sglang0.4.5.post1/python/sglang/srt/layers/quantization/fp8_utils.py

565 lines
21 KiB
Python

import os
from typing import List, Optional, Tuple
import torch
from sglang.srt.layers.quantization.fp8_kernel import (
_enable_jit_deepgemm,
per_token_group_quant_fp8,
static_quant_fp8,
w8a8_block_fp8_matmul,
)
from sglang.srt.utils import (
get_bool_env_var,
get_cuda_version,
get_device_capability,
is_cuda,
is_hip,
)
try:
import vllm
from vllm import _custom_ops as ops
VLLM_AVAILABLE = True
except ImportError:
VLLM_AVAILABLE = False
use_vllm_cutlass_w8a8_fp8_kernel = get_bool_env_var("USE_VLLM_CUTLASS_W8A8_FP8_KERNEL")
_is_hip = is_hip()
if _is_hip and get_bool_env_var("CK_MOE"):
from aiter import gemm_a8w8_blockscale
_is_cuda = is_cuda()
if _is_cuda:
from sgl_kernel import fp8_blockwise_scaled_mm, fp8_scaled_mm
from sglang.srt.custom_op import scaled_fp8_quant as sgl_scaled_fp8_quant
from sglang.srt.layers.quantization.fp8_kernel import sglang_per_token_quant_fp8
# Input scaling factors are no longer optional in _scaled_mm starting
# from pytorch 2.5. Allocating a dummy tensor to pass as input_scale
TORCH_DEVICE_IDENTITY = torch.ones(1, dtype=torch.float32)
_TORCH_VERSION = torch.__version__.split("+")[0]
try:
_TORCH_VERSION_TUPLE = tuple(map(int, _TORCH_VERSION.split(".")[:3]))
except ValueError:
_TORCH_VERSION_TUPLE = (0, 0, 0)
# The condition to determine if it is on a platform that supports
# torch._scaled_mm rowwise feature.
# The condition is determined once as the operations
# are time consuming.
USE_ROWWISE_TORCH_SCALED_MM = (
_is_hip and get_device_capability() >= (9, 4) and _TORCH_VERSION_TUPLE >= (2, 7, 0)
)
def cutlass_fp8_supported():
if not _is_cuda:
return False
major, minor = get_device_capability()
cuda_version = get_cuda_version()
if major >= 9:
return cuda_version >= (12, 0)
elif major == 8 and minor == 9:
return cuda_version >= (12, 4)
return False
def normalize_e4m3fn_to_e4m3fnuz(
weight: torch.Tensor,
weight_scale: torch.Tensor,
input_scale: Optional[torch.Tensor] = None,
) -> Tuple[torch.Tensor, torch.Tensor, Optional[torch.Tensor]]:
assert weight.dtype == torch.float8_e4m3fn
# The bits pattern 10000000(-128) represents zero in e4m3fn
# but NaN in e4m3fnuz. So here we set it to 0.
# https://onnx.ai/onnx/technical/float8.html
weight_as_int8 = weight.view(torch.int8)
ROCM_FP8_NAN_AS_INT = -128
weight_as_int8[weight_as_int8 == ROCM_FP8_NAN_AS_INT] = 0
weight = weight_as_int8.view(torch.float8_e4m3fnuz)
# For the same bits representation, e4m3fnuz value is half of
# the e4m3fn value, so we should double the scaling factor to
# get the same dequantized value.
# https://onnx.ai/onnx/technical/float8.html
weight_scale = weight_scale * 2.0
if input_scale is not None:
input_scale = input_scale * 2.0
return weight, weight_scale, input_scale
def cutlass_block_fp8_supported() -> bool:
if not get_bool_env_var("SUPPORT_CUTLASS_BLOCK_FP8"):
return False
if _is_cuda:
major, minor = torch.cuda.get_device_capability()
sm_version = major * 10 + minor
cuda_version = tuple(map(int, torch.version.cuda.split(".")))
if cuda_version >= (12, 0) and sm_version >= 90:
return True
return False
CUTLASS_BLOCK_FP8_SUPPORTED = cutlass_block_fp8_supported()
def apply_w8a8_block_fp8_linear(
input: torch.Tensor,
weight: torch.Tensor,
block_size: List[int],
weight_scale: torch.Tensor,
input_scale: Optional[torch.Tensor] = None,
bias: Optional[torch.Tensor] = None,
) -> torch.Tensor:
assert input_scale is None
# View input as 2D matrix for fp8 methods
input_2d = input.view(-1, input.shape[-1])
output_shape = [*input.shape[:-1], weight.shape[0]]
# TODO: add more robust shape check here
shape_supported_by_cutlass = (
weight.shape[0] % 128 == 0 and weight.shape[1] % 128 == 0
)
if CUTLASS_BLOCK_FP8_SUPPORTED and shape_supported_by_cutlass:
q_input, x_scale = per_token_group_quant_fp8(
input_2d, block_size[1], column_major_scales=True
)
output = fp8_blockwise_scaled_mm(
q_input, weight.T, x_scale, weight_scale.T, out_dtype=input.dtype
)
elif _is_hip and get_bool_env_var("CK_MOE"):
q_input, x_scale = per_token_group_quant_fp8(
input_2d, block_size[1], column_major_scales=False
)
output = torch.zeros(
[q_input.shape[0], weight.shape[0]],
dtype=input.dtype,
device=q_input.device,
)
gemm_a8w8_blockscale(q_input, weight, x_scale, weight_scale, output)
else:
if _enable_jit_deepgemm:
q_input, x_scale = per_token_group_quant_fp8(
input_2d,
block_size[1],
column_major_scales=True,
scale_tma_aligned=True,
)
else:
q_input, x_scale = per_token_group_quant_fp8(
input_2d, block_size[1], column_major_scales=False
)
output = w8a8_block_fp8_matmul(
q_input, weight, x_scale, weight_scale, block_size, output_dtype=input.dtype
)
if bias is not None:
output = output + bias
return output.to(dtype=input.dtype).view(*output_shape)
def input_to_float8(
x: torch.Tensor, dtype: torch.dtype = torch.float8_e4m3fn
) -> Tuple[torch.Tensor, torch.Tensor]:
"""This function quantizes input values to float8 values with tensor-wise quantization."""
finfo = torch.finfo(dtype)
min_val, max_val = x.aminmax()
amax = torch.maximum(min_val.abs(), max_val.abs()).clamp(min=1e-12)
fp8_max = finfo.max
if _is_hip:
fp8_max = 224.0
scale = fp8_max / amax
x_scl_sat = (x * scale).clamp(min=-fp8_max, max=fp8_max)
return x_scl_sat.to(dtype).contiguous(), scale.float().reciprocal()
def block_quant_to_tensor_quant(
x_q_block: torch.Tensor,
x_s: torch.Tensor,
block_size: List[int],
) -> Tuple[torch.Tensor, torch.Tensor]:
"""This function converts block-wise quantization to tensor-wise quantization.
The inputs are block-wise quantization tensor `x_q_block`, block-wise quantization scale
and the block size.
The outputs are tensor-wise quantization tensor and tensor-wise quantization scale.
Note only float8 is supported for now.
"""
block_n, block_k = block_size[0], block_size[1]
n, k = x_q_block.shape
n_tiles = (n + block_n - 1) // block_n
k_tiles = (k + block_k - 1) // block_k
assert n_tiles == x_s.shape[0]
assert k_tiles == x_s.shape[1]
x_dq_block = x_q_block.to(torch.float32)
x_dq_block_tiles = [
[
x_dq_block[
j * block_n : min((j + 1) * block_n, n),
i * block_k : min((i + 1) * block_k, k),
]
for i in range(k_tiles)
]
for j in range(n_tiles)
]
for i in range(k_tiles):
for j in range(n_tiles):
x_dq_block_tiles[j][i][:, :] = x_dq_block_tiles[j][i] * x_s[j][i]
x_q_tensor, scale = input_to_float8(x_dq_block, dtype=x_q_block.dtype)
return x_q_tensor, scale
def apply_fp8_linear(
input: torch.Tensor,
weight: torch.Tensor,
weight_scale: torch.Tensor,
input_scale: Optional[torch.Tensor] = None,
input_scale_ub: Optional[torch.Tensor] = None,
bias: Optional[torch.Tensor] = None,
cutlass_fp8_supported: bool = True,
use_per_token_if_dynamic: bool = False,
) -> torch.Tensor:
# View input as 2D matrix for fp8 methods
input_2d = input.view(-1, input.shape[-1])
output_shape = [*input.shape[:-1], weight.shape[1]]
# cutlass w8a8 fp8 sgl-kernel only supports per-token scale
if input_scale is not None:
assert input_scale.numel() == 1
# broadcast per-tensor scale to per-token scale when supporting cutlass
qinput, x_scale = static_quant_fp8(
input_2d, input_scale, repeat_scale=cutlass_fp8_supported
)
else:
# default use per-token quantization if dynamic
if _is_cuda:
qinput, x_scale = sglang_per_token_quant_fp8(input_2d)
else:
qinput, x_scale = per_token_group_quant_fp8(
input_2d, group_size=input_2d.shape[1]
)
if cutlass_fp8_supported:
try:
if VLLM_AVAILABLE and use_vllm_cutlass_w8a8_fp8_kernel:
# Fall back to vllm cutlass w8a8 fp8 kernel
output = ops.cutlass_scaled_mm(
qinput,
weight,
out_dtype=input.dtype,
scale_a=x_scale,
scale_b=weight_scale,
bias=bias,
)
else:
assert (
weight_scale.numel() == weight.shape[1]
), "cutlass w8a8 fp8 sgl-kernel only supports per-channel scale"
output = fp8_scaled_mm(
qinput,
weight,
x_scale,
weight_scale,
out_dtype=input.dtype,
bias=bias,
)
return output.view(*output_shape)
except (ImportError, NameError, AttributeError):
pass
# torch.scaled_mm supports per tensor weights + activations only
# so fallback to naive if per channel or per token
else:
per_tensor_weights = weight_scale.numel() == 1
per_tensor_activations = x_scale.numel() == 1
if per_tensor_weights and per_tensor_activations:
# Fused GEMM_DQ
output = torch._scaled_mm(
qinput,
weight,
out_dtype=input.dtype,
scale_a=x_scale,
scale_b=weight_scale,
bias=bias,
)
# A fix for discrepancy in scaled_mm which returns tuple
# for torch < 2.5 and a single value in torch >= 2.5
if type(output) is tuple and len(output) == 2:
output = output[0]
return torch.narrow(output, 0, 0, input_2d.shape[0]).view(*output_shape)
else:
# Fallback for channelwise case, where we use unfused DQ
# due to limitations with scaled_mm
# Symmetric quantized GEMM by definition computes the following:
# C = (s_x * X) (s_w * W) + bias
# This is equivalent to dequantizing the weights and activations
# before applying a GEMM.
#
# In order to compute quantized operands, a quantized kernel
# will rewrite the above like so:
# C = s_w * s_x * (X * W) + bias
#
# For the scaled_mm fallback case, we break this down, since it
# does not support s_w being a vector.
# Making sure the dummy tensor is on the same device as the weight
global TORCH_DEVICE_IDENTITY
if TORCH_DEVICE_IDENTITY.device != weight.device:
TORCH_DEVICE_IDENTITY = TORCH_DEVICE_IDENTITY.to(weight.device)
# GEMM
# This computes C = (X * W).
# Output in fp32 to allow subsequent ops to happen in-place
output = torch._scaled_mm(
qinput,
weight,
scale_a=TORCH_DEVICE_IDENTITY,
scale_b=TORCH_DEVICE_IDENTITY,
out_dtype=torch.float32,
)
# A fix for discrepancy in scaled_mm which returns tuple
# for torch < 2.5 and a single value in torch >= 2.5
if type(output) is tuple and len(output) == 2:
output = output[0]
# Unpad (undo num_token_padding)
output = torch.narrow(output, 0, 0, input_2d.shape[0])
x_scale = torch.narrow(x_scale, 0, 0, input_2d.shape[0])
# DQ
# C = sw * sx * (X * W) + bias
output = output * x_scale * weight_scale.t()
if bias is not None:
output = output + bias
return output.to(dtype=input.dtype).view(*output_shape)
def maybe_create_device_identity():
# Allocate dummy ones tensor for torch._scaled_mm
global TORCH_DEVICE_IDENTITY
if TORCH_DEVICE_IDENTITY is None:
TORCH_DEVICE_IDENTITY = torch.ones(1, dtype=torch.float32)
# Adapted from https://github.com/vllm-project/vllm/blob/main/vllm/model_executor/layers/quantization/utils/w8a8_utils.py
# TODO(luka): follow similar pattern for marlin and block-fp8-linear
# https://github.com/vllm-project/vllm/issues/14397
class Fp8LinearOp:
"""
This class executes a FP8 linear layer using cutlass if supported and
torch.scaled_mm otherwise.
It needs to be a class instead of a method so that config can be read
in the __init__ method, as reading config is not allowed inside forward.
"""
def __init__(
self,
cutlass_fp8_supported: bool = cutlass_fp8_supported(),
use_per_token_if_dynamic: bool = False,
pad_output: Optional[bool] = None,
):
self.cutlass_fp8_supported = cutlass_fp8_supported
self.use_per_token_if_dynamic = use_per_token_if_dynamic
# Note: we pad the input because torch._scaled_mm is more performant
# for matrices with batch dimension > 16.
# This could change in the future.
# We also don't pad when using torch.compile,
# as it breaks with dynamic shapes.
if pad_output is None:
enable_torch_compile = os.environ.get(
"SGLANG_ENABLE_TORCH_COMPILE", "0"
).lower() in ("1", "true", "yes")
pad_output = not enable_torch_compile
self.output_padding = 17 if pad_output else None
def apply(
self,
input: torch.Tensor,
weight: torch.Tensor,
weight_scale: torch.Tensor,
input_scale: Optional[torch.Tensor] = None,
input_scale_ub: Optional[torch.Tensor] = None,
bias: Optional[torch.Tensor] = None,
# TODO(luka) remove this parameter in favor of __init__
use_per_token_if_dynamic: Optional[bool] = None,
) -> torch.Tensor:
# ops.scaled_fp8_quant supports both dynamic and static quant.
# If dynamic, layer.input_scale is None and x_scale computed from x.
# If static, layer.input_scale is scalar and x_scale is input_scale.
# View input as 2D matrix for fp8 methods
input_2d = input.view(-1, input.shape[-1])
output_shape = [*input.shape[:-1], weight.shape[1]]
# TODO(luka) this is here because currently MLA only decides this
# during the forward method instead of in __init__.
if use_per_token_if_dynamic is None:
use_per_token_if_dynamic = self.use_per_token_if_dynamic
# cutlass_scaled_mm supports per tensor/channel W and per tensor/token A
# for sgl-kernel fp8_scaled_mm, it support per channel W now
if self.cutlass_fp8_supported and weight_scale.numel() == weight.shape[1]:
if _is_cuda:
qinput, x_scale = sgl_scaled_fp8_quant(
input_2d,
input_scale,
use_per_token_if_dynamic=use_per_token_if_dynamic,
)
else:
qinput, x_scale = ops.scaled_fp8_quant(
input_2d,
input_scale,
scale_ub=input_scale_ub,
use_per_token_if_dynamic=use_per_token_if_dynamic,
)
# Fused GEMM_DQ
if VLLM_AVAILABLE and use_vllm_cutlass_w8a8_fp8_kernel:
# Fall back to vllm cutlass w8a8 fp8 kernel
output = ops.cutlass_scaled_mm(
qinput,
weight,
out_dtype=input.dtype,
scale_a=x_scale,
scale_b=weight_scale,
bias=bias,
)
else:
assert (
weight_scale.numel() == weight.shape[1]
), "cutlass w8a8 fp8 sgl-kernel only supports per-channel scale"
output = fp8_scaled_mm(
qinput,
weight,
x_scale,
weight_scale,
out_dtype=input.dtype,
bias=bias,
)
return output.view(*output_shape)
# torch.scaled_mm supports per tensor weights + activations only
# so fallback to naive if per channel or per token
else:
# Maybe apply padding to output, see comment in __init__
if _is_cuda:
qinput, x_scale = sgl_scaled_fp8_quant(
input_2d,
input_scale,
use_per_token_if_dynamic=use_per_token_if_dynamic,
)
if self.output_padding:
pad_size = max(self.output_padding - qinput.shape[0], 0)
if pad_size > 0:
qinput = torch.nn.functional.pad(qinput, (0, 0, 0, pad_size))
else:
qinput, x_scale = ops.scaled_fp8_quant(
input_2d,
input_scale,
num_token_padding=self.output_padding,
use_per_token_if_dynamic=use_per_token_if_dynamic,
)
per_tensor_weights = weight_scale.numel() == 1
per_tensor_activations = x_scale.numel() == 1
if per_tensor_weights and per_tensor_activations:
# Fused GEMM_DQ
output = torch._scaled_mm(
qinput,
weight,
out_dtype=input.dtype,
scale_a=x_scale,
scale_b=weight_scale,
bias=bias,
)
# A fix for discrepancy in scaled_mm which returns tuple
# for torch < 2.5 and a single value in torch >= 2.5
if type(output) is tuple and len(output) == 2:
output = output[0]
return torch.narrow(output, 0, 0, input_2d.shape[0]).view(*output_shape)
elif (
use_per_token_if_dynamic
and not per_tensor_weights
and not per_tensor_activations
and USE_ROWWISE_TORCH_SCALED_MM
):
# For now validated on ROCm platform
# fp8 rowwise scaling in torch._scaled_mm is introduced in
# https://github.com/pytorch/pytorch/pull/144432 using hipBLASLt
# and ROCm 6.3, which only exists in torch 2.7 and above.
# For CUDA platform please validate if the
# torch._scaled_mm support rowwise scaled GEMM
# Fused GEMM_DQ Rowwise GEMM
output = torch._scaled_mm(
qinput,
weight,
out_dtype=input.dtype,
scale_a=x_scale,
scale_b=weight_scale.t(),
bias=bias,
)
output = torch.narrow(output, 0, 0, input_2d.shape[0])
output = output.view(*output_shape)
return output
else:
# Fallback for channelwise case, where we use unfused DQ
# due to limitations with scaled_mm
# Symmetric quantized GEMM by definition computes the following:
# C = (s_x * X) (s_w * W) + bias
# This is equivalent to dequantizing the weights and activations
# before applying a GEMM.
#
# In order to compute quantized operands, a quantized kernel
# will rewrite the above like so:
# C = s_w * s_x * (X * W) + bias
#
# For the scaled_mm fallback case, we break this down, since it
# does not support s_w being a vector.
# GEMM
# This computes C = (X * W).
# Output in fp32 to allow subsequent ops to happen in-place
global TORCH_DEVICE_IDENTITY
if TORCH_DEVICE_IDENTITY.device != weight.device:
TORCH_DEVICE_IDENTITY = TORCH_DEVICE_IDENTITY.to(weight.device)
output = torch._scaled_mm(
qinput,
weight,
scale_a=TORCH_DEVICE_IDENTITY,
scale_b=TORCH_DEVICE_IDENTITY,
out_dtype=torch.float32,
)
# A fix for discrepancy in scaled_mm which returns tuple
# for torch < 2.5 and a single value in torch >= 2.5
if type(output) is tuple and len(output) == 2:
output = output[0]
# Unpad (undo num_token_padding)
output = torch.narrow(output, 0, 0, input_2d.shape[0])
x_scale = torch.narrow(x_scale, 0, 0, input_2d.shape[0])
# DQ
# C = sw * sx * (X * W) + bias
output = output * x_scale * weight_scale.t()
if bias is not None:
output = output + bias
return output.to(dtype=input.dtype).view(*output_shape)