diff --git a/agentevolver/module/trainer/ae_ray_trainer.py b/agentevolver/module/trainer/ae_ray_trainer.py
index 5ba5082..f26d9ee 100644
--- a/agentevolver/module/trainer/ae_ray_trainer.py
+++ b/agentevolver/module/trainer/ae_ray_trainer.py
@@ -197,11 +197,12 @@ def compute_grpo_outcome_advantage(
             id2score[index[i]].append(scores[i])
         for idx in id2score:
             if len(id2score[idx]) == 1:
-                id2mean[idx] = torch.tensor(0.0)
-                id2std[idx] = torch.tensor(1.0)
+                id2mean[idx] = id2score[idx][0]
+                id2std[idx] = torch.tensor(1.0, device=scores.device)
             elif len(id2score[idx]) > 1:
-                id2mean[idx] = torch.mean(torch.tensor(id2score[idx]))
-                id2std[idx] = torch.std(torch.tensor([id2score[idx]]))
+                group_scores = torch.stack(id2score[idx])
+                id2mean[idx] = group_scores.mean()
+                id2std[idx] = group_scores.std()
             else:
                 raise ValueError(f"no score in prompt index: {idx}")
         for i in range(bsz):