siglip.py

"""Implementation of SiglipVisionModel intended to be only used
within a vision language model."""

import math
from typing import Iterable, List, Optional, Set, Tuple, Union

import numpy as np
import torch
import torch.nn.functional as F
from PIL import Image
from torch import nn
from transformers import SiglipVisionConfig

from vllm.attention.selector import _Backend
from vllm.config import ModelConfig
from vllm.distributed import divide, get_tensor_model_parallel_world_size
from vllm.inputs import DecoderOnlyInputs, token_inputs
from vllm.model_executor.layers.activation import get_act_fn
from vllm.model_executor.layers.linear import (ColumnParallelLinear,
                                               QKVParallelLinear,
                                               RowParallelLinear)
from vllm.model_executor.layers.quantization import QuantizationConfig
from vllm.model_executor.layers.vocab_parallel_embedding import (
    VocabParallelEmbedding)
from vllm.model_executor.model_loader.weight_utils import default_weight_loader
from vllm.multimodal.utils import (cached_get_tokenizer,
                                   consecutive_placeholder_ranges,
                                   repeat_and_pad_placeholder_tokens,
                                   resolve_visual_encoder_outputs)
from vllm.sequence import SequenceData

from .utils import get_vit_attn_backend


def get_siglip_patch_grid_length(*, image_size: int, patch_size: int) -> int:
    # Since interpolation is applied, the image size need not be divisible
    # assert image_size % patch_size == 0
    return image_size // patch_size


def get_siglip_num_patches(*, image_size: int, patch_size: int) -> int:
    grid_length = get_siglip_patch_grid_length(image_size=image_size,
                                               patch_size=patch_size)
    return grid_length * grid_length


def get_siglip_image_feature_size(hf_config: SiglipVisionConfig) -> int:
    return get_siglip_num_patches(image_size=hf_config.image_size,
                                  patch_size=hf_config.patch_size)


def get_max_siglip_image_tokens(hf_config: SiglipVisionConfig) -> int:
    return get_siglip_image_feature_size(hf_config)


def dummy_seq_data_for_siglip(
    hf_config: SiglipVisionConfig,
    seq_len: int,
    num_images: int,
    *,
    image_token_id: int,
    image_feature_size_override: Optional[int] = None,
    mm_key: str = "image",
):
    if image_feature_size_override is None:
        image_feature_size = get_siglip_image_feature_size(hf_config)
    else:
        image_feature_size = image_feature_size_override

    return SequenceData.from_prompt_token_counts(
        (image_token_id, image_feature_size * num_images),
        (0, seq_len - image_feature_size * num_images),
    ), {
        mm_key:
        consecutive_placeholder_ranges(num_items=num_images,
                                       item_size=image_feature_size)
    }


def dummy_image_for_siglip(
    hf_config: SiglipVisionConfig,
    num_images: int,
    *,
    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 if num_images == 1 else [image] * num_images}


def dummy_video_for_siglip(
    hf_config: SiglipVisionConfig,
    num_frames: int,
    num_videos: int = 1,
    *,
    image_width_override: Optional[int] = None,
    image_height_override: Optional[int] = None,
):
    pil_frame = dummy_image_for_siglip(
        hf_config,
        num_images=1,
        image_width_override=image_width_override,
        image_height_override=image_height_override)
    np_frame = np.array(pil_frame["image"])
    mm_data_per_video = np.repeat([np_frame], num_frames, axis=0)
    video_data = [mm_data_per_video] * num_videos
    mm_data = {"video": video_data}
    return mm_data


def input_processor_for_siglip(
    model_config: ModelConfig,
    hf_config: SiglipVisionConfig,
    inputs: DecoderOnlyInputs,
    *,
    image_token_id: int,
    image_feature_size_override: Optional[Union[int, List[int]]] = None,
):
    multi_modal_data = inputs.get("multi_modal_data")
    if multi_modal_data is None or "image" not in multi_modal_data:
        return inputs

    if "multi_modal_placeholders" in inputs and "image" in inputs[
            "multi_modal_placeholders"]:
        # The inputs already have placeholders.
        return 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_siglip_image_feature_size(hf_config)
        elif isinstance(image_data, torch.Tensor):
            num_images, image_feature_size, hidden_size = image_data.shape
        else:
            raise TypeError(f"Invalid image type: {type(image_data)}")
    else:
        image_feature_size = image_feature_size_override

    new_prompt, new_token_ids, ranges = repeat_and_pad_placeholder_tokens(
        tokenizer,
        inputs.get("prompt"),
        inputs["prompt_token_ids"],
        placeholder_token_id=image_token_id,
        repeat_count=image_feature_size,
    )

    # NOTE: Create a defensive copy of the original inputs
    return token_inputs(prompt_token_ids=new_token_ids,
                        prompt=new_prompt,
                        multi_modal_data=multi_modal_data,
                        multi_modal_placeholders={"image": ranges})


# Adapted from https://github.com/huggingface/transformers/blob/v4.43.3/src/transformers/models/siglip/modeling_siglip.py#L249 # noqa
class SiglipVisionEmbeddings(nn.Module):

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

        self.patch_embedding = nn.Conv2d(
            in_channels=config.num_channels,
            out_channels=self.embed_dim,
            kernel_size=self.patch_size,
            stride=self.patch_size,
            padding="valid",
        )

        self.num_patches = (self.image_size // self.patch_size)**2
        self.num_positions = self.num_patches
        self.position_embedding = VocabParallelEmbedding(
            self.num_positions, self.embed_dim)
        self.register_buffer(
            "position_ids",
            torch.arange(self.num_positions, dtype=torch.int64).expand(
                (1, -1)),
            persistent=False,
        )

    def interpolate_pos_encoding(self, embeddings: torch.Tensor, height: int,
                                 width: int) -> torch.Tensor:
        """
        This method is an adapted method for SigLIP (due to SigLIP not having
        class embedding unlike other ViTs) that allows the model to interpolate
        the pre-trained position encodings such that it can be usable on higher
        resolution images.

        Source:
        https://github.com/facebookresearch/dino/blob/de9ee3df6cf39fac952ab558447af1fa1365362a/vision_transformer.py#L174
        """
        position_embeddings = self.position_embedding.weight.unsqueeze(0)
        num_patches = embeddings.shape[1]
        num_positions = position_embeddings.shape[1]
        if num_patches == num_positions and height == width:
            return position_embeddings

        dim = embeddings.shape[-1]
        height = height // self.patch_size
        width = width // self.patch_size
        # we add a small number to avoid floating point error
        # in the interpolation
        # see discussion at https://github.com/facebookresearch/dino/issues/8
        height, width = height + 0.1, width + 0.1

        patch_pos_embed = position_embeddings.reshape(
            1, int(math.sqrt(num_positions)), int(math.sqrt(num_positions)),
            dim)
        patch_pos_embed = patch_pos_embed.permute(0, 3, 1, 2)
        patch_pos_embed = nn.functional.interpolate(
            patch_pos_embed,
            scale_factor=(
                height / math.sqrt(num_positions),
                width / math.sqrt(num_positions),
            ),
            mode="bicubic",
            align_corners=False,
        )
        if (int(height) != patch_pos_embed.shape[-2]
                or int(width) != patch_pos_embed.shape[-1]):
            raise ValueError("Width or height does not match with "
                             "the interpolated position embeddings")

        patch_pos_embed = patch_pos_embed.permute(0, 2, 3, 1).view(1, -1, dim)
        return patch_pos_embed

    def forward(self,
                pixel_values: torch.Tensor,
                interpolate_pos_encoding: bool = False) -> torch.Tensor:
        _, _, height, width = pixel_values.shape
        target_dtype = self.patch_embedding.weight.dtype
        patch_embeds = self.patch_embedding(pixel_values.to(
            dtype=target_dtype))  # shape = [*, width, grid, grid]
        embeddings = patch_embeds.flatten(2).transpose(1, 2)

        if interpolate_pos_encoding:
            embeddings = embeddings + self.interpolate_pos_encoding(
                embeddings, height, width)
        else:
            embeddings = embeddings + self.position_embedding(
                self.position_ids)
        return embeddings


class SiglipAttention(nn.Module):

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = "",
    ) -> None:
        super().__init__()

        self.config = config
        self.embed_dim = config.hidden_size
        self.num_heads = config.num_attention_heads
        self.head_dim = self.embed_dim // self.num_heads
        if self.head_dim * self.num_heads != self.embed_dim:
            raise ValueError(f"embed_dim must be divisible by num_heads (got "
                             "`embed_dim`: {self.embed_dim} and `num_heads`:"
                             f" {self.num_heads}).")

        self.scale = self.head_dim**-0.5
        self.dropout = config.attention_dropout
        self.qkv_proj = QKVParallelLinear(
            hidden_size=self.embed_dim,
            head_size=self.head_dim,
            total_num_heads=self.num_heads,
            quant_config=quant_config,
            prefix=f"{prefix}.qkv_proj",
        )

        self.out_proj = RowParallelLinear(
            input_size=self.embed_dim,
            output_size=self.embed_dim,
            quant_config=quant_config,
            prefix=f"{prefix}.out_proj",
        )

        self.tp_size = get_tensor_model_parallel_world_size()
        self.num_heads_per_partition = divide(self.num_heads, self.tp_size)

        self.attn_backend = get_vit_attn_backend(support_fa=False)
        if self.attn_backend not in {_Backend.TORCH_SDPA, _Backend.XFORMERS}:
            raise RuntimeError(
                f"SIGLIP does not support {self.attn_backend} backend now.")

    def forward(
        self,
        hidden_states: torch.Tensor,
    ) -> torch.Tensor:
        """Input shape: Batch x Time x Channel"""
        batch_size, q_len, _ = hidden_states.size()

        qkv_states, _ = self.qkv_proj(hidden_states)
        query_states, key_states, value_states = qkv_states.chunk(3, dim=-1)

        query_states = query_states.view(batch_size, q_len,
                                         self.num_heads_per_partition,
                                         self.head_dim)
        key_states = key_states.view(batch_size, q_len,
                                     self.num_heads_per_partition,
                                     self.head_dim)
        value_states = value_states.view(batch_size, q_len,
                                         self.num_heads_per_partition,
                                         self.head_dim)

        if self.attn_backend == _Backend.XFORMERS:
            from xformers import ops as xops

            out = xops.memory_efficient_attention_forward(query_states,
                                                          key_states,
                                                          value_states,
                                                          p=self.dropout,
                                                          scale=self.scale)
        elif self.attn_backend == _Backend.TORCH_SDPA:
            query_states, key_states, value_states = (x.transpose(1, 2)
                                                      for x in (query_states,
                                                                key_states,
                                                                value_states))
            out = F.scaled_dot_product_attention(query_states,
                                                 key_states,
                                                 value_states,
                                                 dropout_p=self.dropout,
                                                 scale=self.scale)
            out = out.transpose(1, 2)

        out = out.view(batch_size, q_len, -1)
        attn_output, _ = self.out_proj(out)

        return attn_output, None


class SiglipMLP(nn.Module):

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = "",
    ) -> None:
        super().__init__()

        self.config = config
        self.activation_fn = get_act_fn(config.hidden_act)

        # For quantization, we require the hidden size to be a multiple of 64
        quantizable = (config.hidden_size % 64 == 0
                       and config.intermediate_size % 64 == 0)
        self.fc1 = ColumnParallelLinear(
            config.hidden_size,
            config.intermediate_size,
            quant_config=quant_config if quantizable else None,
            prefix=f"{prefix}.fc1",
        )
        self.fc2 = RowParallelLinear(
            config.intermediate_size,
            config.hidden_size,
            quant_config=quant_config if quantizable else None,
            prefix=f"{prefix}.fc2",
        )

    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 SiglipEncoderLayer(nn.Module):

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = "",
    ) -> None:
        super().__init__()

        self.embed_dim = config.hidden_size

        self.self_attn = SiglipAttention(
            config,
            quant_config=quant_config,
            prefix=f"{prefix}.self_attn",
        )
        self.layer_norm1 = nn.LayerNorm(self.embed_dim,
                                        eps=config.layer_norm_eps)
        self.mlp = SiglipMLP(
            config,
            quant_config=quant_config,
            prefix=f"{prefix}.mlp",
        )
        self.layer_norm2 = nn.LayerNorm(self.embed_dim,
                                        eps=config.layer_norm_eps)

    def forward(
        self,
        hidden_states: torch.Tensor,
    ) -> Tuple[torch.Tensor, None]:
        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, None


class SiglipEncoder(nn.Module):

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        num_hidden_layers_override: Optional[int] = None,
        prefix: str = "",
    ) -> 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([
            SiglipEncoderLayer(config,
                               quant_config=quant_config,
                               prefix=f"{prefix}.layers.{layer_idx}")
            for layer_idx in range(num_hidden_layers)
        ])

    def forward(
        self,
        inputs_embeds: torch.Tensor,
        return_all_hidden_states: bool,
    ) -> Union[torch.Tensor, list[torch.Tensor]]:
        hidden_states_pool = []
        hidden_states = inputs_embeds

        for encoder_layer in self.layers:
            hidden_states, _ = encoder_layer(hidden_states)
            if return_all_hidden_states:
                hidden_states_pool.append(hidden_states)
        # If we have multiple feature sample layers, we return all hidden
        # states in order and grab the ones we need by index.
        if return_all_hidden_states:
            return hidden_states_pool
        return hidden_states


class SiglipMultiheadAttentionPoolingHead(nn.Module):
    """Multihead Attention Pooling."""

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        prefix: str = "",
    ) -> None:
        super().__init__()

        self.probe = nn.Parameter(torch.randn(1, 1, config.hidden_size))
        # TODO(ChristopherCho): Implement vLLM version of MultiheadAttention
        self.attention = torch.nn.MultiheadAttention(
            config.hidden_size, config.num_attention_heads, batch_first=True)
        self.layernorm = nn.LayerNorm(config.hidden_size,
                                      eps=config.layer_norm_eps)
        self.mlp = SiglipMLP(config=config,
                             quant_config=quant_config,
                             prefix=f"{prefix}.mlp")

    def forward(self, hidden_state: torch.Tensor) -> torch.Tensor:
        batch_size = hidden_state.shape[0]
        probe = self.probe.repeat(batch_size, 1, 1)

        hidden_state = self.attention(probe, hidden_state, hidden_state)[0]

        residual = hidden_state
        hidden_state = self.layernorm(hidden_state)
        hidden_state = residual + self.mlp(hidden_state)

        return hidden_state[:, 0]


class SiglipVisionTransformer(nn.Module):

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        *,
        num_hidden_layers_override: Optional[int] = None,
        require_post_norm: Optional[bool] = None,
        prefix: str = "",
    ) -> None:
        super().__init__()

        self.config = config
        embed_dim = config.hidden_size

        self.embeddings = SiglipVisionEmbeddings(config)

        self.encoder = SiglipEncoder(
            config,
            quant_config=quant_config,
            num_hidden_layers_override=num_hidden_layers_override,
            prefix=f"{prefix}.encoder",
        )

        num_hidden_layers = config.num_hidden_layers
        if len(self.encoder.layers) > config.num_hidden_layers:
            raise ValueError(
                f"The original encoder only has {num_hidden_layers} "
                f"layers, but you requested {len(self.encoder.layers)} layers."
            )

        # If possible, skip post_layernorm to conserve memory
        if require_post_norm is None:
            require_post_norm = len(self.encoder.layers) == num_hidden_layers

        if require_post_norm:
            self.post_layernorm = nn.LayerNorm(embed_dim,
                                               eps=config.layer_norm_eps)
        else:
            self.post_layernorm = None

        self.use_head = (True if not hasattr(config, "vision_use_head") else
                         config.vision_use_head)
        if self.use_head:
            self.head = SiglipMultiheadAttentionPoolingHead(
                config=config,
                quant_config=quant_config,
                prefix=f"{prefix}.head",
            )

    def forward(
        self,
        pixel_values: torch.Tensor,
        interpolate_pos_encoding: bool = True,
        feature_sample_layers: Optional[list[int]] = None,
    ) -> torch.Tensor:

        hidden_states = self.embeddings(
            pixel_values,
            interpolate_pos_encoding=interpolate_pos_encoding,
        )

        return_all_hidden_states = feature_sample_layers is not None

        # Produces either the last layer output or all of the hidden states,
        # depending on if we have feature_sample_layers or not
        encoder_outputs = self.encoder(
            inputs_embeds=hidden_states,
            return_all_hidden_states=return_all_hidden_states,
        )

        # Handle post-norm (if applicable) and stacks feature layers if needed
        encoder_outputs = resolve_visual_encoder_outputs(
            encoder_outputs, feature_sample_layers, self.post_layernorm,
            self.config.num_hidden_layers)

        # TODO: add this back when pooled_output is used in inference.
        # if self.use_head:
        # pooled_output = self.head(encoder_outputs)

        return encoder_outputs


class SiglipVisionModel(nn.Module):
    config_class = SiglipVisionConfig
    main_input_name = "pixel_values"

    def __init__(
        self,
        config: SiglipVisionConfig,
        quant_config: Optional[QuantizationConfig] = None,
        *,
        num_hidden_layers_override: Optional[int] = None,
        require_post_norm: Optional[bool] = None,
        prefix: str = "",
    ) -> None:
        super().__init__()

        self.vision_model = SiglipVisionTransformer(
            config,
            quant_config,
            num_hidden_layers_override=num_hidden_layers_override,
            require_post_norm=require_post_norm,
            prefix=f"{prefix}.vision_model",
        )

    def get_input_embeddings(self) -> nn.Module:
        return self.vision_model.embeddings.patch_embedding

    def forward(
        self,
        pixel_values: torch.Tensor,
        interpolate_pos_encoding: bool = False,
        feature_sample_layers: Optional[list[int]] = None,
    ) -> torch.Tensor:
        return self.vision_model(
            pixel_values=pixel_values,
            interpolate_pos_encoding=interpolate_pos_encoding,
            feature_sample_layers=feature_sample_layers,
        )

    def load_weights(self, weights: Iterable[Tuple[str,
                                                   torch.Tensor]]) -> Set[str]:
        stacked_params_mapping = [
            # (param_name, shard_name, shard_id)
            ("qkv_proj", "q_proj", "q"),
            ("qkv_proj", "k_proj", "k"),
            ("qkv_proj", "v_proj", "v"),
        ]
        params_dict = dict(self.named_parameters())
        loaded_params: Set[str] = set()
        layer_count = len(self.vision_model.encoder.layers)

        for name, loaded_weight in weights:
            # post_layernorm is optional in SiglipVisionModel
            if (name.startswith("vision_model.post_layernorm")
                    and self.vision_model.post_layernorm is None):
                continue

            # omit layers when num_hidden_layers_override is set
            if name.startswith("vision_model.encoder.layers"):
                layer_idx = int(name.split(".")[3])
                if layer_idx >= layer_count:
                    continue

            for (param_name, weight_name, shard_id) in stacked_params_mapping:
                if weight_name not in name:
                    continue
                name = name.replace(weight_name, param_name)

                param = params_dict[name]
                weight_loader = param.weight_loader
                weight_loader(param, loaded_weight, shard_id)
                break
            else:
                param = params_dict[name]
                weight_loader = getattr(param, "weight_loader",
                                        default_weight_loader)
                weight_loader(param, loaded_weight)
            loaded_params.add(name)
        return loaded_params