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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
// -*- c++ -*-
#ifndef INDEX_LSH_H
#define INDEX_LSH_H
#include <vector>
#include <faiss/IndexFlatCodes.h>
#include <faiss/VectorTransform.h>
namespace faiss {
/** The sign of each vector component is put in a binary signature */
struct IndexLSH : IndexFlatCodes {
int nbits; ///< nb of bits per vector
bool rotate_data; ///< whether to apply a random rotation to input
bool train_thresholds; ///< whether we train thresholds or use 0
RandomRotationMatrix rrot; ///< optional random rotation
std::vector<float> thresholds; ///< thresholds to compare with
IndexLSH(
idx_t d,
int nbits,
bool rotate_data = true,
bool train_thresholds = false);
/** Preprocesses and resizes the input to the size required to
* binarize the data
*
* @param x input vectors, size n * d
* @return output vectors, size n * bits. May be the same pointer
* as x, otherwise it should be deleted by the caller
*/
const float* apply_preprocess(idx_t n, const float* x) const;
void train(idx_t n, const float* x) override;
void search(
idx_t n,
const float* x,
idx_t k,
float* distances,
idx_t* labels,
const SearchParameters* params = nullptr) const override;
/// transfer the thresholds to a pre-processing stage (and unset
/// train_thresholds)
void transfer_thresholds(LinearTransform* vt);
~IndexLSH() override {}
IndexLSH();
/* standalone codec interface.
*
* The vectors are decoded to +/- 1 (not 0, 1) */
void sa_encode(idx_t n, const float* x, uint8_t* bytes) const override;
void sa_decode(idx_t n, const uint8_t* bytes, float* x) const override;
};
} // namespace faiss
#endif