cg.h

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/*
 * Copyright (c) 2010-2015:  G-CSC, Goethe University Frankfurt
 * Author: Andreas Vogel
 * 
 * This file is part of UG4.
 * 
 * UG4 is free software: you can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License version 3 (as published by the
 * Free Software Foundation) with the following additional attribution
 * requirements (according to LGPL/GPL v3 §7):
 * 
 * (1) The following notice must be displayed in the Appropriate Legal Notices
 * of covered and combined works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (2) The following notice must be displayed at a prominent place in the
 * terminal output of covered works: "Based on UG4 (www.ug4.org/license)".
 * 
 * (3) The following bibliography is recommended for citation and must be
 * preserved in all covered files:
 * "Reiter, S., Vogel, A., Heppner, I., Rupp, M., and Wittum, G. A massively
 *   parallel geometric multigrid solver on hierarchically distributed grids.
 *   Computing and visualization in science 16, 4 (2013), 151-164"
 * "Vogel, A., Reiter, S., Rupp, M., Nägel, A., and Wittum, G. UG4 -- a novel
 *   flexible software system for simulating pde based models on high performance
 *   computers. Computing and visualization in science 16, 4 (2013), 165-179"
 * 
 * This program 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 Lesser General Public License for more details.
 */
 
#ifndef __H__UG__LIB_DISC__OPERATOR__LINEAR_SOLVER__CG__
#define __H__UG__LIB_DISC__OPERATOR__LINEAR_SOLVER__CG__
 
#include <iostream>
#include <string>
 
#include "lib_algebra/operator/interface/operator.h"
#include "lib_algebra/operator/interface/preconditioned_linear_operator_inverse.h"
#include "common/profiler/profiler.h"
#include "lib_algebra/operator/interface/pprocess.h"
#ifdef UG_PARALLEL
  #include "lib_algebra/parallelization/parallelization.h"
#endif
 
namespace ug{
 
 
template <typename TVector>
class CG
  : public IPreconditionedLinearOperatorInverse<TVector>
{
  public:
    typedef TVector vector_type;
 
    typedef IPreconditionedLinearOperatorInverse<vector_type> base_type;
 
  protected:
    using base_type::convergence_check;
    using base_type::linear_operator;
    using base_type::preconditioner;
    using base_type::write_debug;
 
  public:
    CG() : base_type() {}
 
    CG(SmartPtr<ILinearIterator<vector_type,vector_type> > spPrecond)
      : base_type ( spPrecond )  {}
 
    CG(SmartPtr<ILinearIterator<vector_type,vector_type> > spPrecond, SmartPtr<IConvergenceCheck<vector_type> > spConvCheck)
      : base_type ( spPrecond, spConvCheck)  {}
 
    virtual const char* name() const {return "CG";}
 
    virtual bool supports_parallel() const
    {
      if(preconditioner().valid())
        return preconditioner()->supports_parallel();
      return true;
    }
 
    virtual bool apply_return_defect(vector_type& x, vector_type& b)
    {
      PROFILE_BEGIN_GROUP(CG_apply_return_defect, "CG algebra");
    //  check parallel storage types
      #ifdef UG_PARALLEL
      if(!b.has_storage_type(PST_ADDITIVE) || !x.has_storage_type(PST_CONSISTENT))
        UG_THROW("CG::apply_return_defect:"
                "Inadequate storage format of Vectors.");
      #endif
 
    //  rename r as b (for convenience)
      vector_type& r = b;
 
    //  Build defect:  r := b - J(u)*x
      linear_operator()->apply_sub(r, x);
 
    //  create help vector (h will be consistent r)
      SmartPtr<vector_type> spQ = r.clone_without_values(); vector_type& q = *spQ;
      SmartPtr<vector_type> spZ = x.clone_without_values(); vector_type& z = *spZ;
      SmartPtr<vector_type> spP = x.clone_without_values(); vector_type& p = *spP;
 
      write_debugXR(x, r, convergence_check()->step());
 
    //  Preconditioning
      if(preconditioner().valid())
      {
        enter_precond_debug_section(convergence_check()->step());
        // apply z = M^-1 * s
        if(!preconditioner()->apply(z, r))
        {
          UG_LOG("ERROR in 'CG::apply_return_defect': "
              "Cannot apply preconditioner. Aborting.\n");
          this->leave_vector_debug_writer_section();
          return false;
        }
        this->leave_vector_debug_writer_section();
      }
      else z = r;
      
    //  make z consistent
      #ifdef UG_PARALLEL
      if(!z.change_storage_type(PST_CONSISTENT))
        UG_THROW("CG::apply_return_defect: "
                "Cannot convert z to consistent vector.");
      #endif
 
    //  post-process the correction
      m_corr_post_process.apply (z);
 
    //  compute start defect
      prepare_conv_check();
      convergence_check()->start(r);
 
    //  start search direction
      p = z;
 
    //  start rho
      number rhoOld = VecProd(z, r), rho;
 
    //  Iteration loop
      while(!convergence_check()->iteration_ended())
      {
      //  Build q = A*p (q is additive afterwards)
        linear_operator()->apply(q, p);
 
      //  lambda = (q,p)
        number lambda = VecProd(q, p);
 
      //  check lambda
        if(lambda == 0.0)
        {
            if (p.size())
            {
                UG_LOG("ERROR in 'CG::apply_return_defect': lambda=" <<
                    lambda<< " is not admitted. Aborting solver.\n");
                return false;
            }
            // in cases where a proc has no geometry, we do not want to fail here
            // so we set lambda = 1, this is not harmful
            else
                lambda = 1.0;
        }
 
      //  alpha = rho / (q,p)
        const number alpha = rhoOld/lambda;
 
      //  Update x := x + alpha*p
        VecScaleAdd(x, 1.0, x, alpha, p);
 
      //  Update r := r - alpha*t
        VecScaleAdd(r, 1.0, r, -alpha, q);
 
        write_debugXR(x, r, convergence_check()->step());
 
      //  Check convergence
        convergence_check()->update(r);
        if(convergence_check()->iteration_ended()) break;
 
      //  Preconditioning
        if(preconditioner().valid())
        {
          enter_precond_debug_section(convergence_check()->step());
        //  apply z = M^-1 * r
          if(!preconditioner()->apply(z, r))
          {
            UG_LOG("ERROR in 'CG::apply_return_defect': "
                "Cannot apply preconditioner. Aborting.\n");
            this->leave_vector_debug_writer_section();
            return false;
          }
          this->leave_vector_debug_writer_section();
        }
        else z = r;
        
        #ifdef UG_PARALLEL
      //  make z consistent
        if(!z.change_storage_type(PST_CONSISTENT))
          UG_THROW("CG::apply_return_defect': "
                  "Cannot convert z to consistent vector.");
        #endif
 
      //  post-process the correction
        m_corr_post_process.apply (z);
 
      //  new rho = (z,r)
        rho = VecProd(z, r);
 
      //  new beta = rho / rhoOld
        const number beta = rho/rhoOld;
 
      //  new direction p := beta * p + z
        VecScaleAdd(p, beta, p, 1.0, z);
 
      //  remember old rho
        rhoOld = rho;
      }
 
    //  post output
      return convergence_check()->post();
    }
    
    void add_postprocess_corr (SmartPtr<IPProcessVector<vector_type> > p)
    {
      m_corr_post_process.add (p);
    }
 
    void remove_postprocess_corr (SmartPtr<IPProcessVector<vector_type> > p)
    {
      m_corr_post_process.remove (p);
    }
 
  protected:
    void prepare_conv_check()
    {
    //  set iteration symbol and name
      convergence_check()->set_name(name());
      convergence_check()->set_symbol('%');
 
    //  set preconditioner string
      std::string s;
      if(preconditioner().valid())
        s = std::string(" (Precond: ") + preconditioner()->name() + ")";
      else
        s = " (No Preconditioner) ";
      convergence_check()->set_info(s);
    }
 
    void write_debugXR(vector_type &x, vector_type &r, int loopCnt)
    {
      if(!this->vector_debug_writer_valid()) return;
      char ext[20]; snprintf(ext, 20, "_iter%03d", loopCnt);
      write_debug(r, std::string("CG_Residual") + ext + ".vec");
      write_debug(x, std::string("CG_Solution") + ext + ".vec");
    }
    
    void enter_precond_debug_section(int loopCnt)
    {
      if(!this->vector_debug_writer_valid()) return;
      char ext[20]; snprintf(ext, 20, "_iter%03d", loopCnt);
      this->enter_vector_debug_writer_section(std::string("CG_Precond_") + ext);
    }
 
  protected:
    number VecProd(vector_type& a, vector_type& b)
    {
      return a.dotprod(b);
    }
  
  protected:
 
    PProcessChain<vector_type> m_corr_post_process;
};
 
} // end namespace ug
 
#endif /* __H__UG__LIB_DISC__OPERATOR__LINEAR_SOLVER__CG__ */