Greyscale test fix (#23903)

Signed-off-by: Glenn Jocher <glenn.jocher@ultralytics.com>

tests/test_python.py

@@ -795,11 +795,7 @@ def test_grayscale(task: str, model: str, data: str, tmp_path) -> None:
             npy_file.unlink()
 
     model = YOLO(model)
-    model.train(data=grayscale_data, epochs=1, imgsz=32, close_mosaic=1, cache="disk")
-    # remove npy files in train/val splits if exists, avoiding interference with other tests
-    for split in {"train", "val"}:
-        for npy_file in (Path(data["path"]) / data[split]).glob("*.npy"):
-            npy_file.unlink()
+    model.train(data=grayscale_data, epochs=1, imgsz=32, close_mosaic=1, cache="ram")
     model.val(data=grayscale_data)
     im = np.zeros((32, 32, 1), dtype=np.uint8)
     model.predict(source=im, imgsz=32, save_txt=True, save_crop=True, augment=True)

ultralytics/data/base.py

@@ -280,7 +280,11 @@ class BaseDataset(Dataset):
         """Save an image as an *.npy file for faster loading."""
         f = self.npy_files[i]
         if not f.exists():
-            np.save(f.as_posix(), imread(self.im_files[i], flags=self.cv2_flag), allow_pickle=False)
+            try:
+                np.save(f.as_posix(), imread(self.im_files[i], flags=self.cv2_flag), allow_pickle=False)
+            except Exception as e:
+                f.unlink(missing_ok=True)
+                LOGGER.warning(f"{self.prefix}WARNING ⚠️ Failed to cache image {f}: {e}")
 
     def check_cache_disk(self, safety_margin: float = 0.5) -> bool:
         """Check if there's enough disk space for caching images.

ultralytics/data/utils.py

@@ -806,8 +806,12 @@ def save_dataset_cache_file(prefix: str, path: Path, x: dict, version: str):
     if is_dir_writeable(path.parent):
         if path.exists():
             path.unlink()  # remove *.cache file if exists
-        with open(str(path), "wb") as file:  # context manager here fixes windows async np.save bug
-            np.save(file, x)
-        LOGGER.info(f"{prefix}New cache created: {path}")
+        try:
+            with open(str(path), "wb") as file:  # context manager here fixes windows async np.save bug
+                np.save(file, x)
+            LOGGER.info(f"{prefix}New cache created: {path}")
+        except Exception as e:
+            Path(path).unlink(missing_ok=True)  # remove partially written file
+            LOGGER.warning(f"{prefix}WARNING ⚠️ Failed to save cache to {path}: {e}")
     else:
         LOGGER.warning(f"{prefix}Cache directory {path.parent} is not writable, cache not saved.")

ultralytics/utils/metrics.py

@@ -962,7 +962,7 @@ class Metric(SimpleClass):
     def fitness(self) -> float:
         """Return model fitness as a weighted combination of metrics."""
         w = [0.0, 0.0, 0.0, 1.0]  # weights for [P, R, mAP@0.5, mAP@0.5:0.95]
-        return (np.nan_to_num(np.array(self.mean_results())) * w).sum()
+        return float((np.nan_to_num(np.array(self.mean_results())) * w).sum())
 
     def update(self, results: tuple):
         """Update the evaluation metrics with a new set of results.