BLEU, ROUGE, BERTScore — which is best for LLM output evaluation?

BLEU, ROUGE, BERTScore — which is best for LLM output evaluation?medium

Type: conceptual
Topic: bleu-rouge-bertscore-which-is-best-for-llm-output-evaluati
Frequency: common
Tags: mlops, bleu, rouge, bertscore, which, best

Answer

BLEU measures n-gram precision (designed for translation, poor for open-ended text).

Explanation

BLEU measures n-gram precision (designed for translation, poor for open-ended text). ROUGE measures n-gram recall (designed for summarization). Both are surface-level and miss semantic equivalence. BERTScore uses contextual embeddings for similarity — better for paraphrase-heavy LLM output. For production: none is sufficient alone. Combine with LLM-as-judge and task-specific metrics.

Follow-upCan you give a production example?