[Fix] bin_trim (#237)

Co-authored-by: wangchonghua <wangchonghua@pjlab.org.cn>

opencompass/models/openai_api.py

@@ -281,18 +281,20 @@ class OpenAI(BaseAPIModel):
         pattern = re.compile(r'[\u4e00-\u9fa5]')
         if pattern.search(prompt):
             words = list(jieba.cut(prompt, cut_all=False))
+            sep = ''
         else:
             words = prompt.split(' ')
+            sep = ' '
 
         l, r = 1, len(words)
         while l + 2 < r:
             mid = (l + r) // 2
             if self.mode == 'front':
-                cur_prompt = ' '.join(words[-mid:])
+                cur_prompt = sep.join(words[-mid:])
             elif self.mode == 'mid':
-                cur_prompt = ' '.join(words[:mid]) + ' '.join(words[-mid:])
+                cur_prompt = sep.join(words[:mid]) + sep.join(words[-mid:])
             elif self.mode == 'rear':
-                cur_prompt = ' '.join(words[:mid])
+                cur_prompt = sep.join(words[:mid])
 
             if self.get_token_len(cur_prompt) <= num_token:
                 l = mid  # noqa: E741
@@ -300,9 +302,9 @@ class OpenAI(BaseAPIModel):
                 r = mid
 
         if self.mode == 'front':
-            prompt = ' '.join(words[-l:])
+            prompt = sep.join(words[-l:])
         elif self.mode == 'mid':
-            prompt = ' '.join(words[:l]) + ' '.join(words[-l:])
+            prompt = sep.join(words[:l]) + sep.join(words[-l:])
         elif self.mode == 'rear':
-            prompt = ' '.join(words[:l])
+            prompt = sep.join(words[:l])
         return prompt