From 7e8e54e84c63171e748bbf09516fd517e6821ace Mon Sep 17 00:00:00 2001
From: Gustaf Rydholm <gustaf.rydholm@gmail.com>
Date: Sat, 20 Mar 2021 18:09:06 +0100
Subject: Inital commit for refactoring to lightning

---
 text_recognizer/networks/beam.py | 83 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 text_recognizer/networks/beam.py

(limited to 'text_recognizer/networks/beam.py')

diff --git a/text_recognizer/networks/beam.py b/text_recognizer/networks/beam.py
new file mode 100644
index 0000000..dccccdb
--- /dev/null
+++ b/text_recognizer/networks/beam.py
@@ -0,0 +1,83 @@
+"""Implementation of beam search decoder for a sequence to sequence network.
+
+Stolen from: https://github.com/budzianowski/PyTorch-Beam-Search-Decoding/blob/master/decode_beam.py
+
+"""
+# from typing import List
+# from Queue import PriorityQueue
+
+# from loguru import logger
+# import torch
+# from torch import nn
+# from torch import Tensor
+# import torch.nn.functional as F
+
+
+# class Node:
+#     def __init__(
+#         self, parent: Node, target_index: int, log_prob: Tensor, length: int
+#     ) -> None:
+#         self.parent = parent
+#         self.target_index = target_index
+#         self.log_prob = log_prob
+#         self.length = length
+#         self.reward = 0.0
+
+#     def eval(self, alpha: float = 1.0) -> Tensor:
+#         return self.log_prob / (self.length - 1 + 1e-6) + alpha * self.reward
+
+
+# @torch.no_grad()
+# def beam_decoder(
+#     network, mapper, device, memory: Tensor = None, max_len: int = 97,
+# ) -> Tensor:
+#     beam_width = 10
+#     topk = 1  # How many sentences to generate.
+
+#     trg_indices = [mapper(mapper.init_token)]
+
+#     end_nodes = []
+
+#     node = Node(None, trg_indices, 0, 1)
+#     nodes = PriorityQueue()
+
+#     nodes.put((node.eval(), node))
+#     q_size = 1
+
+#     # Beam search
+#     for _ in range(max_len):
+#         if q_size > 2000:
+#             logger.warning("Could not decoder input")
+#             break
+
+#         # Fetch the best node.
+#         score, n = nodes.get()
+#         decoder_input = n.target_index
+
+#         if n.target_index == mapper(mapper.eos_token) and n.parent is not None:
+#             end_nodes.append((score, n))
+
+#             # If we reached the maximum number of sentences required.
+#             if len(end_nodes) >= 1:
+#                 break
+#             else:
+#                 continue
+
+#         # Forward pass with transformer.
+#         trg = torch.tensor(trg_indices, device=device)[None, :].long()
+#         trg = network.target_embedding(trg)
+#         logits = network.decoder(trg=trg, memory=memory, trg_mask=None)
+#         log_prob = F.log_softmax(logits, dim=2)
+
+#         log_prob, indices = torch.topk(log_prob, beam_width)
+
+#         for new_k in range(beam_width):
+#             # TODO: continue from here
+#             token_index = indices[0][new_k].view(1, -1)
+#             log_p = log_prob[0][new_k].item()
+
+#             node = Node()
+
+#             pass
+
+#     pass
-- 
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