[tab] train.py (python)
import ray
from sglang.srt.constants import GPU_MEMORY_TYPE_KV_CACHE, GPU_MEMORY_TYPE_WEIGHTS

try:
    from sglang.srt.constants import GPU_MEMORY_TYPE_CUDA_GRAPH
except ImportError:
    GPU_MEMORY_TYPE_CUDA_GRAPH = None

from miles.ray.placement_group import create_placement_groups, create_rollout_manager, create_training_models
from miles.utils.arguments import parse_args
from miles.utils.logging_utils import configure_logger
from miles.utils.misc import should_run_periodic_action
from miles.utils.tracking_utils import init_tracking


def train(args):
    configure_logger()
    # allocate the GPUs
    pgs = create_placement_groups(args)
    init_tracking(args)

    # create the rollout manager, with sglang engines inside.
    # need to initialize rollout manager first to calculate num_rollout
    rollout_manager, num_rollout_per_epoch = create_rollout_manager(args, pgs["rollout"], args.prompt_data)
    rollout_manager_eval = None
    if args.val_interval is not None:
        rollout_manager_eval, _ = create_rollout_manager(args, pgs["rollout"], args.val_prompt_data)

    # create the actor and critic models
    actor_model, critic_model = create_training_models(args, pgs, rollout_manager, rollout_manager_eval)

    if args.offload_rollout:
        ray.get(rollout_manager.onload.remote(tags=[GPU_MEMORY_TYPE_WEIGHTS]))

    # always update weight first so that sglang has the loaded weights from training.
    actor_model.update_weights()

    if args.check_weight_update_equal:
        ray.get(rollout_manager.check_weights.remote(action="compare"))

    if args.offload_rollout:
        if GPU_MEMORY_TYPE_CUDA_GRAPH is not None:
            ray.get(rollout_manager.onload.remote(tags=[GPU_MEMORY_TYPE_CUDA_GRAPH]))
        ray.get(rollout_manager.onload.remote(tags=[GPU_MEMORY_TYPE_KV_CACHE]))

    # special case for eval-only
    if args.num_rollout == 0 and args.eval_interval is not None:
        ray.get(rollout_manager.eval.remote(rollout_id=0))

    def offload_train():
        if args.offload_train:
            if args.use_critic:
                critic_model.offload()
                if rollout_id >= args.num_critic_only_steps:
                    actor_model.offload()
            else:
                actor_model.offload()
        else:
            actor_model.clear_memory()

    def onload_rollout():
        if args.offload_rollout:
            ray.get(rollout_manager.onload.remote(tags=[GPU_MEMORY_TYPE_WEIGHTS]))

    # train loop.
    # note that for async training, one can change the position of the sync operation(ray.get).
    for rollout_id in range(args.start_rollout_id, args.num_rollout):

        rollout_data_ref = ray.get(rollout_manager.generate.remote(rollout_id))

        if args.val_interval is not None and rollout_id == 0:
            if args.loss_type == "sft_loss":
                rollout_data_val = [ray.get(rollout_manager_eval.generate.remote(rollout_id)) for _ in range(args.val_steps)]
                ray.get(actor_model.async_val(rollout_id, rollout_data_val))
            else:
                # TODO (mihir): implement val loss for other loss types
                raise NotImplementedError("Validation loss not implemented for loss type: {}".format(args.loss_type))

        if args.eval_interval is not None and rollout_id == 0:
            ray.get(rollout_manager.eval.remote(rollout_id))


        if args.offload_rollout:
            ray.get(rollout_manager.offload.remote())

        if args.use_critic:
            critic_train_handle = critic_model.async_train(rollout_id, rollout_data_ref)
            if rollout_id >= args.num_critic_only_steps:
                ray.get(actor_model.async_train(rollout_id, rollout_data_ref))
            ray.get(critic_train_handle)
        else:
            ray.get(actor_model.async_train(rollout_id, rollout_data_ref))

        if should_run_periodic_action(rollout_id, args.save_interval, num_rollout_per_epoch):
            if (not args.use_critic) or (rollout_id >= args.num_critic_only_steps):
                actor_model.save_model(rollout_id)
            if args.use_critic:
                critic_model.save_model(rollout_id)
            if args.rollout_global_dataset:
                ray.get(rollout_manager.save.remote(rollout_id))

        offload_train()
        onload_rollout()
        actor_model.update_weights()

        if args.offload_rollout:
            if GPU_MEMORY_TYPE_CUDA_GRAPH is not None:
                ray.get(rollout_manager.onload.remote(tags=[GPU_MEMORY_TYPE_CUDA_GRAPH]))
            ray.get(rollout_manager.onload.remote(tags=[GPU_MEMORY_TYPE_KV_CACHE]))

        if should_run_periodic_action(rollout_id, args.val_interval, num_rollout_per_epoch):
            if args.loss_type == "sft_loss":
                rollout_data_val = [ray.get(rollout_manager_eval.generate.remote(rollout_id)) for _ in range(args.val_steps)]
                ray.get(actor_model.async_val(rollout_id, rollout_data_val))
            else:
                # TODO (mihir): implement val loss for other loss types
                raise NotImplementedError("Validation loss not implemented for loss type: {}".format(args.loss_type))

        if should_run_periodic_action(rollout_id, args.eval_interval, num_rollout_per_epoch):
            ray.get(rollout_manager.eval.remote(rollout_id))

    ray.get(rollout_manager.dispose.remote())


if __name__ == "__main__":
    args = parse_args()
    train(args)