fix: add fit emthod logic in onedla

Author: yuejiaointel

onedal/neighbors/neighbors.py

@@ -70,17 +70,33 @@ def _get_onedal_params(self, X, y=None, n_neighbors=None):
 
             fptype = np.float64
 
-        # _fit_method should be set by sklearnex level before calling oneDAL
+        # Handle _fit_method: use if set by sklearnex, otherwise determine it ourselves
         if not hasattr(self, "_fit_method") or self._fit_method is None:
-            raise ValueError(
-                "_fit_method must be set by sklearnex level before calling oneDAL. "
-                "This indicates improper usage - oneDAL neighbors should not be called directly."
-            )
+            # Direct oneDAL usage - determine method ourselves
+            method = getattr(self, "algorithm", "auto")
+            n_samples, n_features = X.shape
+            
+            if method in ["auto", "ball_tree"]:
+                condition = (
+                    self.n_neighbors is not None and self.n_neighbors >= n_samples // 2
+                )
+                if getattr(self, "metric", "minkowski") == "precomputed" or n_features > 15 or condition:
+                    fit_method = "brute"
+                else:
+                    if getattr(self, "effective_metric_", getattr(self, "metric", "minkowski")) == "euclidean":
+                        fit_method = "kd_tree"
+                    else:
+                        fit_method = "brute"
+            else:
+                fit_method = method
+        else:
+            # Use the method set by sklearnex level
+            fit_method = self._fit_method
 
         return {
             "fptype": fptype,
             "vote_weights": "uniform" if weights == "uniform" else "distance",
-            "method": self._fit_method,
+            "method": fit_method,
             "radius": self.radius,
             "class_count": class_count,
             "neighbor_count": self.n_neighbors if n_neighbors is None else n_neighbors,