fn_GT_create_glue_poly.hpp

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/*
 * BELFEM -- The Berkeley Lab Finite Element Framework
 * Copyright (c) 2026, The Regents of the University of California,
 * through Lawrence Berkeley National Laboratory (subject to receipt of any required
 * approvals from the U.S. Dept. of Energy).  All rights reserved.
 *
 * Developers: Christian Messe, Gregory Giard
 *
 * See the top-level LICENSE file for the complete license and disclaimer.
 */
 
#ifndef BELFEM_FN_CREATE_GLUE_POLY_HPP
#define BELFEM_FN_CREATE_GLUE_POLY_HPP
 
#include "typedefs.hpp"
#include "cl_Vector.hpp"
namespace belfem
{
    namespace gastables
    {
        inline void
        create_glue_poly(
                const real          & aX,
                const real          & aDeltaX,
                const Vector <real> & aF,
                      Vector <real> & aC )
        {
            // get boundary conditions on the left side
            const real & f0  = aF( 0 );
            const real & df0 = aF( 1 );
            const real & f1  = aF( 2 );
            const real & f2  = aF( 3 );
            const real & df2 = aF( 4 );
 
            // get some shortcuts
            const real & X  = aX;
            const real   X2 = std::pow( aX, 2 );
            const real   X3 = std::pow( aX, 3 );
            const real   X4 = std::pow( aX, 4 );
 
            const real & dX  = aDeltaX;
            const real   dX2 = std::pow( aDeltaX, 2 );
            const real   dX3 = std::pow( aDeltaX, 3 );
            const real   dX4 = std::pow( aDeltaX, 4 );
 
            const real b = (f0-2.0*f1+f2);
 
            // populate data
            aC.set_size( 5 );
 
            aC( 0 ) = -(df0*dX)+df2*dX-2.0*b;
 
            aC( 1 ) = dX*((df0+df2)*dX+f0-f2)+4.0*(df0*dX-df2*dX+2.0*b)*X;
 
            aC( 2 ) =      dX2*(df0*dX-df2*dX+4.0*b)
                           -3.0*dX*((df0+df2)*dX+f0-f2)*X
                           -6.0*(df0*dX-df2*dX+2*b)*X2;
 
            aC( 3 ) = -(df0*dX*(dX+X)*(dX2+dX*X-4.0*X2))+(dX-X)
                      *(-((dX+X)*(3.0*dX*(f0-f2)+8.0*b*X))
                      +df2*dX*(-dX2+dX*X+4.0*X2));
 
            aC( 4 ) = -2.0*b*X4+dX3*X*(3.0*f0-3.0*f2+df0*X-df2*X)
                      +dX*X3*(-f0+f2-df0*X+df2*X)
                      +dX4*(4.0*f1+(df0+df2)*X)-dX2*X2*(-4.0*b+(df0+df2)*X);
 
            aC /= 4.0 * dX4;
        }
//------------------------------------------------------------------------------
    } /* namespace gastables */
} /* namespace belfem */
 
#endif //BELFEM_FN_CREATE_GLUE_POLY_HPP