verl/workers/actor/base.py

# Copyright 2024 Bytedance Ltd. and/or its affiliates
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
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#     http://www.apache.org/licenses/LICENSE-2.0
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"""
The base class for Actor
"""

from abc import ABC, abstractmethod
from typing import Dict

import torch

from verl import DataProto

__all__ = ["BasePPOActor"]


class BasePPOActor(ABC):
    def __init__(self, config):
        """The base class for PPO actor

        Args:
            config (DictConfig): a config passed to the PPOActor. We expect the type to be
                DictConfig (https://omegaconf.readthedocs.io/), but it can be any namedtuple in general.
        """
        super().__init__()
        self.config = config

    @abstractmethod
    def compute_log_prob(self, data: DataProto) -> torch.Tensor:
        """Compute logits given a batch of data.

        Args:
            data (DataProto): a batch of data represented by DataProto. It must contain key ```input_ids```,
                ```attention_mask``` and ```position_ids```.

        Returns:
            DataProto: a DataProto containing the key ```log_probs```


        """
        pass

    @abstractmethod
    def update_policy(self, data: DataProto) -> Dict:
        """Update the policy with an iterator of DataProto

        Args:
            data (DataProto): an iterator over the DataProto that returns by
                ```make_minibatch_iterator```

        Returns:
            Dict: a dictionary contains anything. Typically, it contains the statistics during updating the model
            such as ```loss```, ```grad_norm```, etc,.

        """
        pass