muvera-python 0.1.1

MuVERA: Multi-Vector Retrieval via Fixed Dimensional Encodings

MuVERA

A Python implementation of Multi-Vector Retrieval via Fixed Dimensional Encoding Algorithm.

Converts multi-vector embeddings (point clouds) into fixed-dimensional single vectors, enabling the use of existing single-vector search infrastructure (MIPS, ANN, etc.) as-is.

Why this library?

The original MuVERA algorithm is described in a research paper and implemented in C++ within Google's graph-mining repository. While a Python reference exists, it exposes low-level config objects and separate functions for queries vs. documents, making it cumbersome to integrate into real workflows.

This library wraps the full algorithm behind a single Muvera class with a minimal, intuitive interface — initialize once, then call encode_documents() and encode_queries(). No config dataclasses, no encoding-type enums, no manual seed juggling. Just NumPy arrays in, NumPy arrays out.

Installation

pip install muvera

Development install:

git clone https://github.com/craftsangjae/muvera-python.git
cd muvera-python
pip install -e .

Quick Start

import numpy as np
from muvera import Muvera

# Initialize encoder
encoder = Muvera(
    num_repetitions=10,
    num_simhash_projections=4,
    dimension=128,
    seed=42,
)

# Encode documents (batch)
# shape: (num_documents, num_vectors_per_doc, embedding_dim)
documents = np.random.randn(100, 80, 128).astype(np.float32)
doc_fdes = encoder.encode_documents(documents)  # (100, output_dimension)

# Encode queries (batch)
queries = np.random.randn(10, 32, 128).astype(np.float32)
query_fdes = encoder.encode_queries(queries)  # (10, output_dimension)

# Compute similarity (dot product)
scores = query_fdes @ doc_fdes.T  # (10, 100)

Parameters

Parameter	Default	Description
num_repetitions	20	Number of FDE repetitions. Higher values improve accuracy but increase output dimension
num_simhash_projections	5	Number of SimHash projections. Number of partitions = 2^n
dimension	16	Input embedding dimension
projection_type	"identity"	"identity" or "ams_sketch"
projection_dimension	None	Projected dimension when using AMS Sketch
fill_empty_partitions	True	Whether to fill empty partitions with the nearest vector
final_projection_dimension	None	Final dimension reduction via Count Sketch
seed	42	Random seed for reproducibility

Benchmark

End-to-end retrieval on NanoFiQA2018 (4598 documents, 50 queries) using raphaelsty/neural-cherche-colbert (dim=128):

=====================================================================================
                                       RESULTS
                            (zeta-alpha-ai/NanoFiQA2018)
=====================================================================================
Retriever                      | Index (s)    | Query (ms)   | Recall@25
-------------------------------------------------------------------------------------
ColBERT (Native MaxSim)        | 240.04       | 836.94       | 0.8400
ColBERT + Muvera FDE           | 77.29        | 69.48        | 0.7600
=====================================================================================

FDE achieves 90% of native MaxSim recall while being 12x faster at query time. See examples/colbert_nanobeir.py to reproduce.

Acknowledgments

This library was inspired by sionic-ai/muvera-py, the first Python implementation of the MuVERA algorithm. Their faithful port of the C++ reference made it possible to validate correctness and understand the algorithm deeply. This project builds on that foundation with a simplified API designed for easier integration.

References

• MuVERA: Multi-Vector Retrieval via Fixed Dimensional Encodings
• Google graph-mining C++ implementation
• sionic-ai/muvera-py