Particle ReduceSum function

[S-Explorer]

In the AMReX_ParticleReduce.H file, the reference provided for ReduceSum is for operations performed on a single variable. Can multiple variables be operated on simultaneously in this step? Here, I have modified part of the source code to achieve this functionality, but I'm not sure what impacts this approach might have.

amrex/Src/Particle/AMReX_ParticleReduce.H

Lines 179 to 180 in de8c576

	using value_type = decltype(particle_detail::call_f(f, typename PC::ConstPTDType(), int()));
	value_type sm = 0;

using value_type = decltype(particle_detail::call_f(f, typename PC::ParticleTileType::ConstParticleTileDataType(), int()));
value_type sm{};

Here I have created a custom data structure.

template<typename T, int size = 6>
class ParallelVector {
public:
    ParallelVector() = default;

    ParallelVector& operator +=(const ParallelVector& v) {
        for (int i = 0; i < size; i++) {
            data[i] += v[i];
        }
        return *this;
    }

    ParallelVector& operator =(int v) {
        for (int i = 0; i < size; i++) {
            data[i] = v;
        }
        return *this;
    }

    T& operator[](size_t v) {
        if (v >= size) {
            throw std::out_of_range("index out of range!");
        }
        return data[v];
    }

    const T& operator[](size_t v) const {
        if (v >= size) {
            throw std::out_of_range("index out of range!");
        }
        return data[v];
    }

    T at(const int index) {
        return data.at(index);
    }

    void setValue(const int index, const T& d) {
        data[index] = d;
    }

private:
    std::array<T, size> data = {};
};

Calling ReduceSum as follows:

auto data = ReduceSum(*mContainer, [=]AMREX_GPU_HOST_DEVICE(const pc& p) {
    if (p.idata(M_ID) == cur_p.id) {
        auto v =  ParallelVector<double>();
        v.setValue(0, p.rdata(P_ATTR_REAL::Fx_Marker));
        v.setValue(1, p.rdata(P_ATTR_REAL::Fy_Marker));
        v.setValue(2, p.rdata(P_ATTR_REAL::Fz_Marker));
        v.setValue(3, p.rdata(P_ATTR_REAL::Mx_Marker));
        v.setValue(4, p.rdata(P_ATTR_REAL::My_Marker));
        v.setValue(5, p.rdata(P_ATTR_REAL::Mz_Marker));
    }
    return ParallelVector<double>();
});
// MPI sum reduce -> current particle all IB force and moment
auto fx = data.at(0);
auto fy = data.at(1);
auto fz = data.at(2);
auto mx = data.at(3);
auto my = data.at(4);
auto mz = data.at(5);

[atmyers]

Hi @S-Explorer,

It's possible to do reductions over multiple variables in the current development branch, using the syntax demonstrated here: https://github.com/AMReX-Codes/amrex/blob/development/Tests/Particles/ParticleReduce/main.cpp#L230

-Andrew

[S-Explorer]

Hi atmyers:

Great, it solved my problem perfectly. Please forgive my carelessness.