BinningTools.h

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#ifndef BINNINGTOOLS_H
#define BINNINGTOOLS_H
 
#include "ParallelReduceTools.h" // needed for HistoReductionMode and maxArrSize
 
namespace ParticleBinning {

    template <typename bin_index_type>
    HistoReductionMode determineHistoReductionMode(HistoReductionMode modePreference, bin_index_type binCount) {
        // Overwrite standard mode if compiled with default host execution space!
        if (std::is_same<Kokkos::DefaultExecutionSpace, Kokkos::DefaultHostExecutionSpace>::value) return HistoReductionMode::HostOnly;
 
        // Otherwise choose automatically if Standard and respect preference if not on host and not standard!
        if (modePreference == HistoReductionMode::Standard) { //  || modePreference == HistoReductionMode::HostOnly
            //if (modePreference == HistoReductionMode::HostOnly) {
            //    std::cerr << "Warning: HostOnly mode is not supported on CUDA! Switching to Standard mode." << std::endl;
            //}
            return (binCount <= maxArrSize<bin_index_type>) ? HistoReductionMode::ParallelReduce : HistoReductionMode::TeamBased;
        } else {
            return modePreference;
        }
    } 
 

    template <typename bunch_type>
    struct CoordinateSelector {
        using value_type = typename bunch_type::Layout_t::value_type;

        using size_type = typename bunch_type::size_type;

        using position_view_type = typename bunch_type::particle_position_type::view_type;
 
        position_view_type data_arr; 
        const int axis;              

        CoordinateSelector(int axis_) 
            : axis(axis_) {}

        void updateDataArr(std::shared_ptr<bunch_type> bunch) { data_arr = bunch->P.getView(); }

        KOKKOS_INLINE_FUNCTION
        value_type operator()(const size_type& i) const {
            //std::cout << "CoordinateSelector: " << i << std::endl; // TODO: debug, remove later
            const value_type value = fabs(data_arr(i)[axis]);
            return value / sqrt(1 + value * value); // Normalize to v/c, so v in [0, 1]
        }
    };
 

    template <typename ViewType>
    void computeFixSum(const ViewType& input_view, const ViewType& post_sum_view) {
        using execution_space = typename ViewType::execution_space;
        using size_type       = typename ViewType::size_type;
        using value_type      = typename ViewType::value_type;
 
        // Ensure the output view has the correct size
        if (post_sum_view.extent(0) != input_view.extent(0) + 1) {
            Inform m("computePostSum");
            m << "Output view must have size input_view.extent(0) + 1" << endl;
            ippl::Comm->abort();
        }
 
        // Initialize the first element to 0
        Kokkos::parallel_for("InitPostSum", Kokkos::RangePolicy<execution_space>(0, 1),
            KOKKOS_LAMBDA(const size_type) {
                post_sum_view(0) = 0;
            });
 
        // Compute the fix sum
        Kokkos::parallel_scan("ComputePostSum", Kokkos::RangePolicy<execution_space>(0, input_view.extent(0)),
            KOKKOS_LAMBDA(const size_type& i, value_type& partial_sum, bool final) {
                partial_sum += input_view(i);
                if (final) {
                    post_sum_view(i + 1) = partial_sum;
                }
            });
    }
 

    template <typename ValueType, typename SizeType, typename HashType>
    bool viewIsSorted (const Kokkos::View<ValueType*> view, HashType indices, SizeType npart) {
        bool sorted = true;
        Kokkos::parallel_reduce("CheckSorted", npart - 1, KOKKOS_LAMBDA(const SizeType& i, bool& update) {
            if (view(indices(i)) > view(indices(i + 1))) update = false;
        }, Kokkos::LAnd<bool>(sorted));
        return sorted;
    }
 
 
} // namespace ParticleBinning
 
#endif // BINNINGTOOLS_H