include/colmap/lib/FLANN/mpi/index.h

/***********************************************************************
 * Software License Agreement (BSD License)
 *
 * Copyright 2008-2010  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2010  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
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#ifndef FLANN_MPI_HPP_
#define FLANN_MPI_HPP_

#include <boost/mpi.hpp>
#include <boost/serialization/array.hpp>
#include <FLANN/flann.hpp>
#include <FLANN/io/hdf5.h>

namespace flann
{
namespace mpi
{

template<typename DistanceType>
struct SearchResults
{
    flann::Matrix<int> indices;
    flann::Matrix<DistanceType> dists;

    template<typename Archive>
    void serialize(Archive& ar, const unsigned int version)
    {
        ar& indices.rows;
        ar& indices.cols;
        if (Archive::is_loading::value) {
            indices = Matrix<int>(new int[indices.rows*indices.cols], indices.rows, indices.cols);
        }
        ar& boost::serialization::make_array(indices.ptr(), indices.rows*indices.cols);
        if (Archive::is_saving::value) {
            delete[] indices.ptr();
        }
        ar& dists.rows;
        ar& dists.cols;
        if (Archive::is_loading::value) {
            dists = Matrix<DistanceType>(new DistanceType[dists.rows*dists.cols], dists.rows, dists.cols);
        }
        ar& boost::serialization::make_array(dists.ptr(), dists.rows*dists.cols);
        if (Archive::is_saving::value) {
            delete[] dists.ptr();
        }
    }
};

template<typename DistanceType>
struct ResultsMerger
{
    SearchResults<DistanceType> operator()(SearchResults<DistanceType> a, SearchResults<DistanceType> b)
    {
        SearchResults<DistanceType> results;
        results.indices = flann::Matrix<int>(new int[a.indices.rows*a.indices.cols],a.indices.rows,a.indices.cols);
        results.dists = flann::Matrix<DistanceType>(new DistanceType[a.dists.rows*a.dists.cols],a.dists.rows,a.dists.cols);


        for (size_t i = 0; i < results.dists.rows; ++i) {
            size_t idx = 0;
            size_t a_idx = 0;
            size_t b_idx = 0;
            while (idx < results.dists.cols) {
                if (a.dists[i][a_idx] <= b.dists[i][b_idx]) {
                    results.dists[i][idx] = a.dists[i][a_idx];
                    results.indices[i][idx] = a.indices[i][a_idx];
                    idx++;
                    a_idx++;
                }
                else {
                    results.dists[i][idx] = b.dists[i][b_idx];
                    results.indices[i][idx] = b.indices[i][b_idx];
                    idx++;
                    b_idx++;
                }
            }
        }
        delete[] a.indices.ptr();
        delete[] a.dists.ptr();
        delete[] b.indices.ptr();
        delete[] b.dists.ptr();
        return results;
    }
};



template<typename Distance>
class Index
{
    typedef typename Distance::ElementType ElementType;
    typedef typename Distance::ResultType DistanceType;

    flann::Index<Distance>* flann_index;
    flann::Matrix<ElementType> dataset;
    int size_;
    int offset_;

public:
    Index(const std::string& file_name,
          const std::string& dataset_name,
          const IndexParams& params);

    ~Index();

    void buildIndex()
    {
        flann_index->buildIndex();
    }

    void knnSearch(const flann::Matrix<ElementType>& queries,
                   flann::Matrix<int>& indices,
                   flann::Matrix<DistanceType>& dists,
                   int knn, const
                   SearchParams& params);

    int radiusSearch(const flann::Matrix<ElementType>& query,
                     flann::Matrix<int>& indices,
                     flann::Matrix<DistanceType>& dists,
                     float radius,
                     const SearchParams& params);

    // void save(std::string filename);

    int veclen() const
    {
        return flann_index->veclen();
    }

    int size() const
    {
        return size_;
    }

    IndexParams getIndexParameters()
    {
        return flann_index->getParameters();
    }
};


template<typename Distance>
Index<Distance>::Index(const std::string& file_name, const std::string& dataset_name, const IndexParams& params)
{
    boost::mpi::communicator world;
    flann_algorithm_t index_type = get_param<flann_algorithm_t>(params,"algorithm");
    if (index_type == FLANN_INDEX_SAVED) {
        throw FLANNException("Saving/loading of MPI indexes is not currently supported.");
    }
    flann::mpi::load_from_file(dataset, file_name, dataset_name);
    flann_index = new flann::Index<Distance>(dataset, params);

    std::vector<int> sizes;
    // get the sizes of all MPI indices
    all_gather(world, (int)flann_index->size(), sizes);
    size_ = 0;
    offset_ = 0;
    for (size_t i = 0; i < sizes.size(); ++i) {
        if ((int)i < world.rank()) offset_ += sizes[i];
        size_ += sizes[i];
    }
}

template<typename Distance>
Index<Distance>::~Index()
{
    delete flann_index;
    delete[] dataset.ptr();
}

template<typename Distance>
void Index<Distance>::knnSearch(const flann::Matrix<ElementType>& queries, flann::Matrix<int>& indices, flann::Matrix<DistanceType>& dists, int knn, const SearchParams& params)
{
    boost::mpi::communicator world;
    flann::Matrix<int> local_indices(new int[queries.rows*knn], queries.rows, knn);
    flann::Matrix<DistanceType> local_dists(new DistanceType[queries.rows*knn], queries.rows, knn);

    flann_index->knnSearch(queries, local_indices, local_dists, knn, params);
    for (size_t i = 0; i < local_indices.rows; ++i) {
        for (size_t j = 0; j < local_indices.cols; ++j) {
            local_indices[i][j] += offset_;
        }
    }
    SearchResults<DistanceType> local_results;
    local_results.indices = local_indices;
    local_results.dists = local_dists;
    SearchResults<DistanceType> results;

    // perform MPI reduce
    reduce(world, local_results, results, ResultsMerger<DistanceType>(), 0);

    if (world.rank() == 0) {
        for (size_t i = 0; i < results.indices.rows; ++i) {
            for (size_t j = 0; j < results.indices.cols; ++j) {
                indices[i][j] = results.indices[i][j];
                dists[i][j] = results.dists[i][j];
            }
        }
        delete[] results.indices.ptr();
        delete[] results.dists.ptr();
    }
}

template<typename Distance>
int Index<Distance>::radiusSearch(const flann::Matrix<ElementType>& query, flann::Matrix<int>& indices, flann::Matrix<DistanceType>& dists, float radius, const SearchParams& params)
{
    boost::mpi::communicator world;
    flann::Matrix<int> local_indices(new int[indices.rows*indices.cols], indices.rows, indices.cols);
    flann::Matrix<DistanceType> local_dists(new DistanceType[dists.rows*dists.cols], dists.rows, dists.cols);

    flann_index->radiusSearch(query, local_indices, local_dists, radius, params);
    for (size_t i = 0; i < local_indices.rows; ++i) {
        for (size_t j = 0; j < local_indices.cols; ++j) {
            local_indices[i][j] += offset_;
        }
    }
    SearchResults<DistanceType> local_results;
    local_results.indices = local_indices;
    local_results.dists = local_dists;
    SearchResults<DistanceType> results;

    // perform MPI reduce
    reduce(world, local_results, results, ResultsMerger<DistanceType>(), 0);

    if (world.rank() == 0) {
        for (int i = 0; i < std::min(results.indices.rows, indices.rows); ++i) {
            for (int j = 0; j < std::min(results.indices.cols, indices.cols); ++j) {
                indices[i][j] = results.indices[i][j];
                dists[i][j] = results.dists[i][j];
            }
        }
        delete[] results.indices.ptr();
        delete[] results.dists.ptr();
    }
    return 0;
}

}
} //namespace flann::mpi

namespace boost { namespace mpi {
template<typename DistanceType>
struct is_commutative<flann::mpi::ResultsMerger<DistanceType>, flann::mpi::SearchResults<DistanceType> > : mpl::true_ { };
} } // end namespace boost::mpi


#endif /* FLANN_MPI_HPP_ */