EvalFunctor.h

// File EvalFunctor.h
// Helper header defining the EvalFunctor struct
// for the FEMPoissonSolver and the PreconditionedFEMPoissonSolver.
// This EvalFunctor represents the action of the matrix A on a
// vector x for the Poisson equation in its FEM formulation Ax=b.
// This functor is passed to the LagrangeSpace in FEMPoissonSolver
// to be used for matrix-free evaluation.
 
#ifndef IPPL_EVALFUNCTOR_H
#define IPPL_EVALFUNCTOR_H
 
#include "FEM/FEMQuadratureData.h"
 
namespace ippl {
    template <typename Tlhs, unsigned Dim, unsigned numElemDOFs>
    struct EvalFunctor {
        const Vector<Tlhs, Dim> DPhiInvT;
        const Tlhs absDetDPhi;
 
        EvalFunctor(Vector<Tlhs, Dim> DPhiInvT, Tlhs absDetDPhi)
            : DPhiInvT(DPhiInvT)
            , absDetDPhi(absDetDPhi) {}
 
        KOKKOS_FUNCTION auto operator()(
            const size_t& i, const size_t& j,
            const QuadratureData<Tlhs, Vector<Tlhs, Dim>, numElemDOFs>& qd) const {
            return dot((DPhiInvT * qd.deriv_q[j]), (DPhiInvT * qd.deriv_q[i])).apply() * absDetDPhi;
        }
    };
}
 
#endif