# Copyright (c) 2022-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
#
# See LICENSE for license information.

"""This module provides predefined FP8 recipes."""
from __future__ import annotations
import os
from enum import Enum
from typing import Any, Literal, Optional, Union, Callable, NamedTuple
from dataclasses import field
from pydantic.dataclasses import dataclass
from torch.utils.cpp_extension import IS_HIP_EXTENSION

class _FormatHelper(NamedTuple):
    """
    Stores max FP8 values for fprop and bprop a `Format`.
    """

    max_fwd: float
    max_bwd: float


class Format(Enum):
    """
    Supported FP8 formats.
    Supported FP4 formats.

    Values
    ------
    E2M1 :
          All FP4 tensors are in e2m1 format
    E4M3 :
          All FP8 tensors are in e4m3 format
    E5M2 :
          All FP8 tensors are in e5m2 format
    HYBRID :
            FP8 tensors in the forward pass are in e4m3 format,
            FP8 tensors in the backward pass are in e5m2 format
    """

    E2M1 = _FormatHelper(max_fwd=6, max_bwd=6)
    E4M3 = _FormatHelper(max_fwd=448, max_bwd=448)
    E5M2 = _FormatHelper(max_fwd=57344, max_bwd=57344)
    HYBRID = _FormatHelper(max_fwd=E4M3.max_fwd, max_bwd=E5M2.max_bwd)


@dataclass(frozen=True)
class MMParams:
    """Matrix multiplication options.

    Parameters
    ----------
    use_split_accumulator : bool, default = True
        Use FP8 fast accumulation on Hopper or Ada. For more details,
        see CUBLASLT_MATMUL_DESC_FAST_ACCUM option for cublasLtMatmul.
    """

    use_split_accumulator: bool = True


@dataclass(frozen=True)
class QParams:
    """Quantization parameters.
    power_2_scale: use power of 2 scale parameter
    amax_epsilon: optional minimum value of abs max
    random_hadamard_transform: whether to use random hadamard transform
    stochastic_rounding: whether to use stocastic rounding
    """

    power_2_scale: bool = False
    amax_epsilon: float = 0.0
    random_hadamard_transform: bool = False
    stochastic_rounding: bool = False
    fp4_2d_quantization: bool = False

    def __repr__(self) -> str:
        return (
            f"Qparams(\npower_2_scale={self.power_2_scale},\n"
            f"amax_epsilon={self.amax_epsilon},\n"
            f"random_hadamard_transform={self.random_hadamard_transform},\n"
            f"stochastic_rounding={self.stochastic_rounding},\n"
            f"fp4_2d_quantization={self.fp4_2d_quantization}\n)"
        )


class Recipe:
    """
    Base recipe class.
    """

    @classmethod
    def nvfp4(cls):
        """Whether the given recipe is NVFP4 1D block scaling."""
        return issubclass(cls, NVFP4BlockScaling)

    @classmethod
    def mxfp8(cls):
        """Whether the given recipe is MXFP8 block scaling."""
        return issubclass(cls, MXFP8BlockScaling)

    @classmethod
    def delayed(cls):
        """Whether the given recipe is delayed scaling."""
        return issubclass(cls, DelayedScaling)

    @classmethod
    def float8_current_scaling(cls):
        """Whether the given recipe is (per-tensor) current scaling."""
        return issubclass(cls, Float8CurrentScaling)

    @classmethod
    def float8_per_tensor_scaling(cls):
        """Whether the given recipe is per-tensor scaling."""
        return issubclass(cls, (DelayedScaling, Float8CurrentScaling))

    @classmethod
    def float8_block_scaling(cls):
        """Whether the given recipe is float8 blockwise scaling."""
        return issubclass(cls, Float8BlockScaling)

    @classmethod
    def custom(cls):
        """Whether the given recipe is custom."""
        return issubclass(cls, CustomRecipe)


@dataclass()
class DelayedScaling(Recipe):
    """
    Use the delayed scaling factor strategy. Use scale factor from previous
    iteration and record amax history of `amax_history_len` steps.

    Parameters
    ----------
    margin : int, default = 0
            Margin for the scaling factor computation.
    fp8_format : {Format.E4M3, Format.HYBRID}, default = Format.HYBRID
                Controls the FP8 data format used during forward and backward
                pass.
    amax_history_len : int, default = 1024
                      The length of the amax history window used for
                      scaling factor computation.
    amax_compute_algo : {'max', 'most_recent', Callable}, default = 'max'
                       Algorithm used for choosing the `amax` value for the
                       scaling factor computation. There are 2 predefined
                       choices: `max` chooses the largest `amax` in the history
                       window, while `most_recent` always chooses the most recently
                       seen value. Alternatively, one may pass a function of the
                       signature:

                       .. code-block:: python

                         def amax_compute(amax_history: Tensor) -> Tensor

                       where `Tensor` is a framework tensor type.
    scaling_factor_compute_algo : Callable, default = None
                                 Algorithm used for computing the new scaling
                                 factor based on the value of `amax`. It should
                                 be a function of the signature:

                                 .. code-block:: python

                                   def scaling_factor_compute(amax: Tensor,
                                                              old_scaling_factor: Tensor,
                                                              fp8_max: Tensor,
                                                              recipe: DelayedScaling) -> Tensor

                                 where `Tensor` is a framework tensor type.
    reduce_amax: bool, default = True
                By default, if `torch.distributed` is initialized, the `amax` value for FP8
                tensors is reduced across the `amax_reduction_group` (specified in the `autocast`
                call). This keeps the amaxes and scaling factors synced across the given
                distributed group. If set to `False`, this reduction is skipped and every
                GPU maintains local amaxes and scaling factors. To ensure results are
                numerically identical across checkpointing boundaries in this case, all
                ranks must checkpoint in order to store the local tensors.
    fp8_dpa: bool, default = False
             Whether to enable FP8 dot product attention (DPA). When the model is placed in an
             `autocast(enabled=True)` region and `fp8_dpa` is set to `True`, DPA casts the
             inputs from higher precision to FP8, performs attention in FP8, and casts tensors
             back to higher precision as outputs. FP8 DPA currently is only supported in the
             `FusedAttention` backend.
    fp8_mha: bool, default = False
            Whether to enable FP8 multi-head attention (MHA). When `True`, it removes the casting
            operations mentioned above at the DPA boundaries. Currently only standard MHA modules
            i.e. `LayerNormLinear/Linear + DPA + Linear`, are supported for this feature. When
            `fp8_mha = False, fp8_dpa = True`, a typical MHA module works as
            `LayerNormLinear (BF16 output) -> (cast to FP8 ) FP8 DPA (cast to BF16) -> Linear`.
            When `fp8_mha = True, fp8_dpa = True`, it becomes
            `LayerNormLinear (FP8 output) -> FP8 DPA -> Linear`.

    Notes
    -----
    * By default (when `scaling_factor_compute_algo` is left as `None`) the scaling
      factor is computed from the final `amax` value using the formula:

      .. code-block:: python

          FP8_MAX = maximum_representable_value(fp8_format)
          new_scaling_factor = (FP8_MAX / amax) / (2 ^ margin)

    * `fp8_dpa` and `fp8_mha` are Beta features, and their API and functionality are
      subject to change in future Transformer Engine releases.
    """

    margin: int = 0
    fp8_format: Format = Format.HYBRID
    amax_history_len: int = 1024
    amax_compute_algo: Union[Literal["max", "most_recent"], Callable] = "max"
    scaling_factor_compute_algo: Optional[Callable] = None
    reduce_amax: bool = True
    fp8_dpa: bool = False
    fp8_mha: bool = False

    def __post_init__(self) -> None:
        assert self.fp8_format != Format.E5M2, "Pure E5M2 training is not supported."

    def __repr__(self) -> str:
        return (
            f"recipe_type={self.__class__.__name__}, "
            f"margin={self.margin}, "
            f"format={str(self.fp8_format).split('.')[1]}, "
            f"amax_history_len={self.amax_history_len}, "
            f"reduce_amax={self.reduce_amax}, "
            f"fp8_dpa={self.fp8_dpa}, "
            f"fp8_mha={self.fp8_mha}"
        )


@dataclass()
class Float8CurrentScaling(Recipe):
    """
    Use the per-tensor current scaling factor strategy.

    Parameters
    ----------
    fp8_format : {Format.E4M3, Format.HYBRID}, default = Format.HYBRID
                Controls the FP8 data format used during forward and backward
                pass.
    """

    use_power_2_scales: bool = os.getenv("NVTE_FP8_CURRENT_SCALING_POWER_2_SCALES", "0") == "1"
    fp8_format: Format = Format.HYBRID
    fp8_quant_fwd_inp = QParams(power_2_scale=use_power_2_scales, amax_epsilon=0.0)
    fp8_quant_fwd_weight = QParams(power_2_scale=use_power_2_scales, amax_epsilon=0.0)
    fp8_quant_bwd_grad = QParams(power_2_scale=use_power_2_scales, amax_epsilon=0.0)
    fp8_gemm_fprop: MMParams = MMParams(use_split_accumulator=False)
    fp8_gemm_dgrad: MMParams = MMParams(use_split_accumulator=True)
    fp8_gemm_wgrad: MMParams = MMParams(use_split_accumulator=True)
    fp8_dpa: bool = False
    fp8_mha: bool = False

    def __post_init__(self) -> None:
        assert self.fp8_format != Format.E5M2, "Pure E5M2 training is not supported."

    def __repr__(self) -> str:
        return (
            f"recipe_type={self.__class__.__name__}, "
            f"format={str(self.fp8_format).split('.')[1]}, "
            f"fp8_quant_fwd_inp={self.fp8_quant_fwd_inp}, "
            f"fp8_quant_fwd_weight={self.fp8_quant_fwd_weight}, "
            f"fp8_quant_bwd_grad={self.fp8_quant_bwd_grad}, "
            f"fp8_gemm_fprop={self.fp8_gemm_fprop}, "
            f"fp8_gemm_dgrad={self.fp8_gemm_dgrad}, "
            f"fp8_gemm_wgrad={self.fp8_gemm_wgrad}, "
            f"fp8_dpa={self.fp8_dpa}, "
            f"fp8_mha={self.fp8_mha}"
        )


@dataclass()
class MXFP8BlockScaling(Recipe):
    """
    Use the MXFP8 scaling factor strategy.

    In this strategy, tensors are scaled in blockwise fashion. Each group
    of 32 consecutive values is scaled together using their own scaling
    factor. The type of the scaling factor is E8M0 (8 bits of exponent,
    0 bits of mantissa), equivalent to scaling by a power of 2.

    Since the scaling happens in a particular direction (either rowwise
    or columnwise), in this recipe the quantized tensor and its transpose
    are not numerically equivalent. Due to this, when Transformer Engine
    needs both the MXFP8 tensor and its transpose (e.g. to calculate both
    forward and backward pass), during the quantization both versions are
    computed from the high precision input to avoid double quantization
    errors.

    Parameters
    ----------
    fp8_format : {Format.E4M3, Format.HYBRID}, default = Format.E4M3
                Controls the FP8 data format used during forward and backward
                pass.
    """

    margin: int = 0
    fp8_format: Format = Format.E4M3
    fp8_dpa: bool = False
    fp8_mha: bool = False

    def __post_init__(self) -> None:
        assert self.fp8_format != Format.E5M2, "Pure E5M2 training is not supported."

    def __repr__(self) -> str:
        return (
            f"recipe_type={self.__class__.__name__}, "
            f"margin={self.margin}, "
            f"format={str(self.fp8_format).split('.')[1]}"
        )


@dataclass()
class Float8BlockScaling(Recipe):
    """
    Use block-wise scaling for FP8 tensors.

    In this strategy, tensors are scaled in blockwise fashion. Values within
    each block share a common scaling factor. The block dimensionality
    can be configured. The scaling factors are float32 containers. They
    will by default be constrained to powers of 2.

    Since the scaling happens in a particular direction (either rowwise
    or columnwise), the quantized tensor and its transpose are not numerically
    equivalent. Due to this, when Transformer Engine needs both the FP8 tensor
    and its transpose (e.g. to calculate both forward and backward pass),
    during the quantization both versions are computed from the high precision
    input to avoid double quantization errors.

    NOTE: To relax the default constraint that scales be powers of 2, set env variable
    NVTE_FP8_BLOCK_SCALING_FP32_SCALES=1 to override it for the recipe defaults.

    Parameters
    ----------
    fp8_format : {Format.E4M3, Format.HYBRID}, default = Format.E4M3
                Controls the FP8 data format used during forward and backward
                pass.
    """

    use_f32_scales: bool = os.getenv("NVTE_FP8_BLOCK_SCALING_FP32_SCALES", "0") == "1"

    fp8_format: Format = Format.E4M3
    fp8_quant_fwd_inp = QParams(power_2_scale=not use_f32_scales, amax_epsilon=0.0)
    fp8_quant_fwd_weight = QParams(power_2_scale=not use_f32_scales, amax_epsilon=0.0)
    fp8_quant_bwd_grad = QParams(power_2_scale=not use_f32_scales, amax_epsilon=0.0)
    x_block_scaling_dim: int = 1
    w_block_scaling_dim: int = 2
    grad_block_scaling_dim: int = 1
    fp8_gemm_fprop: MMParams = MMParams(use_split_accumulator=True)
    fp8_gemm_dgrad: MMParams = MMParams(use_split_accumulator=True)
    fp8_gemm_wgrad: MMParams = MMParams(use_split_accumulator=True)
    fp8_dpa: bool = False
    fp8_mha: bool = False

    def __post_init__(self) -> None:
        assert self.x_block_scaling_dim in [1, 2], "Only 1D or 2D blocks supported for x"
        assert self.w_block_scaling_dim in [1, 2], "Only 1D or 2D blocks supported for w"
        assert self.grad_block_scaling_dim in [1, 2], "Only 1D or 2D blocks supported for grad"
        assert not (
            self.x_block_scaling_dim == 2 and self.w_block_scaling_dim == 2
        ), "2D by 2D block gemm not supported."
        assert not (
            self.x_block_scaling_dim == 2 and self.grad_block_scaling_dim == 2
        ), "2D by 2D block gemm not supported."
        assert not (
            self.w_block_scaling_dim == 2 and self.grad_block_scaling_dim == 2
        ), "2D by 2D block gemm not supported."
        assert self.fp8_gemm_fprop.use_split_accumulator, "Split accumulator required for fprop."
        assert self.fp8_gemm_dgrad.use_split_accumulator, "Split accumulator required for dgrad."
        assert self.fp8_gemm_wgrad.use_split_accumulator, "Split accumulator required for wgrad."
        assert (
            not self.fp8_dpa and not self.fp8_mha
        ), "FP8 attention is not supported for Float8BlockScaling."
        assert self.fp8_format != Format.E5M2, "Pure E5M2 training is not supported."

    def __repr__(self) -> str:
        return (
            f"recipe_type={self.__class__.__name__}, "
            f"format={str(self.fp8_format).split('.')[1]}, "
            f"fp8_quant_fwd_inp={self.fp8_quant_fwd_inp}, "
            f"fp8_quant_fwd_weight={self.fp8_quant_fwd_weight}, "
            f"fp8_quant_bwd_grad={self.fp8_quant_bwd_grad}, "
            f"x_block_scaling_dim={self.x_block_scaling_dim}, "
            f"w_block_scaling_dim={self.w_block_scaling_dim}, "
            f"grad_block_scaling_dim={self.grad_block_scaling_dim}, "
            f"fp8_gemm_fprop={self.fp8_gemm_fprop}, "
            f"fp8_gemm_dgrad={self.fp8_gemm_dgrad}, "
            f"fp8_gemm_wgrad={self.fp8_gemm_wgrad}, "
            f"fp8_dpa={self.fp8_dpa}, "
            f"fp8_mha={self.fp8_mha}"
        )


@dataclass()
class NVFP4BlockScaling(Recipe):
    """
    Use the NVFP4 scaling strategy.

    This is a 2-level block scaling strategy. In level 1, each group of
    16 consecutive values is scaled together using their own scaling
    factor. The type of the scaling factor is E4M3 (4 bits of exponent,
    3 bits of mantissa). In level 2, a global per tensor FP32 scaling
    factor is used to scale the entire tensor.

    Since the scaling happens in a particular direction (either rowwise
    or columnwise), in this recipe the quantized tensor and its transpose
    are not numerically equivalent. Due to this, when Transformer Engine
    needs both the tensor and its transpose (e.g. to calculate both
    forward and backward pass), during the quantization both versions are
    computed from the high precision input to avoid double quantization
    errors.

    The default NVFP4 training recipe implements 3 techniques for quantizing
    to a narrow format (4-bit):

    - For weight tensors a variant of the NVFP4 quantization is used,
      where a single scaling factor is shared by a 2D block of 16x16 elements.
    - When quantizing gradients, stochastic rounding is applied to avoid the bias
      introduced by quantization. With this, values are rounded probabilistically
      to one of their two nearest representable numbers, with probabilities
      inversely proportional to their distances.
    - When quantizing inputs and gradients, random Hadamard transforms are applied
      (16x16 Hadamard matrix) to smooth outliers in the tensor distributions
      and make them easier to represent accurately in NVFP4.

    These techniques are described more comprehensively in the NVFP4 paper titled
    'Pretraining Large Language Models with NVFP4' (https://arxiv.org/abs/2509.25149v1).

    Parameters
    ----------
    fp4_format : {Format.E2M1}, default = Format.E2M1
             FP4 data type.
    disable_rht : bool, default = False
             If set to `True`, random Hadamard transforms are not applied to any tensor.
    disable_stochastic_rounding : bool, default = False
             If set to `True`, stochastic rounding is disabled during quantization for all tensors.
    disable_2d_quantization : bool, default = False
             If set to `True`, 1D block scaling with block size 16 is used for all tensors.
    """

    # Configuration envvars
    disable_rht: bool = os.getenv("NVTE_NVFP4_DISABLE_RHT", "0") == "1"
    disable_stochastic_rounding: bool = (
        os.getenv("NVTE_NVFP4_DISABLE_STOCHASTIC_ROUNDING", "0") == "1"
    )
    disable_2d_quantization: bool = os.getenv("NVTE_NVFP4_DISABLE_2D_QUANTIZATION", "0") == "1"

    fp4_format: Format = Format.E2M1
    fp8_format: Format = Format.E4M3

    # Not applying quantization to attention for now
    fp8_dpa: bool = False
    fp8_mha: bool = False

    def __post_init__(self) -> None:
        assert self.fp4_format == Format.E2M1, "Only E2M1 is supported for NVFP4 scaling"
        assert self.fp8_format == Format.E4M3, "Only E4M3 is supported for NVFP4 scaling"

        # Quantization params
        # Note: RHT is currently only applied to column-wise usage so that
        # it can be used for wgrad GEMM.
        self.fp4_quant_fwd_inp = QParams(
            random_hadamard_transform=not self.disable_rht,
            stochastic_rounding=False,
            fp4_2d_quantization=False,
        )
        self.fp4_quant_fwd_weight = QParams(
            random_hadamard_transform=False,
            stochastic_rounding=False,
            fp4_2d_quantization=not self.disable_2d_quantization,
        )
        self.fp4_quant_bwd_grad = QParams(
            random_hadamard_transform=not self.disable_rht,
            stochastic_rounding=not self.disable_stochastic_rounding,
            fp4_2d_quantization=False,
        )

    def __repr__(self) -> str:
        return (
            f"recipe_type={self.__class__.__name__}, "
            f"fp4_format={str(self.fp4_format).split('.')[1]}, "
            f"fp8_format={str(self.fp8_format).split('.')[1]}, "
            f"fp8_dpa={self.fp8_dpa}, "
            f"fp8_mha={self.fp8_mha}, "
            f"fp4_quant_fwd_inp={self.fp4_quant_fwd_inp}, "
            f"fp4_quant_fwd_weight={self.fp4_quant_fwd_weight}, "
            f"fp4_quant_bwd_grad={self.fp4_quant_bwd_grad}, "
        )


@dataclass()
class CustomRecipe(Recipe):
    """
    Custom recipe that allows users to provide quantizer factories.

    .. warning::
        **EXPERIMENTAL**: Custom recipe is experimental, still under active development,
        and the API is subject to change without notice. Use at your own risk.

    Parameters
    ----------
    qfactory : Callable
        Factory callable that returns a quantizer instance for a
        given semantic tensor role.
        The callable is typically invoked as::

            qfactory(
                role: str,
            )

        Where `role` is one of the following strings for e.g. te.Linear
        (stable public contract):

        - forward:  "linear_input", "linear_weight", "linear_output"
        - backward: "linear_grad_output", "linear_grad_input"
    """

    qfactory: Callable[..., Any]

    fp8_dpa: bool = False
    fp8_mha: bool = False

    def __repr__(self) -> str:
        return f"recipe_type={self.__class__.__name__}, qfactory={self.qfactory}"
