File hamming.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.

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. 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)

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. 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.

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. 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.

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.

Functions

void bitvec_print(const uint8_t *b, size_t d)
void fvecs2bitvecs(const float *x, uint8_t *b, size_t d, size_t n)
void bitvecs2fvecs(const uint8_t *b, float *x, size_t d, size_t n)
void fvec2bitvec(const float *x, uint8_t *b, size_t d)
void bitvec_shuffle(size_t n, size_t da, size_t db, const int *order, const uint8_t *a, uint8_t *b)

Shuffle the bits from b(i, j) := a(i, order[j])

void hammings(const uint8_t *a, const uint8_t *b, size_t na, size_t nb, size_t nbytespercode, hamdis_t *dis)

Compute a set of Hamming distances between na and nb binary vectors

Parameters:

  • a – size na * nbytespercode

  • b – size nb * nbytespercode

  • nbytespercode – should be multiple of 8

  • dis – output distances, size na * nb

void hammings_knn_hc(int_maxheap_array_t *ha, const uint8_t *a, const uint8_t *b, size_t nb, size_t ncodes, int ordered, ApproxTopK_mode_t approx_topk_mode = ApproxTopK_mode_t::EXACT_TOPK)

Return the k smallest Hamming distances for a set of binary query vectors, using a max heap.

Parameters:

  • a – queries, size ha->nh * ncodes

  • b – database, size nb * ncodes

  • nb – number of database vectors

  • ncodes – size of the binary codes (bytes)

  • ordered – if != 0: order the results by decreasing distance (may be bottleneck for k/n > 0.01)

  • approx_topk_mode – allows to use approximate top-k facilities to speedup heap

void hammings_knn(int_maxheap_array_t *ha, const uint8_t *a, const uint8_t *b, size_t nb, size_t ncodes, int ordered)
void hammings_knn_mc(const uint8_t *a, const uint8_t *b, size_t na, size_t nb, size_t k, size_t ncodes, int32_t *distances, int64_t *labels)

Return the k smallest Hamming distances for a set of binary query vectors, using counting max.

Parameters:

  • a – queries, size na * ncodes

  • b – database, size nb * ncodes

  • na – number of query vectors

  • nb – number of database vectors

  • k – number of vectors/distances to return

  • ncodes – size of the binary codes (bytes)

  • distances – output distances from each query vector to its k nearest neighbors

  • labels – output ids of the k nearest neighbors to each query vector

void hamming_range_search(const uint8_t *a, const uint8_t *b, size_t na, size_t nb, int radius, size_t ncodes, RangeSearchResult *result)

same as hammings_knn except we are doing a range search with radius

void hamming_count_thres(const uint8_t *bs1, const uint8_t *bs2, size_t n1, size_t n2, hamdis_t ht, size_t ncodes, size_t *nptr)
size_t match_hamming_thres(const uint8_t *bs1, const uint8_t *bs2, size_t n1, size_t n2, hamdis_t ht, size_t ncodes, int64_t *idx, hamdis_t *dis)
void crosshamming_count_thres(const uint8_t *dbs, size_t n, hamdis_t ht, size_t ncodes, size_t *nptr)
void generalized_hammings_knn_hc(int_maxheap_array_t *ha, const uint8_t *a, const uint8_t *b, size_t nb, size_t code_size, int ordered = true)

generalized Hamming distances (= count number of code bytes that are the same)

void pack_bitstrings(size_t n, size_t M, int nbit, const int32_t *unpacked, uint8_t *packed, size_t code_size)

Pack a set of n codes of size M * nbit

Parameters:

  • n – number of codes to pack

  • M – number of elementary codes per code

  • nbit – number of bits per elementary code

  • unpacked – input unpacked codes, size (n, M)

  • packed – output packed codes, size (n, code_size)

  • code_size – should be >= ceil(M * nbit / 8)

void pack_bitstrings(size_t n, size_t M, const int32_t *nbits, const int32_t *unpacked, uint8_t *packed, size_t code_size)

Pack a set of n codes of variable sizes

Parameters:

nbit – number of bits per entry (size M)

void unpack_bitstrings(size_t n, size_t M, int nbit, const uint8_t *packed, size_t code_size, int32_t *unpacked)

Unpack a set of n codes of size M * nbit

Parameters:

  • n – number of codes to pack

  • M – number of elementary codes per code

  • nbit – number of bits per elementary code

  • unpacked – input unpacked codes, size (n, M)

  • packed – output packed codes, size (n, code_size)

  • code_size – should be >= ceil(M * nbit / 8)

void unpack_bitstrings(size_t n, size_t M, const int32_t *nbits, const uint8_t *packed, size_t code_size, int32_t *unpacked)

Unpack a set of n codes of variable sizes

Parameters:

nbit – number of bits per entry (size M)

Variables

FAISS_API size_t hamming_batch_size
struct BitstringWriter

Public Functions

inline BitstringWriter(uint8_t *code, size_t code_size)
inline void write(uint64_t x, int nbit)

Public Members

uint8_t *code
size_t code_size
size_t i
struct BitstringReader

Public Functions

inline BitstringReader(const uint8_t *code, size_t code_size)
inline uint64_t read(int nbit)

Public Members

const uint8_t *code
size_t code_size
size_t i