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IndexLSH.h
1
2 /**
3 * Copyright (c) 2015-present, Facebook, Inc.
4 * All rights reserved.
5 *
6 * This source code is licensed under the CC-by-NC license found in the
7 * LICENSE file in the root directory of this source tree.
8 */
9
10 // Copyright 2004-present Facebook. All Rights Reserved.
11 // -*- c++ -*-
12
13 #ifndef INDEX_LSH_H
14 #define INDEX_LSH_H
15
16 #include <vector>
17
18 #include "Index.h"
19 #include "VectorTransform.h"
20
21 namespace faiss {
22
23
24 /** The sign of each vector component is put in a binary signature */
25 struct IndexLSH:Index {
26 typedef unsigned char uint8_t;
27
28 int nbits; ///< nb of bits per vector
29 int bytes_per_vec; ///< nb of 8-bits per encoded vector
30 bool rotate_data; ///< whether to apply a random rotation to input
31 bool train_thresholds; ///< whether we train thresholds or use 0
32
33 RandomRotationMatrix rrot; ///< optional random rotation
34
35 std::vector <float> thresholds; ///< thresholds to compare with
36
37 /// encoded dataset
38 std::vector<uint8_t> codes;
39
40 IndexLSH (
41 idx_t d, int nbits,
42 bool rotate_data = true,
43 bool train_thresholds = false);
44
45 /** Preprocesses and resizes the input to the size required to
46 * binarize the data
47 *
48 * @param x input vectors, size n * d
49 * @return output vectors, size n * bits. May be the same pointer
50 * as x, otherwise it should be deleted by the caller
51 */
52 const float *apply_preprocess (idx_t n, const float *x) const;
53
54 virtual void set_typename () override;
55
56 virtual void train (idx_t n, const float *x) override;
57
58 virtual void add (idx_t n, const float *x) override;
59
60 virtual void search (
61 idx_t n,
62 const float *x, idx_t k,
63 float *distances,
64 idx_t *labels) const override;
65
66 virtual void reset() override;
67
68 /// transfer the thresholds to a pre-processing stage (and unset
69 /// train_thresholds)
70 void transfer_thresholds (LinearTransform * vt);
71
72 virtual ~IndexLSH () {}
73
74 IndexLSH ();
75 };
76
77
78
79 }
80
81
82
83
84
85
86 #endif
faiss::RandomRotationMatrix
Randomly rotate a set of vectors.
Definition: VectorTransform.h:118
faiss::IndexLSH::bytes_per_vec
int bytes_per_vec
nb of 8-bits per encoded vector
Definition: IndexLSH.h:29
faiss::IndexLSH::thresholds
std::vector< float > thresholds
thresholds to compare with
Definition: IndexLSH.h:35
faiss::IndexLSH
Definition: IndexLSH.h:25
faiss::IndexLSH::train_thresholds
bool train_thresholds
whether we train thresholds or use 0
Definition: IndexLSH.h:31
faiss::IndexLSH::search
virtual void search(idx_t n, const float *x, idx_t k, float *distances, idx_t *labels) const override
Definition: IndexLSH.cpp:137
faiss::Index::d
int d
vector dimension
Definition: Index.h:66
faiss::IndexLSH::rrot
RandomRotationMatrix rrot
optional random rotation
Definition: IndexLSH.h:33
faiss::IndexLSH::transfer_thresholds
void transfer_thresholds(LinearTransform *vt)
Definition: IndexLSH.cpp:169
faiss::LinearTransform
Definition: VectorTransform.h:78
faiss::Index::idx_t
long idx_t
all indices are this type
Definition: Index.h:64
faiss::IndexLSH::reset
virtual void reset() override
removes all elements from the database.
Definition: IndexLSH.cpp:182
faiss::IndexLSH::add
virtual void add(idx_t n, const float *x) override
Definition: IndexLSH.cpp:124
faiss::IndexLSH::train
virtual void train(idx_t n, const float *x) override
Definition: IndexLSH.cpp:94
faiss::IndexLSH::nbits
int nbits
nb of bits per vector
Definition: IndexLSH.h:28
faiss::Index
Definition: Index.h:61
faiss::IndexLSH::apply_preprocess
const float * apply_preprocess(idx_t n, const float *x) const
Definition: IndexLSH.cpp:59
faiss::IndexLSH::rotate_data
bool rotate_data
whether to apply a random rotation to input
Definition: IndexLSH.h:30
faiss::IndexLSH::codes
std::vector< uint8_t > codes
encoded dataset
Definition: IndexLSH.h:38