File IndexPQFastScan.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 IndexPQFastScan : public faiss::IndexFastScan
#include <IndexPQFastScan.h>

Fast scan version of IndexPQ. Works for 4-bit PQ for now.

The codes are not stored sequentially but grouped in blocks of size bbs. This makes it possible to compute distances quickly with SIMD instructions.

Implementations: 12: blocked loop with internal loop on Q with qbs 13: same with reservoir accumulator to store results 14: no qbs with heap accumulator 15: no qbs with reservoir accumulator

Public Functions

IndexPQFastScan(int d, size_t M, size_t nbits, MetricType metric = METRIC_L2, int bbs = 32)
IndexPQFastScan() = default
explicit IndexPQFastScan(const IndexPQ &orig, int bbs = 32)

build from an existing IndexPQ

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

Perform training on a representative set of vectors

Parameters:
  • n – nb of training vectors

  • x – training vecors, size n * d

virtual void compute_codes(uint8_t *codes, idx_t n, const float *x) const override
virtual void compute_float_LUT(float *lut, idx_t n, const float *x) const override
virtual void sa_decode(idx_t n, const uint8_t *bytes, float *x) const override

Decode a set of vectors.

NOTE: The codes in the IndexPQFastScan object are non-contiguous. But this method requires a contiguous representation.

Parameters:
  • n – number of vectors

  • bytes – input encoded vectors, size n * code_size

  • x – output vectors, size n * d

Public Members

ProductQuantizer pq