calculate_force_FD2.hpp

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#pragma once
 
#include <KokkosBlas.hpp>
#include <KokkosBlas1_scal.hpp>
#include <KokkosBlas1_set.hpp>
#include <Kokkos_Core.hpp>
 
#include "math/vector_operations.hpp"
 
namespace kynema::beams {
 
template <typename DeviceType>
struct CalculateForceFD2 {
    template <typename ValueType>
    using View = Kokkos::View<ValueType, DeviceType>;
    template <typename ValueType>
    using ConstView = typename View<ValueType>::const_type;
 
    KOKKOS_FUNCTION static void invoke(
        const ConstView<double[6][6]>& Duu, const ConstView<double[3]>& xr_prime,
        const ConstView<double[3]>& u_prime, const ConstView<double[6]>& strain_dot,
        const View<double[6]>& FD2
    ) {
        using NoTranspose = KokkosBlas::Trans::NoTranspose;
        using Transpose = KokkosBlas::Trans::Transpose;
        using Default = KokkosBlas::Algo::Gemv::Default;
        using Gemv = KokkosBlas::SerialGemv<NoTranspose, Default>;
        using GemvT = KokkosBlas::SerialGemv<Transpose, Default>;
        using Kokkos::make_pair;
        using Kokkos::subview;
 
        auto xr_plus_u_prime_data = Kokkos::Array<double, 3>{};
        auto xr_plus_u_prime = View<double[3]>(xr_plus_u_prime_data.data());
        for (auto component = 0; component < 3; ++component) {
            xr_plus_u_prime(component) = u_prime(component) + xr_prime(component);
        }
 
        auto xr_plus_u_prime_tilde_data = Kokkos::Array<double, 9>{};
        auto xr_plus_u_prime_tilde = View<double[3][3]>(xr_plus_u_prime_tilde_data.data());
 
        math::VecTilde(xr_plus_u_prime, xr_plus_u_prime_tilde);
 
        KokkosBlas::SerialSet::invoke(0., FD2);
 
        auto eps_kappa_sum_data = Kokkos::Array<double, 3>{};
        auto eps_kappa_sum = View<double[3]>(eps_kappa_sum_data.data());
 
        const auto eps_dot = subview(strain_dot, make_pair(0, 3));
        const auto kappa_dot = subview(strain_dot, make_pair(3, 6));
 
        auto D11 = subview(Duu, make_pair(0, 3), make_pair(0, 3));
        Gemv::invoke(1., D11, eps_dot, 0., eps_kappa_sum);
        auto D12 = subview(Duu, make_pair(0, 3), make_pair(3, 6));
        Gemv::invoke(1., D12, kappa_dot, 1., eps_kappa_sum);
 
        GemvT::invoke(1., xr_plus_u_prime_tilde, eps_kappa_sum, 0., subview(FD2, make_pair(3, 6)));
    }
};
 
}  // namespace kynema::beams