two_level_schwarz.hh

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#ifndef TWO_LEVEL_SCHWARZ_HH
#define TWO_LEVEL_SCHWARZ_HH
 
#if HAVE_SUITESPARSE_UMFPACK
 
#include <dune/common/timer.hh>
 
#include "coarsespace.hh"
 
namespace Dune {
  namespace PDELab {
    namespace ISTL {
 
      template<class GFS, class M, class X, class Y>
      class TwoLevelOverlappingAdditiveSchwarz
        : public Dune::Preconditioner<X,Y>
      {
      public:
        typedef Dune::PDELab::Backend::Native<M> ISTLM;
 
        typedef Dune::BlockVector<Dune::FieldVector<double,1> > COARSE_V;
        typedef Dune::BCRSMatrix<Dune::FieldMatrix<double,1,1> > COARSE_M;
 
        // define the category
        virtual Dune::SolverCategory::Category category() const
        {
          return Dune::SolverCategory::overlapping;
        }
 
        TwoLevelOverlappingAdditiveSchwarz (const GFS& gfs, const M& AF, std::shared_ptr<CoarseSpace<X> > coarse_space, bool coarse_space_active = true, int verbosity = 0)
          : verbosity_(verbosity),
            coarse_space_active_(coarse_space_active),
            gfs_(gfs),
            solverf_(Dune::PDELab::Backend::native(AF),false),
            coarse_space_(coarse_space),
            coarse_solver_ (*coarse_space_->get_coarse_system()),
            coarse_defect_(coarse_space_->basis_size(), coarse_space_->basis_size()),
            prolongated_(gfs_, 0.0)
        { }
 
        virtual void pre (X& x, Y& b)
        { }
 
        virtual void apply (X& v, const Y& d)
        {
          // first the subdomain solves
          Y b(d); // need copy, since solver overwrites right hand side
          Dune::InverseOperatorResult result;
          solverf_.apply(v,b,result);
 
          if (!coarse_space_active_) {
 
            Dune::PDELab::AddDataHandle<GFS,X> adddh(gfs_,v);
            // Just add local results and return in 1-level Schwarz case
            gfs_.gridView().communicate(adddh,Dune::All_All_Interface,Dune::ForwardCommunication);
 
          } else {
 
            gfs_.gridView().comm().barrier();
            Dune::Timer timer_coarse_solve;
 
            coarse_space_->restrict (d, coarse_defect_);
 
            // Solve coarse system
            Dune::InverseOperatorResult result;
            COARSE_V v0(coarse_space_->basis_size(),coarse_space_->basis_size());
            coarse_solver_.apply(v0, coarse_defect_, result);
 
            // Prolongate coarse solution on local domain
            coarse_space_->prolongate(v0, prolongated_);
            v += prolongated_;
 
            coarse_time_ += timer_coarse_solve.elapsed();
            apply_calls_++;
 
            Dune::PDELab::AddDataHandle<GFS,X> result_addh(gfs_,v);
            gfs_.gridView().communicate(result_addh,Dune::All_All_Interface,Dune::ForwardCommunication);
          }
        }
 
        virtual void post (X& x) {
          if (verbosity_ > 0) std::cout << "Coarse time CT=" << coarse_time_ << std::endl;
          if (verbosity_ > 0) std::cout << "Coarse time per apply CTA=" << coarse_time_ / apply_calls_ << std::endl;
        }
 
      private:
        int verbosity_;
        bool coarse_space_active_;
 
        double coarse_time_ = 0.0;
        int apply_calls_ = 0;
 
        const GFS& gfs_;
        Dune::UMFPack<ISTLM> solverf_;
        std::shared_ptr<CoarseSpace<X> > coarse_space_;
        Dune::UMFPack<COARSE_M> coarse_solver_;
 
        typename CoarseSpace<X>::COARSE_V coarse_defect_;
        X prolongated_;
      };
    }
  }
}
#endif
 
#endif