fn_FEM_ghost_switch.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_FEM_GHOST_SWITCH_HPP
#define BELFEM_FN_FEM_GHOST_SWITCH_HPP
 
#include "typedefs.hpp"
#include "assert.hpp"
#include "cl_InputFile.hpp"
#include "cl_Input_Section.hpp"
 
namespace belfem
{
    namespace fem
    {
//------------------------------------------------------------------------------

        inline const input::Section *
        winning_nonlinear_section( const input::Section * aSolver )
        {
            if ( aSolver == nullptr )
            {
                return nullptr ;
            }
            if ( aSolver->section_exists( "nonlinear magnetic" ) )
            {
                return aSolver->section( "nonlinear magnetic" );
            }
            if ( aSolver->section_exists( "nonlinear" ) )
            {
                return aSolver->section( "nonlinear" );
            }
            return nullptr ;
        }
 
//------------------------------------------------------------------------------

        inline real
        read_ghost_eta( const input::Section * aSolver )
        {
            const input::Section * tNonLinear = winning_nonlinear_section( aSolver );
 
            if (    tNonLinear == nullptr
                 || ! tNonLinear->section_exists( "nitsche ghost penalty" ) )
            {
                return -1.0 ;
            }
 
            const input::Section * tGhost = tNonLinear->section( "nitsche ghost penalty" );
 
            BELFEM_ERROR( tGhost->key_exists( "eta" ),
                "a 'nitsche ghost penalty' block requires the key 'eta': a positive value switches "
                "the ghost coupling of the thin-shell layers on, 'eta : 0' switches it off "
                "( so does omitting the block ). 'k_reg' alone does not say which." );
 
            // dimensionless: a dimensioned value ( "eta : 4 mOhm ;" ) is
            // rejected instead of silently SI-scaled
            const value tEta = tGhost->get_value( "eta", "-" );
 
            BELFEM_ERROR( tEta.first >= 0.0, "eta must not be negative, but is %g",
                ( double ) tEta.first );
 
            return tEta.first ;
        }
 
//------------------------------------------------------------------------------

        inline bool
        ghost_facets_requested( const input::Section * aSolver )
        {
            return read_ghost_eta( aSolver ) > 0.0 ;
        }
 
//------------------------------------------------------------------------------

        inline bool
        ghost_facets_requested( const InputFile & aInputFile )
        {
            return aInputFile.section_exists( "solver" ) ?
                ghost_facets_requested( aInputFile.section( "solver" ) ) : false ;
        }
 
//------------------------------------------------------------------------------
    }
}
 
#endif //BELFEM_FN_FEM_GHOST_SWITCH_HPP