File sorting.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.

Functions

void fvec_argsort(size_t n, const float *vals, size_t *perm)

Indirect sort of a floating-point array

Parameters:

  • n – size of the array

  • vals – array to sort, size n

  • perm – output: permutation of [0..n-1], st. vals[perm[i + 1]] >= vals[perm[i]]

void fvec_argsort_parallel(size_t n, const float *vals, size_t *perm)

Same as fvec_argsort, parallelized

void bucket_sort(size_t nval, const uint64_t *vals, uint64_t nbucket, int64_t *lims, int64_t *perm, int nt = 0)

Bucket sort of a list of values

Parameters:

  • vals – values to sort, size nval, max value nbucket - 1

  • lims – output limits of buckets, size nbucket + 1

  • perm – output buckets, the elements of bucket i are in perm[lims[i]:lims[i + 1]]

  • nt – number of threads (0 = pure sequential code)

void matrix_bucket_sort_inplace(size_t nrow, size_t ncol, int32_t *vals, int32_t nbucket, int64_t *lims, int nt = 0)

in-place bucket sort (with attention to memory=>int32) on input the values are in a nrow * col matrix we want to store the row numbers in the output.

Parameters:

  • vals – positive values to sort, size nrow * ncol, max value nbucket - 1

  • lims – output limits of buckets, size nbucket + 1

  • nt – number of threads (0 = pure sequential code)

void matrix_bucket_sort_inplace(size_t nrow, size_t ncol, int64_t *vals, int64_t nbucket, int64_t *lims, int nt = 0)

same with int64 elements

void hashtable_int64_to_int64_init(int log2_capacity, int64_t *tab)

Hashtable implementation for int64 -> int64 with external storage implemented for fast batch add and lookup.

tab is of size 2 * (1 << log2_capacity) n is the number of elements to add or search

adding several values in a same batch: an arbitrary one gets added in different batches: the newer batch overwrites. raises an exception if capacity is exhausted.

void hashtable_int64_to_int64_add(int log2_capacity, int64_t *tab, size_t n, const int64_t *keys, const int64_t *vals)
void hashtable_int64_to_int64_lookup(int log2_capacity, const int64_t *tab, size_t n, const int64_t *keys, int64_t *vals)

Variables

FAISS_API int bucket_sort_verbose

increase verbosity of the bucket_sort functions