fix some bugs of mmlu (#2299)

* fix some bugs of mmlu

* Fix end of file newline issue

---------
Co-authored-by: eyuansu62 <772468951@qq.com>

lm_eval/tasks/mmlu/flan_cot_fewshot/_mmlu.yaml

@@ -26,7 +26,9 @@ task:
       - metric: acc
         weight_by_size: True
 aggregate_metric_list:
-  - metric: acc
+  - aggregation: mean
+    metric: exact_match
     weight_by_size: True
+    filter_list: get-answer
 metadata:
   version: 2

lm_eval/tasks/mmlu/flan_cot_fewshot/_mmlu_flan_cot_fewshot_template_yaml

 dataset_path: hails/mmlu_no_train # a copy of `cais/mmlu` with no auxiliary_train split
 validation_split: validation
 test_split: test
-fewshot_split: dev
 fewshot_config:
   sampler: first_n
 output_type: generate_until
-doc_to_text: "Q: {{question.strip()}}\n(A) {{choices[0]}} (B) {{choices[1]}} (C) {{choices[2]}} (D) {{choices[3]}}\nA: Let's think step by step."
-doc_to_target: "{{['(A)', '(B)', '(C)', '(D)'][answer]}}"
+doc_to_text: "{% if choices is defined%}Q: {{question.strip()}}\n(A) {{choices[0]}} (B) {{choices[1]}} (C) {{choices[2]}} (D) {{choices[3]}}\nA: Let's think step by step.{% else %}Q: {{ question.strip() }}\nA:{% endif %}"
+doc_to_target: "{{['(A)', '(B)', '(C)', '(D)'][answer] if answer is defined else target}}"
 filter_list:
   - name: "get-answer"
     filter:
@@ -18,7 +17,7 @@ generation_kwargs:
     - "</s>"
   do_sample: false
   temperature: 0.0
-num_fewshot: 0
+num_fewshot: 4
 metric_list:
   - metric: exact_match
     aggregation: mean

lm_eval/tasks/mmlu/flan_n_shot/generative/_mmlu_flan_generative_template_yaml

@@ -12,7 +12,7 @@ filter_list:
       - function: "take_first"
   - name: "flexible-extract"
     filter:
-      - function: !function utils.MultiChoiceRegexFilter
+      - function: "multi_choice_regex"
         group_select: 0
         regex_pattern: "(\\([A-Z]\\))"
         ignore_case: true