Fix a bug that engine.test doesn't work with XPU (#3293)

* fix bug

* align with pre-commit

---------

Co-authored-by: Emily <emily.chun@intel.com>

src/otx/algo/strategies/xpu_single.py

@@ -53,13 +53,17 @@ def is_distributed(self) -> bool:
     def setup_optimizers(self, trainer: pl.Trainer) -> None:
         """Sets up optimizers."""
         super().setup_optimizers(trainer)
-        if len(self.optimizers) != 1:  # type: ignore[has-type]
+        if len(self.optimizers) > 1:  # type: ignore[has-type]
             msg = "XPU strategy doesn't support multiple optimizers"
             raise RuntimeError(msg)
         if trainer.task != "SEMANTIC_SEGMENTATION":
-            model, optimizer = torch.xpu.optimize(trainer.model, optimizer=self.optimizers[0])  # type: ignore[has-type]
-            self.optimizers = [optimizer]
-            self.model = model
+            if len(self.optimizers) == 1:  # type: ignore[has-type]
+                model, optimizer = torch.xpu.optimize(trainer.model, optimizer=self.optimizers[0])  # type: ignore[has-type]
+                self.optimizers = [optimizer]
+                self.model = model
+            else:  # for inference
+                trainer.model.eval()
+                self.model = torch.xpu.optimize(trainer.model)
 
 
 StrategyRegistry.register(

src/otx/engine/engine.py

@@ -886,7 +886,7 @@ def _build_trainer(self, **kwargs) -> None:
             if self._device.accelerator == DeviceType.xpu:
                 self._cache.update(strategy="xpu_single")
                 # add plugin for Automatic Mixed Precision on XPU
-                if self._cache.args["precision"] == 16:
+                if self._cache.args.get("precision", 32) == 16:
                     self._cache.update(plugins=[MixedPrecisionXPUPlugin()])
                     self._cache.args["precision"] = None