BelosInnerSolver.hpp

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// @HEADER
// *****************************************************************************
//                 Belos: Block Linear Solvers Package
//
// Copyright 2004-2016 NTESS and the Belos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef __Belos_InnerSolver_hpp
#define __Belos_InnerSolver_hpp

#include <BelosInnerSolveResult.hpp>
#include <BelosLinearProblem.hpp>
#include <BelosMultiVecTraits.hpp>
#include <BelosOperatorTraits.hpp>
#include <Teuchos_ScalarTraits.hpp>

namespace Belos {

  template<class Scalar, class MV, class OP>
  Teuchos::RCP<LinearProblem<Scalar, MV, OP> >
  problemWithNewRHS (const Teuchos::RCP<const LinearProblem<Scalar, MV, OP> >& problem,
         const Teuchos::RCP<const MV>& B)
  {
    using Teuchos::is_null;
    using Teuchos::nonnull;
    using Teuchos::null;
    using Teuchos::RCP;
    using Teuchos::rcp;
    typedef LinearProblem<Scalar, MV, OP> lp_type;
    typedef MultiVecTraits<Scalar, MV> MVT;

    RCP<const OP> A = problem->getOperator (); 
    RCP<MV> X_orig = problem->getLHS ();
    TEUCHOS_TEST_FOR_EXCEPTION(is_null (X_orig), std::invalid_argument,
           "problemWithNewRHS(): The original LinearProblem's "
           "initial guess / current approximate solution (getLHS())"
           " is null.  We need an initial guess or current approxim"
           "ate solution in order to know the domain of the (right-"
           "preconditioned, if applicable) operator.  This is "
           "because Belos::MultiVecTraits does not include the idea"
           " of the domain and range of an operator, or the space "
           "to which a vector belongs.");
    TEUCHOS_TEST_FOR_EXCEPTION(is_null (B), std::invalid_argument,
           "problemWithNewRHS(): the given new right-hand side B "
           "is null.");
    RCP<MV> X = MVT::CloneCopy (problem->getLHS ());

    RCP<lp_type> lp (new lp_type (A, X, B));
    lp->setLeftPrec (problem->getLeftPrec ());
    lp->setRightPrec (problem->getRightPrec ());
    // Compute initial residual(s) and prepare the problem for solution.
    lp->setProblem ();
    return lp;
  }


  template<class Scalar, class MV, class OP>
  class InnerSolver {
  public:
    typedef Scalar scalar_type;
    typedef typename Teuchos::ScalarTraits<Scalar>::magnitudeType magnitude_type;
    typedef MV multivector_type;
    typedef OP operator_type;

    virtual ~InnerSolver() {}

    virtual Teuchos::RCP<const Teuchos::ParameterList> 
    getCurrentParameters() const = 0;

    virtual InnerSolveResult
    solve (const Teuchos::RCP<MV>& X,
     const Teuchos::RCP<const MV>& B,
     const magnitude_type convTol,
     const int maxItersPerRestart,
     const int maxNumRestarts) = 0;

    virtual InnerSolveResult
    solve (const Teuchos::RCP<MV>& X,
     const Teuchos::RCP<const MV>& B) = 0;
  };


  template<class Scalar, class MV, class OP>
  class OperatorTraits<Scalar, MV, InnerSolver<Scalar, MV, OP> > {
  public:
    static void
    Apply (const InnerSolver<Scalar, MV, OP>& Op,
     const MV& x,
     MV& y,
     ETrans trans = NOTRANS)
    {
      using Teuchos::RCP;
      using Teuchos::rcpFromRef;

      TEUCHOS_TEST_FOR_EXCEPTION(trans != NOTRANS, std::invalid_argument,
       "Belos::InnerSolver is not able to solve the "
       "transposed system.");
      RCP<const MV> x_ptr = rcpFromRef (x);
      RCP<MV> y_ptr = rcpFromRef (y);
      (void) Op.solve (y_ptr, x_ptr);
    }

  };

  template<class Scalar, class MV, class OP>
  class UndefinedWrapperType {
  public:
    UndefinedWrapperType() {
      (void) Scalar::this_specialization_is_not_defined();
      (void) MV::this_specialization_is_not_defined();
      (void) OP::this_specialization_is_not_defined();
    }
  };

  template<class Scalar, class MV, class OP>
  class InnerSolverTraits {
  public:
    typedef Scalar scalar_type;
    typedef MV multivector_type;
    typedef OP operator_type;
    typedef InnerSolver<scalar_type, multivector_type, operator_type> inner_solver_type;
    typedef UndefinedWrapperType<Scalar, MV, OP> wrapper_type;

    static Teuchos::RCP<OP>
    makeInnerSolverOperator (const Teuchos::RCP<InnerSolver<Scalar, MV, OP> >& solver)
    {
      using Teuchos::rcp;
      using Teuchos::rcp_implicit_cast;
      // If this class is not specialized for the given combination of
      // (Scalar, MV, OP), the constructor of wrapper_type here will
      // (deliberately) raise a compiler error.
      return rcp_implicit_cast<operator_type> (rcp (new wrapper_type (solver)));
    }

    static Teuchos::RCP<inner_solver_type>
    getInnerSolver (const Teuchos::RCP<operator_type>& op)
    {
      using Teuchos::RCP;
      using Teuchos::rcp_dynamic_cast;
      // If this class is not specialized for the given combination of
      // (Scalar, MV, OP), the instantiation of the wrapper_type class
      // here will (deliberately) raise a compiler error.
      RCP<wrapper_type> wrapper = rcp_dynamic_cast<wrapper_type> (op, true);
      return wrapper->getInnerSolver();
    }
  };

} // namespace Belos

#endif // __Belos_InnerSolver_hpp