rougers

ROUGE metrics in Rust, with scores identical to Google's rouge-score. On CNN/DailyMail, XSum and PubMed test samples it scores 30–80 times faster on one core and 80–350 times faster with all eight cores of an M1 Pro (benchmarks).

rouge-score is the ROUGE implementation behind Hugging Face evaluate and many summarization and LLM evaluation pipelines. It is written in pure Python, so scoring large sets of outputs, or scoring repeatedly, takes noticeable time. rougers reproduces it exactly, down to the last bit of every float, including the tokenizer, NLTK's Porter stemmer and the summary-level rougeLsum.

The Rust crate is rougers; the Python package built on it is rouge-score-rs. This is an independent project, not affiliated with Google or the authors of rouge-score.

Python

pip install rouge-score-rs

Change the import and keep the rest of your code:

from rouge_score_rs import rouge_scorer  # was: from rouge_score import rouge_scorer

scorer = rouge_scorer.RougeScorer(["rouge1", "rouge2", "rougeL", "rougeLsum"], use_stemmer=True)
scores = scorer.score(
    "The quick brown fox jumps over the lazy dog",
    "The quick brown dog jumps on the log.",
)
scores["rouge1"]
# Score(precision=0.75, recall=0.6666666666666666, fmeasure=0.7058823529411765)

score_multi, custom tokenizers, split_summaries, scoring.BootstrapAggregator and tokenize.tokenize work the same way as in rouge-score, and scorers can be pickled for use in worker processes.

To score many pairs, use score_batch. With the default tokenizer it runs on all CPU cores and releases the GIL:

results = scorer.score_batch(references, predictions)  # list of dicts, one per pair

Set RAYON_NUM_THREADS to limit the number of threads. With a custom tokenizer or split_summaries=True, and in a process forked after a parallel call, pairs are scored one by one. The built-in tokenizers described below also run in parallel.

Other languages

The default tokenizer is the one from rouge-score: it keeps only the ASCII letters a–z and digits, so Russian, Arabic, Hindi or Chinese text scores zero. Two opt-in tokenizers cover other languages and run natively, including in score_batch:

from rouge_score_rs import rouge_scorer, tokenizers

scorer = rouge_scorer.RougeScorer(["rouge1", "rougeL"], tokenizer=tokenizers.UnicodeTokenizer())
scorer.score("Правительство объявило новые меры.", "Объявлены новые меры правительства.")

chinese = rouge_scorer.RougeScorer(["rouge1", "rougeL"], tokenizer=tokenizers.CharacterTokenizer())
chinese.score("今天天气很好", "今天天气不错")

Tokenizer	Profile	Tokens
DefaultTokenizer	rouge-score	runs of [a-z0-9] after lowercasing; optional Porter stemming
UnicodeTokenizer	unicode-v1	words by the Unicode word boundary rules (UAX #29) that contain an alphabetic character or a number
CharacterTokenizer	character-v1	grapheme clusters that contain an alphabetic character or a number

Both profiles first normalize the text: NFKC, full Unicode case folding, then NFKC again, so Straße, STRASSE and ｓｔｒａｓｓｅ give the same token.

UnicodeTokenizer suits languages that separate words with spaces. It makes each Chinese or Japanese ideograph a separate token and does not split Thai, Lao, Khmer or Burmese into words; for those, pass your own tokenizer. CharacterTokenizer gives character-level ROUGE, a common choice for Chinese. Neither stems. Scores from these profiles are not comparable with rouge-score defaults or with other tokenization schemes, so report the profile name with your results. The profiles use Unicode 17.0 data from pinned dependencies, so their output does not depend on the platform or the Rust version, and a profile's behaviour will not change under the same name.

Hugging Face Evaluate

The SyntaxSpirits/rouge metric has the same inputs, options and scores as Evaluate's built-in rouge metric and computes them with this package:

import evaluate

rouge = evaluate.load("SyntaxSpirits/rouge")  # was: evaluate.load("rouge")
results = rouge.compute(predictions=predictions, references=references)

It needs pip install evaluate 'rouge-score-rs[aggregate]>=0.1.1'.

Rust

[dependencies]
rougers = "0.2"

use rougers::{RougeScorer, RougeType};

let scorer = RougeScorer::new(["rouge1", "rougeL"], true)?;
let scores = scorer.score(
    "The quick brown fox jumps over the lazy dog",
    "The quick brown dog jumps on the log.",
);
let rouge_l = scores.get(RougeType::L).unwrap();
println!("{:.4}", rouge_l.fmeasure);

RougeScorer is Send + Sync, so it can be shared across threads, for example with Rayon.

Performance

The benchmark uses fixed samples from the CNN/DailyMail, XSum and PubMed test sets with lead-sentence predictions. It checks score parity, measures serial and parallel scoring with and without stemming, and includes Hugging Face Evaluate's default bootstrap aggregation.

See BENCHMARKS.md for measured results, pinned data sources, package comparisons and reproduction commands. Speedups depend on summary length, requested metrics, stemming and thread count; timings for packages computing different scores are reported separately.

Compatibility

The test suite compares rouge-score-rs with rouge-score and fails on any difference in any float:

• the stemmer against NLTK on all 235,976 words of a system dictionary (NLTK 3.8–3.10 stem them identically);
• tokenization against Python's str.lower for every Unicode code point;
• thousands of random texts with repeated words, punctuation, digits, newlines and non-Latin scripts, plus property-based tests on arbitrary Unicode;
• score_multi, custom tokenizers, split_summaries and bootstrap aggregation with a fixed NumPy seed.

Known differences:

• An invalid ROUGE type raises ValueError when the scorer is created, not on the first call to score. Type names must be exactly rouge1…rouge9, rougeL or rougeLsum.
• Texts must be str; rouge-score also accepts UTF-8 bytes.
• BootstrapAggregator needs NumPy (pip install 'rouge-score-rs[aggregate]') and split_summaries=True needs NLTK (pip install 'rouge-score-rs[sentences]'). Without them, rouge-score-rs has no Python dependencies.

Development

cargo test -p rougers
cd bindings/python
uv sync --group dev
uv run pytest

License

Apache-2.0, the same licence as rouge-score and NLTK, whose scoring, tokenization and stemming logic this project ports. See NOTICE.