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[Feat]: Add support for Dynamic Quant 4 bit CPU kleidiai kernels #17112
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135 changes: 135 additions & 0 deletions
135
.../model_executor/layers/quantization/compressed_tensors/schemes/compressed_tensors_w4a8.py
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# SPDX-FileCopyrightText: Copyright 2025 Arm Limited and/or its affiliate open-source-office@arm.com | ||
# SPDX-License-Identifier: Apache-2.0 | ||
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from typing import Callable, List, Optional, Set | ||
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import torch | ||
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from vllm.logger import init_logger | ||
from vllm.model_executor.layers.quantization.compressed_tensors.schemes import ( | ||
CompressedTensorsScheme) | ||
from vllm.model_executor.layers.quantization.kernels.mixed_precision import ( | ||
MPLinearLayerConfig, choose_mp_linear_kernel) | ||
from vllm.model_executor.parameter import (ChannelQuantScaleParameter, | ||
GroupQuantScaleParameter, | ||
ModelWeightParameter) | ||
from vllm.scalar_type import scalar_types | ||
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logger = init_logger(__name__) | ||
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__all__ = ["CompressedTensorsW4A8"] | ||
W4A8_SUPPORTED_TYPES_MAP = { | ||
4: scalar_types.int4, | ||
} | ||
W4A8_SUPPORTED_BITS = list(W4A8_SUPPORTED_TYPES_MAP.keys()) | ||
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class CompressedTensorsW4A8(CompressedTensorsScheme): | ||
_kernel_backends_being_used: Set[str] = set() | ||
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def __init__(self, | ||
strategy: str, | ||
num_bits: int, | ||
group_size: Optional[int] = None, | ||
is_static_input_scheme: bool = False, | ||
input_symmetric: bool = True): | ||
self.strategy = strategy | ||
self.group_size = -1 if group_size is None else group_size | ||
self.is_static_input_scheme = is_static_input_scheme | ||
self.input_symmetric = input_symmetric | ||
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if num_bits not in W4A8_SUPPORTED_TYPES_MAP: | ||
raise ValueError( | ||
f"Unsupported num_bits = {num_bits}." | ||
f"Supported num_bits = {W4A8_SUPPORTED_TYPES_MAP.keys()}") | ||
self.quant_type = W4A8_SUPPORTED_TYPES_MAP[num_bits] | ||
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@classmethod | ||
def get_min_capability(cls) -> int: | ||
return 1 | ||
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def create_weights(self, layer: torch.nn.Module, output_size: int, | ||
input_size: int, output_partition_sizes: List[int], | ||
input_size_per_partition: int, | ||
params_dtype: torch.dtype, weight_loader: Callable, | ||
**kwargs): | ||
output_size_per_partition = sum(output_partition_sizes) | ||
row_parallel = (input_size != input_size_per_partition) | ||
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# Compute effective group_size | ||
if self.group_size == -1: | ||
effective_group_size = (input_size_per_partition | ||
if row_parallel else input_size) | ||
else: | ||
effective_group_size = self.group_size | ||
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# Ensure group_size divides input_size_per_partition | ||
assert input_size_per_partition % effective_group_size == 0, ( | ||
f"input_size_per_partition {input_size_per_partition}" | ||
f" not divisible by group_size {effective_group_size}") | ||
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# Determine scale partitioning | ||
is_channelwise = (self.group_size == -1) | ||
repeat_scales = (is_channelwise and row_parallel) | ||
partition_scales = not repeat_scales | ||
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mp_linear_kernel_config = MPLinearLayerConfig( | ||
full_weight_shape=(input_size, output_size), | ||
partition_weight_shape=(input_size_per_partition, | ||
output_size_per_partition), | ||
weight_type=self.quant_type, | ||
act_type=params_dtype, | ||
group_size=effective_group_size, | ||
zero_points=False, | ||
has_g_idx=False, | ||
) | ||
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kernel_type = choose_mp_linear_kernel(mp_linear_kernel_config) | ||
if kernel_type.__name__ not in self._kernel_backends_being_used: | ||
logger.info("Using %s for CompressedTensorsW4A8", | ||
kernel_type.__name__) | ||
self._kernel_backends_being_used.add(kernel_type.__name__) | ||
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scales_and_zp_size = input_size_per_partition // effective_group_size | ||
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weight = ModelWeightParameter(data=torch.empty( | ||
output_size_per_partition, | ||
input_size_per_partition, | ||
dtype=torch.int8), | ||
input_dim=1, | ||
output_dim=0, | ||
weight_loader=weight_loader) | ||
layer.register_parameter("weight", weight) | ||
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weight_scale_args = { | ||
"weight_loader": | ||
weight_loader, | ||
"data": | ||
torch.empty(output_size_per_partition, | ||
scales_and_zp_size, | ||
dtype=params_dtype) | ||
} | ||
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if partition_scales: | ||
weight_scale = GroupQuantScaleParameter(output_dim=0, | ||
input_dim=1, | ||
**weight_scale_args) | ||
else: | ||
weight_scale = ChannelQuantScaleParameter(output_dim=0, | ||
**weight_scale_args) | ||
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layer.register_parameter("weight_packed", weight) | ||
layer.register_parameter("weight_scale", weight_scale) | ||
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self.kernel = kernel_type(mp_linear_kernel_config, | ||
w_q_param_name="weight_packed", | ||
w_s_param_name="weight_scale", | ||
w_zp_param_name=None, | ||
w_gidx_param_name=None) | ||
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def process_weights_after_loading(self, layer: torch.nn.Module) -> None: | ||
self.kernel.process_weights_after_loading(layer) | ||
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def apply_weights(self, layer: torch.nn.Module, x: torch.Tensor, | ||
bias: Optional[torch.Tensor]) -> torch.Tensor: | ||
return self.kernel.apply_weights(layer, x, bias) |
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92 changes: 92 additions & 0 deletions
92
vllm/model_executor/layers/quantization/kernels/mixed_precision/dynamic_4bit.py
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# SPDX-FileCopyrightText: Copyright 2025 Arm Limited and/or its affiliate open-source-office@arm.com | ||
# SPDX-License-Identifier: Apache-2.0 | ||
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from typing import Optional, Tuple | ||
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import torch | ||
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from vllm.model_executor.layers.quantization.utils import replace_parameter | ||
from vllm.platforms import CpuArchEnum, current_platform | ||
from vllm.scalar_type import scalar_types | ||
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from .MPLinearKernel import MPLinearKernel, MPLinearLayerConfig | ||
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class Dynamic4bitLinearKernel(MPLinearKernel): | ||
SUPPORTED_QUANT_TYPES = [scalar_types.int4] | ||
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@classmethod | ||
def get_min_capability(cls) -> int: | ||
return 1 | ||
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@classmethod | ||
def can_implement(cls, | ||
c: MPLinearLayerConfig) -> Tuple[bool, Optional[str]]: | ||
if not current_platform.is_cpu(): | ||
return False, "Only CPU is supported" | ||
if c.weight_type not in cls.SUPPORTED_QUANT_TYPES: | ||
return False, f"Unsupported quant type {c.weight_type}" | ||
if current_platform.get_cpu_architecture( | ||
) == CpuArchEnum.ARM and c.act_type not in [ | ||
torch.float32, torch.bfloat16 | ||
]: | ||
return False, "Dynamic4bitLinearKernel on Arm requires"\ | ||
" Float32 or Bfloat16 activations" | ||
if c.full_weight_shape[0] % c.group_size != 0: | ||
return False, f"Group size ({c.group_size}) does not evenly divide"\ | ||
" the number of input features "\ | ||
f"({c.full_weight_shape[0]})" | ||
if current_platform.get_cpu_architecture() == CpuArchEnum.ARM: | ||
try: | ||
# Attempt to retrieve the operation | ||
_ = torch.ops.aten._dyn_quant_matmul_4bit | ||
except AttributeError: | ||
return False, f"PyTorch {torch.__version__} does not support"\ | ||
" _dyn_quant_matmul_4bit. Install a newer version" | ||
return True, None | ||
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def process_weights_after_loading(self, layer: torch.nn.Module): | ||
c = self.config | ||
packed_weight = getattr(layer, self.w_q_name) | ||
packed_weight = packed_weight.add(8) | ||
uint8_packed = (packed_weight[::, 1::2] << 4 | ||
| packed_weight[::, ::2]).to(torch.uint8) | ||
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scales = getattr(layer, self.w_s_name) | ||
block_size = c.group_size | ||
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# Handle scaling factors for partitioned weights | ||
if block_size == c.partition_weight_shape[0]: | ||
scales = scales.to( | ||
torch.float32 | ||
) # Float32 & Bfloat16 variants requires float32 scales | ||
scales = scales.view(-1, 1) # Channel-wise scales | ||
if layer.bias is not None: | ||
layer.bias = layer.bias.to( | ||
torch.float32 | ||
) # Float32 & Bfloat16 variants requires float32 bias | ||
else: | ||
# KleidiAI kernel requires bfloat16 scales with groupwise scheme | ||
scales = scales.to(torch.bfloat16) | ||
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# Repack weights as per kernel requirement | ||
w = torch.ops.aten._dyn_quant_pack_4bit_weight( | ||
uint8_packed, scales, layer.bias, block_size, | ||
c.partition_weight_shape[0], c.partition_weight_shape[1]) | ||
replace_parameter(layer, self.w_q_name, | ||
torch.nn.Parameter(w, requires_grad=False)) | ||
setattr(layer, self.w_s_name, None) | ||
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def apply_weights(self, | ||
layer: torch.nn.Module, | ||
x: torch.Tensor, | ||
bias: Optional[torch.Tensor] = None) -> torch.Tensor: | ||
c = self.config | ||
x_2d = x.reshape(-1, x.shape[-1]) | ||
out_shape = x.shape[:-1] + (c.partition_weight_shape[1], ) | ||
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w_q = getattr(layer, self.w_q_name) | ||
output = torch.ops.aten._dyn_quant_matmul_4bit( | ||
x_2d, w_q, c.group_size, c.partition_weight_shape[0], | ||
c.partition_weight_shape[1]) | ||
return output.reshape(out_shape) |
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These are just int8 values in the in4 range I'm assuming?
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Yes, you are correct