refactor: Option to pad observation separately

generals/core/observation.py

@@ -10,7 +10,6 @@ class Observation(dict):
     Observation object to be accessible in dictionary-style format,
     e.g. observation["armies"]. And to allow for providing a
     listing of the keys/attributes.
-
     These steps are necessary because PettingZoo & Gymnasium expect
     dictionary-like Observation objects, but we want the benefits of
     knowing the dictionaries' members which a dataclass/class provides.
@@ -44,26 +43,46 @@ def values(self):
     def items(self):
         return dataclasses.asdict(self).items()
 
+    def pad_observation(self, pad_to: int) -> None:
+        """
+        Pads all the observation arrays to the specified size.
+
+        Args:
+            pad_to (int): The target size to pad to. Must be >= the current observation size.
+        """
+        assert pad_to >= max(self.armies.shape), "Can't pad to a smaller size than the original observation."
+
+        h_pad = (0, pad_to - self.armies.shape[0])
+        w_pad = (0, pad_to - self.armies.shape[1])
+
+        # Regular zero padding for most arrays
+        zero_pad_arrays = [
+            "armies",
+            "generals",
+            "cities",
+            "neutral_cells",
+            "owned_cells",
+            "opponent_cells",
+            "fog_cells",
+            "structures_in_fog",
+        ]
+
+        for array_name in zero_pad_arrays:
+            setattr(self, array_name, np.pad(getattr(self, array_name), (h_pad, w_pad), "constant"))
+
+        # Special case for mountains which are padded with ones
+        self.mountains = np.pad(self.mountains, (h_pad, w_pad), "constant", constant_values=1)
+
     def as_tensor(self, pad_to: int | None = None) -> np.ndarray:
         """
         Returns a 3D tensor of shape (15, rows, cols). Suitable for neural nets.
         """
-        shape = self.armies.shape
         if pad_to is not None:
+            self.pad_observation(pad_to)
             shape = (pad_to, pad_to)
-            assert pad_to >= max(self.armies.shape), "Can't pad to a smaller size than the original observation."
-            # pad every channel with zeros, except for mountains, those are padded with ones
-            h_pad = (0, pad_to - self.armies.shape[0])
-            w_pad = (0, pad_to - self.armies.shape[1])
-            self.armies = np.pad(self.armies, (h_pad, w_pad), "constant")
-            self.generals = np.pad(self.generals, (h_pad, w_pad), "constant")
-            self.cities = np.pad(self.cities, (h_pad, w_pad), "constant")
-            self.mountains = np.pad(self.mountains, (h_pad, w_pad), "constant", constant_values=1)
-            self.neutral_cells = np.pad(self.neutral_cells, (h_pad, w_pad), "constant")
-            self.owned_cells = np.pad(self.owned_cells, (h_pad, w_pad), "constant")
-            self.opponent_cells = np.pad(self.opponent_cells, (h_pad, w_pad), "constant")
-            self.fog_cells = np.pad(self.fog_cells, (h_pad, w_pad), "constant")
-            self.structures_in_fog = np.pad(self.structures_in_fog, (h_pad, w_pad), "constant")
+        else:
+            shape = self.armies.shape
+
         return np.stack(
             [
                 self.armies,