1 files changed, 95 insertions, 0 deletions
diff --git a/training/trainer/callbacks/checkpoint.py b/training/trainer/callbacks/checkpoint.py
new file mode 100644
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+++ b/training/trainer/callbacks/checkpoint.py
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+"""Callback checkpoint for training models."""
+from enum import Enum
+from pathlib import Path
+from typing import Callable, Dict, List, Optional, Type, Union
+
+from loguru import logger
+import numpy as np
+import torch
+from training.trainer.callbacks import Callback
+
+from text_recognizer.models import Model
+
+
+class Checkpoint(Callback):
+    """Saving model parameters at the end of each epoch."""
+
+    mode_dict = {
+        "min": torch.lt,
+        "max": torch.gt,
+    }
+
+    def __init__(
+        self,
+        checkpoint_path: Union[str, Path],
+        monitor: str = "accuracy",
+        mode: str = "auto",
+        min_delta: float = 0.0,
+    ) -> None:
+        """Monitors a quantity that will allow us to determine the best model weights.
+
+        Args:
+            checkpoint_path (Union[str, Path]): Path to the experiment with the checkpoint.
+            monitor (str): Name of the quantity to monitor. Defaults to "accuracy".
+            mode (str): Description of parameter `mode`. Defaults to "auto".
+            min_delta (float): Description of parameter `min_delta`. Defaults to 0.0.
+
+        """
+        super().__init__()
+        self.checkpoint_path = Path(checkpoint_path)
+        self.monitor = monitor
+        self.mode = mode
+        self.min_delta = torch.tensor(min_delta)
+
+        if mode not in ["auto", "min", "max"]:
+            logger.warning(f"Checkpoint mode {mode} is unkown, fallback to auto mode.")
+
+            self.mode = "auto"
+
+        if self.mode == "auto":
+            if "accuracy" in self.monitor:
+                self.mode = "max"
+            else:
+                self.mode = "min"
+            logger.debug(
+                f"Checkpoint mode set to {self.mode} for monitoring {self.monitor}."
+            )
+
+        torch_inf = torch.tensor(np.inf)
+        self.min_delta *= 1 if self.monitor_op == torch.gt else -1
+        self.best_score = torch_inf if self.monitor_op == torch.lt else -torch_inf
+
+    @property
+    def monitor_op(self) -> float:
+        """Returns the comparison method."""
+        return self.mode_dict[self.mode]
+
+    def on_epoch_end(self, epoch: int, logs: Dict) -> None:
+        """Saves a checkpoint for the network parameters.
+
+        Args:
+            epoch (int): The current epoch.
+            logs (Dict): The log containing the monitored metrics.
+
+        """
+        current = self.get_monitor_value(logs)
+        if current is None:
+            return
+        if self.monitor_op(current - self.min_delta, self.best_score):
+            self.best_score = current
+            is_best = True
+        else:
+            is_best = False
+
+        self.model.save_checkpoint(self.checkpoint_path, is_best, epoch, self.monitor)
+
+    def get_monitor_value(self, logs: Dict) -> Union[float, None]:
+        """Extracts the monitored value."""
+        monitor_value = logs.get(self.monitor)
+        if monitor_value is None:
+            logger.warning(
+                f"Checkpoint is conditioned on metric {self.monitor} which is not available. Available"
+                + f" metrics are: {','.join(list(logs.keys()))}"
+            )
+            return None
+        return monitor_value