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Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from abc import ABC, abstractmethod
from typing import Final, Generic, Optional, Protocol, TypeVar, Union
import torch
from transformers import PretrainedConfig
import vllm.envs as envs
from vllm.attention.selector import (backend_name_to_enum,
get_global_forced_attn_backend)
from vllm.logger import init_logger
from vllm.platforms import _Backend, current_platform
logger = init_logger(__name__)
_C = TypeVar("_C", bound=PretrainedConfig)
class VisionEncoderInfo(ABC, Generic[_C]):
def __init__(self, hf_config: _C) -> None:
super().__init__()
self.hf_config = hf_config
self.vision_config = hf_config.vision_config
@abstractmethod
def get_num_image_tokens(
self,
*,
image_width: int,
image_height: int,
) -> int:
raise NotImplementedError
@abstractmethod
def get_image_size(self) -> int:
raise NotImplementedError
@abstractmethod
def get_patch_size(self) -> int:
raise NotImplementedError
@abstractmethod
def get_patch_grid_length(self) -> int:
raise NotImplementedError
class VisionLanguageConfig(Protocol):
vision_config: Final[PretrainedConfig]
def get_vision_encoder_info(
hf_config: VisionLanguageConfig) -> VisionEncoderInfo:
# Avoid circular imports
from .clip import CLIPEncoderInfo, CLIPVisionConfig
from .pixtral import PixtralHFEncoderInfo, PixtralVisionConfig
from .siglip import SiglipEncoderInfo, SiglipVisionConfig
if isinstance(hf_config.vision_config, CLIPVisionConfig):
return CLIPEncoderInfo(hf_config)
if isinstance(hf_config.vision_config, PixtralVisionConfig):
return PixtralHFEncoderInfo(hf_config)
if isinstance(hf_config.vision_config, SiglipVisionConfig):
return SiglipEncoderInfo(hf_config)
msg = f"Unsupported vision config: {type(hf_config.vision_config)}"
raise NotImplementedError(msg)
def get_vit_attn_backend(support_fa: bool = False) -> _Backend:
"""
Get the available attention backend for Vision Transformer.
"""
# TODO(Isotr0py): Remove `support_fa` after support FA for all ViTs attn.
selected_backend: Optional[_Backend] = get_global_forced_attn_backend()
if selected_backend is None:
backend_by_env_var: Optional[str] = envs.VLLM_ATTENTION_BACKEND
if backend_by_env_var is not None:
selected_backend = backend_name_to_enum(backend_by_env_var)
if selected_backend is None:
if current_platform.is_cuda():
device_available = current_platform.has_device_capability(80)
if device_available and support_fa:
from transformers.utils import is_flash_attn_2_available
if is_flash_attn_2_available():
selected_backend = _Backend.FLASH_ATTN
else:
logger.warning_once(
"Current `vllm-flash-attn` has a bug inside vision "
"module, so we use xformers backend instead. You can "
"run `pip install flash-attn` to use flash-attention "
"backend.")
selected_backend = _Backend.XFORMERS
else:
# For Volta and Turing GPUs, use xformers instead.
selected_backend = _Backend.XFORMERS
else:
# Default to torch SDPA for other non-GPU platforms.
selected_backend = _Backend.TORCH_SDPA
return selected_backend
def resolve_visual_encoder_outputs(
encoder_outputs: Union[torch.Tensor, list[torch.Tensor]],
feature_sample_layers: Optional[list[int]],
post_layer_norm: Optional[torch.nn.LayerNorm],
max_possible_layers: int,
) -> torch.Tensor:
"""Given the outputs a visual encoder module that may correspond to the
output of the last layer, or a list of hidden states to be stacked,
handle post normalization and resolve it into a single output tensor.
Args:
encoder_outputs: Output of encoder's last layer or all hidden states.
feature_sample_layers: Optional layer indices to grab from the encoder
outputs; if provided, encoder outputs must be a list.
post_layer_norm: Post norm to apply to the output of the encoder.
max_possible_layers: Total layers in the fully loaded visual encoder.
"""
if feature_sample_layers is None:
if post_layer_norm is not None:
return post_layer_norm(encoder_outputs)
return encoder_outputs
# Get the hidden states corresponding to the layer indices.
# Negative values are relative to the full visual encoder,
# so offset them depending on how many layers were loaded.
# NOTE: this assumes that encoder_outputs is a list containing
# the inputs to the visual encoder, followed by the hidden states
# of each layer.
num_loaded_layers = len(encoder_outputs) - 1
offset = max_possible_layers - num_loaded_layers
hs_pool = [
encoder_outputs[layer_idx]
if layer_idx >= 0 else encoder_outputs[layer_idx + offset]
for layer_idx in feature_sample_layers
]
# Apply post-norm on the final hidden state if we are using it
uses_last_layer = feature_sample_layers[-1] in (len(hs_pool) - 1, -1)
if post_layer_norm is not None and uses_last_layer:
hs_pool[-1] = post_layer_norm(encoder_outputs)
return torch.cat(hs_pool, dim=-1)