File IndexFlat.h

namespace faiss

Copyright (c) Facebook, Inc. and its affiliates.

This source code is licensed under the MIT license found in the LICENSE file in the root directory of this source tree.

Throughout the library, vectors are provided as float * pointers. Most algorithms can be optimized when several vectors are processed (added/searched) together in a batch. In this case, they are passed in as a matrix. When n vectors of size d are provided as float * x, component j of vector i is

x[ i * d + j ]

where 0 <= i < n and 0 <= j < d. In other words, matrices are always compact. When specifying the size of the matrix, we call it an n*d matrix, which implies a row-major storage.

Copyright (c) Facebook, Inc. and its affiliates.

This source code is licensed under the MIT license found in the LICENSE file in the root directory of this source tree. I/O functions can read/write to a filename, a file handle or to an object that abstracts the medium.

The read functions return objects that should be deallocated with delete. All references within these objectes are owned by the object.

Copyright (c) Facebook, Inc. and its affiliates.

This source code is licensed under the MIT license found in the LICENSE file in the root directory of this source tree. Definition of inverted lists + a few common classes that implement the interface.

Copyright (c) Facebook, Inc. and its affiliates.

This source code is licensed under the MIT license found in the LICENSE file in the root directory of this source tree. Since IVF (inverted file) indexes are of so much use for large-scale use cases, we group a few functions related to them in this small library. Most functions work both on IndexIVFs and IndexIVFs embedded within an IndexPreTransform.

Copyright (c) Facebook, Inc. and its affiliates.

This source code is licensed under the MIT license found in the LICENSE file in the root directory of this source tree. In this file are the implementations of extra metrics beyond L2 and inner product

Copyright (c) Facebook, Inc. and its affiliates.

This source code is licensed under the MIT license found in the LICENSE file in the root directory of this source tree. Defines a few objects that apply transformations to a set of vectors Often these are pre-processing steps.

struct IndexFlat : public faiss::Index
#include <IndexFlat.h>

Index that stores the full vectors and performs exhaustive search

Subclassed by faiss::IndexFlatIP, faiss::IndexFlatL2

Public Functions

explicit IndexFlat(idx_t d, MetricType metric = METRIC_L2)
virtual void add(idx_t n, const float *x) override

Add n vectors of dimension d to the index.

Vectors are implicitly assigned labels ntotal .. ntotal + n - 1 This function slices the input vectors in chunks smaller than blocksize_add and calls add_core.

Parameters

x – input matrix, size n * d

virtual void reset() override

removes all elements from the database.

virtual void search(idx_t n, const float *x, idx_t k, float *distances, idx_t *labels) const override

query n vectors of dimension d to the index.

return at most k vectors. If there are not enough results for a query, the result array is padded with -1s.

Parameters
  • x – input vectors to search, size n * d

  • labels – output labels of the NNs, size n*k

  • distances – output pairwise distances, size n*k

virtual void range_search(idx_t n, const float *x, float radius, RangeSearchResult *result) const override

query n vectors of dimension d to the index.

return all vectors with distance < radius. Note that many indexes do not implement the range_search (only the k-NN search is mandatory).

Parameters
  • x – input vectors to search, size n * d

  • radius – search radius

  • result – result table

virtual void reconstruct(idx_t key, float *recons) const override

Reconstruct a stored vector (or an approximation if lossy coding)

this function may not be defined for some indexes

Parameters
  • key – id of the vector to reconstruct

  • recons – reconstucted vector (size d)

void compute_distance_subset(idx_t n, const float *x, idx_t k, float *distances, const idx_t *labels) const

compute distance with a subset of vectors

Parameters
  • x – query vectors, size n * d

  • labels – indices of the vectors that should be compared for each query vector, size n * k

  • distances – corresponding output distances, size n * k

virtual size_t remove_ids(const IDSelector &sel) override

remove some ids. NB that Because of the structure of the indexing structure, the semantics of this operation are different from the usual ones: the new ids are shifted

inline IndexFlat()
virtual DistanceComputer *get_distance_computer() const override

Get a DistanceComputer (defined in AuxIndexStructures) object for this kind of index.

DistanceComputer is implemented for indexes that support random access of their vectors.

virtual size_t sa_code_size() const override

size of the produced codes in bytes

virtual void sa_encode(idx_t n, const float *x, uint8_t *bytes) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • x – input vectors, size n * d

  • bytes – output encoded vectors, size n * sa_code_size()

virtual void sa_decode(idx_t n, const uint8_t *bytes, float *x) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • bytes – input encoded vectors, size n * sa_code_size()

  • x – output vectors, size n * d

Public Members

std::vector<float> xb

database vectors, size ntotal * d

struct IndexFlat1D : public faiss::IndexFlatL2
#include <IndexFlat.h>

optimized version for 1D “vectors”.

Public Functions

explicit IndexFlat1D(bool continuous_update = true)
void update_permutation()

if not continuous_update, call this between the last add and the first search

virtual void add(idx_t n, const float *x) override

Add n vectors of dimension d to the index.

Vectors are implicitly assigned labels ntotal .. ntotal + n - 1 This function slices the input vectors in chunks smaller than blocksize_add and calls add_core.

Parameters

x – input matrix, size n * d

virtual void reset() override

removes all elements from the database.

virtual void search(idx_t n, const float *x, idx_t k, float *distances, idx_t *labels) const override

Warn: the distances returned are L1 not L2.

virtual void range_search(idx_t n, const float *x, float radius, RangeSearchResult *result) const override

query n vectors of dimension d to the index.

return all vectors with distance < radius. Note that many indexes do not implement the range_search (only the k-NN search is mandatory).

Parameters
  • x – input vectors to search, size n * d

  • radius – search radius

  • result – result table

virtual void reconstruct(idx_t key, float *recons) const override

Reconstruct a stored vector (or an approximation if lossy coding)

this function may not be defined for some indexes

Parameters
  • key – id of the vector to reconstruct

  • recons – reconstucted vector (size d)

void compute_distance_subset(idx_t n, const float *x, idx_t k, float *distances, const idx_t *labels) const

compute distance with a subset of vectors

Parameters
  • x – query vectors, size n * d

  • labels – indices of the vectors that should be compared for each query vector, size n * k

  • distances – corresponding output distances, size n * k

virtual size_t remove_ids(const IDSelector &sel) override

remove some ids. NB that Because of the structure of the indexing structure, the semantics of this operation are different from the usual ones: the new ids are shifted

virtual DistanceComputer *get_distance_computer() const override

Get a DistanceComputer (defined in AuxIndexStructures) object for this kind of index.

DistanceComputer is implemented for indexes that support random access of their vectors.

virtual size_t sa_code_size() const override

size of the produced codes in bytes

virtual void sa_encode(idx_t n, const float *x, uint8_t *bytes) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • x – input vectors, size n * d

  • bytes – output encoded vectors, size n * sa_code_size()

virtual void sa_decode(idx_t n, const uint8_t *bytes, float *x) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • bytes – input encoded vectors, size n * sa_code_size()

  • x – output vectors, size n * d

Public Members

bool continuous_update

is the permutation updated continuously?

std::vector<idx_t> perm

sorted database indices

std::vector<float> xb

database vectors, size ntotal * d

struct IndexFlatIP : public faiss::IndexFlat

Public Functions

inline explicit IndexFlatIP(idx_t d)
inline IndexFlatIP()
virtual void add(idx_t n, const float *x) override

Add n vectors of dimension d to the index.

Vectors are implicitly assigned labels ntotal .. ntotal + n - 1 This function slices the input vectors in chunks smaller than blocksize_add and calls add_core.

Parameters

x – input matrix, size n * d

virtual void reset() override

removes all elements from the database.

virtual void search(idx_t n, const float *x, idx_t k, float *distances, idx_t *labels) const override

query n vectors of dimension d to the index.

return at most k vectors. If there are not enough results for a query, the result array is padded with -1s.

Parameters
  • x – input vectors to search, size n * d

  • labels – output labels of the NNs, size n*k

  • distances – output pairwise distances, size n*k

virtual void range_search(idx_t n, const float *x, float radius, RangeSearchResult *result) const override

query n vectors of dimension d to the index.

return all vectors with distance < radius. Note that many indexes do not implement the range_search (only the k-NN search is mandatory).

Parameters
  • x – input vectors to search, size n * d

  • radius – search radius

  • result – result table

virtual void reconstruct(idx_t key, float *recons) const override

Reconstruct a stored vector (or an approximation if lossy coding)

this function may not be defined for some indexes

Parameters
  • key – id of the vector to reconstruct

  • recons – reconstucted vector (size d)

void compute_distance_subset(idx_t n, const float *x, idx_t k, float *distances, const idx_t *labels) const

compute distance with a subset of vectors

Parameters
  • x – query vectors, size n * d

  • labels – indices of the vectors that should be compared for each query vector, size n * k

  • distances – corresponding output distances, size n * k

virtual size_t remove_ids(const IDSelector &sel) override

remove some ids. NB that Because of the structure of the indexing structure, the semantics of this operation are different from the usual ones: the new ids are shifted

virtual DistanceComputer *get_distance_computer() const override

Get a DistanceComputer (defined in AuxIndexStructures) object for this kind of index.

DistanceComputer is implemented for indexes that support random access of their vectors.

virtual size_t sa_code_size() const override

size of the produced codes in bytes

virtual void sa_encode(idx_t n, const float *x, uint8_t *bytes) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • x – input vectors, size n * d

  • bytes – output encoded vectors, size n * sa_code_size()

virtual void sa_decode(idx_t n, const uint8_t *bytes, float *x) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • bytes – input encoded vectors, size n * sa_code_size()

  • x – output vectors, size n * d

Public Members

std::vector<float> xb

database vectors, size ntotal * d

struct IndexFlatL2 : public faiss::IndexFlat

Subclassed by faiss::IndexFlat1D

Public Functions

inline explicit IndexFlatL2(idx_t d)
inline IndexFlatL2()
virtual void add(idx_t n, const float *x) override

Add n vectors of dimension d to the index.

Vectors are implicitly assigned labels ntotal .. ntotal + n - 1 This function slices the input vectors in chunks smaller than blocksize_add and calls add_core.

Parameters

x – input matrix, size n * d

virtual void reset() override

removes all elements from the database.

virtual void search(idx_t n, const float *x, idx_t k, float *distances, idx_t *labels) const override

query n vectors of dimension d to the index.

return at most k vectors. If there are not enough results for a query, the result array is padded with -1s.

Parameters
  • x – input vectors to search, size n * d

  • labels – output labels of the NNs, size n*k

  • distances – output pairwise distances, size n*k

virtual void range_search(idx_t n, const float *x, float radius, RangeSearchResult *result) const override

query n vectors of dimension d to the index.

return all vectors with distance < radius. Note that many indexes do not implement the range_search (only the k-NN search is mandatory).

Parameters
  • x – input vectors to search, size n * d

  • radius – search radius

  • result – result table

virtual void reconstruct(idx_t key, float *recons) const override

Reconstruct a stored vector (or an approximation if lossy coding)

this function may not be defined for some indexes

Parameters
  • key – id of the vector to reconstruct

  • recons – reconstucted vector (size d)

void compute_distance_subset(idx_t n, const float *x, idx_t k, float *distances, const idx_t *labels) const

compute distance with a subset of vectors

Parameters
  • x – query vectors, size n * d

  • labels – indices of the vectors that should be compared for each query vector, size n * k

  • distances – corresponding output distances, size n * k

virtual size_t remove_ids(const IDSelector &sel) override

remove some ids. NB that Because of the structure of the indexing structure, the semantics of this operation are different from the usual ones: the new ids are shifted

virtual DistanceComputer *get_distance_computer() const override

Get a DistanceComputer (defined in AuxIndexStructures) object for this kind of index.

DistanceComputer is implemented for indexes that support random access of their vectors.

virtual size_t sa_code_size() const override

size of the produced codes in bytes

virtual void sa_encode(idx_t n, const float *x, uint8_t *bytes) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • x – input vectors, size n * d

  • bytes – output encoded vectors, size n * sa_code_size()

virtual void sa_decode(idx_t n, const uint8_t *bytes, float *x) const override

encode a set of vectors

Parameters
  • n – number of vectors

  • bytes – input encoded vectors, size n * sa_code_size()

  • x – output vectors, size n * d

Public Members

std::vector<float> xb

database vectors, size ntotal * d