1 files changed, 107 insertions, 0 deletions
diff --git a/src/text_recognizer/networks/metrics.py b/src/text_recognizer/networks/metrics.py
new file mode 100644
index 0000000..af9adb5
--- /dev/null
+++ b/src/text_recognizer/networks/metrics.py
@@ -0,0 +1,107 @@
+"""Utility functions for models."""
+import Levenshtein as Lev
+import torch
+from torch import Tensor
+
+from text_recognizer.networks import greedy_decoder
+
+
+def accuracy_ignore_pad(
+    output: Tensor,
+    target: Tensor,
+    pad_index: int = 79,
+    eos_index: int = 81,
+    seq_len: int = 97,
+) -> float:
+    """Sets all predictions after eos to pad."""
+    start_indices = torch.nonzero(target == eos_index, as_tuple=False).squeeze(1)
+    end_indices = torch.arange(seq_len, target.shape[0] + 1, seq_len)
+    for start, stop in zip(start_indices, end_indices):
+        output[start + 1 : stop] = pad_index
+
+    return accuracy(output, target)
+
+
+def accuracy(outputs: Tensor, labels: Tensor,) -> float:
+    """Computes the accuracy.
+
+    Args:
+        outputs (Tensor): The output from the network.
+        labels (Tensor): Ground truth labels.
+
+    Returns:
+        float: The accuracy for the batch.
+
+    """
+
+    _, predicted = torch.max(outputs, dim=-1)
+
+    acc = (predicted == labels).sum().float() / labels.shape[0]
+    acc = acc.item()
+    return acc
+
+
+def cer(outputs: Tensor, targets: Tensor) -> float:
+    """Computes the character error rate.
+
+    Args:
+        outputs (Tensor): The output from the network.
+        targets (Tensor): Ground truth labels.
+
+    Returns:
+        float: The cer for the batch.
+
+    """
+    target_lengths = torch.full(
+        size=(outputs.shape[1],), fill_value=targets.shape[1], dtype=torch.long,
+    )
+    decoded_predictions, decoded_targets = greedy_decoder(
+        outputs, targets, target_lengths
+    )
+
+    lev_dist = 0
+
+    for prediction, target in zip(decoded_predictions, decoded_targets):
+        prediction = "".join(prediction)
+        target = "".join(target)
+        prediction, target = (
+            prediction.replace(" ", ""),
+            target.replace(" ", ""),
+        )
+        lev_dist += Lev.distance(prediction, target)
+    return lev_dist / len(decoded_predictions)
+
+
+def wer(outputs: Tensor, targets: Tensor) -> float:
+    """Computes the Word error rate.
+
+    Args:
+        outputs (Tensor): The output from the network.
+        targets (Tensor): Ground truth labels.
+
+    Returns:
+        float: The wer for the batch.
+
+    """
+    target_lengths = torch.full(
+        size=(outputs.shape[1],), fill_value=targets.shape[1], dtype=torch.long,
+    )
+    decoded_predictions, decoded_targets = greedy_decoder(
+        outputs, targets, target_lengths
+    )
+
+    lev_dist = 0
+
+    for prediction, target in zip(decoded_predictions, decoded_targets):
+        prediction = "".join(prediction)
+        target = "".join(target)
+
+        b = set(prediction.split() + target.split())
+        word2char = dict(zip(b, range(len(b))))
+
+        w1 = [chr(word2char[w]) for w in prediction.split()]
+        w2 = [chr(word2char[w]) for w in target.split()]
+
+        lev_dist += Lev.distance("".join(w1), "".join(w2))
+
+    return lev_dist / len(decoded_predictions)