Transfomer added, many other changes.

1 files changed, 225 insertions, 0 deletions

diff --git a/src/text_recognizer/networks/densenet.py b/src/text_recognizer/networks/densenet.py
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+"""Defines a Densely Connected Convolutional Networks in PyTorch.
+
+Sources:
+https://arxiv.org/abs/1608.06993
+https://github.com/pytorch/vision/blob/master/torchvision/models/densenet.py
+
+"""
+from typing import List, Optional, Union
+
+from einops.layers.torch import Rearrange
+import torch
+from torch import nn
+from torch import Tensor
+
+from text_recognizer.networks.util import activation_function
+
+
+class _DenseLayer(nn.Module):
+    """A dense layer with pre-batch norm -> activation function -> Conv-layer x 2."""
+
+    def __init__(
+        self,
+        in_channels: int,
+        growth_rate: int,
+        bn_size: int,
+        dropout_rate: float,
+        activation: str = "relu",
+    ) -> None:
+        super().__init__()
+        activation_fn = activation_function(activation)
+        self.dense_layer = [
+            nn.BatchNorm2d(in_channels),
+            activation_fn,
+            nn.Conv2d(
+                in_channels=in_channels,
+                out_channels=bn_size * growth_rate,
+                kernel_size=1,
+                stride=1,
+                bias=False,
+            ),
+            nn.BatchNorm2d(bn_size * growth_rate),
+            activation_fn,
+            nn.Conv2d(
+                in_channels=bn_size * growth_rate,
+                out_channels=growth_rate,
+                kernel_size=3,
+                stride=1,
+                padding=1,
+                bias=False,
+            ),
+        ]
+        if dropout_rate:
+            self.dense_layer.append(nn.Dropout(p=dropout_rate))
+
+        self.dense_layer = nn.Sequential(*self.dense_layer)
+
+    def forward(self, x: Union[Tensor, List[Tensor]]) -> Tensor:
+        if isinstance(x, list):
+            x = torch.cat(x, 1)
+        return self.dense_layer(x)
+
+
+class _DenseBlock(nn.Module):
+    def __init__(
+        self,
+        num_layers: int,
+        in_channels: int,
+        bn_size: int,
+        growth_rate: int,
+        dropout_rate: float,
+        activation: str = "relu",
+    ) -> None:
+        super().__init__()
+        self.dense_block = self._build_dense_blocks(
+            num_layers, in_channels, bn_size, growth_rate, dropout_rate, activation
+        )
+
+    def _build_dense_blocks(
+        self,
+        num_layers: int,
+        in_channels: int,
+        bn_size: int,
+        growth_rate: int,
+        dropout_rate: float,
+        activation: str = "relu",
+    ) -> nn.ModuleList:
+        dense_block = []
+        for i in range(num_layers):
+            dense_block.append(
+                _DenseLayer(
+                    in_channels=in_channels + i * growth_rate,
+                    growth_rate=growth_rate,
+                    bn_size=bn_size,
+                    dropout_rate=dropout_rate,
+                    activation=activation,
+                )
+            )
+        return nn.ModuleList(dense_block)
+
+    def forward(self, x: Tensor) -> Tensor:
+        feature_maps = [x]
+        for layer in self.dense_block:
+            x = layer(feature_maps)
+            feature_maps.append(x)
+        return torch.cat(feature_maps, 1)
+
+
+class _Transition(nn.Module):
+    def __init__(
+        self, in_channels: int, out_channels: int, activation: str = "relu",
+    ) -> None:
+        super().__init__()
+        activation_fn = activation_function(activation)
+        self.transition = nn.Sequential(
+            nn.BatchNorm2d(in_channels),
+            activation_fn,
+            nn.Conv2d(
+                in_channels=in_channels,
+                out_channels=out_channels,
+                kernel_size=1,
+                stride=1,
+                bias=False,
+            ),
+            nn.AvgPool2d(kernel_size=2, stride=2),
+        )
+
+    def forward(self, x: Tensor) -> Tensor:
+        return self.transition(x)
+
+
+class DenseNet(nn.Module):
+    """Implementation of Densenet, a network archtecture that concats previous layers for maximum infomation flow."""
+
+    def __init__(
+        self,
+        growth_rate: int = 32,
+        block_config: List[int] = (6, 12, 24, 16),
+        in_channels: int = 1,
+        base_channels: int = 64,
+        num_classes: int = 80,
+        bn_size: int = 4,
+        dropout_rate: float = 0,
+        classifier: bool = True,
+        activation: str = "relu",
+    ) -> None:
+        super().__init__()
+        self.densenet = self._configure_densenet(
+            in_channels,
+            base_channels,
+            num_classes,
+            growth_rate,
+            block_config,
+            bn_size,
+            dropout_rate,
+            classifier,
+            activation,
+        )
+
+    def _configure_densenet(
+        self,
+        in_channels: int,
+        base_channels: int,
+        num_classes: int,
+        growth_rate: int,
+        block_config: List[int],
+        bn_size: int,
+        dropout_rate: float,
+        classifier: bool,
+        activation: str,
+    ) -> nn.Sequential:
+        activation_fn = activation_function(activation)
+        densenet = [
+            nn.Conv2d(
+                in_channels=in_channels,
+                out_channels=base_channels,
+                kernel_size=3,
+                stride=1,
+                padding=1,
+                bias=False,
+            ),
+            nn.BatchNorm2d(base_channels),
+            activation_fn,
+        ]
+
+        num_features = base_channels
+
+        for i, num_layers in enumerate(block_config):
+            densenet.append(
+                _DenseBlock(
+                    num_layers=num_layers,
+                    in_channels=num_features,
+                    bn_size=bn_size,
+                    growth_rate=growth_rate,
+                    dropout_rate=dropout_rate,
+                    activation=activation,
+                )
+            )
+            num_features = num_features + num_layers * growth_rate
+            if i != len(block_config) - 1:
+                densenet.append(
+                    _Transition(
+                        in_channels=num_features,
+                        out_channels=num_features // 2,
+                        activation=activation,
+                    )
+                )
+                num_features = num_features // 2
+
+        densenet.append(activation_fn)
+
+        if classifier:
+            densenet.append(nn.AdaptiveAvgPool2d((1, 1)))
+            densenet.append(Rearrange("b c h w -> b (c h w)"))
+            densenet.append(
+                nn.Linear(in_features=num_features, out_features=num_classes)
+            )
+
+        return nn.Sequential(*densenet)
+
+    def forward(self, x: Tensor) -> Tensor:
+        """Forward pass of Densenet."""
+        # If batch dimenstion is missing, it needs to be added.
+        if len(x.shape) < 4:
+            x = x[(None,) * (4 - len(x.shape))]
+        return self.densenet(x)