modeling_focalnet.py

# coding=utf-8
# Copyright 2023 Microsoft Research and The HuggingFace Inc. team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
""" PyTorch FocalNet model."""


import collections.abc
import math
from dataclasses import dataclass
from typing import Optional, Tuple, Union

import torch
import torch.utils.checkpoint
from torch import nn
from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, MSELoss

from ...activations import ACT2FN
from ...modeling_outputs import BackboneOutput
from ...modeling_utils import PreTrainedModel
from ...utils import (
    ModelOutput,
    add_code_sample_docstrings,
    add_start_docstrings,
    add_start_docstrings_to_model_forward,
    logging,
    replace_return_docstrings,
)
from ...utils.backbone_utils import BackboneMixin
from .configuration_focalnet import FocalNetConfig


logger = logging.get_logger(__name__)

# General docstring
_CONFIG_FOR_DOC = "FocalNetConfig"

# Base docstring
_CHECKPOINT_FOR_DOC = "microsoft/focalnet-tiny"
_EXPECTED_OUTPUT_SHAPE = [1, 49, 768]

# Image classification docstring
_IMAGE_CLASS_CHECKPOINT = "microsoft/focalnet-tiny"
_IMAGE_CLASS_EXPECTED_OUTPUT = "tabby, tabby cat"


@dataclass
class FocalNetEncoderOutput(ModelOutput):
    """
    FocalNet encoder's outputs, with potential hidden states.

    Args:
        last_hidden_state (`torch.FloatTensor` of shape `(batch_size, sequence_length, hidden_size)`):
            Sequence of hidden-states at the output of the last layer of the model.
        hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, sequence_length, hidden_size)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.

        reshaped_hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, hidden_size, height, width)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs reshaped to
            include the spatial dimensions.
    """

    last_hidden_state: torch.FloatTensor = None
    hidden_states: Optional[Tuple[torch.FloatTensor]] = None
    reshaped_hidden_states: Optional[Tuple[torch.FloatTensor]] = None


@dataclass
class FocalNetModelOutput(ModelOutput):
    """
    FocalNet model's outputs that also contains a pooling of the last hidden states.

    Args:
        last_hidden_state (`torch.FloatTensor` of shape `(batch_size, sequence_length, hidden_size)`):
            Sequence of hidden-states at the output of the last layer of the model.
        pooler_output (`torch.FloatTensor` of shape `(batch_size, hidden_size)`, *optional*, returned when `add_pooling_layer=True` is passed):
            Average pooling of the last layer hidden-state.
        hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, sequence_length, hidden_size)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.
        reshaped_hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, hidden_size, height, width)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs reshaped to
            include the spatial dimensions.
    """

    last_hidden_state: torch.FloatTensor = None
    pooler_output: Optional[torch.FloatTensor] = None
    hidden_states: Optional[Tuple[torch.FloatTensor]] = None
    reshaped_hidden_states: Optional[Tuple[torch.FloatTensor]] = None


@dataclass
class FocalNetMaskedImageModelingOutput(ModelOutput):
    """
    FocalNet masked image model outputs.

    Args:
        loss (`torch.FloatTensor` of shape `(1,)`, *optional*, returned when `bool_masked_pos` is provided):
            Masked image modeling (MLM) loss.
        reconstruction (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`):
            Reconstructed pixel values.
        hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, sequence_length, hidden_size)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.
        reshaped_hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, hidden_size, height, width)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs reshaped to
            include the spatial dimensions.
    """

    loss: Optional[torch.FloatTensor] = None
    reconstruction: torch.FloatTensor = None
    hidden_states: Optional[Tuple[torch.FloatTensor]] = None
    reshaped_hidden_states: Optional[Tuple[torch.FloatTensor]] = None


@dataclass
class FocalNetImageClassifierOutput(ModelOutput):
    """
    FocalNet outputs for image classification.

    Args:
        loss (`torch.FloatTensor` of shape `(1,)`, *optional*, returned when `labels` is provided):
            Classification (or regression if config.num_labels==1) loss.
        logits (`torch.FloatTensor` of shape `(batch_size, config.num_labels)`):
            Classification (or regression if config.num_labels==1) scores (before SoftMax).
        hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, sequence_length, hidden_size)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs.
        reshaped_hidden_states (`tuple(torch.FloatTensor)`, *optional*, returned when `output_hidden_states=True` is passed or when `config.output_hidden_states=True`):
            Tuple of `torch.FloatTensor` (one for the output of the embeddings + one for the output of each stage) of
            shape `(batch_size, hidden_size, height, width)`.

            Hidden-states of the model at the output of each layer plus the initial embedding outputs reshaped to
            include the spatial dimensions.
    """

    loss: Optional[torch.FloatTensor] = None
    logits: torch.FloatTensor = None
    hidden_states: Optional[Tuple[torch.FloatTensor]] = None
    reshaped_hidden_states: Optional[Tuple[torch.FloatTensor]] = None


class FocalNetEmbeddings(nn.Module):
    """
    Construct the patch embeddings and layernorm. Optionally, also the mask token.
    """

    def __init__(self, config, use_mask_token=False):
        super().__init__()

        self.patch_embeddings = FocalNetPatchEmbeddings(
            config=config,
            image_size=config.image_size,
            patch_size=config.patch_size,
            num_channels=config.num_channels,
            embed_dim=config.embed_dim,
            use_conv_embed=config.use_conv_embed,
            is_stem=True,
        )
        self.patch_grid = self.patch_embeddings.grid_size
        self.mask_token = nn.Parameter(torch.zeros(1, 1, config.embed_dim)) if use_mask_token else None

        self.norm = nn.LayerNorm(config.embed_dim, eps=config.layer_norm_eps)
        self.dropout = nn.Dropout(config.hidden_dropout_prob)

    def forward(
        self, pixel_values: Optional[torch.FloatTensor], bool_masked_pos: Optional[torch.BoolTensor] = None
    ) -> Tuple[torch.Tensor]:
        embeddings, output_dimensions = self.patch_embeddings(pixel_values)
        embeddings = self.norm(embeddings)
        batch_size, seq_len, _ = embeddings.size()

        if bool_masked_pos is not None:
            mask_tokens = self.mask_token.expand(batch_size, seq_len, -1)
            # replace the masked visual tokens by mask_tokens
            mask = bool_masked_pos.unsqueeze(-1).type_as(mask_tokens)
            embeddings = embeddings * (1.0 - mask) + mask_tokens * mask

        embeddings = self.dropout(embeddings)
        return embeddings, output_dimensions


class FocalNetPatchEmbeddings(nn.Module):
    def __init__(
        self,
        config,
        image_size,
        patch_size,
        num_channels,
        embed_dim,
        add_norm=False,
        use_conv_embed=False,
        is_stem=False,
    ):
        super().__init__()
        image_size = image_size if isinstance(image_size, collections.abc.Iterable) else (image_size, image_size)
        patch_size = patch_size if isinstance(patch_size, collections.abc.Iterable) else (patch_size, patch_size)
        num_patches = (image_size[1] // patch_size[1]) * (image_size[0] // patch_size[0])
        self.image_size = image_size
        self.patch_size = patch_size
        self.num_channels = num_channels
        self.num_patches = num_patches
        self.grid_size = (image_size[0] // patch_size[0], image_size[1] // patch_size[1])

        if use_conv_embed:
            # if we choose to use conv embedding, then we treat the stem and non-stem differently
            if is_stem:
                kernel_size = 7
                padding = 2
                stride = 4
            else:
                kernel_size = 3
                padding = 1
                stride = 2
            self.projection = nn.Conv2d(
                num_channels, embed_dim, kernel_size=kernel_size, stride=stride, padding=padding
            )
        else:
            self.projection = nn.Conv2d(num_channels, embed_dim, kernel_size=patch_size, stride=patch_size)

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

    def maybe_pad(self, pixel_values, height, width):
        if width % self.patch_size[1] != 0:
            pad_values = (0, self.patch_size[1] - width % self.patch_size[1])
            pixel_values = nn.functional.pad(pixel_values, pad_values)
        if height % self.patch_size[0] != 0:
            pad_values = (0, 0, 0, self.patch_size[0] - height % self.patch_size[0])
            pixel_values = nn.functional.pad(pixel_values, pad_values)
        return pixel_values

    def forward(self, pixel_values: Optional[torch.FloatTensor]) -> Tuple[torch.Tensor, Tuple[int]]:
        _, num_channels, height, width = pixel_values.shape
        if num_channels != self.num_channels:
            raise ValueError(
                "Make sure that the channel dimension of the pixel values match with the one set in the configuration."
            )
        # pad the input to be divisible by self.patch_size, if needed
        pixel_values = self.maybe_pad(pixel_values, height, width)
        embeddings = self.projection(pixel_values)
        _, _, height, width = embeddings.shape
        output_dimensions = (height, width)
        embeddings = embeddings.flatten(2).transpose(1, 2)

        if self.norm is not None:
            embeddings = self.norm(embeddings)

        return embeddings, output_dimensions


# Copied from transformers.models.beit.modeling_beit.drop_path
def drop_path(input: torch.Tensor, drop_prob: float = 0.0, training: bool = False) -> torch.Tensor:
    """
    Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks).

    Comment by Ross Wightman: This is the same as the DropConnect impl I created for EfficientNet, etc networks,
    however, the original name is misleading as 'Drop Connect' is a different form of dropout in a separate paper...
    See discussion: https://github.com/tensorflow/tpu/issues/494#issuecomment-532968956 ... I've opted for changing the
    layer and argument names to 'drop path' rather than mix DropConnect as a layer name and use 'survival rate' as the
    argument.
    """
    if drop_prob == 0.0 or not training:
        return input
    keep_prob = 1 - drop_prob
    shape = (input.shape[0],) + (1,) * (input.ndim - 1)  # work with diff dim tensors, not just 2D ConvNets
    random_tensor = keep_prob + torch.rand(shape, dtype=input.dtype, device=input.device)
    random_tensor.floor_()  # binarize
    output = input.div(keep_prob) * random_tensor
    return output


# Copied from transformers.models.beit.modeling_beit.BeitDropPath with Beit->FocalNet
class FocalNetDropPath(nn.Module):
    """Drop paths (Stochastic Depth) per sample (when applied in main path of residual blocks)."""

    def __init__(self, drop_prob: Optional[float] = None) -> None:
        super().__init__()
        self.drop_prob = drop_prob

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        return drop_path(hidden_states, self.drop_prob, self.training)

    def extra_repr(self) -> str:
        return "p={}".format(self.drop_prob)


class FocalNetModulation(nn.Module):
    def __init__(self, config, index, dim, focal_factor=2, bias=True, projection_dropout=0.0):
        super().__init__()

        self.dim = dim
        self.focal_window = config.focal_windows[index]
        self.focal_level = config.focal_levels[index]
        self.focal_factor = focal_factor
        self.use_post_layernorm_in_modulation = config.use_post_layernorm_in_modulation
        self.normalize_modulator = config.normalize_modulator

        self.projection_in = nn.Linear(dim, 2 * dim + (self.focal_level + 1), bias=bias)
        self.projection_context = nn.Conv2d(dim, dim, kernel_size=1, stride=1, bias=bias)

        self.activation = nn.GELU()
        self.projection_out = nn.Linear(dim, dim)
        self.projection_dropout = nn.Dropout(projection_dropout)
        self.focal_layers = nn.ModuleList()

        self.kernel_sizes = []
        for k in range(self.focal_level):
            kernel_size = self.focal_factor * k + self.focal_window
            self.focal_layers.append(
                nn.Sequential(
                    nn.Conv2d(
                        dim, dim, kernel_size=kernel_size, stride=1, groups=dim, padding=kernel_size // 2, bias=False
                    ),
                    nn.GELU(),
                )
            )
            self.kernel_sizes.append(kernel_size)
        if self.use_post_layernorm_in_modulation:
            self.layernorm = nn.LayerNorm(dim, eps=config.layer_norm_eps)

    def forward(self, hidden_state):
        """
        Args:
            hidden_state:
                Input features with shape of (batch_size, height, width, num_channels)
        """
        num_channels = hidden_state.shape[-1]

        # pre linear projection
        x = self.projection_in(hidden_state).permute(0, 3, 1, 2).contiguous()
        q, ctx, self.gates = torch.split(x, (num_channels, num_channels, self.focal_level + 1), 1)

        # context aggreation
        ctx_all = 0
        for level in range(self.focal_level):
            ctx = self.focal_layers[level](ctx)
            ctx_all = ctx_all + ctx * self.gates[:, level : level + 1]
        ctx_global = self.activation(ctx.mean(2, keepdim=True).mean(3, keepdim=True))
        ctx_all = ctx_all + ctx_global * self.gates[:, self.focal_level :]

        # normalize context
        if self.normalize_modulator:
            ctx_all = ctx_all / (self.focal_level + 1)

        # focal modulation
        self.modulator = self.projection_context(ctx_all)
        x_out = q * self.modulator
        x_out = x_out.permute(0, 2, 3, 1).contiguous()
        if self.use_post_layernorm_in_modulation:
            x_out = self.layernorm(x_out)

        # post linear porjection
        x_out = self.projection_out(x_out)
        x_out = self.projection_dropout(x_out)
        return x_out


class FocalNetMlp(nn.Module):
    def __init__(self, config, in_features, hidden_features=None, out_features=None, drop=0.0):
        super().__init__()
        out_features = out_features or in_features
        hidden_features = hidden_features or in_features
        self.fc1 = nn.Linear(in_features, hidden_features)
        self.activation = ACT2FN[config.hidden_act]
        self.fc2 = nn.Linear(hidden_features, out_features)
        self.drop = nn.Dropout(drop)

    def forward(self, hidden_state):
        hidden_state = self.fc1(hidden_state)
        hidden_state = self.activation(hidden_state)
        hidden_state = self.drop(hidden_state)
        hidden_state = self.fc2(hidden_state)
        hidden_state = self.drop(hidden_state)
        return hidden_state


class FocalNetLayer(nn.Module):
    r"""Focal Modulation Network layer (block).

    Args:
        config (`FocalNetConfig`):
            Model config.
        index (`int`):
            Layer index.
        dim (`int`):
            Number of input channels.
        input_resolution (`Tuple[int]`):
            Input resulotion.
        drop_path (`float`, *optional*, defaults to 0.0):
            Stochastic depth rate.
    """

    def __init__(self, config, index, dim, input_resolution, drop_path=0.0):
        super().__init__()

        self.config = config

        # layer-specific attributes
        self.dim = dim
        self.input_resolution = input_resolution

        # general attributes
        self.drop = config.hidden_dropout_prob
        self.use_post_layernorm = config.use_post_layernorm

        self.norm1 = nn.LayerNorm(dim, eps=config.layer_norm_eps)
        self.modulation = FocalNetModulation(
            config=config,
            index=index,
            dim=dim,
            projection_dropout=self.drop,
        )

        self.drop_path = FocalNetDropPath(drop_path) if drop_path > 0.0 else nn.Identity()
        self.norm2 = nn.LayerNorm(dim, eps=config.layer_norm_eps)
        mlp_hidden_dim = int(dim * config.mlp_ratio)
        self.mlp = FocalNetMlp(config=config, in_features=dim, hidden_features=mlp_hidden_dim, drop=self.drop)

        self.gamma_1 = 1.0
        self.gamma_2 = 1.0
        if config.use_layerscale:
            self.gamma_1 = nn.Parameter(config.layerscale_value * torch.ones((dim)), requires_grad=True)
            self.gamma_2 = nn.Parameter(config.layerscale_value * torch.ones((dim)), requires_grad=True)

    def forward(self, hidden_state, input_dimensions):
        height, width = input_dimensions
        batch_size, _, num_channels = hidden_state.shape
        shortcut = hidden_state

        # Focal Modulation
        hidden_state = hidden_state if self.use_post_layernorm else self.norm1(hidden_state)
        hidden_state = hidden_state.view(batch_size, height, width, num_channels)
        hidden_state = self.modulation(hidden_state).view(batch_size, height * width, num_channels)
        hidden_state = hidden_state if not self.use_post_layernorm else self.norm1(hidden_state)

        # FFN
        hidden_state = shortcut + self.drop_path(self.gamma_1 * hidden_state)
        hidden_state = hidden_state + self.drop_path(
            self.gamma_2
            * (self.norm2(self.mlp(hidden_state)) if self.use_post_layernorm else self.mlp(self.norm2(hidden_state)))
        )

        return hidden_state


class FocalNetStage(nn.Module):
    def __init__(self, config, index, input_resolution):
        super().__init__()

        self.config = config
        self.num_stages = len(config.depths)

        embed_dim = [config.embed_dim * (2**i) for i in range(self.num_stages)]
        dim = embed_dim[index]
        out_dim = embed_dim[index + 1] if (index < self.num_stages - 1) else None
        downsample = FocalNetPatchEmbeddings if (index < self.num_stages - 1) else None

        # stochastic depth decay rule
        dpr = [x.item() for x in torch.linspace(0, config.drop_path_rate, sum(config.depths))]
        drop_path = dpr[sum(config.depths[:index]) : sum(config.depths[: index + 1])]

        self.layers = nn.ModuleList(
            [
                FocalNetLayer(
                    config=config,
                    index=index,
                    dim=dim,
                    input_resolution=input_resolution,
                    drop_path=drop_path[i] if isinstance(drop_path, list) else drop_path,
                )
                for i in range(config.depths[index])
            ]
        )

        if downsample is not None:
            self.downsample = downsample(
                config=config,
                image_size=input_resolution,
                patch_size=2,
                num_channels=dim,
                embed_dim=out_dim,
                add_norm=True,
                use_conv_embed=config.use_conv_embed,
                is_stem=False,
            )
        else:
            self.downsample = None

        self.pointing = False

    def forward(self, hidden_states: torch.Tensor, input_dimensions: Tuple[int, int]) -> Tuple[torch.Tensor]:
        height, width = input_dimensions
        for layer_module in self.layers:
            hidden_states = layer_module(hidden_states, input_dimensions)

        hidden_states_before_downsampling = hidden_states
        if self.downsample is not None:
            height, width = input_dimensions
            hidden_states = hidden_states.transpose(1, 2).reshape(
                hidden_states_before_downsampling.shape[0], -1, height, width
            )
            hidden_states, output_dimensions = self.downsample(hidden_states)

        else:
            output_dimensions = (height, width, height, width)

        stage_outputs = (hidden_states, hidden_states_before_downsampling, output_dimensions)

        return stage_outputs


class FocalNetEncoder(nn.Module):
    def __init__(self, config, grid_size):
        super().__init__()
        self.num_stages = len(config.depths)
        self.config = config

        self.stages = nn.ModuleList(
            [
                FocalNetStage(
                    config=config,
                    index=i_layer,
                    input_resolution=(grid_size[0] // (2**i_layer), grid_size[1] // (2**i_layer)),
                )
                for i_layer in range(self.num_stages)
            ]
        )

        self.gradient_checkpointing = False

    def forward(
        self,
        hidden_states: torch.Tensor,
        input_dimensions: Tuple[int, int],
        output_hidden_states: Optional[bool] = False,
        output_hidden_states_before_downsampling: Optional[bool] = False,
        return_dict: Optional[bool] = True,
    ) -> Union[Tuple, FocalNetEncoderOutput]:
        all_hidden_states = () if output_hidden_states else None
        all_reshaped_hidden_states = () if output_hidden_states else None

        if output_hidden_states:
            batch_size, _, hidden_size = hidden_states.shape
            # rearrange b (h w) c -> b c h w
            reshaped_hidden_state = hidden_states.view(batch_size, *input_dimensions, hidden_size)
            reshaped_hidden_state = reshaped_hidden_state.permute(0, 3, 1, 2)
            all_hidden_states += (hidden_states,)
            all_reshaped_hidden_states += (reshaped_hidden_state,)

        for i, stage_module in enumerate(self.stages):
            if self.gradient_checkpointing and self.training:
                stage_outputs = self._gradient_checkpointing_func(
                    stage_module.__call__,
                    hidden_states,
                    input_dimensions,
                )
            else:
                stage_outputs = stage_module(hidden_states, input_dimensions)

            hidden_states = stage_outputs[0]
            hidden_states_before_downsampling = stage_outputs[1]
            output_dimensions = stage_outputs[2]

            input_dimensions = (output_dimensions[-2], output_dimensions[-1])

            if output_hidden_states and output_hidden_states_before_downsampling:
                batch_size, _, hidden_size = hidden_states_before_downsampling.shape
                # rearrange b (h w) c -> b c h w
                # here we use the original (not downsampled) height and width
                reshaped_hidden_state = hidden_states_before_downsampling.view(
                    batch_size, *(output_dimensions[0], output_dimensions[1]), hidden_size
                )
                reshaped_hidden_state = reshaped_hidden_state.permute(0, 3, 1, 2)
                all_hidden_states += (hidden_states_before_downsampling,)
                all_reshaped_hidden_states += (reshaped_hidden_state,)
            elif output_hidden_states and not output_hidden_states_before_downsampling:
                batch_size, _, hidden_size = hidden_states.shape
                # rearrange b (h w) c -> b c h w
                reshaped_hidden_state = hidden_states.view(batch_size, *input_dimensions, hidden_size)
                reshaped_hidden_state = reshaped_hidden_state.permute(0, 3, 1, 2)
                all_hidden_states += (hidden_states,)
                all_reshaped_hidden_states += (reshaped_hidden_state,)

        if not return_dict:
            return tuple(v for v in [hidden_states, all_hidden_states] if v is not None)

        return FocalNetEncoderOutput(
            last_hidden_state=hidden_states,
            hidden_states=all_hidden_states,
            reshaped_hidden_states=all_reshaped_hidden_states,
        )


# Copied from transformers.models.swin.modeling_swin.SwinPreTrainedModel with Swin->FocalNet,swin->focalnet
class FocalNetPreTrainedModel(PreTrainedModel):
    """
    An abstract class to handle weights initialization and a simple interface for downloading and loading pretrained
    models.
    """

    config_class = FocalNetConfig
    base_model_prefix = "focalnet"
    main_input_name = "pixel_values"
    supports_gradient_checkpointing = True
    _no_split_modules = ["FocalNetStage"]

    def _init_weights(self, module):
        """Initialize the weights"""
        if isinstance(module, (nn.Linear, nn.Conv2d)):
            # Slightly different from the TF version which uses truncated_normal for initialization
            # cf https://github.com/pytorch/pytorch/pull/5617
            module.weight.data.normal_(mean=0.0, std=self.config.initializer_range)
            if module.bias is not None:
                module.bias.data.zero_()
        elif isinstance(module, nn.LayerNorm):
            module.bias.data.zero_()
            module.weight.data.fill_(1.0)


FOCALNET_START_DOCSTRING = r"""
    This model is a PyTorch [torch.nn.Module](https://pytorch.org/docs/stable/nn.html#torch.nn.Module) sub-class. Use
    it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general usage and
    behavior.

    Parameters:
        config ([`FocalNetConfig`]): Model configuration class with all the parameters of the model.
            Initializing with a config file does not load the weights associated with the model, only the
            configuration. Check out the [`~PreTrainedModel.from_pretrained`] method to load the model weights.
"""

FOCALNET_INPUTS_DOCSTRING = r"""
    Args:
        pixel_values (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)`):
            Pixel values. Pixel values can be obtained using [`AutoImageProcessor`]. See
            [`AutoImageProcessor.__call__`] for details.

        output_hidden_states (`bool`, *optional*):
            Whether or not to return the hidden states of all layers. See `hidden_states` under returned tensors for
            more detail.
        return_dict (`bool`, *optional*):
            Whether or not to return a [`~utils.ModelOutput`] instead of a plain tuple.
"""


@add_start_docstrings(
    "The bare FocalNet Model outputting raw hidden-states without any specific head on top.",
    FOCALNET_START_DOCSTRING,
)
class FocalNetModel(FocalNetPreTrainedModel):
    def __init__(self, config, add_pooling_layer=True, use_mask_token=False):
        super().__init__(config)
        self.config = config
        self.num_stages = len(config.depths)
        self.num_features = int(config.embed_dim * 2 ** (self.num_stages - 1))

        self.embeddings = FocalNetEmbeddings(config, use_mask_token=use_mask_token)
        self.encoder = FocalNetEncoder(config, self.embeddings.patch_grid)

        self.layernorm = nn.LayerNorm(self.num_features, eps=config.layer_norm_eps)
        self.pooler = nn.AdaptiveAvgPool1d(1) if add_pooling_layer else None

        # Initialize weights and apply final processing
        self.post_init()

    def get_input_embeddings(self):
        return self.embeddings.patch_embeddings

    @add_start_docstrings_to_model_forward(FOCALNET_INPUTS_DOCSTRING)
    @add_code_sample_docstrings(
        checkpoint=_CHECKPOINT_FOR_DOC,
        output_type=FocalNetModelOutput,
        config_class=_CONFIG_FOR_DOC,
        modality="vision",
        expected_output=_EXPECTED_OUTPUT_SHAPE,
    )
    def forward(
        self,
        pixel_values: Optional[torch.FloatTensor] = None,
        bool_masked_pos: Optional[torch.BoolTensor] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[Tuple, FocalNetModelOutput]:
        r"""
        bool_masked_pos (`torch.BoolTensor` of shape `(batch_size, num_patches)`):
            Boolean masked positions. Indicates which patches are masked (1) and which aren't (0).
        """
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        if pixel_values is None:
            raise ValueError("You have to specify pixel_values")

        embedding_output, input_dimensions = self.embeddings(pixel_values, bool_masked_pos=bool_masked_pos)

        encoder_outputs = self.encoder(
            embedding_output,
            input_dimensions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )

        sequence_output = encoder_outputs[0]
        sequence_output = self.layernorm(sequence_output)

        pooled_output = None
        if self.pooler is not None:
            pooled_output = self.pooler(sequence_output.transpose(1, 2))
            pooled_output = torch.flatten(pooled_output, 1)

        if not return_dict:
            output = (sequence_output, pooled_output) + encoder_outputs[1:]

            return output

        return FocalNetModelOutput(
            last_hidden_state=sequence_output,
            pooler_output=pooled_output,
            hidden_states=encoder_outputs.hidden_states,
            reshaped_hidden_states=encoder_outputs.reshaped_hidden_states,
        )


@add_start_docstrings(
    """FocalNet Model with a decoder on top for masked image modeling.

    This follows the same implementation as in [SimMIM](https://arxiv.org/abs/2111.09886).

    <Tip>

    Note that we provide a script to pre-train this model on custom data in our [examples
    directory](https://github.com/huggingface/transformers/tree/main/examples/pytorch/image-pretraining).

    </Tip>
    """,
    FOCALNET_START_DOCSTRING,
)
class FocalNetForMaskedImageModeling(FocalNetPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)

        self.focalnet = FocalNetModel(config, add_pooling_layer=False, use_mask_token=True)

        self.num_stages = len(config.depths)
        num_features = int(config.embed_dim * 2 ** (self.num_stages - 1))
        self.decoder = nn.Sequential(
            nn.Conv2d(
                in_channels=num_features, out_channels=config.encoder_stride**2 * config.num_channels, kernel_size=1
            ),
            nn.PixelShuffle(config.encoder_stride),
        )

        # Initialize weights and apply final processing
        self.post_init()

    @add_start_docstrings_to_model_forward(FOCALNET_INPUTS_DOCSTRING)
    @replace_return_docstrings(output_type=FocalNetMaskedImageModelingOutput, config_class=_CONFIG_FOR_DOC)
    def forward(
        self,
        pixel_values: Optional[torch.FloatTensor] = None,
        bool_masked_pos: Optional[torch.BoolTensor] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[Tuple, FocalNetMaskedImageModelingOutput]:
        r"""
        bool_masked_pos (`torch.BoolTensor` of shape `(batch_size, num_patches)`):
            Boolean masked positions. Indicates which patches are masked (1) and which aren't (0).

        Returns:

        Examples:
        ```python
        >>> from transformers import AutoImageProcessor, FocalNetConfig, FocalNetForMaskedImageModeling
        >>> import torch
        >>> from PIL import Image
        >>> import requests

        >>> url = "http://images.cocodataset.org/val2017/000000039769.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)

        >>> image_processor = AutoImageProcessor.from_pretrained("microsoft/focalnet-base-simmim-window6-192")
        >>> config = FocalNetConfig()
        >>> model = FocalNetForMaskedImageModeling(config)

        >>> num_patches = (model.config.image_size // model.config.patch_size) ** 2
        >>> pixel_values = image_processor(images=image, return_tensors="pt").pixel_values
        >>> # create random boolean mask of shape (batch_size, num_patches)
        >>> bool_masked_pos = torch.randint(low=0, high=2, size=(1, num_patches)).bool()

        >>> outputs = model(pixel_values, bool_masked_pos=bool_masked_pos)
        >>> loss, reconstructed_pixel_values = outputs.loss, outputs.logits
        >>> list(reconstructed_pixel_values.shape)
        [1, 3, 192, 192]
        ```"""
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        outputs = self.focalnet(
            pixel_values,
            bool_masked_pos=bool_masked_pos,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )

        sequence_output = outputs[0]
        # Reshape to (batch_size, num_channels, height, width)
        sequence_output = sequence_output.transpose(1, 2)
        batch_size, num_channels, sequence_length = sequence_output.shape
        height = width = math.floor(sequence_length**0.5)
        sequence_output = sequence_output.reshape(batch_size, num_channels, height, width)

        # Reconstruct pixel values
        reconstructed_pixel_values = self.decoder(sequence_output)

        masked_im_loss = None
        if bool_masked_pos is not None:
            size = self.config.image_size // self.config.patch_size
            bool_masked_pos = bool_masked_pos.reshape(-1, size, size)
            mask = (
                bool_masked_pos.repeat_interleave(self.config.patch_size, 1)
                .repeat_interleave(self.config.patch_size, 2)
                .unsqueeze(1)
                .contiguous()
            )
            reconstruction_loss = nn.functional.l1_loss(pixel_values, reconstructed_pixel_values, reduction="none")
            masked_im_loss = (reconstruction_loss * mask).sum() / (mask.sum() + 1e-5) / self.config.num_channels

        if not return_dict:
            output = (reconstructed_pixel_values,) + outputs[2:]
            return ((masked_im_loss,) + output) if masked_im_loss is not None else output

        return FocalNetMaskedImageModelingOutput(
            loss=masked_im_loss,
            reconstruction=reconstructed_pixel_values,
            hidden_states=outputs.hidden_states,
            reshaped_hidden_states=outputs.reshaped_hidden_states,
        )


@add_start_docstrings(
    """
    FocalNet Model with an image classification head on top (a linear layer on top of the pooled output) e.g. for
    ImageNet.
    """,
    FOCALNET_START_DOCSTRING,
)
class FocalNetForImageClassification(FocalNetPreTrainedModel):
    # Copied from transformers.models.swin.modeling_swin.SwinForImageClassification.__init__ with Swin->FocalNet, swin->focalnet
    def __init__(self, config):
        super().__init__(config)

        self.num_labels = config.num_labels
        self.focalnet = FocalNetModel(config)

        # Classifier head
        self.classifier = (
            nn.Linear(self.focalnet.num_features, config.num_labels) if config.num_labels > 0 else nn.Identity()
        )

        # Initialize weights and apply final processing
        self.post_init()

    @add_start_docstrings_to_model_forward(FOCALNET_INPUTS_DOCSTRING)
    @add_code_sample_docstrings(
        checkpoint=_IMAGE_CLASS_CHECKPOINT,
        output_type=FocalNetImageClassifierOutput,
        config_class=_CONFIG_FOR_DOC,
        expected_output=_IMAGE_CLASS_EXPECTED_OUTPUT,
    )
    def forward(
        self,
        pixel_values: Optional[torch.FloatTensor] = None,
        labels: Optional[torch.LongTensor] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[Tuple, FocalNetImageClassifierOutput]:
        r"""
        labels (`torch.LongTensor` of shape `(batch_size,)`, *optional*):
            Labels for computing the image classification/regression loss. Indices should be in `[0, ...,
            config.num_labels - 1]`. If `config.num_labels == 1` a regression loss is computed (Mean-Square loss), If
            `config.num_labels > 1` a classification loss is computed (Cross-Entropy).
        """
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        outputs = self.focalnet(
            pixel_values,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )

        pooled_output = outputs[1]

        logits = self.classifier(pooled_output)

        loss = None
        if labels is not None:
            if self.config.problem_type is None:
                if self.num_labels == 1:
                    self.config.problem_type = "regression"
                elif self.num_labels > 1 and (labels.dtype == torch.long or labels.dtype == torch.int):
                    self.config.problem_type = "single_label_classification"
                else:
                    self.config.problem_type = "multi_label_classification"

            if self.config.problem_type == "regression":
                loss_fct = MSELoss()
                if self.num_labels == 1:
                    loss = loss_fct(logits.squeeze(), labels.squeeze())
                else:
                    loss = loss_fct(logits, labels)
            elif self.config.problem_type == "single_label_classification":
                loss_fct = CrossEntropyLoss()
                loss = loss_fct(logits.view(-1, self.num_labels), labels.view(-1))
            elif self.config.problem_type == "multi_label_classification":
                loss_fct = BCEWithLogitsLoss()
                loss = loss_fct(logits, labels)

        if not return_dict:
            output = (logits,) + outputs[2:]
            return ((loss,) + output) if loss is not None else output

        return FocalNetImageClassifierOutput(
            loss=loss,
            logits=logits,
            hidden_states=outputs.hidden_states,
            reshaped_hidden_states=outputs.reshaped_hidden_states,
        )


@add_start_docstrings(
    """
    FocalNet backbone, to be used with frameworks like X-Decoder.
    """,
    FOCALNET_START_DOCSTRING,
)
class FocalNetBackbone(FocalNetPreTrainedModel, BackboneMixin):
    def __init__(self, config: FocalNetConfig):
        super().__init__(config)
        super()._init_backbone(config)

        self.num_features = [config.embed_dim] + config.hidden_sizes
        self.focalnet = FocalNetModel(config)

        # initialize weights and apply final processing
        self.post_init()

    @add_start_docstrings_to_model_forward(FOCALNET_INPUTS_DOCSTRING)
    @replace_return_docstrings(output_type=BackboneOutput, config_class=_CONFIG_FOR_DOC)
    def forward(
        self,
        pixel_values: torch.Tensor,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> BackboneOutput:
        """
        Returns:

        Examples:

        ```python
        >>> from transformers import AutoImageProcessor, AutoBackbone
        >>> import torch
        >>> from PIL import Image
        >>> import requests

        >>> url = "http://images.cocodataset.org/val2017/000000039769.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)

        >>> processor = AutoImageProcessor.from_pretrained("microsoft/focalnet-tiny-lrf")
        >>> model = AutoBackbone.from_pretrained("microsoft/focalnet-tiny-lrf")

        >>> inputs = processor(image, return_tensors="pt")
        >>> outputs = model(**inputs)
        ```"""
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )

        outputs = self.focalnet(pixel_values, output_hidden_states=True, return_dict=True)

        hidden_states = outputs.reshaped_hidden_states

        feature_maps = ()
        for idx, stage in enumerate(self.stage_names):
            if stage in self.out_features:
                feature_maps += (hidden_states[idx],)

        if not return_dict:
            output = (feature_maps,)
            if output_hidden_states:
                output += (outputs.hidden_states,)
            return output

        return BackboneOutput(
            feature_maps=feature_maps,
            hidden_states=outputs.hidden_states if output_hidden_states else None,
            attentions=None,
        )