File IVFlib.h

namespace faiss

Implementation of k-means clustering with many variants.

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.

IDSelector is intended to define a subset of vectors to handle (for removal or as subset to search)

PQ4 SIMD packing and accumulation functions

The basic kernel accumulates nq query vectors with bbs = nb * 2 * 16 vectors and produces an output matrix for that. It is interesting for nq * nb <= 4, otherwise register spilling becomes too large.

The implementation of these functions is spread over 3 cpp files to reduce parallel compile times. Templates are instantiated explicitly.

This file contains callbacks for kernels that compute distances.

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.

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.

Definition of inverted lists + a few common classes that implement the interface.

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.

In this file are the implementations of extra metrics beyond L2 and inner product

Implements a few neural net layers, mainly to support QINCo

Defines a few objects that apply transformations to a set of vectors Often these are pre-processing steps.

namespace ivflib

Functions

void check_compatible_for_merge(const Index *index1, const Index *index2)

check if two indexes have the same parameters and are trained in the same way, otherwise throw.

const IndexIVF *extract_index_ivf(const Index *index)

get an IndexIVF from an index. The index may be an IndexIVF or some wrapper class that encloses an IndexIVF

throws an exception if this is not the case.

IndexIVF *extract_index_ivf(Index *index)
const IndexIVF *try_extract_index_ivf(const Index *index)

same as above but returns nullptr instead of throwing on failure

IndexIVF *try_extract_index_ivf(Index *index)
void merge_into(Index *index0, Index *index1, bool shift_ids)

Merge index1 into index0. Works on IndexIVF’s and IndexIVF’s embedded in a IndexPreTransform. On output, the index1 is empty.

Parameters:

shift_ids – translate the ids from index1 to index0->prev_ntotal

void search_centroid(Index *index, const float *x, int n, idx_t *centroid_ids)
void search_and_return_centroids(Index *index, size_t n, const float *xin, long k, float *distances, idx_t *labels, idx_t *query_centroid_ids, idx_t *result_centroid_ids)
ArrayInvertedLists *get_invlist_range(const Index *index, long i0, long i1)

Get a subset of inverted lists [i0, i1)

void set_invlist_range(Index *index, long i0, long i1, ArrayInvertedLists *src)

Set a subset of inverted lists.

void search_with_parameters(const Index *index, idx_t n, const float *x, idx_t k, float *distances, idx_t *labels, const IVFSearchParameters *params, size_t *nb_dis = nullptr, double *ms_per_stage = nullptr)

search an IndexIVF, possibly embedded in an IndexPreTransform with given parameters. This is a way to set the nprobe and get statdistics in a thread-safe way.

Optionally returns (if non-nullptr):

  • nb_dis: number of distances computed

  • ms_per_stage: [0]: preprocessing time [1]: coarse quantization, [2]: list scanning

void range_search_with_parameters(const Index *index, idx_t n, const float *x, float radius, RangeSearchResult *result, const IVFSearchParameters *params, size_t *nb_dis = nullptr, double *ms_per_stage = nullptr)

same as search_with_parameters but for range search

IndexIVFResidualQuantizer *ivf_residual_from_quantizer(const ResidualQuantizer&, int nlevel)

Build an IndexIVFResidualQuantizer from an ResidualQuantizer, using the nlevel first components as coarse quantizer and the rest as codes in invlists

void ivf_residual_add_from_flat_codes(IndexIVFResidualQuantizer *ivfrq, size_t ncode, const uint8_t *codes, int64_t code_size = -1)

add from codes. NB that the norm component is not used, so the code_size can be provided.

Parameters:

  • ivfrq – index to populate with the codes

  • codes – codes to add, size (ncode, code_size)

  • code_size – override the ivfrq’s code_size, useful if the norm encoding is different

struct SlidingIndexWindow
#include <IVFlib.h>

A set of IndexIVFs concatenated together in a FIFO fashion. at each “step”, the oldest index slice is removed and a new index is added.

Public Functions

SlidingIndexWindow(Index *index)

index should be initially empty and trained

void step(const Index *sub_index, bool remove_oldest)

Add one index to the current index and remove the oldest one.

Parameters:

  • sub_index – slice to swap in (can be NULL)

  • remove_oldest – if true, remove the oldest slices

Public Members

Index *index

common index that contains the sliding window

ArrayInvertedLists *ils

InvertedLists of index.

int n_slice

number of slices currently in index

size_t nlist

same as index->nlist

std::vector<std::vector<size_t>> sizes

cumulative list sizes at each slice