Average.hpp

/*
 * Average.hpp
 *
 *  Created on: Nov 18, 2015
 *      Author: Pietro Incardona
 */

#ifndef OPENFPM_NUMERICS_SRC_FINITEDIFFERENCE_AVERAGE_HPP_
#define OPENFPM_NUMERICS_SRC_FINITEDIFFERENCE_AVERAGE_HPP_


#define CENTRAL 0
#define CENTRAL_B_ONE_SIDE 1
#define FORWARD 2
#define BACKWARD 3

#include "util/mathutil.hpp"
#include "Vector/map_vector.hpp"
#include "Grid/comb.hpp"
#include "FiniteDifference/util/common.hpp"
#include "util/util_num.hpp"

template<unsigned int d, typename Field, typename Sys_eqs, unsigned int impl=CENTRAL>
class Avg
{
    inline static void value(const grid_key_dx<Sys_eqs::dims> & pos, const grid_sm<Sys_eqs::dims,void> & gs, std::unordered_map<long int,typename Sys_eqs::stype > & cols, typename Sys_eqs::stype coeff)
    {
        std::cerr << "Error " << __FILE__ << ":" << __LINE__ << " only CENTRAL, FORWARD, BACKWARD derivative are defined";
    }

    inline static grid_key_dx<Sys_eqs::dims> position(grid_key_dx<Sys_eqs::dims> & pos, const grid_sm<Sys_eqs::dims,void> & gs, const openfpm::vector<comb<Sys_eqs::dims>> & s_pos = openfpm::vector<comb<Sys_eqs::dims>>())
    {
        std::cerr << "Error " << __FILE__ << ":" << __LINE__ << " only CENTRAL, FORWARD, BACKWARD derivative are defined";
    }
};

template<unsigned int d, typename arg, typename Sys_eqs>
class Avg<d,arg,Sys_eqs,CENTRAL>
{
    public:

    inline static void value(const typename stub_or_real<Sys_eqs,Sys_eqs::dims,typename Sys_eqs::stype,typename Sys_eqs::b_grid::decomposition::extended_type>::type & g_map, grid_dist_key_dx<Sys_eqs::dims> & kmap , const grid_sm<Sys_eqs::dims,void> & gs, typename Sys_eqs::stype (& spacing )[Sys_eqs::dims] , std::unordered_map<long int,typename Sys_eqs::stype > & cols, typename Sys_eqs::stype coeff)
    {
        // if the system is staggered the CENTRAL derivative is equivalent to a forward derivative
        if (is_grid_staggered<Sys_eqs>::value())
        {
            Avg<d,arg,Sys_eqs,BACKWARD>::value(g_map,kmap,gs,spacing,cols,coeff);
            return;
        }

        long int old_val = kmap.getKeyRef().get(d);
        kmap.getKeyRef().set_d(d, kmap.getKeyRef().get(d) + 1);
        arg::value(g_map,kmap,gs,spacing,cols,coeff/2);
        kmap.getKeyRef().set_d(d,old_val);


        old_val = kmap.getKeyRef().get(d);
        kmap.getKeyRef().set_d(d, kmap.getKeyRef().get(d) - 1);
        arg::value(g_map,kmap,gs,spacing,cols,coeff/2);
        kmap.getKeyRef().set_d(d,old_val);
    }


    inline static grid_key_dx<Sys_eqs::dims> position(grid_key_dx<Sys_eqs::dims> & pos, const grid_sm<Sys_eqs::dims,void> & gs, const comb<Sys_eqs::dims> (& s_pos)[Sys_eqs::nvar])
    {
        auto arg_pos = arg::position(pos,gs,s_pos);
        if (is_grid_staggered<Sys_eqs>::value())
        {
            if (arg_pos.get(d) == -1)
            {
                arg_pos.set_d(d,0);
                return arg_pos;
            }
            else
            {
                arg_pos.set_d(d,-1);
                return arg_pos;
            }
        }

        return arg_pos;
    }
};

template<unsigned int d, typename arg, typename Sys_eqs>
class Avg<d,arg,Sys_eqs,FORWARD>
{
    public:

    inline static void value(const typename stub_or_real<Sys_eqs,Sys_eqs::dims,typename Sys_eqs::stype,typename Sys_eqs::b_grid::decomposition::extended_type>::type & g_map, grid_dist_key_dx<Sys_eqs::dims> & kmap , const grid_sm<Sys_eqs::dims,void> & gs, typename Sys_eqs::stype (& spacing )[Sys_eqs::dims] , std::unordered_map<long int,typename Sys_eqs::stype > & cols, typename Sys_eqs::stype coeff)
    {

        long int old_val = kmap.getKeyRef().get(d);
        kmap.getKeyRef().set_d(d, kmap.getKeyRef().get(d) + 1);
        arg::value(g_map,kmap,gs,spacing,cols,coeff/2);
        kmap.getKeyRef().set_d(d,old_val);

        // backward
        arg::value(g_map,kmap,gs,spacing,cols,coeff/2);
    }


    inline static grid_key_dx<Sys_eqs::dims> position(grid_key_dx<Sys_eqs::dims> & pos, const grid_sm<Sys_eqs::dims,void> & gs, const comb<Sys_eqs::dims> (& s_pos)[Sys_eqs::nvar])
    {
        return arg::position(pos,gs,s_pos);
    }
};

template<unsigned int d, typename arg, typename Sys_eqs>
class Avg<d,arg,Sys_eqs,BACKWARD>
{
    public:

    inline static void value(const typename stub_or_real<Sys_eqs,Sys_eqs::dims,typename Sys_eqs::stype,typename Sys_eqs::b_grid::decomposition::extended_type>::type & g_map, grid_dist_key_dx<Sys_eqs::dims> & kmap , const grid_sm<Sys_eqs::dims,void> & gs, typename Sys_eqs::stype (& spacing )[Sys_eqs::dims], std::unordered_map<long int,typename Sys_eqs::stype > & cols, typename Sys_eqs::stype coeff)
    {
        long int old_val = kmap.getKeyRef().get(d);
        kmap.getKeyRef().set_d(d, kmap.getKeyRef().get(d) - 1);
        arg::value(g_map,kmap,gs,spacing,cols,coeff/2);
        kmap.getKeyRef().set_d(d,old_val);

        // forward
        arg::value(g_map,kmap,gs,spacing,cols,coeff/2);
    }


    inline static grid_key_dx<Sys_eqs::dims> position(grid_key_dx<Sys_eqs::dims> & pos, const grid_sm<Sys_eqs::dims,void> & gs, const comb<Sys_eqs::dims> (& s_pos)[Sys_eqs::nvar])
    {
        return arg::position(pos,gs,s_pos);
    }
};

#endif /* OPENFPM_NUMERICS_SRC_FINITEDIFFERENCE_AVERAGE_HPP_ */