BelosOpAkx.hpp

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#ifndef __Belos_OpAkx_hpp
#define __Belos_OpAkx_hpp

#include <BelosAkx.hpp>
#include <BelosOperatorTraits.hpp>
#include <Teuchos_OrdinalTraits.hpp>
#include <Teuchos_SerialDenseVector.hpp>

namespace Belos {

  template<class Scalar, class MV, class OP>
  class OpAkx : public Akx<Scalar, MV> {
  public:
    OpAkx (const Teuchos::RCP<const OP>& A, 
     const Teuchos::RCP<const OP>& M_left, 
     const Teuchos::RCP<const OP>& M_right,
     const int recommendedBasisLength) :
      A_ (A), 
      M_left_ (M_left), 
      M_right_ (M_right),
      recommendedBasisLength_ (validatedBasisLength (recommendedBasisLength))
    {}
  
    int maxCandidateBasisLength () const { 
      // We're not using a special matrix powers kernel implementation
      // here, just whatever operator(s) we were given, so we can
      // apply them as many times as we want.  Of course, this doesn't
      // account for memory or time constraints.
      return Teuchos::OrdinalTraits<int>::max(); 
    }

    int recommendedCandidateBasisLength () const {
      return recommendedBasisLength_;
    }

  protected:
    void 
    applyOp (const MV& v_prv, MV& v_cur) 
    {
      // We use v_scratch_ as scratch space, since
      // OperatorTraits::Apply() doesn't allow aliasing of the input
      // and output vectors when applying an operator.  We only
      // allocate v_scratch_ if necessary.
      if (! M_right_.is_null())
  {
    if (v_scratch_.is_null())
      v_scratch_ = MVT::Clone (v_cur);
    OPT::Apply (*M_right_, v_prv, *v_scratch_);
    OPT::Apply (*A_, *v_scratch_, v_cur);
    if (! M_left_.is_null())
      {
        MVT::Assign (v_cur, *v_scratch_);
        OPT::Apply (*M_left_, *v_scratch_, v_cur);
      }
  }
      else if (! M_left_.is_null())
  {
    if (v_scratch_.is_null())
      v_scratch_ = MVT::Clone (v_cur);
    OPT::Apply (*A_, v_prv, *v_scratch_);
    OPT::Apply (*M_left_, *v_scratch_, v_cur);
  }
      else
  OPT::Apply (*A_, v_prv, v_cur);
    }

    void
    applyFlexibleOp (const MV& v_prv, MV& z_cur, MV& v_cur)
    {
      TEUCHOS_TEST_FOR_EXCEPTION(! M_left_.is_null(), std::logic_error,
       "Flexible GMRES only works with a right "
       "preconditioner, not a left or split "
       "preconditioner.");
      if (! M_right_.is_null())
  { 
    OPT::Apply (*M_right_, v_prv, z_cur);
    OPT::Apply (*A_, z_cur, v_cur);
  }
      else
  { // In this case, the right preconditioner is the identity
    // operator, so we only have to copy v_prv into z_cur.
    MVT::Assign (v_prv, z_cur);
    OPT::Apply (*A_, z_cur, v_cur);
  }
    }

  private:
    int validatedBasisLength (const int len) const {
      if (len < 1)
  throw std::invalid_argument("Invalid recommended candidate basis length");
      else
  return len;
    }

    Teuchos::RCP<const OP> A_;
    Teuchos::RCP<const OP> M_left_;
    Teuchos::RCP<const OP> M_right_;
    Teuchos::RCP<const MV> v_scratch_;

    int recommendedBasisLength_
  };

} // namespace Belos

#endif // __Belos_OpAkx_hpp