compressed_tensors: port w8a16 fp8 from vllm (#4852)

python/sglang/srt/layers/quantization/compressed_tensors/compressed_tensors.py

@@ -33,6 +33,7 @@ from sglang.srt.layers.quantization.compressed_tensors.compressed_tensors_moe im
 from sglang.srt.layers.quantization.compressed_tensors.schemes import (
     CompressedTensorsScheme,
     CompressedTensorsW8A8Fp8,
+    CompressedTensorsW8A16Fp8,
 )
 from sglang.srt.layers.quantization.compressed_tensors.utils import (
     find_matched_target,

python/sglang/srt/layers/quantization/compressed_tensors/schemes/__init__.py

@@ -2,8 +2,10 @@
 
 from .compressed_tensors_scheme import CompressedTensorsScheme
 from .compressed_tensors_w8a8_fp8 import CompressedTensorsW8A8Fp8
+from .compressed_tensors_w8a16_fp8 import CompressedTensorsW8A16Fp8
 
 __all__ = [
     "CompressedTensorsScheme",
     "CompressedTensorsW8A8Fp8",
+    "CompressedTensorsW8A16Fp8",
 ]

python/sglang/srt/layers/quantization/compressed_tensors/schemes/compressed_tensors_w8a16_fp8.py

@@ -0,0 +1,153 @@
+# Adapted from https://github.com/vllm-project/vllm/tree/main/vllm/model_executor/layers/quantization/compressed_tensors
+# SPDX-License-Identifier: Apache-2.0
+
+from typing import Callable, List, Optional
+
+import torch
+from compressed_tensors.quantization import QuantizationStrategy
+
+from sglang.srt.layers.parameter import (
+    ChannelQuantScaleParameter,
+    ModelWeightParameter,
+    PerTensorScaleParameter,
+)
+from sglang.srt.layers.quantization.compressed_tensors.schemes import (
+    CompressedTensorsScheme,
+)
+from sglang.srt.layers.quantization.utils import convert_to_channelwise
+
+try:
+    from vllm.model_executor.layers.quantization.utils.marlin_utils_fp8 import (
+        apply_fp8_marlin_linear,
+        prepare_fp8_layer_for_marlin,
+    )
+
+    MARLIN_FP8_AVAILABLE = True
+except ImportError:
+    MARLIN_FP8_AVAILABLE = False
+
+    def apply_fp8_marlin_linear(*args, **kwargs):
+        raise ImportError("vllm is not installed")
+
+    def prepare_fp8_layer_for_marlin(*args, **kwargs):
+        raise ImportError("vllm is not installed")
+
+
+__all__ = ["CompressedTensorsW8A16Fp8"]
+
+SUPPORTED_STRATEGIES = [QuantizationStrategy.CHANNEL, QuantizationStrategy.TENSOR]
+
+
+class CompressedTensorsW8A16Fp8(CompressedTensorsScheme):
+    def __init__(self, strategy: str, is_static_input_scheme: bool):
+        self.strategy = strategy
+        self.is_static_input_scheme = is_static_input_scheme
+
+        if not MARLIN_FP8_AVAILABLE:
+            raise ImportError(
+                "vllm is not installed. To use CompressedTensorsW8A16Fp8, please install vllm"
+            )
+
+    @classmethod
+    def get_min_capability(cls) -> int:
+        # ampere and up
+        return 80
+
+    # W8A8-Fp8 kernels support only per-tensor and per-channel cases.
+    # So if we have a fused module (QKV, MLP) with per tensor scales,
+    # we expand each scale to its shard's channels.
+    def process_weights_after_loading(self, layer) -> None:
+        if self.strategy == QuantizationStrategy.TENSOR:
+            ws_channelwise = convert_to_channelwise(
+                layer.weight_scale, layer.logical_widths
+            )
+            layer.weight_scale = torch.nn.Parameter(ws_channelwise, requires_grad=False)
+        else:
+            # required by torch.compile to be torch.nn.Parameter
+            layer.weight_scale = torch.nn.Parameter(
+                layer.weight_scale.data, requires_grad=False
+            )
+
+        # Weights must be transposed for marlin
+        layer.weight = torch.nn.Parameter(layer.weight.t(), requires_grad=False)
+
+        if self.is_static_input_scheme:
+            # required by torch.compile to be torch.nn.Parameter
+            layer.input_scale = torch.nn.Parameter(
+                layer.input_scale.data, requires_grad=False
+            )
+        prepare_fp8_layer_for_marlin(layer, strategy="channel")
+
+    def create_weights(
+        self,
+        layer: torch.nn.Module,
+        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)
+        layer.logical_widths = output_partition_sizes
+        layer.input_size_per_partition = input_size_per_partition
+        layer.output_size_per_partition = output_size_per_partition
+        layer.orig_dtype = params_dtype
+
+        # WEIGHT
+        weight = ModelWeightParameter(
+            data=torch.empty(
+                output_size_per_partition,
+                input_size_per_partition,
+                dtype=torch.float8_e4m3fn,
+            ),
+            input_dim=1,
+            output_dim=0,
+            weight_loader=weight_loader,
+        )
+        layer.register_parameter("weight", weight)
+
+        # WEIGHT SCALE
+        if self.strategy == QuantizationStrategy.CHANNEL:
+            weight_scale = ChannelQuantScaleParameter(
+                data=torch.empty((sum(output_partition_sizes), 1), dtype=torch.float32),
+                output_dim=0,
+                weight_loader=weight_loader,
+            )
+        elif self.strategy == QuantizationStrategy.TENSOR:
+            weight_scale = PerTensorScaleParameter(
+                data=torch.empty(len(output_partition_sizes), dtype=torch.float32),
+                weight_loader=weight_loader,
+            )
+        else:
+            raise ValueError(
+                f"Unsupported weight strategy={self.strategy}, "
+                f"supported strategies are {SUPPORTED_STRATEGIES}"
+            )
+
+        weight_scale[:] = torch.finfo(torch.float32).min
+        layer.register_parameter("weight_scale", weight_scale)
+
+        # INPUT SCALE (to deal with converted checkpoints)
+        if self.is_static_input_scheme:
+            input_scale = PerTensorScaleParameter(
+                data=torch.empty(len(output_partition_sizes), dtype=torch.float32),
+                weight_loader=weight_loader,
+            )
+            layer.register_parameter("input_scale", input_scale)
+
+    def apply_weights(
+        self,
+        layer: torch.nn.Module,
+        x: torch.Tensor,
+        bias: Optional[torch.Tensor] = None,
+    ) -> torch.Tensor:
+        return apply_fp8_marlin_linear(
+            input=x,
+            weight=layer.weight,
+            weight_scale=layer.weight_scale,
+            workspace=layer.workspace,
+            size_n=layer.output_size_per_partition,
+            size_k=layer.input_size_per_partition,
+            bias=bias,
+        )