From 4e60c836fb710baceba570c28c06437db3ad5c9b Mon Sep 17 00:00:00 2001
From: Gustaf Rydholm <gustaf.rydholm@gmail.com>
Date: Sat, 24 Apr 2021 23:09:20 +0200
Subject: Implementing CoaT transformer, continue tomorrow...

---
 text_recognizer/networks/coat/__init__.py          |  0
 text_recognizer/networks/coat/factor_attention.py  |  9 +++
 text_recognizer/networks/coat/patch_embedding.py   | 38 +++++++++++
 .../networks/coat/positional_encodings.py          | 76 ++++++++++++++++++++++
 4 files changed, 123 insertions(+)
 create mode 100644 text_recognizer/networks/coat/__init__.py
 create mode 100644 text_recognizer/networks/coat/factor_attention.py
 create mode 100644 text_recognizer/networks/coat/patch_embedding.py
 create mode 100644 text_recognizer/networks/coat/positional_encodings.py

(limited to 'text_recognizer')

diff --git a/text_recognizer/networks/coat/__init__.py b/text_recognizer/networks/coat/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/text_recognizer/networks/coat/factor_attention.py b/text_recognizer/networks/coat/factor_attention.py
new file mode 100644
index 0000000..f91c5ef
--- /dev/null
+++ b/text_recognizer/networks/coat/factor_attention.py
@@ -0,0 +1,9 @@
+"""Factorized attention with convolutional relative positional encodings."""
+from torch import nn
+
+
+class FactorAttention(nn.Module):
+    """Factorized attention with relative positional encodings."""
+    def __init__(self, dim: int, num_heads: int) -> None:
+        pass
+
diff --git a/text_recognizer/networks/coat/patch_embedding.py b/text_recognizer/networks/coat/patch_embedding.py
new file mode 100644
index 0000000..3b7b76a
--- /dev/null
+++ b/text_recognizer/networks/coat/patch_embedding.py
@@ -0,0 +1,38 @@
+"""Patch embedding for images and feature maps."""
+from typing import Sequence, Tuple
+
+from einops import rearrange
+from loguru import logger
+from torch import nn
+from torch import Tensor
+
+
+class PatchEmbedding(nn.Module):
+    """Patch embedding of images."""
+
+    def __init__(
+        self,
+        image_shape: Sequence[int],
+        patch_size: int = 16,
+        in_channels: int = 1,
+        embedding_dim: int = 512,
+    ) -> None:
+        if image_shape[0] % patch_size == 0 and image_shape[1] % patch_size == 0:
+            logger.error(
+                f"Image shape {image_shape} not divisable by patch size {patch_size}"
+            )
+
+        self.patch_size = patch_size
+        self.embedding = nn.Conv2d(
+            in_channels, embedding_dim, kernel_size=patch_size, stride=patch_size
+        )
+        self.norm = nn.LayerNorm(embedding_dim)
+
+    def forward(self, x: Tensor) -> Tuple[Tensor, Tuple[int, int]]:
+        """Embeds image or feature maps with patch embedding."""
+        _, _, h, w = x.shape
+        h_out, w_out = h // self.patch_size, w // self.patch_size
+        x = self.embedding(x)
+        x = rearrange(x, "b c h w -> b (h w) c")
+        x = self.norm(x)
+        return x, (h_out, w_out)
diff --git a/text_recognizer/networks/coat/positional_encodings.py b/text_recognizer/networks/coat/positional_encodings.py
new file mode 100644
index 0000000..925db04
--- /dev/null
+++ b/text_recognizer/networks/coat/positional_encodings.py
@@ -0,0 +1,76 @@
+"""Positional encodings for input sequence to transformer."""
+from typing import Dict, Union, Tuple
+
+from einops import rearrange
+from loguru import logger
+import torch
+from torch import nn
+from torch import Tensor
+
+
+class RelativeEncoding(nn.Module):
+    """Relative positional encoding."""
+    def __init__(self, channels: int, heads: int, windows: Union[int, Dict[int, int]]) -> None:
+        super().__init__()
+        self.windows = {windows: heads} if isinstance(windows, int) else windows
+        self.heads = list(self.windows.values())
+        self.channel_heads = [head * channels for head in self.heads]
+        self.convs = nn.ModuleList([
+            nn.Conv2d(in_channels=head * channels,
+                             out_channels=head * channels,
+                             kernel_shape=window,
+                             padding=window // 2,
+                             dilation=1,
+                             groups=head * channels,
+            ) for window, head in self.windows.items()])
+
+    def forward(self, q: Tensor, v: Tensor, shape: Tuple[int, int]) -> Tensor:
+        """Applies relative positional encoding."""
+        b, heads, hw, c = q.shape
+        h, w = shape
+        if hw != h * w:
+            logger.exception(f"Query width {hw} neq to height x width {h * w}")
+            raise ValueError
+        
+        v = rearrange(v, "b heads (h w) c -> b (heads c) h w", h=h, w=w)
+        v = torch.split(v, self.channel_heads, dim=1)
+        v = [conv(x) for conv, x in zip(self.convs, v)]
+        v = torch.cat(v, dim=1)
+        v = rearrange(v, "b (heads c) h w -> b heads (h w) c", heads=heads)
+
+        encoding = q * v
+        zeros = torch.zeros((b, heads, 1, c), dtype=q.dtype, layout=q.layout, device=q.device)
+        encoding = torch.cat((zeros, encoding), dim=2)
+        return encoding
+
+
+class PositionalEncoding(nn.Module):
+    """Convolutional positional encoding."""
+    def __init__(self, dim: int, k: int = 3) -> None:
+        super().__init__()
+        self.encode = nn.Conv2d(in_channels=dim, out_channels=dim, kernel_size=k, stride=1, padding=k//2, groups=dim)
+
+    def forward(self, x: Tensor, shape: Tuple[int, int]) -> Tensor:
+        """Applies convolutional encoding."""
+        _, hw, _ = x.shape
+        h, w = shape
+
+        if hw != h * w:
+            logger.exception(f"Query width {hw} neq to height x width {h * w}")
+            raise ValueError
+
+        # Depthwise convolution.
+        x = rearrange(x, "b (h w) c -> b c h w", h=h, w=w)
+        x = self.encode(x) + x
+        x = rearrange(x, "b c h w -> b (h w) c")
+        return x
+
+
+        
+
+
+
+            
+            
+
+        
-- 
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