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       1                 :            : // *****************************************************************************
       2                 :            : /*!
       3                 :            :   \file      src/PDE/Riemann/RiemannSolver.hpp
       4                 :            :   \copyright 2012-2015 J. Bakosi,
       5                 :            :              2016-2018 Los Alamos National Security, LLC.,
       6                 :            :              2019-2021 Triad National Security, LLC.
       7                 :            :              All rights reserved. See the LICENSE file for details.
       8                 :            :   \brief     Riemann solver interface class for various Riemann solvers
       9                 :            :   \details   This file defines a generic Riemann solver interface class. The
      10                 :            :     class uses runtime polymorphism without client-side inheritance: inheritance
      11                 :            :     is confined to the internals of the class, invisible to client-code. The
      12                 :            :     class exclusively deals with ownership enabling client-side value semantics.
      13                 :            :     Credit for this idea goes to Sean Parent at Adobe:
      14                 :            :     https://github.com/sean-parent/sean-parent.github.com/wiki/
      15                 :            :     Papers-and-Presentations.
      16                 :            : */
      17                 :            : // *****************************************************************************
      18                 :            : #ifndef RiemannSolver_h
      19                 :            : #define RiemannSolver_h
      20                 :            : 
      21                 :            : #include <array>
      22                 :            : #include <vector>
      23                 :            : #include <memory>
      24                 :            : 
      25                 :            : #include "Types.hpp"
      26                 :            : #include "Fields.hpp"
      27                 :            : #include "FunctionPrototypes.hpp"
      28                 :            : 
      29                 :            : namespace inciter {
      30                 :            : 
      31                 :            : //! \brief Generic Riemann solver interface class for various Riemann solvers
      32                 :            : //! \details This class uses runtime polymorphism without client-side
      33                 :            : //!   inheritance: inheritance is confined to the internals of this class,
      34                 :            : //!   invisble to client-code. The class exclusively deals with ownership
      35                 :            : //!   enabling client-side value semantics. Credit for this idea goes to Sean
      36                 :            : //!   Parent at Adobe:
      37                 :            : //!   https://github.com/sean-parent/sean-parent.github.com/wiki/
      38                 :            : //!   Papers-and-Presentations.
      39                 :          0 : class RiemannSolver {
      40                 :            : 
      41                 :            :   public:
      42                 :            :     //! \brief Constructor taking an object modeling Concept
      43                 :            :     //! \details The object of class T comes pre-constructed.
      44                 :            :     //! \param[in] x Instantiated object of type T given by the template
      45                 :            :     //!   argument.
      46                 :            :     template< typename T > explicit RiemannSolver( T x ) :
      47                 :            :       self( std::make_unique< Model<T> >( std::move(x) ) ) {}
      48                 :            : 
      49                 :            :     //! \brief Constructor taking a function pointer (std::function) to a
      50                 :            :     //!   constructor of an object modeling Concept.
      51                 :            :     //! \details Passing std::function allows late execution of the constructor,
      52                 :            :     //!   i.e., as late as inside this class' constructor, and thus usage from
      53                 :            :     //!   a factory. Note that there are at least two different ways of using
      54                 :            :     //!   this constructor:
      55                 :            :     //!   - Bind T's constructor arguments and place it in std::function<T()>
      56                 :            :     //!   and passing no arguments as args.... This case then instantiates the
      57                 :            :     //!   model via its constructor and stores it in here.
      58                 :            :     //!   - Bind a single placeholder argument to T's constructor and pass it in
      59                 :            :     //!   as host's args..., which then forwards it to model's constructor. This
      60                 :            :     //!   allows late binding, i.e., binding the argument only here.
      61                 :            :     //! \see See also the wrapper tk::recordModel() which does the former for
      62                 :            :     //!   arbitrary number of model constructor arguments and
      63                 :            :     //!   tk::recordModelLate() for a single model constructor argument which
      64                 :            :     //!   does the latter, both defined in src/Base/Factory.h.
      65                 :            :     //! \param[in] x Function pointer (std::function) to a constructor of an
      66                 :            :     //!    object modeling Concept.
      67                 :            :     //! \param[in] args Zero or more constructor arguments
      68                 :            :     template< typename T, typename...Args >
      69         [ -  + ]:        220 :     explicit RiemannSolver( std::function<T(Args...)> x, Args&&... args ) :
      70                 :            :       self( std::make_unique< Model<T> >(
      71 [ +  - ][ -  + ]:        220 :               std::move( x( std::forward<Args>(args)... ) ) ) ) {}
      72                 :            : 
      73                 :            :     //! Public interface to computing the Riemann flux
      74                 :            :     std::vector< tk::real >
      75                 :            :     flux( const std::array< tk::real, 3 >& fn,
      76                 :            :           const std::array< std::vector< tk::real >, 2 >& u,
      77                 :            :           const std::vector< std::array< tk::real, 3 > >& v ) const
      78                 :   78495834 :     { return self->flux( fn, u, v ); }
      79                 :            : 
      80                 :            :     //! Copy assignment
      81                 :            :     RiemannSolver& operator=( const RiemannSolver& x )
      82                 :            :     { RiemannSolver tmp(x); *this = std::move(tmp); return *this; }
      83                 :            :     //! Copy constructor
      84                 :          0 :     RiemannSolver( const RiemannSolver& x ) : self( x.self->copy() ) {}
      85                 :            :     //! Move assignment
      86                 :            :     RiemannSolver& operator=( RiemannSolver&& ) noexcept = default;
      87                 :            :     //! Move constructor
      88                 :            :     RiemannSolver( RiemannSolver&& ) noexcept = default;
      89                 :            : 
      90                 :            :   private:
      91                 :            :     //! \brief Concept is a pure virtual base class specifying the requirements
      92                 :            :     //!   of polymorphic objects deriving from it, i.e., those functions that
      93                 :            :     //!   can be overridden
      94                 :            :     struct Concept {
      95                 :            :       Concept() = default;
      96                 :          0 :       Concept( const Concept& ) = default;
      97                 :            :       virtual ~Concept() = default;
      98                 :            :       virtual Concept* copy() const = 0;
      99                 :            :       virtual std::vector< tk::real >
     100                 :            :         flux( const std::array< tk::real, 3 >&,
     101                 :            :               const std::array< std::vector< tk::real >, 2 >&,
     102                 :            :               const std::vector< std::array< tk::real, 3 > >& ) const = 0;
     103                 :            :     };
     104                 :            : 
     105                 :            :     //! \brief Model models the Concept above by deriving from it and overriding
     106                 :            :     //!   the virtual functions required by Concept
     107                 :            :     template< typename T >
     108         [ -  - ]:          0 :     struct Model : Concept {
     109                 :        220 :       explicit Model( T x ) : data( std::move(x) ) {}
     110                 :          0 :       Concept* copy() const override { return new Model( *this ); }
     111                 :            :       std::vector< tk::real >
     112                 :   78495834 :         flux( const std::array< tk::real, 3 >& fn,
     113                 :            :               const std::array< std::vector< tk::real >, 2 >& u,
     114                 :            :               const std::vector< std::array< tk::real, 3 > >& v ) const override
     115                 :   78495834 :       { return data.flux( fn, u, v ); }
     116                 :            :       T data;
     117                 :            :     };
     118                 :            : 
     119                 :            :     std::unique_ptr< Concept > self;    //!< Base pointer used polymorphically
     120                 :            : };
     121                 :            : 
     122                 :            : } // inciter::
     123                 :            : 
     124                 :            : #endif // RiemannSolver_h