File quantize_lut.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.

namespace quantize_lut

Functions to quantize PQ floating-point Look Up Tables (LUT) to uint8, and biases to uint16. The accumulation is supposed to take place in uint16. The quantization coefficients are float (a, b) such that

 original_value = quantized_value * a / b

The hardest part of the quantization is with multiple LUTs that need to be added up together. In that case, coefficient a has to be chosen so that the sum fits in a uint16 accumulator.

Functions

void round_uint8_per_column(float *tab, size_t n, size_t d, float *a_out = nullptr, float *b_out = nullptr)
void round_uint8_per_column_multi(float *tab, size_t m, size_t n, size_t d, float *a_out = nullptr, float *b_out = nullptr)
void quantize_LUT_and_bias(size_t nprobe, size_t M, size_t ksub, bool lut_is_3d, const float *LUT, const float *bias, uint8_t *LUTq, size_t M2, uint16_t *biasq, float *a_out = nullptr, float *b_out = nullptr)

LUT quantization to uint8 and bias to uint16.

(nprobe, M, ksub, lut_is_3d) determine the size of the the LUT

LUT input:

  • 2D size (M, ksub): single matrix per probe (lut_is_3d=false)

  • 3D size (nprobe, M, ksub): separate LUT per probe (lut_is_3d=true) bias input:

  • nullptr: bias is 0

  • size (nprobe): one bias per probe Output:

  • LUTq uint8 version of the LUT (M size is rounded up to M2)

  • biasq (or nullptr): uint16 version of the LUT

  • a, b: scalars to approximate the true distance