FastFinder.h

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// -*- LSST-C++ -*-
/*
 * This file is part of jointcal.
 *
 * Developed for the LSST Data Management System.
 * This product includes software developed by the LSST Project
 * (https://www.lsst.org).
 * See the COPYRIGHT file at the top-level directory of this distribution
 * for details of code ownership.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
#ifndef LSST_JOINTCAL_FAST_FINDER_H
#define LSST_JOINTCAL_FAST_FINDER_H
 
#include <vector>
#include "lsst/jointcal/BaseStar.h"
 
namespace lsst {
namespace jointcal {



class FastFinder {
public:
    const BaseStarList baselist;  // shallow copy of the initial list of stars (not used, acts as a
                                  // conservatory). The need is arguable.
    unsigned count;               // total number of objects (size of input list stars).
                                  /* the sorted pointer array: It does not seem very wise to use smart
                                     pointers here because reference counts will uselessly jump around
                                     during sorting */
    // Unfortunately we *must* use shared_ptr here because the return value of findClosest is used to pass
    // ownership
    std::vector<std::shared_ptr<const BaseStar>> stars;
    unsigned nslice;              // number of (X) slices
    std::vector<unsigned> index;  // index in "stars" of first object of each slice.
    double xmin, xmax, xstep;     // x bounds, slice size
 
    using stars_element = decltype(stars)::value_type;
    using pstar = decltype(stars)::const_iterator;

    FastFinder(const BaseStarList &list, unsigned nXSlice = 100);

    std::shared_ptr<const BaseStar> findClosest(const Point &where, double maxDist,
                                                bool (*SkipIt)(const BaseStar &) = nullptr) const;

    std::shared_ptr<const BaseStar> secondClosest(const Point &where, double maxDist,
                                                  std::shared_ptr<const BaseStar> &closest,
                                                  bool (*SkipIt)(const BaseStar &) = nullptr) const;

    void print(std::ostream &out) const;

 
    class Iterator {
    public:  // could be made private, but what for??
        const FastFinder &finder;
        int currentSlice, endSlice;
        double yStart, yEnd;  // Y limits ( for all stripes)
        /* pointers to the first and beyond last stars in the y range for
           the current stripe :  */
        pstar current, pend;
        pstar null_value;  // with pointers being iterators, the null value is not NULL
 
        void check() const;
 
    public:
        Iterator(const FastFinder &f, const Point &where, double maxDist);
        void operator++();
        stars_element operator*() const;
    };
 
    Iterator beginScan(const Point &where, double maxDist) const;
 
    void findRangeInSlice(int iSlice, double yStart, double yEnd, pstar &start,
                          pstar &end) const;
    pstar locateYStart(pstar begin, pstar end, double yVal) const;
    pstar locateYEnd(pstar begin, pstar end, double yVal) const;
};
}  // namespace jointcal
}  // namespace lsst
#endif  // LSST_JOINTCAL_FAST_FINDER_H