import ctypes
import random
from contextlib import contextmanager
from functools import partial
from types import MethodType
from typing import Any, Callable, Iterator, List, Optional, OrderedDict, Tuple, Union

import numpy as np
import torch
import torch.distributed as dist
from torch import Tensor, inf
from torch.distributed import ProcessGroup, get_world_size
from torch.nn import Module, SyncBatchNorm
from torch.nn.parallel import DistributedDataParallel as DDP
from torch.optim import Optimizer
from torch.optim.lr_scheduler import _LRScheduler as LRScheduler
from torch.utils._pytree import tree_map
from torch.utils.data import DataLoader
from torch.utils.data.distributed import DistributedSampler

from colossalai.amp.naive_amp.mixed_precision_optimizer import MixedPrecisionOptimizer
from colossalai.checkpoint_io import CheckpointIO, HybridParallelCheckpointIO
from colossalai.cluster import ProcessGroupMesh
from colossalai.interface import ModelWrapper, OptimizerWrapper
from colossalai.pipeline.schedule import OneForwardOneBackwardSchedule
from colossalai.pipeline.stage_manager import PipelineStageManager
from colossalai.shardformer import ShardConfig, ShardFormer
from colossalai.shardformer.layer.utils import SeqParallelUtils
from colossalai.shardformer.policies.base_policy import Policy
from colossalai.tensor.d_tensor.api import is_distributed_tensor
from colossalai.zero.low_level import LowLevelZeroOptimizer

from .pp_plugin_base import PipelinePluginBase

DP_AXIS, PP_AXIS, TP_AXIS = 0, 1, 2


def _convert_floating_point(x, dtype: torch.dtype = torch.float16):
    if isinstance(x, torch.Tensor) and torch.is_floating_point(x):
        return x.to(dtype)
    return x


class HybridParallelModule(ModelWrapper):
    def __init__(
        self,
        module: Module,
        precision: str,
        shard_config: ShardConfig,
        dp_group: ProcessGroup,
        tp_group: ProcessGroup,
        use_ddp: bool,
        ddp_config: dict,
        custom_policy: Policy,
    ) -> None:
        self.stage_manager = shard_config.pipeline_stage_manager
        self.shard_config = shard_config
        self.dp_group = dp_group
        self.tp_group = tp_group
        self.use_dpp = use_ddp
        self.require_grad_sync = True

        shardformer = ShardFormer(shard_config)
        if custom_policy is not None:
            assert isinstance(custom_policy, object)
        module, self.shared_params = shardformer.optimize(module, policy=custom_policy)

        # setting process groups for shared parameters
        self.shared_param_process_groups = []
        for shared_param in self.shared_params:
            if len(shared_param) > 0:
                self.shared_param_process_groups.append(
                    self.stage_manager.init_process_group_by_stages(list(shared_param.keys()))
                )

        # setting mixed_precision
        self.mixed_precision = None
        if precision == "fp16":
            self.mixed_precision = torch.float16
        elif precision == "bf16":
            self.mixed_precision = torch.bfloat16
        if self.mixed_precision is not None:
            module = module.to(self.mixed_precision)
        module = module.cuda()

        # setting input type cast when using mixed precision
        self.convert_fn = None
        if self.mixed_precision is not None:
            self.convert_fn = partial(_convert_floating_point, dtype=self.mixed_precision)

        # setting ddp configs
        if use_ddp:
            # convert model to sync bn
            module = SyncBatchNorm.convert_sync_batchnorm(module, dp_group)
            # wrap the model with PyTorch DDP
            module = DDP(module, process_group=dp_group, **ddp_config)

        super().__init__(module)

    def sync_shared_params(self):
        for shared_param, group in zip(self.shared_params, self.shared_param_process_groups):
            if self.stage_manager.stage in shared_param:
                param = shared_param[self.stage_manager.stage]
                dist.all_reduce(param.grad, group=group)
            dist.barrier()

    @contextmanager
    def no_sync(self):
        r"""
        A context manager to disable automatic gradient synchronization (all-reduce) and allow manual synchronization
        when 'no_sync' is active. Alternatively, synchronization will occur in the first forward-backward pass
        when exiting the context.
        """

        # Store the current value of 'require_grad_sync' to restore it later.
        old_require_grad_sync = self.require_grad_sync
        # Disable automatic gradient synchronization.
        self.require_grad_sync = False
        try:
            if self.use_dpp:
                # If using data parallel processing (use_dpp), disable synchronization too.
                with self.module.no_sync():
                    yield
            else:
                yield
        finally:
            # Restore the original value of 'require_grad_sync'.
            self.require_grad_sync = old_require_grad_sync

    def sync_dp_grads(self):
        r"""
        Synchronize gradients across data parallelism (DP) if the DP group size is greater than 1.
        This function performs an all-reduce operation to combine gradients from different devices in the DP group.

        Args:
            None

        Returns:
            None
        """

        # Check if the DP group size is 1, meaning no synchronization is needed.
        if self.dp_group.size() == 1:
            return

        # Iterate through the model's parameters and perform gradient synchronization.
        for p in self.module.parameters():
            if p.grad is not None:
                # Perform all-reduce to combine gradients from different devices.
                dist.all_reduce(p.grad, group=self.dp_group)
                # Normalize the gradient by dividing it by the DP group size.
                p.grad.div_(self.dp_group.size())

    def sync_sp_grads(self, grads: Optional[List[torch.Tensor]] = None):
        r"""
        Synchronize gradients that are partially derived within sequence parallelism
        if sequence parallelism is enabled. Gradients can be provided explicitly or extracted
        from the module.

        Args:
            grads (Optional[List[torch.Tensor]]): A list of gradient tensors to synchronize. If not
                provided, gradients will be extracted from the model.

        Returns:
            None
        """

        if self.tp_group.size() > 1 and self.shard_config.enable_sequence_parallelism:
            if grads is not None:
                # Synchronize provided gradient tensors across the tensor parallelism group.
                SeqParallelUtils.allreduce_partial_data_grad(tp_group=self.tp_group, grads=grads)
            else:
                # Synchronize gradients from the model across the tensor parallelism group.
                SeqParallelUtils.allreduce_partial_data_grad(tp_group=self.tp_group, model=self.module)

    def forward(self, *args, **kwargs):
        if self.convert_fn is not None:
            args = tree_map(self.convert_fn, args)
            kwargs = tree_map(self.convert_fn, kwargs)
        return super().forward(*args, **kwargs)

    def unwrap(self):
        module = super().unwrap()
        if isinstance(module, DDP):
            module = module.module
        return module


def get_param_info(optim: Optimizer):
    # Get a backup of necessary information of parameters for future use, which includes:
    # 1. A complete param_group, with params in the form of param_id
    # 2. A mapping from param address (obtained using id(param)) to integer param_id
    # 3. A mapping from integer param_id to param address.
    # 4. A mapping from param_address (obtained using id(param)) to the original shape of parameter before sharding.
    # When Zero is used, the params here are fp16/bf16 model params rather than fp32 master params in optimizer.

    if optim is None:
        return {}
    param_info = {"param_groups": [], "param2id": {}, "id2param": {}, "param2shape": {}}
    start_index = 0
    for group in optim.param_groups:
        packed_group = {k: v for k, v in group.items() if k != "params"}
        packed_group["params"] = []

        for param_id, param in enumerate(group["params"], start_index):
            original_shape = param.shape if isinstance(param, torch.Tensor) else None
            packed_group["params"].append(param_id)
            param_info["param2id"][id(param)] = param_id
            param_info["id2param"][param_id] = id(param)
            param_info["param2shape"][id(param)] = original_shape

        param_info["param_groups"].append(packed_group)
        start_index += len(group["params"])

    return param_info


def init_pipeline_optimizer(optim: Optimizer, model: Module):
    model_params = set(model.parameters())
    new_param_groups = []
    for group in optim.param_groups:
        params = [p for p in group["params"] if p in model_params]
        new_param_groups.append({**group, "params": params})
    optim.__setstate__({"param_groups": new_param_groups})


class HybridParallelNaiveOptimizer(OptimizerWrapper):
    def __init__(
        self,
        optim: Optimizer,
        model: HybridParallelModule,
        use_pipeline: bool,
        param_info: OrderedDict,
        max_norm: float = 0,
        tp_process_group: Optional[ProcessGroup] = None,  # if using tp
        pp_process_group: Optional[ProcessGroup] = None,  # if using pp
    ):
        self.param_info = param_info
        if use_pipeline:
            init_pipeline_optimizer(optim, model)
        self.model = model
        self.stage_manager = model.stage_manager
        self.shared_params = model.shared_params
        self.max_norm = max_norm
        self.tp_pg = tp_process_group
        self.pp_pg = pp_process_group
        self.tp_size = get_world_size(self.tp_pg) if self.tp_pg is not None else 1
        self.pp_size = get_world_size(self.pp_pg) if self.pp_pg is not None else 1
        super().__init__(optim)

    def backward(self, loss: Tensor, *args, **kwargs):
        r"""
        Backpropagate gradients through the model and optionally synchronize sequence parallelism gradients.

        This method performs backward pass for gradient computation. If sequence parallelism is enabled
        and gradient synchronization is required, it will synchronize gradients that are partially derived
        within sequence parallelism across tp parallelism groups.

        Args:
            loss (Tensor): The loss tensor to compute gradients with respect to.
            *args: Additional positional arguments to be passed to the superclass backward method.
            **kwargs: Additional keyword arguments to be passed to the superclass backward method.

        Returns:
            None
        """

        # Call the superclass backward method to compute gradients.
        super().backward(loss, *args, **kwargs)

        if self.model.require_grad_sync:
            # If gradient synchronization is required, sync sequence parallelism gradients.
            self.model.sync_sp_grads()
        else:
            # If gradient synchronization is is not required, return.
            return

    def backward_by_grad(self, tensor: Tensor, grad: Tensor):
        """
        Backpropagate gradients through the model using a precomputed gradient and optionally synchronize sequence parallelism gradients.

        This method performs a backward pass for gradient computation using a precomputed gradient tensor.
        If sequence parallelism is enabled and gradient synchronization is required, it will synchronize
        gradients that are partially derived within sequence parallelism across tp parallelism groups.

        Args:
            tensor (Tensor): The input tensor for which gradients are computed.
            grad (Tensor): The precomputed gradient tensor to compute gradients with respect to the input tensor.

        Returns:
            None
        """

        # Call the superclass backward method to compute gradients.
        super().backward_by_grad(tensor, grad)

        if self.model.require_grad_sync:
            # If gradient synchronization is required, sync sequence parallelism gradients.
            self.model.sync_sp_grads()
        else:
            # If gradient synchronization is is not required, return.
            return

    def step(self, *args, **kwargs):
        r"""
        Perform an optimization step.

        Args:
            *args: Variable-length positional arguments to be passed to the optimizer's step function.
            **kwargs: Keyword arguments to be passed to the optimizer's step function.
        """

        if self.max_norm > 0:
            # Compute the total gradient norm.
            param_gradient_pairs = [
                (p, p.grad) for group in self.optim.param_groups for p in group["params"] if p.grad is not None
            ]
            total_norm = self._compute_grad_norm(param_gradient_pairs)

            # Clip the gradients to prevent exploding gradients.
            self._clip_grad_norm(total_norm)

        # Perform the optimization step using the underlying optimizer.
        self.optim.step(*args, **kwargs)

    def _compute_grad_norm(self, param_gradient_pairs: List[Tuple[Tensor]], norm_type: int = 2) -> int:
        r"""
        Compute and return the gradient norm for gradient clipping.

        Args:
            param_gradient_pairs (List[Tuple[Tensor]]): List of (parameter, gradient) pairs; gradients are used for norm calculation.
            norm_type (int, optional): Type of the norm used (e.g., 2 for L2 norm). Defaults to 2.

        Returns:
            float: The total norm of the given gradients.
        """

        if len(param_gradient_pairs) == 0:
            return 0.0

        norm_type = float(norm_type)

        # gradients used for norm calculation.
        gradients = [grad for param, grad in param_gradient_pairs]

        if norm_type == inf:
            total_norm = max(grad.data.abs().max() for grad in gradients)
            total_norm_cuda = torch.cuda.FloatTensor([float(total_norm)])
            if self.tp_size > 1:
                dist.all_reduce(tensor=total_norm_cuda, op=dist.ReduceOp.MAX, group=self.tp_pg)
            if self.pp_size > 1:
                dist.all_reduce(tensor=total_norm_cuda, op=dist.ReduceOp.MAX, group=self.pp_pg)
            total_norm = total_norm_cuda.item()
        else:
            # gradients used for norm calculation.
            gradients = [grad for param, grad in param_gradient_pairs]
            # grad_to_param_mapping is used to check which gradients are not distributed across devices of the 'tp_group'.
            grad_to_param_mapping = {id(grad): param for param, grad in param_gradient_pairs}

            total_norm_exponentiated = 0.0
            for grad in gradients:
                grad_norm_exponentiated = grad.data.double().norm(norm_type) ** norm_type

                # If 'tp_size' is greater than 1 and the parameter for the gradient is not a distributed tensor,
                # it indicates that the parameter is not distributed across devices of the 'tp_group'.
                # Consequently, there is no need to perform an 'all_reduce' operation for 'grad_norm'.
                # However, we still perform the 'all_reduce' operation for the sake of good coding practices.
                # To ensure mathematical equivalence, we divide the 'grad_norm' by 'tp_size.'
                if self.tp_size > 1:
                    param_for_grad = grad_to_param_mapping[id(grad)]
                    if not is_distributed_tensor(param_for_grad):
                        grad_norm_exponentiated /= self.tp_size

                # If 'pp_size' is greater than 1 and the gradient belongs to shared parameters,
                # it means that this parameter is used in two different pipeline stages.
                # To avoid redundant norm calculations, we divide the exponent of this norm by
                # the number of shared stages.
                if self.pp_size > 1:
                    for shared_param in self.shared_params:
                        if self.stage_manager.stage in shared_param:
                            stage_shared_param = shared_param[self.stage_manager.stage]
                            if grad is stage_shared_param.grad:
                                grad_norm_exponentiated /= len(shared_param)

                total_norm_exponentiated += grad_norm_exponentiated

            total_norm_exponentiated_cuda = torch.cuda.FloatTensor([float(total_norm_exponentiated)])
            if self.tp_size > 1:
                # compute norm in tp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.tp_pg)
            if self.pp_size > 1:
                # compute norm in pp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.pp_pg)

            # compute the total_norm
            total_norm = total_norm_exponentiated_cuda.item() ** (1.0 / norm_type)

        return total_norm

    def _clip_grad_norm(self, total_norm: float) -> None:
        r"""
        Clips the gradients of the model's parameters to prevent exploding gradients.

        Args:
            total_norm (float): The computed total gradient norm.

        Returns:
            None
        """
        clip_coef = torch.tensor(self.max_norm / (total_norm + 1e-6))
        clip_coef_clamped = torch.clamp(clip_coef, max=1.0)

        for group in self.optim.param_groups:
            for p in group["params"]:
                if p.grad is None:
                    continue
                p.grad.data.mul_(clip_coef_clamped)

    def update_master_params(self, model: Module):
        pass

    def get_working_to_master_map(self):
        return None

    def get_master_to_working_map(self):
        return None


class HybridParallelAMPOptimizer(MixedPrecisionOptimizer):
    def __init__(
        self,
        optim: Optimizer,
        model: HybridParallelModule,
        use_pipeline: bool,
        param_info: OrderedDict,
        precision: str = "fp16",
        initial_scale: float = 2**16,
        min_scale: float = 1,
        growth_factor: float = 2,
        backoff_factor: float = 0.5,
        growth_interval: int = 1000,
        hysteresis: int = 2,
        max_scale: float = 2**32,
        max_norm: float = 0,
        tp_process_group: Optional[ProcessGroup] = None,  # if using tp
        pp_process_group: Optional[ProcessGroup] = None,  # if using pp
    ):
        self.model = model
        self.param_info = param_info
        self.stage_manager = model.stage_manager
        self.shared_params = model.shared_params
        self.tp_pg = tp_process_group
        self.pp_pg = pp_process_group
        self.tp_size = get_world_size(self.tp_pg) if self.tp_pg is not None else 1
        self.pp_size = get_world_size(self.pp_pg) if self.pp_pg is not None else 1
        if use_pipeline:
            init_pipeline_optimizer(optim, model)
        super().__init__(
            optim,
            precision=precision,
            initial_scale=initial_scale,
            min_scale=min_scale,
            growth_factor=growth_factor,
            backoff_factor=backoff_factor,
            growth_interval=growth_interval,
            hysteresis=hysteresis,
            max_scale=max_scale,
            max_norm=max_norm,
        )

    def backward(self, loss: Tensor, *args, **kwargs):
        r"""
        Backpropagate gradients through the model and optionally synchronize sequence parallelism gradients.

        This method performs backward pass for gradient computation. If sequence parallelism is enabled
        and gradient synchronization is required, it will synchronize gradients that are partially derived
        within sequence parallelism across tp parallelism groups.

        Args:
            loss (Tensor): The loss tensor to compute gradients with respect to.
            *args: Additional positional arguments to be passed to the superclass backward method.
            **kwargs: Additional keyword arguments to be passed to the superclass backward method.

        Returns:
            None
        """

        # Call the superclass backward method to compute gradients.
        super().backward(loss, *args, **kwargs)

        if self.model.require_grad_sync:
            # If gradient synchronization is required, sync sequence parallelism gradients.
            self.model.sync_sp_grads()
        else:
            # If gradient synchronization is is not required, return.
            return

    def backward_by_grad(self, tensor: Tensor, grad: Tensor):
        """
        Backpropagate gradients through the model using a precomputed gradient and optionally synchronize sequence parallelism gradients.

        This method performs a backward pass for gradient computation using a precomputed gradient tensor.
        If sequence parallelism is enabled and gradient synchronization is required, it will synchronize
        gradients that are partially derived within sequence parallelism across tp parallelism groups.

        Args:
            tensor (Tensor): The input tensor for which gradients are computed.
            grad (Tensor): The precomputed gradient tensor to compute gradients with respect to the input tensor.

        Returns:
            None
        """

        # Call the superclass backward method to compute gradients.
        super().backward_by_grad(tensor, grad)

        if self.model.require_grad_sync:
            # If gradient synchronization is required, sync sequence parallelism gradients.
            self.model.sync_sp_grads()
        else:
            # If gradient synchronization is is not required, return.
            return

    def _compute_grad_norm(self, param_gradient_pairs: List[Tuple[Tensor]], norm_type: int = 2) -> int:
        r"""
        Compute and return the gradient norm for gradient clipping.

        Args:
            param_gradient_pairs (List[Tuple[Tensor]]): List of (parameter, gradient) pairs; gradients are used for norm calculation.
            norm_type (int, optional): Type of the norm used (e.g., 2 for L2 norm). Defaults to 2.

        Returns:
            float: The total norm of the given gradients.
        """
        if len(param_gradient_pairs) == 0:
            return 0.0

        norm_type = float(norm_type)

        if norm_type == inf:
            # The parent class calculates the norm of 'dp' gradients,
            # so we need to calculate the norm of 'tp' and 'pp' gradients.
            total_norm = super()._compute_grad_norm(param_gradient_pairs, norm_type)

            total_norm_cuda = torch.cuda.FloatTensor([float(total_norm)])

            if self.tp_size > 1:
                dist.all_reduce(tensor=total_norm_cuda, op=dist.ReduceOp.MAX, group=self.tp_pg)
            if self.pp_size > 1:
                dist.all_reduce(tensor=total_norm_cuda, op=dist.ReduceOp.MAX, group=self.pp_pg)

            total_norm = total_norm_cuda.item()

        else:
            # gradients used for norm calculation.
            gradients = [grad for param, grad in param_gradient_pairs]
            # grad_to_param_mapping is used to check which gradients are not distributed in tensor parallelism.
            grad_to_param_mapping = {id(grad): param for param, grad in param_gradient_pairs}

            total_norm_exponentiated = 0.0
            for grad in gradients:
                grad_norm_exponentiated = grad.data.double().norm(norm_type) ** norm_type

                # If 'tp_size' is greater than 1 and the parameter for the gradient is not a distributed tensor,
                # it indicates that the parameter is not distributed across devices of the 'tp_group'.
                # Consequently, there is no need to perform an 'all_reduce' operation for 'grad_norm'.
                # However, we still perform the 'all_reduce' operation for the sake of good coding practices.
                # To ensure mathematical equivalence, we divide the 'grad_norm' by 'tp_size.'
                if self.tp_size > 1:
                    param_for_grad = grad_to_param_mapping[id(grad)]
                    if not is_distributed_tensor(param_for_grad):
                        grad_norm_exponentiated /= self.tp_size

                # If 'pp_size' is greater than 1 and the gradient belongs to shared parameters,
                # it means that this parameter is used in two different pipeline stages.
                # To avoid redundant norm calculations, we divide the exponent of this norm by
                # the number of shared stages.
                if self.pp_size > 1:
                    for shared_param in self.shared_params:
                        if self.stage_manager.stage in shared_param:
                            stage_working_shared_param = shared_param[self.stage_manager.stage]
                            stage_master_shared_param = self.working_to_master_map[stage_working_shared_param]
                            if grad is stage_master_shared_param.grad:
                                grad_norm_exponentiated /= len(shared_param)

                total_norm_exponentiated += grad_norm_exponentiated

            total_norm_exponentiated_cuda = torch.cuda.FloatTensor([float(total_norm_exponentiated)])
            if self.tp_size > 1:
                # compute norm in tp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.tp_pg)
            if self.pp_size > 1:
                # compute norm in pp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.pp_pg)

            # compute the total_norm
            total_norm = total_norm_exponentiated_cuda.item() ** (1.0 / norm_type)

        return total_norm


class HybridParallelZeroOptimizer(LowLevelZeroOptimizer):
    def __init__(
        self,
        optimizer: Optimizer,
        model: HybridParallelModule,
        use_pipeline: bool,
        param_info: OrderedDict,
        initial_scale: int = 2**16,  # grad scaler config
        min_scale: int = 1,
        growth_factor: float = 2.0,
        backoff_factor: float = 0.5,
        growth_interval: int = 2000,
        hysteresis: int = 2,
        max_scale: int = 2**24,
        clip_grad_norm: float = 0.0,  # grad clipping
        verbose: bool = False,
        reduce_bucket_size: int = 1024 * 1024,  # communication
        communication_dtype: Optional[torch.dtype] = None,
        overlap_communication: bool = True,
        partition_grad: bool = False,  # stage 2 flag
        cpu_offload: bool = False,  # cpu offload
        dp_process_group: Optional[ProcessGroup] = None,  # the dp pg for comm
        tp_process_group: Optional[ProcessGroup] = None,  # if using tp
        pp_process_group: Optional[ProcessGroup] = None,  # if using pp
        forced_dtype: Optional[torch.dtype] = None,
    ):
        self.model = model
        self.param_info = param_info
        self.stage_manager = model.stage_manager
        self.shared_params = model.shared_params
        self.dp_pg = dp_process_group
        self.tp_pg = tp_process_group
        self.pp_pg = pp_process_group
        if use_pipeline:
            init_pipeline_optimizer(optimizer, model)
        super().__init__(
            optimizer=optimizer,
            initial_scale=initial_scale,
            min_scale=min_scale,
            growth_factor=growth_factor,
            backoff_factor=backoff_factor,
            growth_interval=growth_interval,
            hysteresis=hysteresis,
            max_scale=max_scale,
            clip_grad_norm=clip_grad_norm,
            verbose=verbose,
            reduce_bucket_size=reduce_bucket_size,
            communication_dtype=communication_dtype,
            overlap_communication=overlap_communication,
            partition_grad=partition_grad,
            cpu_offload=cpu_offload,
            dp_process_group=dp_process_group,
            forced_dtype=forced_dtype,
        )

    def sync_dp_grads(self):
        r"""
        Synchronize gradients in the data parallelism dimension.

        This method wraps the existing `_sync_grad` method in order to explicitly synchronize gradients
        in the data parallelism dimension. It is necessary due to the introduction of new parallel dimensions,
        namely tp (tensor parallelism) and pp (pipeline parallelism). This ensures better code organization
        and readability.

        Args:
            None

        Returns:
            None
        """

        # Call the superclass `_sync_grad` method to synchronize gradients.
        super()._sync_grad()

    def _sync_sp_grads(self):
        r"""
        Synchronize gradients that are partially derived within sequence parallelism.

        This method is responsible for synchronizing partially derived gradients across tp parallelism groups.
        It identifies gradients that ara partially derived or not and synchronizes them.
        If synchronization is required and gradients are found to be synchronized,
        it performs the synchronization.

        Args:
            None

        Returns:
            None
        """

        def _get_all_working_grads() -> List[Tensor]:
            """Retrieve all working gradients from different parameter groups."""
            all_working_grads = []
            for group_id in range(self.num_param_groups):
                working_grads = self._grad_store.get_working_grads_by_group_id(group_id)
                all_working_grads.extend(working_grads)
            return all_working_grads

        def _get_grads_to_sync(all_working_grads) -> Union[List[Tensor], None]:
            """Identify gradients to be synchronized in the sequence parallelism."""
            grads_to_sync = []
            for grad in all_working_grads:
                param_id_for_grad = self._grad_store.get_param_id_for_grad(grad)
                param_for_grad = ctypes.cast(param_id_for_grad, ctypes.py_object).value
                if SeqParallelUtils.is_sp_partial_derived_param(param_for_grad):
                    grads_to_sync.append(grad)

            if len(grads_to_sync) > 0:
                return grads_to_sync
            else:
                return None

        # Get all working gradients and gradients to be synchronized.
        all_working_grads = _get_all_working_grads()
        grads_to_sync = _get_grads_to_sync(all_working_grads)

        if self.require_grad_sync and grads_to_sync is not None:
            # Synchronize sequence parallelism gradients if required.
            SeqParallelUtils.allreduce_partial_data_grad(tp_group=self.tp_pg, grads=grads_to_sync)
        else:
            return

    def backward(self, loss, retain_graph=False):
        """
        Backpropagate gradients through the model and optionally synchronize sequence parallelism gradients.

        This method performs the backward pass for gradient computation based on a given loss tensor.
        If sequence parallelism is enabled and gradient synchronization is required, it will synchronize
        gradients that are partially derived within sequence parallelism across TP parallelism groups.

        Args:
            loss: The loss tensor to compute gradients with respect to.
            retain_graph (bool): Whether to retain the computation graph.

        Returns:
            None
        """
        # Call the superclass backward method to compute gradients.
        super().backward(loss, retain_graph)

        if self.require_grad_sync and self.model.shard_config.enable_sequence_parallelism:
            # If gradient synchronization is required, sync sequence parallelism gradients.
            self._sync_sp_grads()
        else:
            # If gradient synchronization is is not required, return.
            return

    def backward_by_grad(self, tensor, grad):
        """
        Backpropagate gradients through the model using a precomputed gradient and optionally synchronize sequence parallelism gradients.

        This method performs a backward pass for gradient computation based on a precomputed gradient tensor.
        If sequence parallelism is enabled and gradient synchronization is required, it will synchronize
        gradients that are partially derived within sequence parallelism across TP parallelism groups.

        Args:
            tensor: The input tensor for which gradients are computed.
            grad: The precomputed gradient tensor to compute gradients with respect to the input tensor.

        Returns:
            None
        """
        # Call the superclass backward_by_grad method to compute gradients.
        super().backward_by_grad(tensor, grad)

        if self.require_grad_sync and self.model.shard_config.enable_sequence_parallelism:
            # If gradient synchronization is required, sync sequence parallelism gradients.
            self._sync_sp_grads()
        else:
            # If gradient synchronization is is not required, return.
            return

    def _compute_grad_norm(self, gradients: List[Tensor], norm_type: int = 2) -> float:
        r"""
        Compute and return the gradient norm for gradient clipping.

        Args:
            gradients (List[Tensor]): A list of tensors containing gradients.
            norm_type (int, optional): Type of the p-norm to be computed. Defaults to 2.

        Returns:
            float: The computed gradient norm.
        """

        # Check if the list of gradients is empty
        if len(gradients) == 0:
            return 0.0

        dp_size = get_world_size(self.dp_pg) if self.dp_pg is not None else 1
        tp_size = get_world_size(self.tp_pg) if self.tp_pg is not None else 1
        pp_size = get_world_size(self.pp_pg) if self.pp_pg is not None else 1
        norm_type = float(norm_type)

        if norm_type == inf:
            # The parent class calculates the norm of 'dp' gradients,
            # so we only need to calculate the norm 'tp' of 'pp' gradients.
            total_norm = super()._compute_grad_norm(gradients, norm_type)

            total_norm_cuda = torch.cuda.FloatTensor([float(total_norm)])

            if tp_size > 1:
                dist.all_reduce(tensor=total_norm_cuda, op=dist.ReduceOp.MAX, group=self.tp_pg)
            if pp_size > 1:
                dist.all_reduce(tensor=total_norm_cuda, op=dist.ReduceOp.MAX, group=self.pp_pg)

            total_norm = total_norm_cuda.item()
        else:
            total_norm_exponentiated = 0.0
            for grad in gradients:
                grad_norm_exponentiated = grad.data.double().norm(norm_type) ** norm_type

                # If 'tp_size' is greater than 1 and the parameter for the gradient is not a distributed tensor,
                # it indicates that the parameter is not distributed across devices of the 'tp_group'.
                # Consequently, there is no need to perform an 'all_reduce' operation for 'grad_norm'.
                # However, we still perform the 'all_reduce' operation for the sake of good coding practices.
                # To ensure mathematical equivalence, we divide the 'grad_norm' by 'tp_size.'
                if tp_size > 1:
                    param_id_for_grad = self._grad_store.get_param_id_for_grad(grad)
                    param_for_grad = ctypes.cast(param_id_for_grad, ctypes.py_object).value

                    if not is_distributed_tensor(param_for_grad):
                        grad_norm_exponentiated /= tp_size

                # If 'pp_size' is greater than 1 and the gradient belongs to shared parameters,
                # it means that this parameter is used in two different pipeline stages.
                # To avoid redundant norm calculations, we divide the exponent of this norm by
                # the number of shared stages.
                if pp_size > 1:
                    for shared_param in self.shared_params:
                        if self.stage_manager.stage in shared_param:
                            stage_shared_param = shared_param[self.stage_manager.stage]
                            working_grad = self._grad_store.get_working_grad_by_param_id(id(stage_shared_param))
                            if grad is working_grad:
                                grad_norm_exponentiated /= len(shared_param)

                total_norm_exponentiated += grad_norm_exponentiated

            total_norm_exponentiated_cuda = torch.cuda.FloatTensor([float(total_norm_exponentiated)])
            if dp_size > 1:
                # compute norm in dp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.dp_pg)
            if tp_size > 1:
                # compute norm in tp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.tp_pg)
            if pp_size > 1:
                # compute norm in pp process group
                dist.all_reduce(tensor=total_norm_exponentiated_cuda, op=dist.ReduceOp.SUM, group=self.pp_pg)

            # Compute the 'total_norm' from 'total_norm_exponentiated'
            total_norm = total_norm_exponentiated_cuda.item() ** (1.0 / norm_type)

        return total_norm


class HybridParallelPlugin(PipelinePluginBase):
    """
    Plugin for Hybrid Parallel Training.
    Tensor parallel, pipeline parallel and data parallel(DDP/ZeRO) can be picked and combined in this plugin.
    The size of tp and pp should be passed in by user, then the size of dp is automatically calculated from dp_size = world_size / (tp_size * pp_size).

    ```python
    from colossalai.booster import Booster
    from colossalai.booster.plugin import HybridParallelPlugin

    model, train_dataset, optimizer, criterion = ...
    plugin =  HybridParallelPlugin(tp_size=2, pp_size=2)

    train_dataloader = plugin.prepare_dataloader(train_dataset, batch_size=8)
    booster = Booster(plugin=plugin)
    model, optimizer, criterion, train_dataloader, _ = booster.boost(model, optimizer, criterion, train_dataloader)
    ```

    Args:
        tp_size (int): The size of tensor parallelism. Tensor parallelism will not be used when tp_size is set to 1.
        pp_size (int): The number of pipeline stages in pipeline parallelism. Pipeline parallelism will not be used when pp_size is set to 1.
        precision (str, optional): Specifies the precision of parameters during training.
                                    Auto-mixied precision will be used when this argument is set to 'fp16' or 'bf16', otherwise model is trained with 'fp32'.
                                    Defaults to 'fp16'.
        zero_stage (int, optional): The stage of ZeRO for data parallelism. Can only be choosed from [0, 1, 2].
                                        When set to 0, ZeRO will not be used. Defaults to 0.
        enable_all_optimization (bool, optional): Whether to switch on all the optimizations supported by Shardformer.
                                                    Currently all the optimization methods include fused normalization, flash attention and JIT.
                                                    Defaults to False.
        enable_fused_normalization (bool, optional): Whether to switch on fused normalization in Shardformer. Defaults to False.
        enable_flash_attention (bool, optional): Whether to switch on flash attention in Shardformer. Defaults to False.
        enable_jit_fused (bool, optional): Whether to switch on JIT in Shardformer. Default to False.
        enable_sequence_parallelism (bool): Whether to turn on sequence parallelism in Shardformer. Defaults to False.
        enable_sequence_overlap (bool): Whether to turn on sequence overlap in Shardformer. Defaults to False.
        num_microbatches (int, optional): Number of microbatches when using pipeline parallelism. Defaults to None.
        microbatch_size (int, optional): Microbatch size when using pipeline parallelism.
            Either ``num_microbatches`` or ``microbatch_size`` should be provided if using pipeline.
            If ``num_microbatches`` is provided, this will be ignored. Defaults to None.
        initial_scale (float, optional): The initial loss scale of AMP. Defaults to 2**16.
        min_scale (float, optional): The minimum loss scale of AMP. Defaults to 1.
        growth_factor (float, optional): The multiplication factor for increasing loss scale when using AMP. Defaults to 2.
        backoff_factor (float, optional): The multiplication factor for decreasing loss scale when using AMP. Defaults to 0.5.
        growth_interval (int, optional): The number of steps to increase loss scale when no overflow occurs when using AMP. Defaults to 1000.
        hysteresis (int, optional):  The number of overflows before decreasing loss scale when using AMP. Defaults to 2.
        max_scale (float, optional): The maximum loss scale of AMP. Defaults to 2**32.
        max_norm (float, optional): Maximum norm for gradient clipping. Defaults to 0.
        broadcast_buffers (bool, optional): Whether to broadcast buffers in the beginning of training when using DDP. Defaults to True.
        ddp_bucket_cap_mb (int, optional): The bucket size in MB when using DDP. Defaults to 25.
        find_unused_parameters (bool, optional): Whether to find unused parameters when using DDP. Defaults to False.
        check_reduction (bool, optional): Whether to check reduction when using DDP. Defaults to False.
        gradient_as_bucket_view (bool, optional): Whether to use gradient as bucket view when using DDP. Defaults to False.
        static_graph (bool, optional): Whether to use static graph when using DDP. Defaults to False.
        zero_bucket_size_in_m (int, optional): Gradient reduce bucket size in million elements when using ZeRO. Defaults to 12.
        cpu_offload (bool, optional): Whether to open cpu_offload when using ZeRO. Defaults to False.
        communication_dtype (torch.dtype, optional): Communication dtype when using ZeRO. If not specified, the dtype of param will be used. Defaults to None.
        overlap_communication (bool, optional): Whether to overlap communication and computation when using ZeRO. Defaults to True.
        custom_policy (Policy, optional): Custom policy for Shardformer. Defaults to None.
    """

    def __init__(
        self,
        tp_size: int,
        pp_size: int,
        precision: str = "fp16",
        zero_stage: int = 0,
        enable_all_optimization: bool = False,
        enable_fused_normalization: bool = False,
        enable_flash_attention: bool = False,
        enable_jit_fused: bool = False,
        enable_sequence_parallelism: bool = False,
        enable_sequence_overlap: bool = False,
        num_microbatches: Optional[int] = None,
        microbatch_size: Optional[int] = None,
        initial_scale: float = 2**16,
        min_scale: float = 1,
        growth_factor: float = 2,
        backoff_factor: float = 0.5,
        growth_interval: int = 1000,
        hysteresis: int = 2,
        max_scale: float = 2**32,
        max_norm: float = 0,
        broadcast_buffers: bool = True,
        ddp_bucket_cap_mb: int = 25,
        find_unused_parameters: bool = False,
        check_reduction: bool = False,
        gradient_as_bucket_view: bool = False,
        static_graph: bool = False,
        zero_bucket_size_in_m: int = 12,
        cpu_offload: bool = False,
        communication_dtype: Optional[torch.dtype] = None,
        overlap_communication: bool = True,
        custom_policy: Policy = None,
    ) -> None:
        super().__init__()
        assert (
            dist.get_world_size() % (tp_size * pp_size) == 0
        ), f"world size {dist.get_world_size()} is not divisible by tp_size {tp_size} * pp_size {pp_size}"

        if enable_sequence_parallelism:
            assert tp_size > 1, "Sequence parallelism must be enabled when using tensor parallelism"

        self.tp_size = tp_size
        self.pp_size = pp_size
        self.dp_size = dist.get_world_size() // (tp_size * pp_size)
        self.precision = precision
        self.zero_stage = zero_stage
        self.cpu_offload = cpu_offload
        self.enable_all_optimization = enable_all_optimization
        self.enable_fused_normalization = enable_fused_normalization
        self.enable_flash_attention = enable_flash_attention
        self.enable_jit_fused = enable_jit_fused
        self.enable_sequence_parallelism = enable_sequence_parallelism
        self.pg_mesh = ProcessGroupMesh(self.dp_size, self.pp_size, self.tp_size)
        self.stage_manager = None
        self.schedule = None
        self.custom_policy = custom_policy
        assert zero_stage in (0, 1, 2)
        if self.pp_size > 1:
            assert (
                num_microbatches is not None or microbatch_size is not None
            ), "num_microbatches or microbatch_size must be specified when using pipeline parallelism"
            assert self.zero_stage <= 1, "zero stage must be 0 or 1 when using pipeline parallelism"
            self.stage_manager = PipelineStageManager(self.pg_mesh, PP_AXIS)
            self.schedule = OneForwardOneBackwardSchedule(
                self.stage_manager, num_microbatches=num_microbatches, microbatch_size=microbatch_size
            )
        self.tp_group = self.pg_mesh.get_group_along_axis(TP_AXIS)
        self.dp_group = self.pg_mesh.get_group_along_axis(DP_AXIS)
        self.pp_group = self.pg_mesh.get_group_along_axis(PP_AXIS)
        self.shard_config = ShardConfig(
            tensor_parallel_process_group=self.tp_group,
            pipeline_stage_manager=self.stage_manager,
            enable_tensor_parallelism=self.tp_size > 1,
            enable_all_optimization=self.enable_all_optimization,
            enable_fused_normalization=self.enable_fused_normalization,
            enable_flash_attention=self.enable_flash_attention,
            enable_jit_fused=self.enable_jit_fused,
            enable_sequence_parallelism=enable_sequence_parallelism,
            enable_sequence_overlap=enable_sequence_overlap,
        )
        self.amp_config = dict(
            initial_scale=initial_scale,
            growth_factor=growth_factor,
            backoff_factor=backoff_factor,
            growth_interval=growth_interval,
            hysteresis=hysteresis,
            min_scale=min_scale,
            max_scale=max_scale,
        )

        self.ddp_config = dict(
            broadcast_buffers=broadcast_buffers,
            bucket_cap_mb=ddp_bucket_cap_mb,
            find_unused_parameters=find_unused_parameters,
            check_reduction=check_reduction,
            gradient_as_bucket_view=gradient_as_bucket_view,
            static_graph=static_graph,
        )

        self.zero_config = dict(
            reduce_bucket_size=zero_bucket_size_in_m * 1024 * 1024,
            communication_dtype=communication_dtype,
            overlap_communication=overlap_communication,
            cpu_offload=cpu_offload,
            partition_grad=(self.zero_stage == 2),
        )

        self.max_norm = max_norm

    @property
    def enable_pipeline_parallelism(self) -> bool:
        return self.pp_size > 1

    def supported_devices(self) -> List[str]:
        return ["cuda"]

    def supported_precisions(self) -> List[str]:
        return ["fp16", "bf16", "fp32"]

    def control_device(self) -> bool:
        return True

    def control_precision(self) -> bool:
        return True

    def support_no_sync(self) -> bool:
        return False

    def control_checkpoint_io(self) -> bool:
        return True

    def configure(
        self,
        model: Module,
        optimizer: Optional[Optimizer] = None,
        criterion: Optional[Callable] = None,
        dataloader: Optional[DataLoader] = None,
        lr_scheduler: Optional[LRScheduler] = None,
    ) -> Tuple[Module, OptimizerWrapper, Callable, DataLoader, LRScheduler]:
        param_info = get_param_info(optimizer)
        if not isinstance(model, ModelWrapper):
            use_ddp = self.dp_size > 1 and self.pp_size == 1 and self.zero_stage == 0
            model = HybridParallelModule(
                model,
                precision=self.precision,
                shard_config=self.shard_config,
                dp_group=self.dp_group,
                tp_group=self.tp_group,
                use_ddp=use_ddp,
                ddp_config=self.ddp_config,
                custom_policy=self.custom_policy,
            )
        if optimizer is not None and not isinstance(optimizer, OptimizerWrapper):
            if self.zero_stage == 0:
                if self.precision in ["fp16", "bf16"]:
                    optimizer = HybridParallelAMPOptimizer(
                        optimizer,
                        model,
                        use_pipeline=self.enable_pipeline_parallelism,
                        param_info=param_info,
                        precision=self.precision,
                        max_norm=self.max_norm,
                        pp_process_group=self.pp_group,
                        tp_process_group=self.tp_group,
                        **self.amp_config,
                    )
                else:
                    optimizer = HybridParallelNaiveOptimizer(
                        optimizer,
                        model,
                        use_pipeline=self.enable_pipeline_parallelism,
                        param_info=param_info,
                        max_norm=self.max_norm,
                        pp_process_group=self.pp_group,
                        tp_process_group=self.tp_group,
                    )
            else:
                assert self.dp_size > 1, "Please use Zero when data parallel size is greater than 1."
                assert self.precision != "fp32", "Please set precision to 'fp16' or 'bf16' when using ZeRO."
                optimizer = HybridParallelZeroOptimizer(
                    optimizer,
                    model,
                    use_pipeline=self.enable_pipeline_parallelism,
                    param_info=param_info,
                    dp_process_group=self.dp_group,
                    tp_process_group=self.tp_group,
                    pp_process_group=self.pp_group,
                    verbose=True,
                    clip_grad_norm=self.max_norm,
                    **self.zero_config,
                    **self.amp_config,
                )
            # inject update_master_params
            model.update_master_params = MethodType(optimizer.update_master_params, model)
        return model, optimizer, criterion, dataloader, lr_scheduler

    def execute_pipeline(
        self,
        data_iter: Iterator,
        model: HybridParallelModule,
        criterion: Callable[[Any, Any], torch.Tensor],
        optimizer: Optional[
            Union[HybridParallelNaiveOptimizer, HybridParallelAMPOptimizer, HybridParallelZeroOptimizer]
        ] = None,
        return_loss: bool = True,
        return_outputs: bool = False,
    ) -> dict:
        assert self.enable_pipeline_parallelism, "pipeline parallelism is not enabled"

        # Create a context for gradient synchronization based on the optimizer type.
        # If it's a HybridParallelZeroOptimizer, use optimizer.no_sync(); otherwise, use model.no_sync().
        # This is to avoid redundant gradient reduction in pipeline parallelism (multiple microbatch values should be reduced once),
        # so we disable it, performing manual reduction instead.
        ctx = optimizer.no_sync() if isinstance(optimizer, HybridParallelZeroOptimizer) else model.no_sync()

        with ctx:
            outputs = self.schedule.forward_backward_step(
                model, data_iter, criterion, optimizer, return_loss, return_outputs
            )

        # Synchronize the grads of shared parameters of the model.
        model.sync_shared_params()

        # Synchronize sequence parallelism gradients of the model.
        model.sync_sp_grads()

        # Check if the optimizer is a HybridParallelZeroOptimizer and synchronize data parallelism gradients if so.
        # Otherwise, synchronize data parallelism gradients of the model.
        # This is because these are two different forms of data parallelism.
        if isinstance(optimizer, HybridParallelZeroOptimizer):
            optimizer.sync_dp_grads()
        else:
            model.sync_dp_grads()

        return outputs

    def prepare_dataloader(
        self, dataset, batch_size, shuffle=False, seed=1024, drop_last=False, pin_memory=False, num_workers=0, **kwargs
    ):
        r"""
        Prepare a dataloader for distributed training. The dataloader will be wrapped by
        `torch.utils.data.DataLoader` and `torch.utils.data.DistributedSampler`.


        Args:
            dataset (`torch.utils.data.Dataset`): The dataset to be loaded.
            shuffle (bool, optional): Whether to shuffle the dataset. Defaults to False.
            seed (int, optional): Random worker seed for sampling, defaults to 1024.
            add_sampler: Whether to add ``DistributedDataParallelSampler`` to the dataset. Defaults to True.
            drop_last (bool, optional): Set to True to drop the last incomplete batch, if the dataset size
                is not divisible by the batch size. If False and the size of dataset is not divisible by
                the batch size, then the last batch will be smaller, defaults to False.
            pin_memory (bool, optional): Whether to pin memory address in CPU memory. Defaults to False.
            num_workers (int, optional): Number of worker threads for this dataloader. Defaults to 0.
            kwargs (dict): optional parameters for ``torch.utils.data.DataLoader``, more details could be found in
                    `DataLoader <https://pytorch.org/docs/stable/_modules/torch/utils/data/dataloader.html#DataLoader>`_.

        Returns:
            :class:`torch.utils.data.DataLoader`: A DataLoader used for training or testing.
        """
        _kwargs = kwargs.copy()
        sampler = DistributedSampler(
            dataset, num_replicas=self.pg_mesh.size(DP_AXIS), rank=self.pg_mesh.coordinate(DP_AXIS), shuffle=shuffle
        )

        # Deterministic dataloader
        def seed_worker(worker_id):
            worker_seed = seed
            np.random.seed(worker_seed)
            torch.manual_seed(worker_seed)
            random.seed(worker_seed)

        return DataLoader(
            dataset,
            batch_size=batch_size,
            sampler=sampler,
            worker_init_fn=seed_worker,
            drop_last=drop_last,
            pin_memory=pin_memory,
            num_workers=num_workers,
            **_kwargs,
        )

    def get_checkpoint_io(self) -> CheckpointIO:
        return HybridParallelCheckpointIO(self.dp_group, self.pp_group, self.tp_group, self.zero_stage)

    def no_sync(self, model: Module) -> Iterator[None]:
        raise NotImplementedError
