modified_helmholtz_3d_hypersingular_off_diagonal_kernel_functor.hpp

// Copyright (C) 2011-2012 by the BEM++ Authors
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#ifndef fiber_modified_helmholtz_3d_hypersingular_off_diagonal_kernel_functor_hpp
#define fiber_modified_helmholtz_3d_hypersingular_off_diagonal_kernel_functor_hpp

#include "../common/common.hpp"

#include "geometrical_data.hpp"
#include "scalar_traits.hpp"

namespace Fiber
{

template <typename ValueType_>
class ModifiedHelmholtz3dHypersingularOffDiagonalKernelFunctor
{
public:
    typedef ValueType_ ValueType;
    typedef typename ScalarTraits<ValueType>::RealType CoordinateType;

    explicit ModifiedHelmholtz3dHypersingularOffDiagonalKernelFunctor(
            ValueType waveNumber) :
        m_waveNumber(waveNumber)
    {}

    int kernelCount() const { return 1; }
    int kernelRowCount(int /* kernelIndex */) const { return 1; }
    int kernelColCount(int /* kernelIndex */) const { return 1; }

    void addGeometricalDependencies(size_t& testGeomDeps, size_t& trialGeomDeps) const {
        testGeomDeps |= GLOBALS | NORMALS;
        trialGeomDeps |= GLOBALS | NORMALS;
    }

    ValueType waveNumber() const { return m_waveNumber; }

    template <template <typename T> class CollectionOf2dSlicesOfNdArrays>
    void evaluate(
            const ConstGeometricalDataSlice<CoordinateType>& testGeomData,
            const ConstGeometricalDataSlice<CoordinateType>& trialGeomData,
            CollectionOf2dSlicesOfNdArrays<ValueType>& result) const {
        const int coordCount = 3;
        const ValueType waveNumber = m_waveNumber;

        CoordinateType distanceSq = 0.;
        CoordinateType nTest_diff = 0;
        CoordinateType nTrial_diff = 0;
        CoordinateType nTest_nTrial = 0.;
        for (int coordIndex = 0; coordIndex < coordCount; ++coordIndex) {
            CoordinateType diff = trialGeomData.global(coordIndex) -
                    testGeomData.global(coordIndex);
            distanceSq += diff * diff;
            nTest_diff += diff * testGeomData.normal(coordIndex);
            nTrial_diff += diff * trialGeomData.normal(coordIndex);
            nTest_nTrial += testGeomData.normal(coordIndex) *
                    trialGeomData.normal(coordIndex);
        }
        CoordinateType distance = sqrt(distanceSq);
        ValueType kr = waveNumber * distance;
        const CoordinateType ONE = 1., THREE = 3.;
        result[0](0, 0) =
                static_cast<CoordinateType>(1.0 / (4.0 * M_PI)) /
                (distance * distanceSq * distanceSq) *
                (-distanceSq * nTest_nTrial * (ONE + kr) +
                 nTest_diff * nTrial_diff *
                 (THREE + THREE * kr + kr * kr)) *
                exp(-kr);
    }

    CoordinateType estimateRelativeScale(CoordinateType distance) const {
        return exp(-realPart(m_waveNumber) * distance);
    }

private:
    ValueType m_waveNumber;
};

} // namespace Fiber

#endif