algorithm.h

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#ifndef GEOGRAM_BASIC_ALGORITHM
#define GEOGRAM_BASIC_ALGORITHM
 
#include <geogram/basic/common.h>
#include <geogram/basic/numeric.h>
#include <algorithm>
#include <random>
 
#ifdef GEO_PARALLEL_STL
#include <execution>
#endif
 
namespace GEO {
 
    bool GEOGRAM_API uses_parallel_algorithm(size_t size=0);
 
    template <typename ITERATOR>
    inline void sort(
        const ITERATOR& begin, const ITERATOR& end
    ) {
#ifdef GEO_PARALLEL_STL
        if(uses_parallel_algorithm(size_t(end - begin))) {
            std::sort(std::execution::par, begin, end);
        } else
#endif
        {
            std::sort(begin, end);
        }
    }
 
    template <typename ITERATOR, typename CMP>
    inline void sort(
        const ITERATOR& begin, const ITERATOR& end, const CMP& cmp
    ) {
#ifdef GEO_PARALLEL_STL
        if(uses_parallel_algorithm(size_t(end - begin))) {
            std::sort(std::execution::par, begin, end, cmp);
        } else
#endif
        {
            std::sort(begin, end, cmp);
        }
    }
 
 
    template <typename VECTOR> inline void sort_unique(VECTOR& v) {
        std::sort(v.begin(), v.end());
        // Note that std::unique leaves a 'queue' of duplicated elements
        // at the end of the vector, and returns an iterator that
        // indicates where to stop.
        v.erase(
            std::unique(v.begin(), v.end()), v.end()
        );
    }
 
    template <typename ITERATOR> inline void sort_3(ITERATOR items) {
        if (items[0]> items[1]) {
            std::swap(items[0], items[1]);
        }
        if (items[1]> items[2]) {
            std::swap(items[1], items[2]);
        }
        if (items[0]> items[1]) {
            std::swap(items[0], items[1]);
        }
    }
 
    template <typename ITERATOR> inline void sort_4(ITERATOR items) {
        if (items[1] < items[0]) {
            std::swap(items[0], items[1]);
        }
        if (items[3] < items[2]) {
            std::swap(items[2], items[3]);
        }
        if (items[2] < items[0]) {
            std::swap(items[0], items[2]);
            std::swap(items[1], items[3]);
        }
        if (items[2] < items[1]) {
            std::swap(items[1], items[2]);
        }
        if (items[3] < items[2]) {
            std::swap(items[2], items[3]);
        }
    }
 
    template <typename ITERATOR>
    inline void random_shuffle(const ITERATOR& begin, const ITERATOR& end) {
        Numeric::int32 seed = Numeric::random_int32();
        std::mt19937 urng{Numeric::uint32(seed)};
        std::shuffle(begin, end, urng);
    }
 
}
 
#endif