fix finetune RMSE result (#123)

* fix finetune RMSE result

The previous RMSE result was actually MAE instead.

See also deepmodeling/deepmd-kit#2860.

* apply changes in deepmodeling/deepmd-kit#2860

deepmd_pt/model/task/fitting.py

@@ -155,9 +155,13 @@ def change_energy_bias(self, config, model, old_type_map, new_type_map, bias_shi
             delta_bias = np.linalg.lstsq(type_numbs, bias_diff, rcond=None)[0]
             unbias_e = energy_predict + type_numbs @ delta_bias
             atom_numbs = type_numbs.sum(-1)
-            rmse_ae = (
-                np.sqrt(np.square(unbias_e - energy_ground_truth).reshape(-1)) / atom_numbs
-            ).mean()
+            rmse_ae = np.sqrt(
+                np.mean(
+                    np.square(
+                        (unbias_e.ravel() - energy_ground_truth.ravel()) / atom_numbs
+                    )
+                )
+            )
             self.bias_atom_e[idx_type_map] += torch.from_numpy(delta_bias.reshape(-1)).to(DEVICE)
             logging.info(
                 "RMSE of atomic energy after linear regression is: {:10.5e} eV/atom.".format(