surya/model/detection/segformer.py

import gc
import warnings

from transformers.activations import ACT2FN
from transformers.pytorch_utils import find_pruneable_heads_and_indices, prune_linear_layer

warnings.filterwarnings("ignore", message="torch.utils._pytree._register_pytree_node is deprecated")

import math
from typing import Optional, Tuple, Union

from transformers import SegformerConfig, SegformerForSemanticSegmentation, SegformerDecodeHead, \
    SegformerPreTrainedModel
from surya.model.detection.processor import SegformerImageProcessor
import torch
from torch import nn

from transformers.modeling_outputs import SemanticSegmenterOutput, BaseModelOutput
from surya.settings import settings


def load_model(checkpoint=settings.DETECTOR_MODEL_CHECKPOINT, device=settings.TORCH_DEVICE_DETECTION, dtype=settings.MODEL_DTYPE_DETECTION):
    config = SegformerConfig.from_pretrained(checkpoint)
    model = SegformerForRegressionMask.from_pretrained(checkpoint, torch_dtype=dtype, config=config)
    if "mps" in device:
        print("Warning: MPS may have poor results. This is a bug with MPS, see here - https://github.com/pytorch/pytorch/issues/84936")
    model = model.to(device)
    model = model.eval()
    print(f"Loaded detection model {checkpoint} on device {device} with dtype {dtype}")
    return model


def load_processor(checkpoint=settings.DETECTOR_MODEL_CHECKPOINT):
    processor = SegformerImageProcessor.from_pretrained(checkpoint)
    return processor


class SegformerForMaskMLP(nn.Module):
    def __init__(self, config: SegformerConfig, input_dim, output_dim):
        super().__init__()
        self.proj = nn.Linear(input_dim, output_dim)

    def forward(self, hidden_states: torch.Tensor):
        hidden_states = hidden_states.flatten(2).transpose(1, 2)
        hidden_states = self.proj(hidden_states)
        return hidden_states


class SegformerForMaskDecodeHead(SegformerDecodeHead):
    def __init__(self, config):
        super().__init__(config)
        decoder_layer_hidden_size = getattr(config, "decoder_layer_hidden_size", config.decoder_hidden_size)

        # linear layers which will unify the channel dimension of each of the encoder blocks to the same config.decoder_hidden_size
        mlps = []
        for i in range(config.num_encoder_blocks):
            mlp = SegformerForMaskMLP(config, input_dim=config.hidden_sizes[i], output_dim=decoder_layer_hidden_size)
            mlps.append(mlp)
        self.linear_c = nn.ModuleList(mlps)

        # the following 3 layers implement the ConvModule of the original implementation
        self.linear_fuse = nn.Conv2d(
            in_channels=decoder_layer_hidden_size * config.num_encoder_blocks,
            out_channels=config.decoder_hidden_size,
            kernel_size=1,
            bias=False,
        )
        self.batch_norm = nn.BatchNorm2d(config.decoder_hidden_size)
        self.activation = nn.ReLU()

        self.classifier = nn.Conv2d(config.decoder_hidden_size, config.num_labels, kernel_size=1)

        self.config = config

    def forward(self, encoder_hidden_states: torch.FloatTensor) -> torch.Tensor:
        batch_size = encoder_hidden_states[-1].shape[0]

        all_hidden_states = ()
        for encoder_hidden_state, mlp in zip(encoder_hidden_states, self.linear_c):
            if self.config.reshape_last_stage is False and encoder_hidden_state.ndim == 3:
                height = width = int(math.sqrt(encoder_hidden_state.shape[-1]))
                encoder_hidden_state = (
                    encoder_hidden_state.reshape(batch_size, height, width, -1).permute(0, 3, 1, 2).contiguous()
                )

            # unify channel dimension
            height, width = encoder_hidden_state.shape[2], encoder_hidden_state.shape[3]
            encoder_hidden_state = mlp(encoder_hidden_state)
            encoder_hidden_state = encoder_hidden_state.permute(0, 2, 1)
            encoder_hidden_state = encoder_hidden_state.reshape(batch_size, -1, height, width)
            # upsample
            encoder_hidden_state = encoder_hidden_state.contiguous()
            encoder_hidden_state = nn.functional.interpolate(
                encoder_hidden_state, size=encoder_hidden_states[0].size()[2:], mode="bilinear", align_corners=False
            )
            all_hidden_states += (encoder_hidden_state,)

        hidden_states = self.linear_fuse(torch.cat(all_hidden_states[::-1], dim=1))
        hidden_states = self.batch_norm(hidden_states)
        hidden_states = self.activation(hidden_states)

        # logits are of shape (batch_size, num_labels, height/4, width/4)
        logits = self.classifier(hidden_states)

        return logits


class SegformerOverlapPatchEmbeddings(nn.Module):
    """Construct the overlapping patch embeddings."""

    def __init__(self, patch_size, stride, num_channels, hidden_size):
        super().__init__()
        self.proj = nn.Conv2d(
            num_channels,
            hidden_size,
            kernel_size=patch_size,
            stride=stride,
            padding=patch_size // 2,
        )

        self.layer_norm = nn.LayerNorm(hidden_size)

    def forward(self, pixel_values):
        embeddings = self.proj(pixel_values)
        _, _, height, width = embeddings.shape
        # (batch_size, num_channels, height, width) -> (batch_size, num_channels, height*width) -> (batch_size, height*width, num_channels)
        # this can be fed to a Transformer layer
        embeddings = embeddings.flatten(2).transpose(1, 2)
        embeddings = self.layer_norm(embeddings)
        return embeddings, height, width


class SegformerEfficientSelfAttention(nn.Module):
    """SegFormer's efficient self-attention mechanism. Employs the sequence reduction process introduced in the [PvT
    paper](https://arxiv.org/abs/2102.12122)."""

    def __init__(self, config, hidden_size, num_attention_heads, sequence_reduction_ratio):
        super().__init__()
        self.hidden_size = hidden_size
        self.num_attention_heads = num_attention_heads

        if self.hidden_size % self.num_attention_heads != 0:
            raise ValueError(
                f"The hidden size ({self.hidden_size}) is not a multiple of the number of attention "
                f"heads ({self.num_attention_heads})"
            )

        self.attention_head_size = int(self.hidden_size / self.num_attention_heads)
        self.all_head_size = self.num_attention_heads * self.attention_head_size

        self.query = nn.Linear(self.hidden_size, self.all_head_size)
        self.key = nn.Linear(self.hidden_size, self.all_head_size)
        self.value = nn.Linear(self.hidden_size, self.all_head_size)

        self.sr_ratio = sequence_reduction_ratio
        if sequence_reduction_ratio > 1:
            self.sr = nn.Conv2d(
                hidden_size, hidden_size, kernel_size=sequence_reduction_ratio, stride=sequence_reduction_ratio
            )
            self.layer_norm = nn.LayerNorm(hidden_size)

    def transpose_for_scores(self, hidden_states):
        new_shape = hidden_states.size()[:-1] + (self.num_attention_heads, self.attention_head_size)
        hidden_states = hidden_states.view(new_shape)
        return hidden_states.permute(0, 2, 1, 3)

    def forward(
        self,
        hidden_states,
        height,
        width,
        output_attentions=False,
    ):
        query_layer = self.transpose_for_scores(self.query(hidden_states))

        if self.sr_ratio > 1:
            batch_size, seq_len, num_channels = hidden_states.shape
            # Reshape to (batch_size, num_channels, height, width)
            hidden_states = hidden_states.permute(0, 2, 1).reshape(batch_size, num_channels, height, width)
            # Apply sequence reduction
            hidden_states = self.sr(hidden_states)
            # Reshape back to (batch_size, seq_len, num_channels)
            hidden_states = hidden_states.reshape(batch_size, num_channels, -1).permute(0, 2, 1)
            hidden_states = self.layer_norm(hidden_states)

        key_layer = self.transpose_for_scores(self.key(hidden_states))
        value_layer = self.transpose_for_scores(self.value(hidden_states))

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))

        attention_scores = attention_scores / math.sqrt(self.attention_head_size)

        # Normalize the attention scores to probabilities.
        attention_probs = nn.functional.softmax(attention_scores, dim=-1)

        context_layer = torch.matmul(attention_probs, value_layer)

        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
        new_context_layer_shape = context_layer.size()[:-2] + (self.all_head_size,)
        context_layer = context_layer.view(new_context_layer_shape)

        outputs = (context_layer, attention_probs) if output_attentions else (context_layer,)

        return outputs

class SegformerEncoder(nn.Module):
    def __init__(self, config):
        super().__init__()
        self.config = config

        # patch embeddings
        embeddings = []
        for i in range(config.num_encoder_blocks):
            embeddings.append(
                SegformerOverlapPatchEmbeddings(
                    patch_size=config.patch_sizes[i],
                    stride=config.strides[i],
                    num_channels=config.num_channels if i == 0 else config.hidden_sizes[i - 1],
                    hidden_size=config.hidden_sizes[i],
                )
            )
        self.patch_embeddings = nn.ModuleList(embeddings)

        # Transformer blocks
        blocks = []
        cur = 0
        for i in range(config.num_encoder_blocks):
            # each block consists of layers
            layers = []
            if i != 0:
                cur += config.depths[i - 1]
            for j in range(config.depths[i]):
                layers.append(
                    SegformerLayer(
                        config,
                        hidden_size=config.hidden_sizes[i],
                        num_attention_heads=config.num_attention_heads[i],
                        sequence_reduction_ratio=config.sr_ratios[i],
                        mlp_ratio=config.mlp_ratios[i],
                    )
                )
            blocks.append(nn.ModuleList(layers))

        self.block = nn.ModuleList(blocks)

        # Layer norms
        self.layer_norm = nn.ModuleList(
            [nn.LayerNorm(config.hidden_sizes[i]) for i in range(config.num_encoder_blocks)]
        )

    def forward(
        self,
        pixel_values: torch.FloatTensor,
        output_attentions: Optional[bool] = False,
        output_hidden_states: Optional[bool] = False,
        return_dict: Optional[bool] = True,
    ) -> Union[Tuple, BaseModelOutput]:
        all_hidden_states = () if output_hidden_states else None

        batch_size = pixel_values.shape[0]

        hidden_states = pixel_values
        for idx, x in enumerate(zip(self.patch_embeddings, self.block, self.layer_norm)):
            embedding_layer, block_layer, norm_layer = x
            # first, obtain patch embeddings
            hidden_states, height, width = embedding_layer(hidden_states)
            # second, send embeddings through blocks
            for i, blk in enumerate(block_layer):
                layer_outputs = blk(hidden_states, height, width, output_attentions)
                hidden_states = layer_outputs[0]
            # third, apply layer norm
            hidden_states = norm_layer(hidden_states)
            # fourth, optionally reshape back to (batch_size, num_channels, height, width)
            if idx != len(self.patch_embeddings) - 1 or (
                idx == len(self.patch_embeddings) - 1 and self.config.reshape_last_stage
            ):
                hidden_states = hidden_states.reshape(batch_size, height, width, -1).permute(0, 3, 1, 2).contiguous()
            all_hidden_states = all_hidden_states + (hidden_states,)

        return all_hidden_states

class SegformerSelfOutput(nn.Module):
    def __init__(self, config, hidden_size):
        super().__init__()
        self.dense = nn.Linear(hidden_size, hidden_size)

    def forward(self, hidden_states, input_tensor):
        hidden_states = self.dense(hidden_states)
        return hidden_states


class SegformerAttention(nn.Module):
    def __init__(self, config, hidden_size, num_attention_heads, sequence_reduction_ratio):
        super().__init__()
        self.self = SegformerEfficientSelfAttention(
            config=config,
            hidden_size=hidden_size,
            num_attention_heads=num_attention_heads,
            sequence_reduction_ratio=sequence_reduction_ratio,
        )
        self.output = SegformerSelfOutput(config, hidden_size=hidden_size)
        self.pruned_heads = set()

    def prune_heads(self, heads):
        if len(heads) == 0:
            return
        heads, index = find_pruneable_heads_and_indices(
            heads, self.self.num_attention_heads, self.self.attention_head_size, self.pruned_heads
        )

        # Prune linear layers
        self.self.query = prune_linear_layer(self.self.query, index)
        self.self.key = prune_linear_layer(self.self.key, index)
        self.self.value = prune_linear_layer(self.self.value, index)
        self.output.dense = prune_linear_layer(self.output.dense, index, dim=1)

        # Update hyper params and store pruned heads
        self.self.num_attention_heads = self.self.num_attention_heads - len(heads)
        self.self.all_head_size = self.self.attention_head_size * self.self.num_attention_heads
        self.pruned_heads = self.pruned_heads.union(heads)

    def forward(self, hidden_states, height, width, output_attentions=False):
        self_outputs = self.self(hidden_states, height, width, output_attentions)

        attention_output = self.output(self_outputs[0], hidden_states)
        outputs = (attention_output,) + self_outputs[1:]  # add attentions if we output them
        return outputs

class SegformerDWConv(nn.Module):
    def __init__(self, dim=768):
        super().__init__()
        self.dwconv = nn.Conv2d(dim, dim, 3, 1, 1, bias=True, groups=dim)

    def forward(self, hidden_states, height, width):
        batch_size, seq_len, num_channels = hidden_states.shape
        hidden_states = hidden_states.transpose(1, 2).view(batch_size, num_channels, height, width)
        hidden_states = self.dwconv(hidden_states)
        hidden_states = hidden_states.flatten(2).transpose(1, 2)

        return hidden_states


class SegformerMixFFN(nn.Module):
    def __init__(self, config, in_features, hidden_features=None, out_features=None):
        super().__init__()
        out_features = out_features or in_features
        self.dense1 = nn.Linear(in_features, hidden_features)
        self.dwconv = SegformerDWConv(hidden_features)
        if isinstance(config.hidden_act, str):
            self.intermediate_act_fn = ACT2FN[config.hidden_act]
        else:
            self.intermediate_act_fn = config.hidden_act
        self.dense2 = nn.Linear(hidden_features, out_features)

    def forward(self, hidden_states, height, width):
        hidden_states = self.dense1(hidden_states)
        hidden_states = self.dwconv(hidden_states, height, width)
        hidden_states = self.intermediate_act_fn(hidden_states)
        hidden_states = self.dense2(hidden_states)
        return hidden_states


class SegformerLayer(nn.Module):
    """This corresponds to the Block class in the original implementation."""

    def __init__(self, config, hidden_size, num_attention_heads, sequence_reduction_ratio, mlp_ratio):
        super().__init__()
        self.layer_norm_1 = nn.LayerNorm(hidden_size)
        self.attention = SegformerAttention(
            config,
            hidden_size=hidden_size,
            num_attention_heads=num_attention_heads,
            sequence_reduction_ratio=sequence_reduction_ratio,
        )
        self.layer_norm_2 = nn.LayerNorm(hidden_size)
        mlp_hidden_size = int(hidden_size * mlp_ratio)
        self.mlp = SegformerMixFFN(config, in_features=hidden_size, hidden_features=mlp_hidden_size)

    def forward(self, hidden_states, height, width, output_attentions=False):
        self_attention_outputs = self.attention(
            self.layer_norm_1(hidden_states),  # in Segformer, layernorm is applied before self-attention
            height,
            width,
            output_attentions=output_attentions,
        )

        attention_output = self_attention_outputs[0]
        outputs = self_attention_outputs[1:]  # add self attentions if we output attention weights

        # first residual connection (with stochastic depth)
        hidden_states = attention_output + hidden_states

        mlp_output = self.mlp(self.layer_norm_2(hidden_states), height, width)

        # second residual connection (with stochastic depth)
        layer_output = mlp_output + hidden_states

        outputs = (layer_output,) + outputs

        return outputs

class SegformerModel(SegformerPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)
        self.config = config

        # hierarchical Transformer encoder
        self.encoder = SegformerEncoder(config)

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

    def _prune_heads(self, heads_to_prune):
        """
        Prunes heads of the model. heads_to_prune: dict of {layer_num: list of heads to prune in this layer} See base
        class PreTrainedModel
        """
        for layer, heads in heads_to_prune.items():
            self.encoder.layer[layer].attention.prune_heads(heads)

    def forward(
        self,
        pixel_values: torch.FloatTensor,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[Tuple, BaseModelOutput]:
        encoder_outputs = self.encoder(
            pixel_values,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
        )
        return encoder_outputs

class SegformerForRegressionMask(SegformerForSemanticSegmentation):
    def __init__(self, config, **kwargs):
        super().__init__(config)
        self.segformer = SegformerModel(config)
        self.decode_head = SegformerForMaskDecodeHead(config)

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

    def forward(
        self,
        pixel_values: torch.FloatTensor,
        **kwargs
    ) -> Union[Tuple, SemanticSegmenterOutput]:

        encoder_hidden_states = self.segformer(
            pixel_values,
            output_attentions=False,
            output_hidden_states=True,  # we need the intermediate hidden states
            return_dict=False,
        )

        logits = self.decode_head(encoder_hidden_states)
        # Apply sigmoid to get 0-1 output
        sigmoid_logits = torch.special.expit(logits)

        return SemanticSegmenterOutput(
            loss=None,
            logits=sigmoid_logits,
            hidden_states=None,
            attentions=None,
        )