jax.Array,
    replicated_sharding: NamedSharding,
    val_iterator: Optional[grain.DataLoaderIterator],
    restore_step: Optional[int] = None,
) -> tuple[
    int,
    nnx.ModelAndOptimizer,
    grain.DataLoaderIterator,
    grain.DataLoaderIterator,
    jax.Array,
]:
    step = 0
    if checkpoint_manager and restore_step is None:
        restore_step = checkpoint_manager.latest_step()
    if args.restore_ckpt:
        assert checkpoint_manager is not None
        abstract_optimizer = nnx.eval_shape(lambda: optimizer)
        abstract_optimizer_state = nnx.state(abstract_optimizer)
        if val_iterator:
            restore_args = ocp.args.Composite(
                model_state=ocp.args.PyTreeRestore(abstract_optimizer_state),  # type: ignore
                train_dataloader_state=grain.checkpoint.CheckpointRestore(train_iterator),  # type: ignore
                val_dataloader_state=grain.checkpoint.CheckpointRestore(val_iterator),  # type: ignore
            )
        else:
            restore_args = ocp.args.Composite(
                model_state=ocp.args.PyTreeRestore(abstract_optimizer_state),  # type: ignore
                train_dataloader_state=grain.checkpoint.CheckpointRestore(train_iterator),  # type: ignore
            )
        restored = checkpoint_manager.restore(
            checkpoint_manager.latest_step(), args=restore_args
        )
        restored_optimizer_state = restored["model_state"]
        nnx.update(optimizer, restored_optimizer_state)
        train_iterator = restored["train_dataloader_state"]
        if val_iterator:
            val_iterator = restored["val_dataloader_state"]
        step = checkpoint_manager.latest_step() or 0
        print(f"Restored dataloader and model state from step {step}")
    else:
        # Restore from pre-trained tokenizer (and LAM)
        rng, _rng = jax.random.split(rng)
        optimizer = restore_genie_components(optimizer, replicated_sharding, _rng, args)
    return step, optimizer, train_iterator, val_iterator, rng


def _calculate_step_metrics(
    outputs: dict[str, jax.Array],
    gt: jax.Array,
    num_actions: int,
    num_patch_latents: int,
) -> tuple[jax.Array, dict]:
    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"])
    gt_val = gt.clip(0, 1).reshape(-1, *gt.shape[2:])
    recon = outputs["recon"].clip(0, 1).reshape(-1, *outputs["recon"].shape[2:])
    psnr = jnp.asarray(pix.psnr(gt_val, recon)).mean()
    ssim = jnp.asarray(pix.ssim(gt_val, recon)).mean()
    _, index_counts_tokenizer = jnp.unique_counts(
        jnp.ravel(outputs["video_tokens"]),
        size=num_patch_latents,
        fill_value=0,
    )
    codebook_usage_tokenizer = (index_counts_tokenizer != 0).mean()
    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(),
        psnr=psnr,
        ssim=ssim,
        codebook_usage_tokenizer=codebook_usage_tokenizer,
    )
    if "lam_indices" in outputs.keys():
        _, index_counts_lam = jnp.unique_counts(
            jnp.ravel(outputs["lam_indices"]),
            size=num_actions,
            fill_value=0,
        )
        codebook_usage_lam = (index_counts_lam != 0).mean()
        metrics["codebook_usage_lam"] = codebook_usage_lam
    return ce_loss, metrics


def main(args: Args) -> None:
    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}."
        )

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

    # --- Initialize model ---
    genie, rng = build_model(args, rng)
    _, params, _ = nnx.split(genie, nnx.Param, ...)
    param_counts = count_parameters_by_component(params)

    if args.log and jax.process_index() == 0:
        wandb_init_kwargs = {
            "entity": args.entity,
            "project": args.project,
            "name": args.name,
            "tags": args.tags,
            "group": "debug",
            "config": args,
        }

        if args.wandb_id:
            wandb_init_kwargs.update(
                {
                    "id": args.wandb_id,
                    "resume": "allow",
                }
            )
        wandb.init(**wandb_init_kwargs)

        wandb.config.update({"model_param_count": param_counts})

    print("Parameter counts:")
    print(param_counts)

    # --- Initialize optimizer ---
    optimizer = build_optimizer(genie, args)
    del genie

    # FIXME: switch to create_hybrid_device_mesh for runs spanning multiple nodes
    _, replicated_sharding, videos_sharding, actions_sharding = build_mesh_and_sharding(
        num_devices
    )

    shard_optimizer_states(optimizer, replicated_sharding)

    # --- Initialize checkpoint manager ---
    checkpoint_manager = build_checkpoint_manager(args)

    # --- Create DataLoaderIterator from dataloader ---
    train_iterator = build_dataloader(args, args.data_dir)
    val_iterator = None
    if args.val_data_dir:
        val_iterator = build_dataloader(args, args.val_data_dir)

    # --- Restore checkpoint ---
    step, optimizer, train_iterator, val_iterator, rng = (
        restore_or_initialize_components(
            args,
            checkpoint_manager,
            optimizer,
            train_iterator,
            rng,
            replicated_sharding,
            val_iterator,
        )
    )

    # --- Define loss and train step (close over args) ---
    def dynamics_loss_fn(
        model: Genie,
        inputs: dict,
    ) -> tuple[jax.Array, tuple[jax.Array, dict]]:
        gt = jnp.asarray(inputs["videos"], dtype=jnp.float32) / 255.0
        inputs["videos"] = gt.astype(args.dtype)
        outputs = model(inputs)
        ce_loss, metrics = _calculate_step_metrics(
            outputs, gt, args.num_actions, args.num_patch_latents
        )
        return ce_loss, (outputs["recon"], metrics)