nag_algorithms/common/policies.hpp

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//This file is part of Bertini 2.
//
//bertini2/nag_algorithms/common/policies.hpp is free software: you can redistribute it and/or modify
//it under the terms of the GNU General Public License as published by
//the Free Software Foundation, either version 3 of the License, or
//(at your option) any later version.
//
//bertini2/nag_algorithms/common/policies.hpp is distributed in the hope that it will be useful,
//but WITHOUT ANY WARRANTY; without even the implied warranty of
//MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//GNU General Public License for more details.
//
//You should have received a copy of the GNU General Public License
//along with bertini2/nag_algorithms/common/policies.hpp.  If not, see <http://www.gnu.org/licenses/>.
//
// Copyright(C) 2015 - 2021 by Bertini2 Development Team
//
// See <http://www.gnu.org/licenses/> for a copy of the license, 
// as well as COPYING.  Bertini2 is provided with permitted 
// additional terms in the b2/licenses/ directory.
 
// individual authors of this file include:
// silviana amethyst, university of wisconsin-eau claire

 
#pragma once
 
 
namespace bertini {
 
    namespace policy{
 
 

        template<    typename D,
                     typename SystemType, typename StartSystemType
                    ,typename StoredSystemType, typename StoredStartSystemType>
        struct SysMgmtPolicy
        {
 
            using SystemT = SystemType;
            using StartSystemT = StartSystemType;
 
            using StoredSystemT = StoredSystemType;
            using StoredStartSystemT = StoredStartSystemType;
 
private:
            // convert the base endgame into the derived type.
            const D& AsDerived() const
            {
                return static_cast<const D&>(*this);
            }
 
            // convert the base endgame into the derived type.
            D& AsDerived()          
            {
                return static_cast<D&>(*this);
            }
 
public:
            const SystemT& TargetSystem() const
            {
                return AsDerived().target_system_;
            }

            const SystemT& Homotopy() const
            {
                return AsDerived().homotopy_;
            }

            const StartSystemT & StartSystem() const
            {
                return AsDerived().start_system_;
            }
 
 

            void TargetSystem(StoredSystemT const& sys)
            {
                AsDerived().target_system_ = sys;
            }

            void Homotopy(StoredSystemT const& sys)
            {
                AsDerived().homotopy_ = sys;
            }

            void StartSystem(StoredStartSystemT const& sys)
            {
                AsDerived().start_system_ = sys;
            }
        };
 
 
 

        template<typename SystemType, typename StartSystemType>
        struct CloneGiven : public SysMgmtPolicy<CloneGiven<SystemType, StartSystemType>, SystemType, StartSystemType, SystemType, StartSystemType>
        {
 
            using SMP = SysMgmtPolicy<CloneGiven<SystemType, StartSystemType>, SystemType, StartSystemType, SystemType, StartSystemType>;
            friend SMP;
 
            using StoredSystemT = typename SMP::StoredSystemT;
            using StoredStartSystemT = typename SMP::StoredStartSystemT;
 
            using SMP::TargetSystem;
            using SMP::StartSystem;
            using SMP::Homotopy;
 
            using SystemT = SystemType;
            using StartSystemT = StartSystemType;
            
private:
            StoredSystemT target_system_;
            StoredStartSystemT start_system_;
            StoredSystemT homotopy_;
 
 
public:
            CloneGiven(SystemType const& target) : target_system_(AtConstruct(target))
            {}
 
 
            static
            StoredSystemT AtConstruct(SystemType const& sys)
            {
                return Clone(sys);
            }
 

            template<typename T>
            static
            T AtSet(T const& sys)
            {
                return sys;
            }
 

            static 
            void PrepareTarget(SystemType & target)
            {
                // target system came from the constructor
                target.Homogenize(); // work over projective coordinates
                target.AutoPatch(); // then patch if needed
            }
 
            static void FormStart(StartSystemType & start, SystemType const& target)
            {
                start = StartSystemType(target);    
            }
 
            static
            void FormHomotopy(SystemType & homotopy, SystemType const& target, StartSystemType const& start, std::string const& path_variable_name)
            {
                auto t = node::Variable::Make(path_variable_name); 
 
                homotopy = (1-t)*target + node::Rational::Make(node::Rational::Rand())*t*start;
                homotopy.AddPathVariable(t);
            }

            void SystemSetup(std::string const& path_variable_name)
            {
                PrepareTarget(TargetSystem());
 
                // now we populate the start system
                FormStart(StartSystem(), TargetSystem());
 
                FormHomotopy(Homotopy(), TargetSystem(), StartSystem(), path_variable_name);
            }
 

            SystemT& TargetSystem() 
            {
                return target_system_;
            }

            SystemT& Homotopy() 
            {
                return homotopy_;
            }

            StartSystemT & StartSystem() 
            {
                return start_system_;
            }
        };
 

        template<typename SystemType, typename StartSystemType>
        struct RefToGiven : public SysMgmtPolicy<RefToGiven<SystemType, StartSystemType>, SystemType, StartSystemType, 
                                std::reference_wrapper< const SystemType>, std::reference_wrapper< const StartSystemType>>
        {
            using SMP = SysMgmtPolicy<RefToGiven<SystemType, StartSystemType>, SystemType, StartSystemType, 
                                std::reference_wrapper< const SystemType>, std::reference_wrapper< const StartSystemType>>;
            friend SMP;
 
            using StoredSystemT = typename SMP::StoredSystemT;
            using StoredStartSystemT = typename SMP::StoredStartSystemT;
 
            using SMP::TargetSystem;
            using SMP::StartSystem;
            using SMP::Homotopy;
 
 
private:
            StoredSystemT target_system_; 
            StoredStartSystemT start_system_; 
            StoredSystemT homotopy_; 
 
 
public:
            RefToGiven(SystemType const& target, StartSystemType const& start, SystemType const& hom)
             : 
                target_system_(std::ref(target)), 
                start_system_(std::ref(start)), 
                homotopy_(std::ref(hom))
            {}
 

            static
            StoredSystemT AtConstruct(SystemType const& sys)
            {
                return std::ref(sys);
            }

            template<typename T>
            static
            T AtSet(T const& sys)
            {
                return std::ref(sys);
            }
 
            void SystemSetup(std::string const& path_variable_name) const
            { }
 
        };
    } // ns policy
} // ns bertini