Unified model loading with backwards compatibility (#132)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

ultralytics/yolo/engine/validator.py

@@ -106,6 +106,9 @@ class BaseValidator:
                 data = check_dataset_yaml(self.args.data)
             else:
                 data = check_dataset(self.args.data)
+
+            if self.device.type == 'cpu':
+                self.args.workers = 0  # faster CPU val as time dominated by inference, not dataloading
             self.dataloader = self.dataloader or \
                               self.get_dataloader(data.get("val") or data.set("test"), self.args.batch_size)