修复CrossEntropyLoss在seq_len不为None的时候会出现计算错误

fastNLP/core/losses.py

@@ -228,17 +228,18 @@ class CrossEntropyLoss(LossBase):
         self.class_in_dim = class_in_dim
     
     def get_loss(self, pred, target, seq_len=None):
+        if seq_len is not None and target.dim()>1:
+            mask = seq_len_to_mask(seq_len, max_len=target.size(1)).eq(0)
+            target = target.masked_fill(mask, self.padding_idx)
+
         if pred.dim() > 2:
             if self.class_in_dim == -1:
                 if pred.size(1) != target.size(1):  # 有可能顺序替换了
                     pred = pred.transpose(1, 2)
             else:
-                pred = pred.tranpose(-1, pred)
+                pred = pred.transpose(1, 2)
             pred = pred.reshape(-1, pred.size(-1))
             target = target.reshape(-1)
-        if seq_len is not None and target.dim()>1:
-            mask = seq_len_to_mask(seq_len, max_len=target.size(1)).reshape(-1).eq(0)
-            target = target.masked_fill(mask, self.padding_idx)
 
         return F.cross_entropy(input=pred, target=target,
                                ignore_index=self.padding_idx, reduction=self.reduction)