clip.py

"""Minimal implementation of CLIPVisionModel intended to be only used 
within a vision language model."""
from typing import Iterable, Optional, Tuple

import torch
import torch.nn as nn
from PIL import Image
from transformers import CLIPVisionConfig
from transformers.models.clip.modeling_clip import CLIPAttention

from vllm.config import ModelConfig
from vllm.inputs import LLMInputs
from vllm.model_executor.layers.activation import get_act_fn
from vllm.model_executor.layers.linear import (ColumnParallelLinear,
                                               RowParallelLinear)
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.model_loader.weight_utils import default_weight_loader
from vllm.multimodal.image import (cached_get_tokenizer,
                                   repeat_and_pad_image_tokens)
from vllm.sequence import SequenceData


def get_clip_patch_grid_length(*, image_size: int, patch_size: int) -> int:
    assert image_size % patch_size == 0
    return image_size // patch_size


def get_clip_num_patches(*, image_size: int, patch_size: int) -> int:
    grid_length = get_clip_patch_grid_length(image_size=image_size,
                                             patch_size=patch_size)
    return grid_length * grid_length


def get_clip_image_feature_size(hf_config: CLIPVisionConfig) -> int:
    return get_clip_num_patches(image_size=hf_config.image_size,
                                patch_size=hf_config.patch_size) + 1


def get_max_clip_image_tokens(hf_config: CLIPVisionConfig) -> int:
    return get_clip_image_feature_size(hf_config)


def dummy_seq_data_for_clip(
    hf_config: CLIPVisionConfig,
    seq_len: int,
    *,
    image_token_id: int,
    image_feature_size_override: Optional[int] = None,
):
    if image_feature_size_override is None:
        image_feature_size = get_clip_image_feature_size(hf_config)
    else:
        image_feature_size = image_feature_size_override

    token_ids = [image_token_id] * image_feature_size
    token_ids += [0] * (seq_len - image_feature_size)
    return SequenceData(token_ids)


def dummy_image_for_clip(
    hf_config: CLIPVisionConfig,
    *,
    image_width_override: Optional[int] = None,
    image_height_override: Optional[int] = None,
):
    width = height = hf_config.image_size
    if image_width_override is not None:
        width = image_width_override
    if image_height_override is not None:
        height = image_height_override

    image = Image.new("RGB", (width, height), color=0)
    return {"image": image}


def input_processor_for_clip(
    model_config: ModelConfig,
    hf_config: CLIPVisionConfig,
    llm_inputs: LLMInputs,
    *,
    image_token_id: int,
    image_feature_size_override: Optional[int] = None,
):
    multi_modal_data = llm_inputs.get("multi_modal_data")
    if multi_modal_data is None or "image" not in multi_modal_data:
        return llm_inputs

    tokenizer = cached_get_tokenizer(model_config.tokenizer)

    if image_feature_size_override is None:
        image_data = multi_modal_data["image"]
        if isinstance(image_data, Image.Image):
            image_feature_size = get_clip_image_feature_size(hf_config)
        elif isinstance(image_data, torch.Tensor):
            image_feature_size = image_data.shape[0]
        else:
            raise TypeError(f"Invalid image type: {type(image_data)}")
    else:
        image_feature_size = image_feature_size_override

    new_prompt, new_token_ids = repeat_and_pad_image_tokens(
        tokenizer,
        llm_inputs.get("prompt"),
        llm_inputs["prompt_token_ids"],
        image_token_id=image_token_id,
        repeat_count=image_feature_size,
    )

    # NOTE: Create a defensive copy of the original inputs
    return LLMInputs(prompt_token_ids=new_token_ids,
                     prompt=new_prompt,
                     multi_modal_data=multi_modal_data)


# Adapted from https://github.com/huggingface/transformers/blob/v4.39.0/src/transformers/models/clip/modeling_clip.py#L164 # noqa
class CLIPVisionEmbeddings(nn.Module):

    def __init__(self, config: CLIPVisionConfig):
        super().__init__()
        self.config = config
        self.embed_dim = config.hidden_size
        self.image_size = config.image_size
        self.patch_size = config.patch_size

        self.class_embedding = nn.Parameter(torch.randn(self.embed_dim))

        self.patch_embedding = nn.Conv2d(
            in_channels=config.num_channels,
            out_channels=self.embed_dim,
            kernel_size=self.patch_size,
            stride=self.patch_size,
            bias=False,
        )

        self.num_patches = get_clip_num_patches(image_size=self.image_size,
                                                patch_size=self.patch_size)
        self.num_positions = self.num_patches + 1
        self.position_embedding = nn.Embedding(self.num_positions,
                                               self.embed_dim)
        self.register_buffer("position_ids",
                             torch.arange(self.num_positions).expand((1, -1)),
                             persistent=False)

    def forward(self, pixel_values: torch.Tensor) -> torch.Tensor:
        batch_size = pixel_values.shape[0]
        target_dtype = self.patch_embedding.weight.dtype
        patch_embeds = self.patch_embedding(pixel_values.to(
            dtype=target_dtype))  # shape = [*, width, grid, grid]
        patch_embeds = patch_embeds.flatten(2).transpose(1, 2)

        class_embeds = self.class_embedding.expand(batch_size, 1, -1)
        embeddings = torch.cat([class_embeds, patch_embeds], dim=1)
        embeddings = embeddings + self.position_embedding(self.position_ids)

        return embeddings


class CLIPMLP(nn.Module):

    def __init__(self,
                 config: CLIPVisionConfig,
                 quant_config: Optional[QuantizationConfig] = None):
        super().__init__()
        self.config = config
        self.activation_fn = get_act_fn(config.hidden_act)
        self.fc1 = ColumnParallelLinear(config.hidden_size,
                                        config.intermediate_size,
                                        bias=True,
                                        quant_config=quant_config)
        self.fc2 = RowParallelLinear(config.intermediate_size,
                                     config.hidden_size,
                                     bias=True,
                                     quant_config=quant_config)

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states, _ = self.fc1(hidden_states)
        hidden_states = self.activation_fn(hidden_states)
        hidden_states, _ = self.fc2(hidden_states)

        return hidden_states


class CLIPEncoderLayer(nn.Module):

    def __init__(self,
                 config: CLIPVisionConfig,
                 quant_config: Optional[QuantizationConfig] = None):
        super().__init__()

        self.self_attn = CLIPAttention(config)
        self.layer_norm1 = nn.LayerNorm(config.hidden_size,
                                        eps=config.layer_norm_eps)
        self.mlp = CLIPMLP(config, quant_config=quant_config)
        self.layer_norm2 = nn.LayerNorm(config.hidden_size,
                                        eps=config.layer_norm_eps)

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:

        residual = hidden_states

        hidden_states = self.layer_norm1(hidden_states)
        hidden_states, _ = self.self_attn(hidden_states=hidden_states)
        hidden_states = residual + hidden_states

        residual = hidden_states
        hidden_states = self.layer_norm2(hidden_states)
        hidden_states = self.mlp(hidden_states)
        hidden_states = residual + hidden_states

        return hidden_states


class CLIPEncoder(nn.Module):
    """
    Transformer encoder consisting of `config.num_hidden_layers` self 
    attention layers. Each layer is a [`CLIPEncoderLayer`].

    Args:
        config: CLIPConfig
    """

    def __init__(self,
                 config: CLIPVisionConfig,
                 quant_config: Optional[QuantizationConfig] = None,
                 num_hidden_layers_override: Optional[int] = None):
        super().__init__()
        self.config = config

        if num_hidden_layers_override is None:
            num_hidden_layers = config.num_hidden_layers
        else:
            num_hidden_layers = num_hidden_layers_override
        self.layers = nn.ModuleList([
            CLIPEncoderLayer(config=config, quant_config=quant_config)
            for _ in range(num_hidden_layers)
        ])

    def forward(self, inputs_embeds: torch.Tensor):

        hidden_states = inputs_embeds
        for encoder_layer in self.layers:
            hidden_states = encoder_layer(hidden_states)

        return hidden_states


class CLIPVisionTransformer(nn.Module):

    def __init__(self,
                 config: CLIPVisionConfig,
                 quant_config: Optional[QuantizationConfig] = None,
                 num_hidden_layers_override: Optional[int] = None):
        super().__init__()
        self.config = config
        embed_dim = config.hidden_size

        self.embeddings = CLIPVisionEmbeddings(config)

        # NOTE: This typo of "layrnorm" is not fixed on purpose to match
        # the original transformers code and name of the model weights.
        self.pre_layrnorm = nn.LayerNorm(embed_dim, eps=config.layer_norm_eps)
        self.encoder = CLIPEncoder(
            config=config,
            quant_config=quant_config,
            num_hidden_layers_override=num_hidden_layers_override)

    def forward(
        self,
        pixel_values: torch.Tensor,
    ) -> torch.Tensor:

        hidden_states = self.embeddings(pixel_values)
        hidden_states = self.pre_layrnorm(hidden_states)
        hidden_states = self.encoder(inputs_embeds=hidden_states)

        return hidden_states


class CLIPVisionModel(nn.Module):

    config_class = CLIPVisionConfig
    main_input_name = "pixel_values"

    def __init__(self,
                 config: CLIPVisionConfig,
                 quant_config: Optional[QuantizationConfig] = None,
                 num_hidden_layers_override: Optional[int] = None):
        super().__init__()
        self.vision_model = CLIPVisionTransformer(
            config=config,
            quant_config=quant_config,
            num_hidden_layers_override=num_hidden_layers_override)

    def forward(self, pixel_values: Optional[torch.Tensor] = None):

        return self.vision_model(pixel_values=pixel_values)

    @property
    def device(self):
        return next(self.parameters()).device

    def load_weights(self, weights: Iterable[Tuple[str, torch.Tensor]]):
        params_dict = dict(self.named_parameters())
        layer_count = len(self.vision_model.encoder.layers)

        for name, loaded_weight in weights:
            # post_layernorm is not needed in CLIPVisionModel
            if "vision_model.post_layernorm" in name:
                continue
            # omit layers when num_hidden_layers_override is set
            if "vision_model.encoder.layers." in name:
                layer_idx = int(name.split(".")[3])
                if layer_idx >= layer_count:
                    continue

            param = params_dict[name]
            weight_loader = getattr(param, "weight_loader",
                                    default_weight_loader)
            weight_loader(param, loaded_weight)