laplace_3d_double_layer_potential_kernel_functor.hpp

// Copyright (C) 2011-2012 by the BEM++ Authors
//
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// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
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// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
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#ifndef fiber_laplace_3d_double_layer_potential_kernel_functor_hpp
#define fiber_laplace_3d_double_layer_potential_kernel_functor_hpp

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

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

namespace Fiber
{

template <typename ValueType_>
class Laplace3dDoubleLayerPotentialKernelFunctor
{
public:
    typedef ValueType_ ValueType;
    typedef typename ScalarTraits<ValueType>::RealType CoordinateType;

    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;
        trialGeomDeps |= GLOBALS | NORMALS;
    }

    template <template <typename T> class CollectionOf2dSlicesOfNdArrays>
    void evaluate(
            const ConstGeometricalDataSlice<CoordinateType>& testGeomData,
            const ConstGeometricalDataSlice<CoordinateType>& trialGeomData,
            CollectionOf2dSlicesOfNdArrays<ValueType>& result) const {
        const int coordCount = 3;
        assert(testGeomData.dimWorld() == coordCount);
        assert(result.size() == 1);

        CoordinateType numeratorSum = 0., distanceSq = 0.;
        for (int coordIndex = 0; coordIndex < coordCount; ++coordIndex) {
            CoordinateType diff = trialGeomData.global(coordIndex) -
                    testGeomData.global(coordIndex);
            distanceSq += diff * diff;
            numeratorSum += diff * trialGeomData.normal(coordIndex);
        }
        CoordinateType distance = sqrt(distanceSq);
        result[0](0, 0) = -numeratorSum /
                (static_cast<CoordinateType>(4. * M_PI) * distance * distanceSq);
    }
};

} // namespace Fiber

#endif