# Copyright 2024 Bytedance Ltd. and/or its affiliates
# Copyright (c) 2024, NVIDIA CORPORATION. All rights reserved.
# Copyright 2023-2024 SGLang Team
# Copyright 2025 ModelBest Inc. 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
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Pretrain utilities."""

import gc
import inspect
import logging
import os
import warnings
from dataclasses import dataclass
from typing import Any

import torch
import torch.nn.functional as F
from megatron.core import ModelParallelConfig, mpu, parallel_state, tensor_parallel
from megatron.core.distributed import DistributedDataParallel as DDP
from megatron.core.distributed import DistributedDataParallelConfig
from megatron.core.enums import ModelType
from megatron.core.optimizer import ChainedOptimizer
from megatron.core.parallel_state import get_global_memory_buffer
from megatron.core.transformer import MLATransformerConfig, TransformerConfig
from megatron.core.transformer.module import Float16Module
from megatron.core.transformer.multi_token_prediction import MTPLossLoggingHelper
from megatron.core.utils import get_attr_wrapped_model
from transformers import PretrainedConfig

import verl.utils.megatron.tensor_parallel as tp_utils
from verl.utils.device import get_device_id, get_device_name, get_torch_device
from verl.utils.fs import local_mkdir_safe
from verl.utils.model import normalize_model_name
from verl.utils.torch_dtypes import PrecisionType
from verl.workers.config import HFModelConfig, McoreEngineConfig

logger = logging.getLogger(__file__)
logger.setLevel(os.getenv("VERL_LOGGING_LEVEL", "WARN"))


def get_model_config(model):
    return get_attr_wrapped_model(model, "config", allow_none=False)


def get_model(
    model_provider_func,
    model_type=ModelType.encoder_or_decoder,
    wrap_with_ddp=True,
    use_distributed_optimizer=True,
    transformer_config=None,
    override_ddp_config=None,
):
    """Build the model."""
    # Build model.
    if (
        mpu.get_pipeline_model_parallel_world_size() > 1
        and mpu.get_virtual_pipeline_model_parallel_world_size() is not None
    ):
        assert model_type != ModelType.encoder_and_decoder, (
            "Interleaved schedule not supported for model with both encoder and decoder"
        )
        model = []
        has_vp_stage = inspect.signature(mpu.is_pipeline_first_stage).parameters.get("vp_stage", None) is not None
        for i in range(mpu.get_virtual_pipeline_model_parallel_world_size()):
            mpu.set_virtual_pipeline_model_parallel_rank(i)
            # Set pre_process and post_process only after virtual rank is set.
            extra_kwargs = {} if not has_vp_stage else {"ignore_virtual": False, "vp_stage": i}
            pre_process = mpu.is_pipeline_first_stage(**extra_kwargs)
            post_process = mpu.is_pipeline_last_stage(**extra_kwargs)
            this_model = model_provider_func(pre_process=pre_process, post_process=post_process, vp_stage=i)
            this_model.model_type = model_type
            model.append(this_model)
        mpu.set_virtual_pipeline_model_parallel_rank(0)
    else:
        pre_process = mpu.is_pipeline_first_stage()
        post_process = mpu.is_pipeline_last_stage()
        add_encoder = True
        add_decoder = True
        assert model_type != ModelType.encoder_and_decoder, "Model type encoder_and_decoder is not supported"
        if model_type == ModelType.encoder_and_decoder:
            if mpu.get_pipeline_model_parallel_world_size() > 1:
                assert mpu.get_pipeline_model_parallel_split_rank() is not None, (
                    "Split rank needs to be specified for model with both encoder and decoder"
                )
                rank = mpu.get_pipeline_model_parallel_rank()
                split_rank = mpu.get_pipeline_model_parallel_split_rank()
                world_size = mpu.get_pipeline_model_parallel_world_size()
                pre_process = rank == 0 or rank == split_rank
                post_process = (rank == (split_rank - 1)) or (rank == (world_size - 1))
                add_encoder = mpu.is_pipeline_stage_before_split()
                add_decoder = mpu.is_pipeline_stage_after_split()
            model = model_provider_func(
                pre_process=pre_process, post_process=post_process, add_encoder=add_encoder, add_decoder=add_decoder
            )
        else:
            model = model_provider_func(pre_process=pre_process, post_process=post_process)
        model.model_type = model_type

    if not isinstance(model, list):
        model = [model]

    # Set tensor model parallel attributes if not set.
    # Only parameters that are already tensor model parallel have these
    # attributes set for them. We should make sure the default attributes
    # are set for all params so the optimizer can use them.
    for model_module in model:
        for param in model_module.parameters():
            tensor_parallel.set_defaults_if_not_set_tensor_model_parallel_attributes(param)

    # Print number of parameters.
    if mpu.get_data_parallel_rank() == 0:
        print(
            " > number of parameters on (tensor, pipeline) model parallel rank ({}, {}): {}".format(
                mpu.get_tensor_model_parallel_rank(),
                mpu.get_pipeline_model_parallel_rank(),
                sum([sum([p.nelement() for p in model_module.parameters()]) for model_module in model]),
            ),
            flush=True,
        )

    # GPU allocation.
    if transformer_config is None or (not transformer_config.use_cpu_initialization):
        for model_module in model:
            model_module.to(f"{get_device_name()}:{get_device_id()}")

    # Fp16 conversion.
    config: TransformerConfig = get_model_config(model[0])
    config.fp8 = None
    tfconfig: TransformerConfig = model[0].config
    if config.fp16 or config.bf16:  # the ModelParallelConfig in GPTModel
        model = [Float16Module(config, model_module) for model_module in model]

    if wrap_with_ddp:
        ddp_models = []
        ddp_config_dict = {
            "use_distributed_optimizer": use_distributed_optimizer,
            "grad_reduce_in_fp32": True,
            "overlap_grad_reduce": False,
        }
        if override_ddp_config is not None:
            ddp_config_dict.update(override_ddp_config)
        ddp_config = DistributedDataParallelConfig(**ddp_config_dict)
        for model_chunk_idx, model_chunk in enumerate(model):
            ddp_model = DDP(
                config=tfconfig,
                module=model_chunk,
                disable_bucketing=(model_chunk_idx > 0),
                ddp_config=ddp_config,
            )
            ddp_models.append(ddp_model)
        model = ddp_models
        # # Broadcast params from data parallel src rank to other data parallel ranks.
        # # if args.data_parallel_random_init:
        for model_module in model:
            model_module.broadcast_params()
    return model


@dataclass
class McoreModuleWrapperConfig:
    """Configuration for Mcore module wrapper."""

    is_value_model: bool = False
    share_embeddings_and_output_weights: bool = False
    wrap_with_ddp: bool = True
    use_distributed_optimizer: bool = True


def make_megatron_module(
    wrap_config: McoreModuleWrapperConfig,
    tf_config: TransformerConfig,
    hf_config: PretrainedConfig,
    bridge: Any = None,
    provider: Any = None,
    override_model_config: dict[str, Any] = None,
    override_ddp_config: dict[str, Any] = None,
    peft_cls: Any = None,
    peft_config: Any = None,
):
    if override_model_config is None:
        override_model_config = {}

    if bridge is not None:
        if provider is None:
            from verl.models.mcore.mbridge import freeze_moe_router, make_value_model

            value_model_hook = make_value_model
        else:
            from verl.models.mcore.bridge import freeze_moe_router, make_value_model

            hidden_size = (
                hf_config.text_config.hidden_size if hasattr(hf_config, "text_config") else hf_config.hidden_size
            )
            value_model_hook = make_value_model(hidden_size, provider.sequence_parallel)

        post_model_creation_callbacks = []
        if wrap_config.is_value_model:
            post_model_creation_callbacks.append(value_model_hook)
        if override_model_config.get("moe_config", {}).get("freeze_moe_router", False):
            post_model_creation_callbacks.append(freeze_moe_router)
        if provider is not None:
            # When using PEFT with Megatron-Bridge, we must apply PEFT transformation
            # BEFORE wrapping the model in DDP. This is required because:
            # 1. PEFT freezes base model parameters (requires_grad=False)
            # 2. DDP must be aware of which parameters are trainable when building gradient buckets
            # 3. The distributed optimizer must only track trainable (adapter) parameters
            # See Megatron-Bridge docs: training/peft.md

            # Register PEFT transformation as pre-wrap hook if peft_cls is specified
            # This must happen BEFORE DDP wrapping to avoid KeyError with frozen parameters
            if peft_cls is not None:
                from verl.utils.megatron_peft_utils import load_adapter_checkpoint, print_adapter_info

                def peft_pre_wrap_hook(model):
                    """Pre-wrap hook that applies PEFT transformation."""
                    # Apply PEFT transformation - this will freeze base model and add adapters
                    # The PEFT callable handles both freezing and transformation
                    transformed_model = peft_cls(model, training=True)

                    # Set parameters to save (adapter-only checkpointing)
                    peft_cls.set_params_to_save(transformed_model)

                    # Load adapter weights if adapter_path is specified
                    adapter_path = getattr(peft_config, "adapter_path", None)
                    if adapter_path is not None and adapter_path:
                        print(f"Loading adapter weights from: {adapter_path}")
                        load_adapter_checkpoint(transformed_model, adapter_path)

                    # Print PEFT statistics
                    if torch.distributed.get_rank() == 0:
                        print_adapter_info(transformed_model)

                    return transformed_model

                provider.register_pre_wrap_hook(peft_pre_wrap_hook)

            # Register post-creation callbacks (make_value_model, freeze_moe_router) as pre-wrap hooks
            for callback in post_model_creation_callbacks:
                provider.register_pre_wrap_hook(callback)

            # Create DDP config if needed
            ddp_config = None
            if wrap_config.wrap_with_ddp:
                from megatron.bridge.training.config import DistributedDataParallelConfig

                ddp_config_dict = {
                    "use_distributed_optimizer": wrap_config.use_distributed_optimizer,
                }
                # Apply any DDP config overrides
                if override_ddp_config is not None:
                    ddp_config_dict.update(override_ddp_config)

                ddp_config = DistributedDataParallelConfig(**ddp_config_dict)
                ddp_config.finalize()

            # Now call provide_distributed_model with all hooks registered
            # Hooks will be applied automatically before DDP wrapping
            model = provider.provide_distributed_model(
                wrap_with_ddp=wrap_config.wrap_with_ddp,
                ddp_config=ddp_config,
                fp16=provider.fp16,
                bf16=provider.bf16,
            )

            # Extract TransformerConfig from the created model
            tf_config = get_model_config(model[0] if isinstance(model, list) else model)
        else:
            model = bridge.get_model(
                post_model_creation_callbacks=post_model_creation_callbacks,
                wrap_with_ddp=wrap_config.wrap_with_ddp,
                fp16=tf_config.fp16,
                bf16=tf_config.bf16,
                ddp_config=override_ddp_config,
            )

        if isinstance(tf_config, MLATransformerConfig):
            # Keep the same behavior as hf_to_mcore_config_dpskv3
            from verl.models.mcore.patch import apply_patch

            apply_patch()
    else:

        def megatron_model_provider(pre_process, post_process, vp_stage=None):
            from verl.models.mcore import init_mcore_model

            parallel_model = init_mcore_model(
                tf_config,
                hf_config,
                pre_process,
                post_process,
                share_embeddings_and_output_weights=wrap_config.share_embeddings_and_output_weights,
                value=wrap_config.is_value_model,
                freeze_moe_router=override_model_config.get("moe_config", {}).get("freeze_moe_router", False),
                vp_stage=vp_stage,
            )
            parallel_model.to(get_device_name())
            return parallel_model

        model = get_model(
            megatron_model_provider,
            wrap_with_ddp=wrap_config.wrap_with_ddp,
            use_distributed_optimizer=wrap_config.use_distributed_optimizer,
            override_ddp_config=override_ddp_config,
        )
    return model, tf_config


ALL_MODULE_WRAPPER_CLASSNAMES = (DDP, Float16Module)


def unwrap_model(model, module_instances=ALL_MODULE_WRAPPER_CLASSNAMES):
    return_list = True
    if not isinstance(model, list):
        model = [model]
        return_list = False
    unwrapped_model = []
    for model_module in model:
        while isinstance(model_module, module_instances):
            model_module = model_module.module
        unwrapped_model.append(model_module)
    if not return_list:
        return unwrapped_model[0]
    return unwrapped_model


def convert_config(hf_config: PretrainedConfig, megatron_config) -> TransformerConfig:
    """[Deprecated] convert config

    Args:
        hf_config (PretrainedConfig): _description_
        megatron_config (_type_): _description_

    Returns:
        TransformerConfig: _description_
    """

    warnings.warn("[deprecated] use config converter for more model support", stacklevel=2)
    print(f"megatron config {megatron_config}")
    dt = PrecisionType.to_dtype(megatron_config.params_dtype)
    print(f"pipeline_dtype=megatron_config {dt}")
    qkv_bias = True if "Qwen2ForCausalLM" in hf_config.architectures else getattr(hf_config, "attention_bias", False)
    overlap_p2p_comm = (
        mpu.get_virtual_pipeline_model_parallel_world_size() is not None
        and mpu.get_virtual_pipeline_model_parallel_world_size() > 1
    )
    batch_p2p_comm = False
    transformer_config = TransformerConfig(
        num_layers=hf_config.num_hidden_layers,
        hidden_size=hf_config.hidden_size,
        num_attention_heads=hf_config.num_attention_heads,
        num_query_groups=hf_config.num_key_value_heads,
        ffn_hidden_size=hf_config.intermediate_size,
        #    max_position_embeddings=hf_config.max_position_embeddings,
        activation_func=F.silu,
        normalization="RMSNorm",
        #    rotary_percent=False, # default,
        gated_linear_unit=True,  # for llama
        use_cpu_initialization=True,
        apply_residual_connection_post_layernorm=False,  # check what's this mean
        add_bias_linear=False,
        tensor_model_parallel_size=mpu.get_tensor_model_parallel_world_size(),
        pipeline_model_parallel_size=mpu.get_pipeline_model_parallel_world_size(),
        virtual_pipeline_model_parallel_size=mpu.get_virtual_pipeline_model_parallel_world_size(),
        context_parallel_size=mpu.get_context_parallel_world_size(),
        overlap_p2p_comm=overlap_p2p_comm,
        batch_p2p_comm=batch_p2p_comm,
        pipeline_dtype=dt,
        params_dtype=dt,
        sequence_parallel=mpu.get_tensor_model_parallel_world_size() > 1,
        variable_seq_lengths=True,
        masked_softmax_fusion=True,
        moe_token_dispatcher_type="alltoall",
        attention_dropout=hf_config.attention_dropout,
        hidden_dropout=getattr(hf_config, "hidden_dropout", 0.0),
        add_qkv_bias=qkv_bias,
        bf16=dt is torch.bfloat16,
    )

    return transformer_config


def mcore_model_parallel_config(
    sequence_parallel: bool,
    params_dtype: torch.dtype,
) -> ModelParallelConfig:
    # WARNING: Code should not reach this point. This function is deprecated and will be removed.
    # Please use hf_to_mcore_config_dense() from verl.models.mcore.config_converter instead.
    warnings.warn(
        "Code should not reach this point. This function is deprecated and will be removed. Please use "
        "hf_to_mcore_config_dense() from verl.models.mcore.config_converter instead.",
        DeprecationWarning,
        stacklevel=2,
    )
    return ModelParallelConfig(
        tensor_model_parallel_size=mpu.get_tensor_model_parallel_world_size(),
        pipeline_model_parallel_size=mpu.get_pipeline_model_parallel_world_size(),
        virtual_pipeline_model_parallel_size=mpu.get_virtual_pipeline_model_parallel_world_size(),
        context_parallel_size=mpu.get_context_parallel_world_size(),
        sequence_parallel=sequence_parallel,
        params_dtype=params_dtype,
        pipeline_dtype=params_dtype,
        bf16=True,
        fp16=False,
        timers=None,
    )


@torch.no_grad()
def offload_megatron_model_to_cpu(models):
    """
    In megatron, the model and optimizer storage are:
    - bf16 parameter data chunked in model parallel group
    - fp32 grad chunked in model parallel group
    - fp32 main_parameter chunked in model and dp group
    - fp32 optimizer state chunked in model and dp group
    """
    for model_chunk in models:
        if isinstance(model_chunk, DDP):
            model_chunk_all_buffers = [model_chunk.buffers, model_chunk.expert_parallel_buffers]
            for buffers in model_chunk_all_buffers:
                for buffer in buffers:
                    # offload parameters
                    if buffer.param_data.storage().size() > 0:
                        buffer.param_data.cpu_data = buffer.param_data.data.cpu().pin_memory()
                        buffer.param_data_size = buffer.param_data.storage().size()
                        buffer.param_data.storage().resize_(0)

                    assert buffer.param_data_size == buffer.param_data.cpu_data.storage().size()

                    if buffer.grad_data.storage().size() > 0:
                        # if the grad_data size is already zero, we assume that it is already offloaded
                        buffer.grad_data_size = buffer.grad_data.storage().size()
                        buffer.grad_data.storage().resize_(0)
            # Offload frozen parameters not in DDP buffers (e.g. base model in LoRA/PEFT)
            # DDP buffers only contain requires_grad=True params, so frozen params must be offloaded separately.
            for param in model_chunk.module.parameters():
                if not param.requires_grad and param.device.type != "cpu":
                    param.data = param.data.to("cpu", non_blocking=True)
        else:
            # we need this for ref module
            for _, param in model_chunk.named_parameters():
                param.data = param.data.to("cpu", non_blocking=True)
                if param.grad is not None:
                    param.grad = param.grad.to("cpu", non_blocking=True)
    gc.collect()
    get_torch_device().empty_cache()


@torch.no_grad()
def load_megatron_model_to_gpu(models, load_grad=True, load_frozen_params=True):
    """
    Load megatron model to GPU.
    Args:
        models: The model to load.
        load_grad: Whether to load gradients.
        load_frozen_params: Whether to load frozen parameters.
    """
    for model_chunk in models:
        if isinstance(model_chunk, DDP):
            model_chunk_all_buffers = [model_chunk.buffers, model_chunk.expert_parallel_buffers]
            for buffers in model_chunk_all_buffers:
                for buffer in buffers:
                    # sometimes, we don't want to load grad for pure inference
                    if load_grad and hasattr(buffer, "grad_data_size"):
                        current_storage_size = buffer.grad_data.storage().size()
                        if current_storage_size == 0 or current_storage_size == buffer.grad_data_size:
                            buffer.grad_data.storage().resize_(buffer.grad_data_size)
                            buffer.grad_data.zero_()
                        else:
                            # Non-standard layers (e.g. GatedDeltaNet) may have grad
                            # buffers with mismatched storage size; skip resize and
                            # zero in-place with current storage.
                            buffer.grad_data.zero_()

                    if buffer.param_data.storage().size() == 0:
                        buffer.param_data.storage().resize_(buffer.param_data_size)
                        # copy data from cpu to cuda
                        buffer.param_data.copy_(buffer.param_data.cpu_data, non_blocking=True)

            # Load frozen parameters that were offloaded (e.g. base model in LoRA/PEFT)
            if load_frozen_params:
                device_id = get_device_id()
                for param in model_chunk.module.parameters():
                    if not param.requires_grad and param.device.type == "cpu":
                        param.data = param.data.to(device_id, non_blocking=True)
        else:
            # we need this for ref module
            device_id = get_device_id()
            for _, param in model_chunk.named_parameters():
                param.data = param.data.to(device_id, non_blocking=True)
                if param.grad is not None:
                    param.grad = param.grad.to(device_id, non_blocking=True)
    gc.collect()
    get_torch_device().empty_cache()


@torch.no_grad()
def offload_megatron_copy_params(optimizers):
    """
    Offload optimizer parameters to CPU. Supports both Megatron optimizers
    and `ChainedOptimizer`, which wraps a list of underlying optimizers.

    Args:
        optimizers: The optimizer or ChainedOptimizer instance.
    """

    def _iter_opts(opt):
        if isinstance(opt, ChainedOptimizer):
            return opt.chained_optimizers
        return [opt]

    def offload_tensor_to_cpu(tensor):
        if tensor is None:
            return
        tensor.data = tensor.data.to("cpu", non_blocking=True)

    def offload_group_to_cpu(group):
        if group is None:
            return

        if isinstance(group, list):
            for param_group in group:
                if isinstance(param_group, list):
                    for param in param_group:
                        offload_tensor_to_cpu(param)
                else:
                    offload_tensor_to_cpu(param_group)
        else:
            offload_tensor_to_cpu(group)

    # Offload all parameter groups to CPU for each underlying optimizer

    for _opt in _iter_opts(optimizers):
        if hasattr(_opt, "shard_fp32_from_float16_groups"):
            offload_group_to_cpu(_opt.shard_fp32_from_float16_groups)


@torch.no_grad()
def load_megatron_copy_params(optimizers):
    """
    Load optimizer parameters back to GPU. Handles ChainedOptimizer.

    Args:
        optimizers: Optimizer or ChainedOptimizer instance.
    """

    def _iter_opts(opt):
        if isinstance(opt, ChainedOptimizer):
            return opt.chained_optimizers
        return [opt]

    def load_tensor_to_gpu(tensor):
        if tensor is None:
            return
        device_id = get_device_id()
        tensor.data = tensor.data.to(device_id, non_blocking=True)

    def load_group_to_gpu(group):
        if group is None:
            return

        if isinstance(group, list):
            for param_group in group:
                if isinstance(param_group, list):
                    for param in param_group:
                        load_tensor_to_gpu(param)
                else:
                    load_tensor_to_gpu(param_group)
        else:
            load_tensor_to_gpu(group)

    # Load all parameter groups to GPU for each underlying optimizer

    for _opt in _iter_opts(optimizers):
        if hasattr(_opt, "shard_fp32_from_float16_groups"):
            load_group_to_gpu(_opt.shard_fp32_from_float16_groups)


@torch.no_grad()
def offload_megatron_optimizer(optimizers):
    def _iter_opts(opt):
        if isinstance(opt, ChainedOptimizer):
            return opt.chained_optimizers
        return [opt]

    for _opt in _iter_opts(optimizers):
        offload_megatron_copy_params(_opt)
        ## worker may hold zero parameter when enabling custom pipeline layout
        if _opt.optimizer is not None:
            # HybridDeviceOptimizer: offload all sub-optimizer states to CPU
            # TODO: this should be a method in Megatron-LM's HybridDeviceOptimizer
            hdo = _opt.optimizer
            if all(hasattr(hdo, attr) for attr in ("sub_optimizers", "inner_param_to_orig_param", "state")):
                for optimizer in hdo.sub_optimizers:
                    for param, state in optimizer.state.items():
                        for k, v in state.items():
                            if not isinstance(v, torch.Tensor):
                                continue
                            orig_param = hdo.inner_param_to_orig_param.get(param, param)
                            hdo.state[orig_param][k] = state[k] = v.to("cpu")
            else:
                opt_state_dict_values = _opt.optimizer.state.values()
                for v in opt_state_dict_values:
                    if "exp_avg" in v:
                        v["exp_avg"] = v["exp_avg"].to("cpu", non_blocking=True)
                    if "exp_avg_sq" in v:
                        v["exp_avg_sq"] = v["exp_avg_sq"].to("cpu", non_blocking=True)

        try:
            # Free TransformerEngine's dummy weight gradients cache
            # https://github.com/NVIDIA/TransformerEngine/blob/release_v2.10/transformer_engine/pytorch/module/base.py#L64
            from transformer_engine.pytorch.module.base import _dummy_wgrads

            _dummy_wgrads.clear()
        except ImportError:
            pass

        # Free Megatron-LM's global memory buffer
        get_global_memory_buffer().buffer.clear()

        gc.collect()
        get_torch_device().empty_cache()


@torch.no_grad()
def load_megatron_optimizer(optimizers):
    def _iter_opts(opt):
        if isinstance(opt, ChainedOptimizer):
            return opt.chained_optimizers
        return [opt]

    for _opt in _iter_opts(optimizers):
        load_megatron_copy_params(_opt)
        ## worker may hold zero parameter when enabling custom pipeline layout
        if _opt.optimizer is not None:
            # if we are using HybridDeviceOptimizer, we need to only move gpu optimizer state to gpu
            if hasattr(_opt.optimizer, "_move_new_state_to_right_device"):
                _opt.optimizer._move_new_state_to_right_device()
            else:
                opt_state_dict_values = _opt.optimizer.state.values()
                for v in opt_state_dict_values:
                    if "exp_avg" in v:
                        v["exp_avg"] = v["exp_avg"].to(get_device_id(), non_blocking=True)
                    if "exp_avg_sq" in v:
                        v["exp_avg_sq"] = v["exp_avg_sq"].to(get_device_id(), non_blocking=True)
        gc.collect()
        get_torch_device().empty_cache()


def get_dist_checkpoint_path(checkpoint_path):
    local_mkdir_safe(checkpoint_path)
    local_mkdir_safe(os.path.join(checkpoint_path, "dist_ckpt"))
    return os.path.join(checkpoint_path, "dist_ckpt")


def get_hf_model_checkpoint_path(checkpoint_path):
    local_mkdir_safe(checkpoint_path)
    local_mkdir_safe(os.path.join(checkpoint_path, "huggingface"))
    return os.path.join(checkpoint_path, "huggingface")


def get_transformer_config_checkpoint_path(checkpoint_path):
    os.makedirs(checkpoint_path, exist_ok=True)
    return os.path.join(checkpoint_path, "transformer_config.json")


def convert_megatron_model_to_transformers_model(
    name,
    param,
    config: PretrainedConfig,
    tp_size: int,
    num_query_groups: int,
    convert_qkv_gate_up_by_trunk_concat=False,
):
    """Convert megatron model to transformers model."""
    new_params = {}

    def convert_qkv_shard(full_tensor, q_name, k_name, v_name):
        nonlocal config
        nonlocal tp_size
        nonlocal num_query_groups

        q_shard_list = []
        k_shard_list = []
        v_shard_list = []
        hidden_size_per_head = getattr(config, "head_dim", config.hidden_size // config.num_attention_heads)

        if config.num_key_value_heads >= tp_size:
            q_size_tp = hidden_size_per_head * config.num_attention_heads // tp_size
            kv_size_tp = hidden_size_per_head * config.num_key_value_heads // tp_size
            total_size = q_size_tp + 2 * kv_size_tp
            for i in range(tp_size):
                num_query_groups_per_partition = num_query_groups // tp_size
                qkv_part = full_tensor[i * total_size : (i + 1) * total_size]
                q_size_chunk = q_size_tp // num_query_groups_per_partition
                kv_size_chunk = kv_size_tp // num_query_groups_per_partition
                for qkv_part_chunk in qkv_part.chunk(num_query_groups_per_partition):
                    q_part = qkv_part_chunk[:q_size_chunk]
                    k_part = qkv_part_chunk[q_size_chunk : q_size_chunk + kv_size_chunk]
                    v_part = qkv_part_chunk[q_size_chunk + kv_size_chunk :]
                    q_shard_list.append(q_part)
                    k_shard_list.append(k_part)
                    v_shard_list.append(v_part)
        else:
            q_size_tp = hidden_size_per_head * config.num_attention_heads // tp_size
            kv_size_tp = hidden_size_per_head
            total_size = q_size_tp + 2 * kv_size_tp
            for i in range(tp_size):
                num_query_groups_per_partition = num_query_groups // tp_size
                qkv_part = full_tensor[i * total_size : (i + 1) * total_size]
                q_size_chunk = q_size_tp // num_query_groups_per_partition
                kv_size_chunk = kv_size_tp // num_query_groups_per_partition
                for qkv_part_chunk in qkv_part.chunk(num_query_groups_per_partition):
                    q_part = qkv_part_chunk[:q_size_chunk]
                    k_part = qkv_part_chunk[q_size_chunk : q_size_chunk + kv_size_chunk]
                    v_part = qkv_part_chunk[q_size_chunk + kv_size_chunk :]
                    q_shard_list.append(q_part)
                    if i * config.num_key_value_heads % tp_size == 0:
                        k_shard_list.append(k_part)
                        v_shard_list.append(v_part)

        new_params[q_name] = torch.cat(q_shard_list, dim=0)
        new_params[k_name] = torch.cat(k_shard_list, dim=0)
        new_params[v_name] = torch.cat(v_shard_list, dim=0)

    def convert_gate_up_shard(full_tensor, gate_name, up_name):
        nonlocal config
        nonlocal tp_size

        intermediate_size_tp = config.intermediate_size // tp_size
        gate_weight_list = []
        up_weight_list = []
        for i in range(tp_size):
            gate_up_weight_tp = full_tensor[intermediate_size_tp * 2 * i : intermediate_size_tp * 2 * (i + 1)]
            gate_weight_tp = gate_up_weight_tp[:intermediate_size_tp]
            up_weight_tp = gate_up_weight_tp[intermediate_size_tp:]
            gate_weight_list.append(gate_weight_tp)
            up_weight_list.append(up_weight_tp)

        new_params[gate_name] = torch.cat(gate_weight_list, dim=0)
        new_params[up_name] = torch.cat(up_weight_list, dim=0)

    if name == "embedding.word_embeddings.weight":
        new_params["model.embed_tokens.weight"] = param
    elif "self_attention" in name:
        splitted_name = name.split(".")
        layer_number = splitted_name[2]
        component = splitted_name[4]
        param_type = splitted_name[5]
        if component == "linear_proj":
            new_params[f"model.layers.{layer_number}.self_attn.o_proj.weight"] = param
        elif component == "linear_qkv" and not isinstance(param, list):
            if param_type == "layer_norm_weight":
                new_params[f"model.layers.{layer_number}.input_layernorm.weight"] = param
            else:
                if convert_qkv_gate_up_by_trunk_concat:
                    convert_qkv_shard(
                        param,
                        f"model.layers.{layer_number}.self_attn.q_proj.{param_type}",
                        f"model.layers.{layer_number}.self_attn.k_proj.{param_type}",
                        f"model.layers.{layer_number}.self_attn.v_proj.{param_type}",
                    )
                else:
                    new_params[f"model.layers.{layer_number}.self_attn.qkv_proj.{param_type}"] = param
        elif component == "q_layernorm" or component == "k_layernorm":
            hf_component = component.replace("layer", "")
            new_params[f"model.layers.{layer_number}.self_attn.{hf_component}.weight"] = param
        else:
            assert isinstance(param, list) and len(param) == 3
            assert param_type == "weight" or param_type == "bias"
            new_params[f"model.layers.{layer_number}.self_attn.q_proj.{param_type}"] = param[0]
            new_params[f"model.layers.{layer_number}.self_attn.k_proj.{param_type}"] = param[1]
            new_params[f"model.layers.{layer_number}.self_attn.v_proj.{param_type}"] = param[2]
    elif "mlp" in name:
        splitted_name = name.split(".")
        layer_number = splitted_name[2]
        component = splitted_name[4]
        param_type = splitted_name[5]
        if component == "linear_fc1" and not isinstance(param, list):
            if param_type == "layer_norm_weight":
                new_params[f"model.layers.{layer_number}.post_attention_layernorm.weight"] = param
            elif param_type == "weight":
                if convert_qkv_gate_up_by_trunk_concat:
                    convert_gate_up_shard(
                        param,
                        f"model.layers.{layer_number}.mlp.gate_proj.weight",
                        f"model.layers.{layer_number}.mlp.up_proj.weight",
                    )
                else:
                    new_params[f"model.layers.{layer_number}.mlp.gate_up_proj.weight"] = param
        elif component == "linear_fc1" and isinstance(param, list):
            assert len(param) == 2
            assert param_type == "weight" or param_type == "bias"
            new_params[f"model.layers.{layer_number}.mlp.gate_proj.weight"] = param[0]
            new_params[f"model.layers.{layer_number}.mlp.up_proj.weight"] = param[1]
        elif component == "linear_fc2":
            new_params[f"model.layers.{layer_number}.mlp.down_proj.weight"] = param
    elif name == "decoder.final_layernorm.weight":
        new_params["model.norm.weight"] = param
    elif name == "output_layer.weight":
        new_params["lm_head.weight"] = param
    else:
        raise ValueError(f"Unknown param name: {name}")
    return new_params.keys(), new_params.values()


def broadcast_from_megatron_pp(tensor: torch.Tensor):
    # tensor is not None only in one of the pp ranks
    if tensor is not None:
        shape = tensor.shape
        dtype = tensor.dtype
        tensor_parallel = getattr(tensor, "tensor_model_parallel", None)
        partition_dim = getattr(tensor, "partition_dim", None)
        tensor_spec = (shape, dtype, tensor_parallel, partition_dim)
    else:
        tensor_spec = None
    tensor_spec_output = [None] * mpu.get_pipeline_model_parallel_world_size()
    torch.distributed.all_gather_object(
        object_list=tensor_spec_output, obj=tensor_spec, group=mpu.get_pipeline_model_parallel_group()
    )
    # find the src rank
    target_tensor_spec = None
    src_rank = None
    for rank, tensor_spec in enumerate(tensor_spec_output):
        if tensor_spec is not None:
            if target_tensor_spec is None:
                target_tensor_spec = tensor_spec
            else:
                raise ValueError("A tensor exists on two pp ranks")
            src_rank = rank
    assert target_tensor_spec is not None
    if tensor is None:
        tensor = torch.empty(size=target_tensor_spec[0], dtype=target_tensor_spec[1], device=get_device_id())
        if target_tensor_spec[2] is not None:
            tensor.tensor_model_parallel = target_tensor_spec[2]
        if target_tensor_spec[3] is not None:
            tensor.partition_dim = target_tensor_spec[3]

    global_rank = torch.distributed.get_global_rank(group=mpu.get_pipeline_model_parallel_group(), group_rank=src_rank)
    torch.distributed.broadcast(tensor=tensor, src=global_rank, group=mpu.get_pipeline_model_parallel_group())
    return tensor


def broadcast_str_from_megatron_pp(obj: Any):
    obj_output = [None] * mpu.get_pipeline_model_parallel_world_size()
    torch.distributed.all_gather_object(object_list=obj_output, obj=obj, group=mpu.get_pipeline_model_parallel_group())

    src_rank = None
    target_obj = None
    for rank, item in enumerate(obj_output):
        if item is not None:
            if target_obj is not None:
                raise ValueError("An object exists on two pp ranks")
            target_obj = item
            src_rank = rank

    assert target_obj is not None, "No valid object found to broadcast."

    global_rank = torch.distributed.get_global_rank(group=mpu.get_pipeline_model_parallel_group(), group_rank=src_rank)

    obj_output = [None] * torch.distributed.get_world_size(group=mpu.get_pipeline_model_parallel_group())
    obj_output[0] = target_obj
    torch.distributed.broadcast_object_list(
        object_list=obj_output, src=global_rank, group=mpu.get_pipeline_model_parallel_group()
    )

    return obj_output[0]


def default_tp_concat_fn(
    layer_name_mapping,
    name,
    train_params,
    infer_params,
    model_config,
    hf_config=None,
    convert_qkv_gate_up_by_simple_split=False,
):
    """
    name: name of the parameter
    train_params: training parameters
    infer_params (Iterable[torch.Tensor]): a iterator towards list of parameters all-gathered from micro_dp_group
    model_config: huggingface model_config
    TODO(zhangchi.usc1992): currently, the implementation is adhoc. We can move this function to the model
    definition so that it is model-agnostic. If the model doesn't implement this function,
    we can throw an error to force user disable TP HybridEngine.
    """
    from megatron.core import mpu

    train_tp_size = mpu.get_tensor_model_parallel_world_size()
    if layer_name_mapping.get("qkv_layer_name") in name and "layer_norm" not in name:
        # if the tensor is qkv, for each param on tp, split into q, k, v
        # concat q, k, v separately.
        q_lst = []
        k_lst = []
        v_lst = []
        num_attention_heads = model_config.num_attention_heads
        num_key_value_heads = model_config.num_key_value_heads
        if "vision_model" in name:
            num_attention_heads = hf_config.vision_config.num_heads
            num_key_value_heads = hf_config.vision_config.num_heads
        assert num_attention_heads % num_key_value_heads == 0
        num_q_per_kv = num_attention_heads // num_key_value_heads
        assert infer_params[0].shape[0] % (num_q_per_kv + 2) == 0, (
            f"param '{name}' shape '{infer_params[0].shape}' dim0 is not divisible by {num_q_per_kv + 2}"
        )
        kv_size_per_tp = infer_params[0].shape[0] // (num_q_per_kv + 2)
        split_size = [kv_size_per_tp * num_q_per_kv, kv_size_per_tp, kv_size_per_tp]
        for infer_param in infer_params:
            num_query_groups_per_partition = num_key_value_heads // train_tp_size
            for chunk in infer_param.chunk(num_query_groups_per_partition):
                split_size = [
                    kv_size_per_tp * num_q_per_kv // num_query_groups_per_partition,
                    kv_size_per_tp // num_query_groups_per_partition,
                    kv_size_per_tp // num_query_groups_per_partition,
                ]
                q, k, v = chunk.split(split_size)
                q_lst.append(q)
                k_lst.append(k)
                v_lst.append(v)
        q = torch.cat(q_lst, dim=0)
        k = torch.cat(k_lst, dim=0)
        v = torch.cat(v_lst, dim=0)
        infer_params = torch.cat((q, k, v), dim=0) if not convert_qkv_gate_up_by_simple_split else [q, k, v]

    elif (
        layer_name_mapping.get("gate_proj_layer_name") in name
        and "layer_norm" not in name
        and "vision_model.projection" not in name
    ):
        # if the tensor is gate and proj
        gate_lst = []
        up_lst = []
        for infer_param in infer_params:
            gate, up = infer_param.chunk(2)
            gate_lst.append(gate)
            up_lst.append(up)
        gate = torch.cat(gate_lst, dim=0)
        up = torch.cat(up_lst, dim=0)
        infer_params = torch.cat((gate, up), dim=0) if not convert_qkv_gate_up_by_simple_split else [gate, up]

    elif "mlp.experts.linear_fc2.weight" in name:  # moe
        infer_params = torch.cat(infer_params, dim=1)

    else:
        # concat tensor
        infer_params = torch.cat(infer_params, dim=tp_utils.get_tensor_parallel_partition_dim(train_params))

    return infer_params


def per_tensor_generator(
    actor_module,
    model_config,
    weight_converter,
    transformer_config,
    layer_name_mapping,
    convert_qkv_gate_up_by_simple_split=True,
):
    from megatron.core import parallel_state as mpu

    pp_rank = mpu.get_pipeline_model_parallel_rank()
    ep_size = mpu.get_expert_model_parallel_world_size()
    etp_size = mpu.get_expert_tensor_parallel_world_size()
    ep_group = mpu.get_expert_model_parallel_group()
    etp_group = mpu.get_expert_tensor_parallel_group()
    vpp_size = len(actor_module)
    all_gather_group = mpu.get_tensor_model_parallel_group()
    all_gather_group_size = torch.distributed.get_world_size(group=all_gather_group)

    def tensor_generator():
        for scan_vpp_idx in range(vpp_size):
            existing_keys = set()
            model = unwrap_model(actor_module[scan_vpp_idx])
            for name, param in model.named_parameters():
                existing_keys.add(name)
                yield name, param
            # note
            # there is a bug in megatron GPTModel
            # decoder.layers[n].mlp.router.expert_bias" in GPTModel is not registered in named_parameter, but in
            # state_dict(). for now we patch it by adding those keys to extra_keys.
            extra_keys = [x for x in model.state_dict().keys() if "_extra_state" not in x and x not in existing_keys]
            for name in extra_keys:
                yield name, model.state_dict()[name].to(get_device_id())

    # we need first make all rank get full model information
    meta_info = []
    for scan_vpp_idx in range(vpp_size):
        existing_keys = set()
        model = unwrap_model(actor_module[scan_vpp_idx])
        for idx, (name, _) in enumerate(model.named_parameters()):
            existing_keys.add(name)
            meta_info.append((pp_rank, scan_vpp_idx, idx, name))
        extra_keys = [x for x in model.state_dict().keys() if "_extra_state" not in x and x not in existing_keys]
        for name in extra_keys:
            meta_info.append((pp_rank, scan_vpp_idx, idx, name))

    obj_spec_output = [None] * mpu.get_pipeline_model_parallel_world_size()
    torch.distributed.all_gather_object(
        object_list=obj_spec_output, obj=meta_info, group=mpu.get_pipeline_model_parallel_group()
    )
    layer_list_meta = [item for sublist in obj_spec_output for item in sublist]

    gen_func = tensor_generator()

    # lazy load tensor for full model
    for cur_pp_rank, scan_vpp_idx, idx, name in layer_list_meta:
        if model_config.tie_word_embeddings and ("output_layers" in name):
            import warnings

            warnings.warn(
                "Current model sharing word and embedding weights, skip output layer conversion", stacklevel=2
            )
            continue

        if cur_pp_rank == pp_rank:
            try:
                cur_name, cur_tensor = next(gen_func)
            except StopIteration:
                cur_name, cur_tensor = None, None
            cur_name = normalize_model_name(name, cur_pp_rank, scan_vpp_idx, transformer_config)
        else:
            cur_tensor, cur_name = None, None

        # pp broadcast model tensor and name
        cur_name = broadcast_str_from_megatron_pp(cur_name)
        broad_pp_tensor = broadcast_from_megatron_pp(cur_tensor)

        # (xya): this is a hack to fix the name of the parameters
        while cur_name.startswith("module."):
            cur_name = cur_name[len("module.") :]

        # EP
        if ".mlp.experts.linear_fc" in cur_name and ep_size > 1:
            num_experts = weight_converter.mcore_config.num_moe_experts
            num_experts_per_rank = num_experts // ep_size
            infer_params = [torch.empty_like(broad_pp_tensor) for _ in range(ep_size)]
            torch.distributed.all_gather(infer_params, broad_pp_tensor, group=ep_group)

            name_prefix, local_expert_id = cur_name.split(".weight")
            local_expert_id = int(local_expert_id)
            global_expert_ids = [num_experts_per_rank * ep_rank + local_expert_id for ep_rank in range(ep_size)]
            global_expert_names = [f"{name_prefix}.weight{expert_id}" for expert_id in global_expert_ids]

            for name, param in zip(global_expert_names, infer_params, strict=True):
                if etp_size > 1:
                    # gather etp
                    etp_params = [torch.empty_like(param) for _ in range(etp_size)]
                    torch.distributed.all_gather(etp_params, param, group=etp_group)
                    params = etp_params
                else:
                    params = [param]

                merge_params = default_tp_concat_fn(
                    layer_name_mapping,
                    name,
                    broad_pp_tensor,
                    params,
                    model_config,
                    weight_converter.hf_config,
                    convert_qkv_gate_up_by_simple_split,
                )
                if not isinstance(merge_params, list):
                    merge_params = [merge_params]
                converted_names, converted_params = weight_converter.convert_param(name, merge_params)

                yield from zip(converted_names, [param.detach() for param in converted_params], strict=True)
            continue

        # tp all gather
        if tp_utils.is_tensor_parallel_param(broad_pp_tensor):
            # allocate a new tensor with proper size
            if all_gather_group_size <= 1:
                infer_params = [broad_pp_tensor]
            else:
                infer_params = [torch.empty_like(broad_pp_tensor) for _ in range(all_gather_group_size)]
                torch.distributed.all_gather(infer_params, broad_pp_tensor, group=mpu.get_tensor_model_parallel_group())
            infer_params = default_tp_concat_fn(
                layer_name_mapping,
                cur_name,
                broad_pp_tensor,
                infer_params,
                model_config,
                weight_converter.hf_config,
                convert_qkv_gate_up_by_simple_split,
            )
        else:
            infer_params = broad_pp_tensor

        if not isinstance(infer_params, list):
            infer_params = [infer_params]
        converted_names, converted_params = weight_converter.convert_param(cur_name, infer_params)

        yield from zip(converted_names, [param.detach() for param in converted_params], strict=True)


def get_transformer_layer_offset(pipeline_rank, vp_stage, config: TransformerConfig):
    """
    Get the index offset of any pipeline stage, given the level of pipelining.

    Make pipeline_rank and vp_stage as two arguments to make it more flexible,
    which is able to fetch layer offset for any pipeline stage.
    The original function only returns the layer offset for current pipeline stage.

    Extension to https://github.com/NVIDIA/Megatron-LM/blob/main/megatron/core/transformer/transformer_layer.py::get_transformer_layer_offset
    """

    has_vp_stage = (
        inspect.signature(parallel_state.is_pipeline_first_stage).parameters.get("vp_stage", None) is not None
    )
    extra_kwargs = {} if not has_vp_stage else {"ignore_virtual": False, "vp_stage": vp_stage}

    if config.pipeline_model_parallel_size > 1:
        if hasattr(config, "pipeline_model_parallel_layout") and config.pipeline_model_parallel_layout:
            from megatron.core.transformer.enums import LayerType

            offset = config.pipeline_model_parallel_layout.get_layer_offset(
                layer_type=LayerType.decoder, vp_stage=vp_stage
            )
        elif (
            config.num_layers_in_first_pipeline_stage is not None
            or config.num_layers_in_last_pipeline_stage is not None
        ):
            # Calculate number of pipeline stages to distribute the remaining Transformer
            # layers after deducting the Transformer layers in the first or the last stages
            middle_pipeline_stages = config.pipeline_model_parallel_size
            middle_pipeline_stages -= sum(
                [
                    1 if x is not None else 0
                    for x in (
                        config.num_layers_in_first_pipeline_stage,
                        config.num_layers_in_last_pipeline_stage,
                    )
                ]
            )

            # Calculate layers to distribute in each pipeline stage. If the
            # num_layers_in_first_pipeline_stage and num_layers_in_last_pipeline_stage
            # are not set, we will not enable uneven pipeline. All layers will be treated
            # as middle layers.
            num_layers_in_first_pipeline_stage = (
                0 if config.num_layers_in_first_pipeline_stage is None else config.num_layers_in_first_pipeline_stage
            )
            num_layers_in_last_pipeline_stage = (
                0 if config.num_layers_in_last_pipeline_stage is None else config.num_layers_in_last_pipeline_stage
            )

            middle_num_layers = (
                config.num_layers - num_layers_in_first_pipeline_stage - num_layers_in_last_pipeline_stage
            )

            if (vp_size := config.virtual_pipeline_model_parallel_size) is not None:
                assert vp_stage is not None, "vp_stage must be provided if virtual pipeline model parallel size is set"

                # Calculate number of layers in each virtual model chunk
                # If the num_layers_in_first_pipeline_stage and
                # num_layers_in_last_pipeline_stage are not set, all pipeline stages
                # will be treated as middle pipeline stages in the calculation
                num_layers_per_virtual_model_chunk_in_first_pipeline_stage = (
                    0
                    if config.num_layers_in_first_pipeline_stage is None
                    else config.num_layers_in_first_pipeline_stage // vp_size
                )

                num_layers_per_virtual_model_chunk_in_last_pipeline_stage = (
                    0
                    if config.num_layers_in_last_pipeline_stage is None
                    else config.num_layers_in_last_pipeline_stage // vp_size
                )

                num_layers_per_vritual_model_chunk_in_middle_pipeline_stage = middle_num_layers // vp_size

                # First stage + middle stage + last stage
                total_virtual_chunks = (
                    num_layers_per_virtual_model_chunk_in_first_pipeline_stage
                    + num_layers_per_vritual_model_chunk_in_middle_pipeline_stage
                    + num_layers_per_virtual_model_chunk_in_last_pipeline_stage
                )

                # Calculate the layer offset with interleaved uneven pipeline parallelism
                if pipeline_rank == 0:
                    offset = vp_stage * total_virtual_chunks
                else:
                    offset = (
                        vp_stage * total_virtual_chunks
                        + num_layers_per_virtual_model_chunk_in_first_pipeline_stage
                        + (pipeline_rank - 1)
                        * (num_layers_per_vritual_model_chunk_in_middle_pipeline_stage // middle_pipeline_stages)
                    )
            else:
                if middle_pipeline_stages > 0:
                    num_layers_per_pipeline_rank = middle_num_layers // middle_pipeline_stages
                else:
                    num_layers_per_pipeline_rank = 0

                middle_pipeline_rank = (
                    pipeline_rank if config.num_layers_in_first_pipeline_stage is None else pipeline_rank - 1
                )

                if pipeline_rank == 0:
                    offset = 0
                else:
                    offset = (middle_pipeline_rank * num_layers_per_pipeline_rank) + num_layers_in_first_pipeline_stage
        else:
            num_layers = config.num_layers

            # Increase the number of layers by one if we include the embedding (loss)
            # layer into pipeline parallelism partition and placement
            if config.account_for_embedding_in_pipeline_split:
                num_layers += 1

            if config.account_for_loss_in_pipeline_split:
                num_layers += 1

            num_layers_per_pipeline_rank = num_layers // config.pipeline_model_parallel_size

            if (vp_size := config.virtual_pipeline_model_parallel_size) is not None:
                assert vp_stage is not None, "vp_stage must be provided if virtual pipeline model parallel size is set"

                num_layers_per_virtual_rank = num_layers_per_pipeline_rank // vp_size
                total_virtual_chunks = num_layers // vp_size
                offset = vp_stage * total_virtual_chunks + (pipeline_rank * num_layers_per_virtual_rank)

                # Reduce the offset of embedding layer from the total layer number
                if config.account_for_embedding_in_pipeline_split and not parallel_state.is_pipeline_first_stage(
                    **extra_kwargs
                ):
                    offset -= 1
            else:
                offset = pipeline_rank * num_layers_per_pipeline_rank

                # Reduce the offset of embedding layer from the total layer number
                if config.account_for_embedding_in_pipeline_split and not parallel_state.is_pipeline_first_stage(
                    **extra_kwargs
                ):
                    offset -= 1
    else:
        offset = 0
    return offset


def register_megatron_training_hooks(model: list[torch.nn.Module], optimizer):
    from megatron.core.distributed import finalize_model_grads
    from megatron.core.utils import get_model_config

    try:
        from megatron.core.distributed.fsdp.mcore_fsdp_adapter import FullyShardedDataParallel as megatron_FSDP
    except ImportError:
        megatron_FSDP = DDP

    # register some callbacks for megatron training, following https://github.com/NVIDIA/Megatron-LM/blob/core_v0.15.0rc7/megatron/training/training.py#L2039-L2057
    for one_model in model:
        config = get_model_config(one_model)
        config.grad_scale_func = optimizer.scale_loss
        config.finalize_model_grads_func = finalize_model_grads

        overlap_param_gather = getattr(optimizer.config, "overlap_param_gather", False)
        overlap_grad_reduce = getattr(one_model.ddp_config, "overlap_grad_reduce", False)
        align_grad_reduce = True  # default to True, seldom to be false
        align_param_gather = getattr(one_model.ddp_config, "align_param_gather", False)

        if isinstance(model[0], megatron_FSDP | DDP) and overlap_grad_reduce:
            assert config.no_sync_func is None, (
                "When overlap_grad_reduce is True, config.no_sync_func must be None; "
                "a custom no_sync_func is not supported when overlapping grad-reduce"
            )
            config.no_sync_func = [model_chunk.no_sync for model_chunk in model]
            if len(model) == 1:
                config.no_sync_func = config.no_sync_func[0]
            if align_grad_reduce:
                config.grad_sync_func = [model_chunk.start_grad_sync for model_chunk in model]
                if len(model) == 1:
                    config.grad_sync_func = config.grad_sync_func[0]
        if overlap_param_gather and align_param_gather:
            config.param_sync_func = [model_chunk.start_param_sync for model_chunk in model]
            if len(model) == 1:
                config.param_sync_func = config.param_sync_func[0]


def mapping_string_to_attn_backend(args: dict) -> dict:
    if "attention_backend" in args and isinstance(args["attention_backend"], str):
        from megatron.core.transformer.enums import AttnBackend

        args["attention_backend"] = AttnBackend[args["attention_backend"]]
    return args


def get_megatron_mtp_loss(n_micro_batch):
    # Calculate MTP loss scale similar to Megatron-LM implementation
    mtp_loss_scale = 1.0 / n_micro_batch

    # Create a dummy total_loss_dict to collect MTP metrics
    total_loss_dict = {}

    # Track MTP metrics - this will populate total_loss_dict with MTP losses
    MTPLossLoggingHelper.track_mtp_metrics(
        loss_scale=mtp_loss_scale, iteration=0, writer=None, wandb_writer=None, total_loss_dict=total_loss_dict
    )
    # Add MTP metrics to losses_reduced if any were collected
    # total_loss_dict: {'mtp_1 loss': tensor(value, device='cuda:0')}
    output = {}
    if total_loss_dict:
        for key, value in total_loss_dict.items():
            # Convert key to have proper prefix and format
            formatted_key = f"mtp_losses/{key.replace(' ', '_')}"
            # only added to the 0th batch, the MTP loss obtained is a global value, and will be the same for every batch
            output[formatted_key] = value.cpu().item()
    return output


def get_megatron_module_device(models: list[Any]) -> str:
    if not models:
        return "cpu"

    model_chunk = models[0]
    if not model_chunk.buffers:
        try:
            return next(model_chunk.module.parameters()).device.type
        except StopIteration:
            return "cpu"

    buffer = model_chunk.buffers[0]
    if buffer.param_data.storage().size() == 0:
        return "cpu"
    else:
        return get_device_name()


def check_mtp_config(model_config: HFModelConfig, engine_config: McoreEngineConfig):
    """
    Check and configure MTP (Multi-Token Prediction) settings.

    Cases:
        - mtp.enable == False and no MTP layers: return directly
        - mtp.enable == False and has MTP layers: set num_nextn_predict_layers = 0
        - mtp.enable == True and has MTP layers: configure override_transformer_config
        - mtp.enable == True and no MTP layers: raise ValueError
    """
    has_mtp = (
        model_config.hf_config.num_nextn_predict_layers > 0
        if hasattr(model_config.hf_config, "num_nextn_predict_layers")
        else False
    )
    enable_mtp = model_config.mtp.enable

    if not enable_mtp and not has_mtp:
        return
    elif not enable_mtp and has_mtp:
        model_config.hf_config.num_nextn_predict_layers = 0
    elif enable_mtp and not has_mtp:
        raise ValueError("enable mtp while model has no mtp layer, please use a model with mtp layer")
    elif enable_mtp and has_mtp:
        if "mtp_loss_scaling_factor" not in engine_config.override_transformer_config:
            engine_config.override_transformer_config["mtp_loss_scaling_factor"] = (
                model_config.mtp.mtp_loss_scaling_factor
            )
    return


def patch_engine_mtp(module, model_config):
    """
    Apply MTP patches to the model module.

    Args:
        module: The model module to patch. Can be a single module or a list of modules.
        model_config: The model configuration containing MTP settings.
    """
    logger.warning("Applying mtp patch...")
    from verl.models.mcore.mtp_patch import patch_mtp_layer_get_embeddings, patch_postprocess

    print(module)

    modules = module if isinstance(module, list) else [module]
    for m in modules:
        patch_postprocess(m)
        if model_config.mtp.detach_encoder:
            patch_mtp_layer_get_embeddings(m)


@torch.no_grad()
def copy_megatron_model_to_cpu(models):
    """
    Copy Megatron model parameters to CPU memory (non-destructive copy).
    Unlike offload_megatron_model_to_cpu which moves data, this function creates
    independent copies on CPU while keeping GPU data intact.

    Args:
        models: List of model chunks (DDP-wrapped or unwrapped)

    Returns:
        dict: CPU state containing copied parameters and buffers
    """
    cpu_state = {}

    for model_idx, model_chunk in enumerate(models):
        if isinstance(model_chunk, DDP):
            # Handle DDP-wrapped models
            model_chunk_all_buffers = [model_chunk.buffers, model_chunk.expert_parallel_buffers]
            buffer_states = []

            for buffers in model_chunk_all_buffers:
                buffer_list = []
                for buffer in buffers:
                    buffer_state = {}

                    # Copy parameter data to CPU
                    if buffer.param_data.storage().size() > 0:
                        buffer_state["param_data"] = buffer.param_data.data.cpu().clone().pin_memory()

                    buffer_list.append(buffer_state)
                buffer_states.append(buffer_list)

            cpu_state[f"model_chunk_{model_idx}"] = {"buffer_states": buffer_states, "is_ddp": True}
        else:
            # Handle non-DDP models (ref module)
            model_state = {}
            for name, param in model_chunk.named_parameters():
                param_state = {"data": param.data.cpu().clone().pin_memory()}
                model_state[name] = param_state

            cpu_state[f"model_chunk_{model_idx}"] = {"model_state": model_state, "is_ddp": False}

    return cpu_state


@torch.no_grad()
def restore_megatron_model_from_cpu(models, cpu_state):
    """
    Restore Megatron model parameters from CPU memory back to GPU.

    Args:
        models: List of model chunks to restore to
        cpu_state: CPU state dict returned from copy_megatron_model_to_cpu
    """
    for model_idx, model_chunk in enumerate(models):
        chunk_key = f"model_chunk_{model_idx}"
        if chunk_key not in cpu_state:
            continue

        chunk_state = cpu_state[chunk_key]

        if chunk_state["is_ddp"] and isinstance(model_chunk, DDP):
            # Restore DDP buffers
            model_chunk_all_buffers = [model_chunk.buffers, model_chunk.expert_parallel_buffers]
            buffer_states = chunk_state["buffer_states"]

            for buffers, buffer_list in zip(model_chunk_all_buffers, buffer_states, strict=False):
                for buffer, buffer_state in zip(buffers, buffer_list, strict=False):
                    # Restore parameter data
                    if "param_data" in buffer_state:
                        buffer.param_data.data.copy_(buffer_state["param_data"].to(buffer.param_data.device))

        elif not chunk_state["is_ddp"] and not isinstance(model_chunk, DDP):
            # Restore non-DDP models
            model_state = chunk_state["model_state"]
            for name, param in model_chunk.named_parameters():
                if name in model_state:
                    param_state = model_state[name]
                    param.data.copy_(param_state["data"].to(param.device))
