cpp_extensions.py

# Copyright (c) 2022-2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
#
# See LICENSE for license information.

"""TE FP8 extensions and GEMMs"""
from typing import Optional, Tuple, Union
import torch
import transformer_engine_extensions as tex
from .constants import TE_DType


def fp8_gemm(
    A: torch.Tensor,
    A_scale_inv: torch.Tensor,
    A_dtype: tex.DType,
    B: torch.Tensor,
    B_scale_inv: torch.Tensor,
    B_dtype: tex.DType,
    out_dtype: torch.dtype,
    workspace: torch.Tensor,
    accumulate: bool = False,
    out: Optional[torch.Tensor] = None,
    bias: Optional[torch.Tensor] = None,
    use_bias: bool = False,
    fp32_output: bool = False,
    use_split_accumulator: bool = False,
) -> torch.Tensor:
    """TN layout GEMM with fp8 inputs."""

    empty_tensor = torch.Tensor()

    return_output = False
    if out is None:
        out = torch.empty(
            B.shape[0],
            A.shape[0],
            dtype=torch.float32 if fp32_output else out_dtype,
            device="cuda",
        )
        return_output = True

    out_dtype = tex.DType.kFloat32 if fp32_output else TE_DType[out_dtype]

    tex.te_gemm(
        A,
        A_scale_inv,
        A_dtype,
        True,  # transa
        B,
        B_scale_inv,
        B_dtype,
        False,  # transb
        out,
        out_dtype,
        bias if use_bias else empty_tensor,
        empty_tensor,
        False,  # grad
        workspace,
        workspace.shape[0],
        accumulate,
        use_split_accumulator,
    )

    if return_output:
        return out
    return None


def gemm(
    A: torch.Tensor,
    B: torch.Tensor,
    dtype: torch.dtype,
    workspace: torch.Tensor,
    gelu: bool = False,
    gelu_input: Optional[torch.Tensor] = None,
    grad: bool = False,
    accumulate: bool = False,
    layout: str = "TN",
    out: Optional[torch.Tensor] = None,
    bias: Optional[torch.Tensor] = None,
    use_bias: bool = False,
    fp32_output: bool = False,
) -> Tuple[Union[torch.Tensor, None], ...]:
    """Non FP8 GEMM."""

    assert layout in ("TN", "NN", "NT"), f"GEMM layout {layout} not supported."
    transa = layout[0] == "T"
    transb = layout[1] == "T"
    empty_tensor = torch.Tensor()

    input_dtype = TE_DType[dtype]
    output_dtype = tex.DType.kFloat32 if fp32_output else input_dtype

    return_output = False
    if out is None:
        out = torch.empty(
            B.shape[1] if transb else B.shape[0],
            A.shape[0] if transa else A.shape[1],
            dtype=torch.float32 if fp32_output else dtype,
            device="cuda",
        )
        return_output = True

    if gelu and not grad:
        gelu_input = torch.empty_like(out, dtype=dtype)
    elif not gelu:
        gelu_input = empty_tensor

    if grad and use_bias:
        grad_bias = torch.empty(
            B.shape[1], dtype=torch.float32 if fp32_output else dtype, device="cuda"
        )
    else:
        grad_bias = empty_tensor

    bias = bias if use_bias else empty_tensor

    tex.te_gemm(
        A,
        empty_tensor,
        input_dtype,
        transa,
        B,
        empty_tensor,
        input_dtype,
        transb,
        out,
        output_dtype,
        grad_bias if grad else bias,
        gelu_input,
        grad,
        workspace,
        workspace.shape[0],
        accumulate,
        False,  # use_split_accumulator
    )

    if return_output:
        return out, grad_bias, gelu_input
    return None, grad_bias, gelu_input


def fp8_cast_transpose_fused(
    inp: torch.Tensor,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    otype: tex.DType,
    cast_out: Optional[torch.Tensor] = None,
    transpose_out: Optional[torch.Tensor] = None,
) -> Union[Tuple[torch.Tensor, torch.Tensor], None]:
    """Cast + Transpose with FP8 output"""

    return_outputs = False
    if cast_out is None or transpose_out is None:
        cast_out = torch.empty_like(inp, dtype=torch.int8)
        transpose_out = torch.empty(
            inp.shape[1], inp.shape[0], device="cuda", dtype=torch.int8
        )
        return_outputs = True

    tex.fused_cast_transpose(
        inp,
        fp8_meta_tensor.scale[fp8_tensor],
        fp8_meta_tensor.amax_history[0][fp8_tensor],
        fp8_meta_tensor.scale_inv[fp8_tensor],
        cast_out,
        transpose_out,
        otype,
    )

    if return_outputs:
        return cast_out, transpose_out
    return None


def fp8_cast_transpose_bgrad_fused(
    inp: torch.Tensor,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    otype: tex.DType,
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
    """Cast + Transpose + BGRAD with FP8 output"""
    return tex.fused_cast_transpose_bgrad(
        inp,
        fp8_meta_tensor.scale[fp8_tensor],
        fp8_meta_tensor.amax_history[0][fp8_tensor],
        fp8_meta_tensor.scale_inv[fp8_tensor],
        otype,
    )


def fp8_cast_transpose_bgrad_dgelu_fused(
    grad_output: torch.Tensor,
    gelu_input: torch.Tensor,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    otype: tex.DType,
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
    """Cast + Transpose + BGRAD + DGELU with FP8 output"""
    return tex.fused_cast_transpose_bgrad_dgelu(
        grad_output,
        gelu_input,
        fp8_meta_tensor.scale[fp8_tensor],
        fp8_meta_tensor.amax_history[0][fp8_tensor],
        fp8_meta_tensor.scale_inv[fp8_tensor],
        otype,
    )


def fp8_gelu(
    inp: torch.Tensor,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    otype: tex.DType,
) -> torch.Tensor:
    """GeLU with FP8 output"""
    return tex.fp8_gelu(
        inp,
        fp8_meta_tensor.scale[fp8_tensor],
        fp8_meta_tensor.amax_history[0][fp8_tensor],
        fp8_meta_tensor.scale_inv[fp8_tensor],
        otype,
    )


def layernorm_fwd_fp8(
    inp: torch.Tensor,
    weight: torch.Tensor,
    bias: torch.Tensor,
    eps: float,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    otype: tex.DType,
) -> Tuple[torch.Tensor, torch.Tensor, torch.Tensor]:
    """LayerNorm with FP8 output"""
    return tex.layernorm_fwd_fp8(
        inp,
        weight,
        bias,
        eps,
        fp8_meta_tensor.scale[fp8_tensor],
        fp8_meta_tensor.amax_history[0][fp8_tensor],
        fp8_meta_tensor.scale_inv[fp8_tensor],
        otype,
    )


def cast_to_fp8(
    inp: torch.Tensor,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    otype: tex.DType,
) -> torch.Tensor:
    """Cast input to FP8"""
    return tex.cast_to_fp8(
        inp,
        fp8_meta_tensor.scale[fp8_tensor],
        fp8_meta_tensor.amax_history[0][fp8_tensor],
        fp8_meta_tensor.scale_inv[fp8_tensor],
        otype,
    )


def cast_from_fp8(
    inp: torch.Tensor,
    fp8_meta_tensor: tex.FP8TensorMeta,
    fp8_tensor: Union[tex.FP8FwdTensors, tex.FP8BwdTensors],
    itype: tex.DType,
    otype: tex.DType,
) -> torch.Tensor:
    """Cast input from FP8"""
    return tex.cast_from_fp8(
        inp,
        fp8_meta_tensor.scale_inv[fp8_tensor],
        itype,
        otype,
    )