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#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
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# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# limitations under the License
import re

_SOLUTION_CLIP_CHARS = 300


def extract_solution(solution_str, method="strict"):
  assert method in ["strict", "flexible"]

  # Optimization: Regular expression matching on very long strings can be slow.
  # For math problems, the final answer is usually at the end.
  # We only match on the last 300 characters, which is a safe approximation for 300 tokens.
  if len(solution_str) > _SOLUTION_CLIP_CHARS:
    solution_str = solution_str[-_SOLUTION_CLIP_CHARS:]

  if method == "strict":
    # this also tests the formatting of the model
    solutions = re.findall("#### (\\-?[0-9\\.\\,]+)", solution_str)
    if len(solutions) == 0:
      final_answer = None
    else:
      # take the last solution
      final_answer = solutions[-1].replace(",", "").replace("$", "")
  elif method == "flexible":
    answer = re.findall("(\\-?[0-9\\.\\,]+)", solution_str)
    final_answer = None
    if len(answer) == 0:
      # no reward is there is no answer
      pass
    else:
      invalid_str = ["", "."]
      # find the last number that is not '.'
      for final_answer in reversed(answer):
        if final_answer not in invalid_str:
          break
  return final_answer


def compute_score(
    solution_str, ground_truth, method="strict", format_score=0.0, score=1.0
):
  """The scoring function for GSM8k.

  Reference: Trung, Luong, et al. "Reft: Reasoning with reinforced fine-tuning."
  Proceedings of the 62nd Annual
  Meeting of the Association for Computational Linguistics (Volume 1: Long
  Papers). 2024.

  Args:
      solution_str: the solution text
      ground_truth: the ground truth
      method: the method to extract the solution, choices are 'strict' and
        'flexible'
      format_score: the score for the format
      score: the score for the correct answer
  """
  answer = extract_solution(solution_str=solution_str, method=method)
  if answer is None:
    return 0
  else:
    if answer == ground_truth:
      return score
    else:
      return format_score
