BM25 Turbo ⚡

Rust · Python · WASM · CLI

The fastest BM25 scoring engine. Period.

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**28,217 queries/second** on 8.8 million documents. **8.6ms P50 latency**. Precomputed sparse BM25 with BMW pruning, memory-mapped persistence, and zero-copy index loading. Built for RAG pipelines, search applications, and ML workflows.

use bm25_turbo::{BM25Builder, Method};

let index = BM25Builder::new()
    .method(Method::Lucene)       // Robertson, Lucene, ATIRE, BM25L, BM25+
    .k1(1.5).b(0.75)
    .build_from_corpus(&[
        "Rust is a systems programming language",
        "BM25 is a ranking function used in information retrieval",
        "Machine learning models benefit from fast retrieval",
    ])?;

let results = index.search("information retrieval", 10)?;
for (id, score) in results.doc_ids.iter().zip(results.scores.iter()) {
    println!("doc {} → {:.4}", id, score);
}

Why BM25 Turbo?

Most BM25 libraries compute scores at query time — scanning inverted indexes on every request. BM25 Turbo takes the opposite approach: **precompute every BM25 score at index time** into a compressed sparse column (CSC) matrix. Queries become sparse vector lookups with no math at serving time.

This makes BM25 Turbo the right choice when:

• You query the same index many times (RAG, r