Reformatting of positional encodings and ViT working

1 files changed, 39 insertions, 0 deletions

diff --git a/text_recognizer/networks/transformer/positional_encodings/rotary_embedding.py b/text_recognizer/networks/transformer/positional_encodings/rotary_embedding.py
new file mode 100644
index 0000000..5e80572
--- /dev/null
+++ b/text_recognizer/networks/transformer/positional_encodings/rotary_embedding.py
@@ -0,0 +1,39 @@
+"""Roatary embedding.
+
+Stolen from lucidrains:
+    https://github.com/lucidrains/x-transformers/blob/main/x_transformers/x_transformers.py
+
+Explanation of roatary:
+    https://blog.eleuther.ai/rotary-embeddings/
+
+"""
+from typing import Tuple
+
+from einops import rearrange
+import torch
+from torch import nn
+from torch import Tensor
+
+
+class RotaryEmbedding(nn.Module):
+    def __init__(self, dim: int):
+        super().__init__()
+        inv_freq = 1.0 / (10000 ** (torch.arange(0, dim, 2).float() / dim))
+        self.register_buffer("inv_freq", inv_freq)
+
+    def forward(self, x: Tensor, seq_dim: int = 1) -> Tensor:
+        t = torch.arange(x.shape[seq_dim], device=x.device).type_as(self.inv_freq)
+        freqs = torch.einsum("i , j -> i j", t, self.inv_freq)
+        emb = torch.cat((freqs, freqs), dim=-1)
+        return emb[None, :, :]
+
+
+def rotate_half(x: Tensor) -> Tensor:
+    x = rearrange(x, "... (j d) -> ... j d", j=2)
+    x1, x2 = x.unbind(dim=-2)
+    return torch.cat((-x2, x1), dim=-1)
+
+
+def apply_rotary_pos_emb(q: Tensor, k: Tensor, freqs: Tensor) -> Tuple[Tensor, Tensor]:
+    q, k = map(lambda t: (t * freqs.cos()) + (rotate_half(t) * freqs.sin()), (q, k))
+    return q, k