syssolver_mdagm_cg.h

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// -*- C++ -*-
/*! \file
 *  \brief Solve a MdagM*psi=chi linear system by CG2
 */
 
#ifndef __syssolver_mdagm_cg_h__
#define __syssolver_mdagm_cg_h__
#include "chroma_config.h"
 
#include "handle.h"
#include "syssolver.h"
#include "linearop.h"
#include "lmdagm.h"
#include "actions/ferm/invert/syssolver_mdagm.h"
#include "actions/ferm/invert/syssolver_cg_params.h"
#include "actions/ferm/invert/invcg2.h"
 
 
namespace Chroma
{
 
  //! CG2 system solver namespace
  namespace MdagMSysSolverCGEnv
  {
    //! Register the syssolver
    bool registerAll();
  }
 
 
  //! Solve a CG2 system. Here, the operator is NOT assumed to be hermitian
  /*! \ingroup invert
   */
  template<typename T>
  class MdagMSysSolverCG : public MdagMSystemSolver<T>
  {
  public:
    //! Constructor
    /*!
     * \param M_        Linear operator ( Read )
     * \param invParam  inverter parameters ( Read )
     */
    MdagMSysSolverCG(Handle< LinearOperator<T> > A_,
                     const SysSolverCGParams& invParam_) : 
      A(A_), invParam(invParam_) 
      {}
 
    //! Destructor is automatic
    ~MdagMSysSolverCG() {}
 
    //! Return the subset on which the operator acts
    const Subset& subset() const {return A->subset();}
 
    //! Solver the linear system
    /*!
     * \param psi      solution ( Modify )
     * \param chi      source ( Read )
     * \return syssolver results
     */
    SystemSolverResults_t operator() (T& psi, const T& chi) const
      {
        START_CODE();
        StopWatch swatch;
        swatch.reset(); swatch.start();
 
        SystemSolverResults_t res;  // initialized by a constructor
        res = InvCG2(*A, chi, psi, invParam.RsdCG, invParam.MaxCG);
 
#ifdef CHROMA_DO_ONE_CG_RESTART
        int n_count = res.n_count;
        res = InvCG2(*A, chi, psi, invParam.RsdCGRestart, invParam.MaxCGRestart);
        res.n_count += n_count;
#endif 
        { // Find true residuum
          T tmp=zero;
          T r=zero;
          (*A)(tmp,psi, PLUS);
          (*A)(r,tmp, MINUS);
          r[A->subset()] -= chi;
          res.resid = sqrt(norm2(r,A->subset()));
        }
        
        swatch.stop();
        QDPIO::cout << "CG_SOLVER: " << res.n_count 
                    << " iterations. Rsd = " << res.resid 
                    << " Relative Rsd = " << res.resid/sqrt(norm2(chi,A->subset())) << std::endl;
        
        double time = swatch.getTimeInSeconds();
        QDPIO::cout << "CG_SOLVER_TIME: "<<time<< " sec" << std::endl;
        
 
        END_CODE();
 
        return res;
      }
 
 
    //! Solve the linear system starting with a chrono guess 
    /*! 
     * \param psi solution (Write)
     * \param chi source   (Read)
     * \param predictor   a chronological predictor (Read)
     * \return syssolver results
     */
 
    SystemSolverResults_t operator()(T& psi, const T& chi, 
                                     AbsChronologicalPredictor4D<T>& predictor) const 
    {
      
      START_CODE();
 
      // This solver uses InvCG2, so A is just the matrix.
      // I need to predict with A^\dagger A
      {
        Handle< LinearOperator<T> > MdagM( new MdagMLinOp<T>(A) );
        predictor(psi, (*MdagM), chi);
      }
      // Do solve
      SystemSolverResults_t res=(*this)(psi,chi);
 
      // Store result
      predictor.newVector(psi);
      END_CODE();
      return res;
    }
 
  private:
    // Hide default constructor
    MdagMSysSolverCG() {}
 
    Handle< LinearOperator<T> > A;
    SysSolverCGParams invParam;
  };
 
 
} // End namespace
 
#endif