# Copyright 2024 Bytedance Ltd. and/or its affiliates
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# Licensed under the Apache License, Version 2.0 (the "License");
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from dataclasses import dataclass
from typing import Optional

from omegaconf import MISSING

from verl.base_config import BaseConfig

__all__ = ["OptimizerConfig", "FSDPOptimizerConfig", "McoreOptimizerConfig"]


@dataclass
class OptimizerConfig(BaseConfig):
    """Base optimizer configuration.

    Args:
        lr (float): learning rate. Must be specified.
        lr_warmup_steps_ratio (float): Warmup steps ratio; total steps will be injected at runtime.
        total_training_steps (int): Total training steps (must be overridden at runtime).
        weight_decay (float): Weight decay factor.
        lr_warmup_steps (Optional[int]): Number of warmup steps; None delegates to lr_warmup_steps_ratio.
    """

    lr: float = MISSING
    lr_warmup_steps_ratio: float = 0.0
    total_training_steps: int = -1
    weight_decay: float = 0.01
    lr_warmup_steps: Optional[int] = -1

    def __post_init__(self):
        assert self.lr != MISSING


@dataclass
class FSDPOptimizerConfig(OptimizerConfig):
    """FSDP optimizer configuration extending base OptimizerConfig.

    Args:
        lr (float): Learning rate.
        min_lr_ratio (Optional[float]): Minimum LR ratio for cosine schedule.
        warmup_style (str): LR warmup style: "constant" or "cosine".
        num_cycles (float): Number of cosine cycles in LR schedule.
    """

    min_lr_ratio: Optional[float] = None
    warmup_style: str = "constant"
    num_cycles: float = 0.5

    def __post_init__(self):
        assert self.warmup_style in ["constant", "cosine"]
        return super().__post_init__()


@dataclass
class McoreOptimizerConfig(OptimizerConfig):
    """Mcore optimizer configuration extending base OptimizerConfig.

    Args:
        optimizer (str): Optimizer name; default is "adam".
        lr (float): Learning rate.
        clip_grad (float): Gradient clipping norm.
        lr_warmup_init (float): Initial learning rate for warmup; defaults to 0.0.
        lr_decay_steps (Optional[int]): Number of decay steps.
        lr_decay_style (str): LR decay style: "constant", "linear", "cosine", or "inverse_square_root".
        min_lr (float): Minimum learning rate.
        weight_decay_incr_style (str): Weight decay increment style: "constant" or "cosine".
        lr_wsd_decay_style (str): Weight-standard-deviation decay style: "constant", "exponential", or "cosine".
        lr_wsd_decay_steps (Optional[int]): Number of steps for weight-standard-deviation decay.
        use_checkpoint_opt_param_scheduler (bool): Whether to use checkpoint optimizer parameter scheduler.
    """

    optimizer: str = "adam"
    clip_grad: float = 1.0
    lr_warmup_init: float = 0.0
    lr_decay_steps: Optional[int] = None
    lr_decay_style: str = "linear"
    min_lr: float = 0.0
    weight_decay_incr_style: str = "constant"
    lr_wsd_decay_style: str = "exponential"
    lr_wsd_decay_steps: Optional[int] = None
    use_checkpoint_opt_param_scheduler: bool = False
