Thyra Version of the Day
Loading...
Searching...
No Matches
sillyPowerMethod.hpp
1// @HEADER
2// ***********************************************************************
3//
4// Thyra: Interfaces and Support for Abstract Numerical Algorithms
5// Copyright (2004) Sandia Corporation
6//
7// Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
8// license for use of this work by or on behalf of the U.S. Government.
9//
10// Redistribution and use in source and binary forms, with or without
11// modification, are permitted provided that the following conditions are
12// met:
13//
14// 1. Redistributions of source code must retain the above copyright
15// notice, this list of conditions and the following disclaimer.
16//
17// 2. Redistributions in binary form must reproduce the above copyright
18// notice, this list of conditions and the following disclaimer in the
19// documentation and/or other materials provided with the distribution.
20//
21// 3. Neither the name of the Corporation nor the names of the
22// contributors may be used to endorse or promote products derived from
23// this software without specific prior written permission.
24//
25// THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "AS IS" AND ANY
26// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
27// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
28// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SANDIA CORPORATION OR THE
29// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
30// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
31// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
32// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
33// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
34// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
35// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36//
37// Questions? Contact Roscoe A. Bartlett (bartlettra@ornl.gov)
38//
39// ***********************************************************************
40// @HEADER
41
42#ifndef THYRA_SILLY_POWER_METHOD_HPP
43#define THYRA_SILLY_POWER_METHOD_HPP
44
45#include "Thyra_LinearOpBase.hpp"
46#include "Thyra_VectorStdOps.hpp"
47
48
60template<class Scalar>
61bool sillyPowerMethod(
63 const int maxNumIters,
64 const typename Teuchos::ScalarTraits<Scalar>::magnitudeType tolerance,
65 const Teuchos::Ptr<Scalar> &lambda,
66 std::ostream &out
67 )
68{
69
70 // Create some typedefs and some other stuff to make the code cleaner
71 typedef Teuchos::ScalarTraits<Scalar> ST; typedef typename ST::magnitudeType ScalarMag;
72 using Thyra::apply;
73 const Scalar one = ST::one(); using Thyra::NOTRANS;
74 //typedef Teuchos::RCP<const Thyra::VectorSpaceBase<Scalar> > VectorSpacePtr; // unused
76
77 // Initialize
78 out << "\nStarting power method (target tolerance = "<<tolerance<<") ...\n\n";
79 VectorPtr q = createMember(A.domain()), z = createMember(A.range()), r = createMember(A.range());
80 Thyra::seed_randomize<Scalar>(0);
81 Thyra::randomize( Scalar(-one), Scalar(+one), z.ptr() );
82
83 // Perform iterations
84 for( int iter = 0; iter < maxNumIters; ++iter ) {
85 const ScalarMag z_nrm = norm(*z); // Compute natural norm of z
86 V_StV( q.ptr(), Scalar(one/z_nrm), *z ); // q = (1/||z||)*z
87 apply<Scalar>( A, NOTRANS , *q, z.ptr() ); // z = A*q
88 *lambda = scalarProd(*q,*z); // lambda = <q,z>
89 if( iter%(maxNumIters/10) == 0 || iter+1 == maxNumIters ) {
90 V_StVpV(r.ptr(),Scalar(-*lambda),*q,*z); // r = -lambda*q + z
91 const ScalarMag r_nrm = norm(*r); // Compute natural norm of r
92 out << "Iter = " << iter << ", lambda = " << (*lambda)
93 << ", ||A*q-lambda*q|| = " << r_nrm << std::endl;
94 if( r_nrm < tolerance )
95 return true; // Success!
96 }
97 }
98
99 out << "\nMaximum number of iterations exceeded with ||-lambda*q + z||"
100 " > tolerence = " << tolerance << "\n";
101 return false; // Failure
102
103} // end sillyPowerMethod
104
105
106#endif // THYRA_SILLY_POWER_METHOD_HPP
Base class for all linear operators.
virtual RCP< const VectorSpaceBase< Scalar > > range() const =0
Return a smart pointer for the range space for this operator.
virtual RCP< const VectorSpaceBase< Scalar > > domain() const =0
Return a smart pointer for the domain space for this operator.
@ NOTRANS
Use the non-transposed operator.