180 lines
6.1 KiB
Python
180 lines
6.1 KiB
Python
from typing import Any, Dict, List, Optional
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import torch
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from torch.nn.parameter import Parameter
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from sglang.srt.layers.linear import LinearMethodBase
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from sglang.srt.layers.parameter import ChannelQuantScaleParameter, ModelWeightParameter
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from sglang.srt.layers.quantization.base_config import (
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QuantizationConfig,
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QuantizeMethodBase,
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)
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from sglang.srt.layers.quantization.fp8_kernel import per_token_group_quant_fp8
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from sglang.srt.layers.quantization.fp8_utils import (
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apply_fp8_linear,
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cutlass_fp8_supported,
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input_to_float8,
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normalize_e4m3fn_to_e4m3fnuz,
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)
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from sglang.srt.utils import is_hip
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_is_hip = is_hip()
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class W8A8Fp8Config(QuantizationConfig):
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"""Config class for W8A8 FP8 Quantization.
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Weight Quantization:
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- Method: Static quantization
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- Granularity: Per-channel
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- Type: Symmetric
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Activation Quantization:
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- Method: Dynamic quantization
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- Granularity: Per-token
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- Type: Symmetric
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Note:
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- For models without offline quantization, weights will be quantized during model loading
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- If CUTLASS is supported: Per-channel weight quantization is used
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- If CUTLASS is not supported: Falls back to per-tensor weight quantization
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"""
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def __init__(self, is_checkpoint_fp8_serialized: bool = False):
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self.is_checkpoint_fp8_serialized = is_checkpoint_fp8_serialized
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@classmethod
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def get_supported_act_dtypes(cls) -> List[torch.dtype]:
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return [torch.float16, torch.bfloat16]
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@classmethod
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def get_min_capability(cls) -> int:
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return 89
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@classmethod
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def get_name(self) -> str:
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return "w8a8_fp8"
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@classmethod
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def get_config_filenames(cls) -> List[str]:
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return []
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@classmethod
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def from_config(cls, config: Dict[str, Any]) -> "W8A8Fp8Config":
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quant_method = cls.get_from_keys(config, ["quant_method"])
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is_checkpoint_fp8_serialized = "compressed-tensors" in quant_method
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return cls(is_checkpoint_fp8_serialized=is_checkpoint_fp8_serialized)
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def get_quant_method(
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self,
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layer: torch.nn.Module,
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prefix: str,
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) -> Optional["QuantizeMethodBase"]:
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from sglang.srt.layers.linear import LinearBase
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if isinstance(layer, LinearBase):
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return W8A8Fp8LinearMethod(self)
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return None
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def get_scaled_act_names(self) -> List[str]:
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return []
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class W8A8Fp8LinearMethod(LinearMethodBase):
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def __init__(self, quantization_config: W8A8Fp8Config):
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self.cutlass_fp8_supported = cutlass_fp8_supported()
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self.quantization_config = quantization_config
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def process_weights_after_loading(self, layer: torch.nn.Module) -> None:
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weight = layer.weight
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if self.quantization_config.is_checkpoint_fp8_serialized:
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weight_scale = layer.weight_scale.detach()
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# If checkpoint offline quantized with w8a8_fp8, load the weight and weight_scale directly.
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if _is_hip:
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weight, weight_scale, _ = normalize_e4m3fn_to_e4m3fnuz(
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weight=weight, weight_scale=weight_scale
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)
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layer.weight = Parameter(weight.t(), requires_grad=False)
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layer.weight_scale = Parameter(weight_scale, requires_grad=False)
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else:
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# If checkpoint not offline quantized, quantize the weights with per-channel quantization.
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if self.cutlass_fp8_supported:
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# if cutlass supported, we use cutlass_scaled_mm
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# which requires per-channel quantization on weight
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qweight, weight_scale = per_token_group_quant_fp8(
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layer.weight, layer.weight.shape[-1]
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)
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weight_scale = weight_scale.t().contiguous()
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if _is_hip:
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weight, weight_scale, _ = normalize_e4m3fn_to_e4m3fnuz(
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weight=weight, weight_scale=weight_scale
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)
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else:
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# if cutlass not supported, we fall back to use torch._scaled_mm
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# which requires per tensor quantization on weight
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fp8_dtype = torch.float8_e4m3fnuz if _is_hip else torch.float8_e4m3fn
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qweight, weight_scale = input_to_float8(layer.weight, dtype=fp8_dtype)
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# Update the layer with the new values.
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layer.weight = Parameter(qweight.t(), requires_grad=False)
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layer.weight_scale = Parameter(weight_scale, requires_grad=False)
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layer.input_scale = None
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def create_weights(
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self,
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layer: torch.nn.Module,
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input_size_per_partition: int,
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output_partition_sizes: List[int],
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input_size: int,
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output_size: int,
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params_dtype: torch.dtype,
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**extra_weight_attrs
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):
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weight_dtype = (
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torch.float8_e4m3fn
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if self.quantization_config.is_checkpoint_fp8_serialized
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else params_dtype
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)
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weight_loader = extra_weight_attrs.get("weight_loader")
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self.logical_widths = output_partition_sizes
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weight = ModelWeightParameter(
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data=torch.empty(
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sum(output_partition_sizes),
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input_size_per_partition,
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dtype=weight_dtype,
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),
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input_dim=1,
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output_dim=0,
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weight_loader=weight_loader,
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)
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layer.register_parameter("weight", weight)
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if self.quantization_config.is_checkpoint_fp8_serialized:
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weight_scale = ChannelQuantScaleParameter(
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data=torch.empty((sum(output_partition_sizes), 1), dtype=torch.float32),
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output_dim=0,
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weight_loader=weight_loader,
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)
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layer.register_parameter("weight_scale", weight_scale)
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else:
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layer.weight_scale = None
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def apply(
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self,
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layer: torch.nn.Module,
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x: torch.Tensor,
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bias: Optional[torch.Tensor] = None,
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):
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return apply_fp8_linear(
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x,
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layer.weight,
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layer.weight_scale,
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bias=bias,
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cutlass_fp8_supported=self.cutlass_fp8_supported,
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)
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