Index.cpp

/**
 * 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.
 */

// -*- c++ -*-

#include <faiss/Index.h>

#include <faiss/impl/AuxIndexStructures.h>
#include <faiss/impl/FaissAssert.h>
#include <faiss/utils/distances.h>

#include <cstring>


namespace faiss {

Index::~Index ()
{
}


void Index::train(idx_t /*n*/, const float* /*x*/) {
    // does nothing by default
}


void Index::range_search (idx_t , const float *, float,
                          RangeSearchResult *) const
{
  FAISS_THROW_MSG ("range search not implemented");
}

void Index::assign (idx_t n, const float * x, idx_t * labels, idx_t k)
{
  float * distances = new float[n * k];
  ScopeDeleter<float> del(distances);
  search (n, x, k, distances, labels);
}

void Index::add_with_ids(
    idx_t /*n*/,
    const float* /*x*/,
    const idx_t* /*xids*/) {
  FAISS_THROW_MSG ("add_with_ids not implemented for this type of index");
}

size_t Index::remove_ids(const IDSelector& /*sel*/) {
  FAISS_THROW_MSG ("remove_ids not implemented for this type of index");
  return -1;
}


void Index::reconstruct (idx_t, float * ) const {
  FAISS_THROW_MSG ("reconstruct not implemented for this type of index");
}


void Index::reconstruct_n (idx_t i0, idx_t ni, float *recons) const {
  for (idx_t i = 0; i < ni; i++) {
    reconstruct (i0 + i, recons + i * d);
  }
}


void Index::search_and_reconstruct (idx_t n, const float *x, idx_t k,
                                    float *distances, idx_t *labels,
                                    float *recons) const {
  search (n, x, k, distances, labels);
  for (idx_t i = 0; i < n; ++i) {
    for (idx_t j = 0; j < k; ++j) {
      idx_t ij = i * k + j;
      idx_t key = labels[ij];
      float* reconstructed = recons + ij * d;
      if (key < 0) {
        // Fill with NaNs
        memset(reconstructed, -1, sizeof(*reconstructed) * d);
      } else {
        reconstruct (key, reconstructed);
      }
    }
  }
}

void Index::compute_residual (const float * x,
                              float * residual, idx_t key) const {
  reconstruct (key, residual);
  for (size_t i = 0; i < d; i++) {
    residual[i] = x[i] - residual[i];
  }
}

void Index::compute_residual_n (idx_t n, const float* xs,
                                float* residuals,
                                const idx_t* keys) const {
#pragma omp parallel for
  for (idx_t i = 0; i < n; ++i) {
    compute_residual(&xs[i * d], &residuals[i * d], keys[i]);
  }
}



size_t Index::sa_code_size () const
{
    FAISS_THROW_MSG ("standalone codec not implemented for this type of index");
}

void Index::sa_encode (idx_t, const float *,
                             uint8_t *) const
{
    FAISS_THROW_MSG ("standalone codec not implemented for this type of index");
}

void Index::sa_decode (idx_t, const uint8_t *,
                            float *) const
{
    FAISS_THROW_MSG ("standalone codec not implemented for this type of index");
}


namespace {


// storage that explicitly reconstructs vectors before computing distances
struct GenericDistanceComputer : DistanceComputer {
  size_t d;
  const Index& storage;
  std::vector<float> buf;
  const float *q;

  explicit GenericDistanceComputer(const Index& storage)
      : storage(storage) {
    d = storage.d;
    buf.resize(d * 2);
  }

  float operator () (idx_t i) override {
    storage.reconstruct(i, buf.data());
    return fvec_L2sqr(q, buf.data(), d);
  }

  float symmetric_dis(idx_t i, idx_t j) override {
    storage.reconstruct(i, buf.data());
    storage.reconstruct(j, buf.data() + d);
    return fvec_L2sqr(buf.data() + d, buf.data(), d);
  }

  void set_query(const float *x) override {
    q = x;
  }

};


}  // namespace


DistanceComputer * Index::get_distance_computer() const {
    if (metric_type == METRIC_L2) {
        return new GenericDistanceComputer(*this);
    } else {
        FAISS_THROW_MSG ("get_distance_computer() not implemented");
    }
}


}