Ifpack2 Templated Preconditioning Package Version 1.0
Ifpack2_Condest.hpp
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00042 
00043 #ifndef IFPACK2_CONDEST_HPP
00044 #define IFPACK2_CONDEST_HPP
00045 
00046 #include "Ifpack2_ConfigDefs.hpp"
00047 #include "Ifpack2_CondestType.hpp"
00048 #include "Ifpack2_Preconditioner.hpp"
00049 #include <Teuchos_Ptr.hpp>
00050 
00051 namespace Ifpack2 {
00052 
00092 template<class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
00093 typename Teuchos::ScalarTraits<Scalar>::magnitudeType
00094 Condest (const Ifpack2::Preconditioner<Scalar, LocalOrdinal, GlobalOrdinal, Node>& TIFP,
00095          const Ifpack2::CondestType CT,
00096          const int MaxIters = 1550,
00097          const typename Teuchos::ScalarTraits<Scalar>::magnitudeType& Tol = Teuchos::as<Scalar> (1e-9),
00098          const Teuchos::Ptr<const Tpetra::RowMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node> >& matrix_in = Teuchos::null)
00099 {
00100   using Teuchos::Ptr;
00101   typedef Teuchos::ScalarTraits<Scalar> STS;
00102   typedef typename STS::magnitudeType MT;
00103   typedef Teuchos::ScalarTraits<MT> STM;
00104   typedef Tpetra::RowMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node> row_matrix_type;
00105   typedef Tpetra::Vector<Scalar, LocalOrdinal, GlobalOrdinal, Node> vec_type;
00106 
00107   MT condNumEst = -STS::magnitude( STS::one() );
00108 
00109   // Users may either provide a matrix for which to estimate the
00110   // condition number, or use the Preconditioner's built-in matrix.
00111   Ptr<const row_matrix_type> matrix = matrix_in;
00112   if (matrix_in == Teuchos::null) {
00113     matrix = TIFP.getMatrix ().ptr ();
00114     TEUCHOS_TEST_FOR_EXCEPTION(
00115       matrix == Teuchos::null,
00116       std::logic_error,
00117       "Ifpack2::Condest: Both the input matrix (matrix_in) and the Ifpack2 "
00118       "preconditioner's matrix are null, so we have no matrix with which to "
00119       "compute a condition number estimate.  This probably indicates a bug "
00120       "in Ifpack2, since no Ifpack2::Preconditioner subclass should accept a"
00121       "null matrix.");
00122   }
00123 
00124   if (CT == Ifpack2::Cheap) {
00125     vec_type ones (TIFP.getDomainMap ()); // Vector of ones
00126     ones.putScalar (STS::one ());
00127     vec_type onesResult (TIFP.getRangeMap ()); // A*ones
00128     onesResult.putScalar (STS::zero ());
00129     TIFP.apply (ones, onesResult);
00130     condNumEst = onesResult.normInf (); // max (abs (A*ones))
00131     TEUCHOS_TEST_FOR_EXCEPTION(
00132       STM::isnaninf (condNumEst),
00133       std::runtime_error,
00134       "Ifpack2::Condest: $\\|A*[1, ..., 1]^T\\|_{\\infty}$ = " << condNumEst << " is NaN or Inf.");
00135   } else if (CT == Ifpack2::CG) {
00136     TEUCHOS_TEST_FOR_EXCEPTION(
00137       true, std::logic_error,
00138       "Ifpack2::Condest: Condition number estimation using CG is not currently supported.");
00139   } else if (CT == Ifpack2::GMRES) {
00140     TEUCHOS_TEST_FOR_EXCEPTION(
00141       true, std::logic_error,
00142       "Ifpack2::Condest: Condition number estimation using GMRES is not currently supported.");
00143   }
00144   return condNumEst;
00145 }
00146 
00147 }//namespace Ifpack2
00148 
00149 #endif // IFPACK2_CONDEST_HPP
00150 
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