MMLU answer extraction regex fails with repeated "Answer: LETTER" pattern

[lucasresck]

Description

The regular expression used to extract answers for MMLU in common.py fails when the pattern "Answer: LETTER" appears multiple times in the LLM output, affecting model performance.

Example

The following example demonstrates the issue with a German output. The model correctly selects "C", but the regex extracts "A" as the answer.

Explanation

The regular expression mistakenly only considers the first occurrence of "Answer: LETTER".

simple-evals/common.py

Lines 25 to 71 in a8e85cc

	MULTILINGUAL_ANSWER_PATTERN_TEMPLATE = (
	"(?i){}\s*([A-D]|[أ-د]|[অ]|[ব]|[ড]|[ঢ]|[Ａ]|[Ｂ]|[Ｃ]|[Ｄ])"
	)
	# All the different ways "Answer" is written in different languages
	MULTILINGUAL_ANSWER_REGEXES = [
	"Answer\s*:",
	"Answer\s*:​​​​​​", # Korean invisible character
	"উত্তর\s*:",
	"उत्तर\s*:",
	"উত্তরঃ",
	"উত্তর\s*:",
	"Antwort\s*:",
	"답변\s*:",
	"정답\s*:",
	"답\s*:",
	"答案\s*：",
	"答案\s*:",
	"答\s*：",
	"答\s*:",
	"答复\s*：",
	"答曰\s*：",
	"الإجابة:",
	"الجواب:",
	"إجابة:",
	"الإجابة النهائية:",
	"الإجابة الصحيحة:",
	"الإجابة الصحيحة هي:",
	"الإجابة هي:",
	"Respuesta\s*:",
	"Risposta\s*:",
	"答え\s*:",
	"答え\s*：",
	"回答\s*:",
	"回答\s*：",
	"解答\s*:",
	"Jawaban\s*:",
	"Réponse\s*:",
	"Resposta\s*:",
	"Jibu\s*:",
	"Idahun\s*:",
	"Ìdáhùn\s*:",
	"Idáhùn\s*:",
	"Àmọ̀nà\s*:",
	"Àdáhùn\s*:",
	"Ànúgọ\s*:",
	"Àṣàyàn\s*:",
	]

In the German example above, it extracts the answer "A" from "Antwort:\n\nAntwort: C" because "Antwort:\n\nAntwort: C".

Impact

This bug significantly impacts the evaluation results for certain languages. In my experiments, German experienced this issue with ~20% of the samples, and Indonesian showed a ~4% impact. Other languages seem less affected.