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armijo.hpp
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1/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2
3/*
4 Copyright (C) 2001, 2002, 2003 Nicolas Di Césaré
5
6 This file is part of QuantLib, a free-software/open-source library
7 for financial quantitative analysts and developers - http://quantlib.org/
8
9 QuantLib is free software: you can redistribute it and/or modify it
10 under the terms of the QuantLib license. You should have received a
11 copy of the license along with this program; if not, please email
12 <quantlib-dev@lists.sf.net>. The license is also available online at
13 <http://quantlib.org/license.shtml>.
14
15 This program is distributed in the hope that it will be useful, but WITHOUT
16 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
17 FOR A PARTICULAR PURPOSE. See the license for more details.
18*/
19
20/*! \file armijo.hpp
21 \brief Armijo line-search class
22*/
23
24#ifndef quantlib_optimization_armijo_hpp
25#define quantlib_optimization_armijo_hpp
26
28
29namespace QuantLib {
30
31 class EndCriteria;
32
33 //! Armijo line search.
34 /*! Let \f$ \alpha \f$ and \f$ \beta \f$ be 2 scalars in \f$ [0,1]
35 \f$. Let \f$ x \f$ be the current value of the unknown, \f$ d
36 \f$ the search direction and \f$ t \f$ the step. Let \f$ f \f$
37 be the function to minimize. The line search stops when \f$ t
38 \f$ verifies
39 \f[ f(x + t \cdot d) - f(x) \leq -\alpha t f'(x+t \cdot d) \f]
40 and
41 \f[ f(x+\frac{t}{\beta} \cdot d) - f(x) > -\frac{\alpha}{\beta}
42 t f'(x+t \cdot d) \f]
43
44 (see Polak, Algorithms and consistent approximations, Optimization,
45 volume 124 of Applied Mathematical Sciences, Springer-Verlag, NY,
46 1997)
47 */
49 public:
50 //! Default constructor
52 Real alpha = 0.05,
53 Real beta = 0.65)
54 : LineSearch(eps), alpha_(alpha), beta_(beta) {}
55
56 //! Perform line search
57 Real operator()(Problem& P, // Optimization problem
58 EndCriteria::Type& ecType,
59 const EndCriteria&,
60 Real t_ini) override; // initial value of line-search step
61 private:
63 };
64
65}
66
67#endif
Armijo line search.
Definition: armijo.hpp:48
Real operator()(Problem &P, EndCriteria::Type &ecType, const EndCriteria &, Real t_ini) override
Perform line search.
Definition: armijo.cpp:26
ArmijoLineSearch(Real eps=1e-8, Real alpha=0.05, Real beta=0.65)
Default constructor.
Definition: armijo.hpp:51
Criteria to end optimization process:
Definition: endcriteria.hpp:40
Base class for line search.
Definition: linesearch.hpp:38
Constrained optimization problem.
Definition: problem.hpp:42
QL_REAL Real
real number
Definition: types.hpp:50
Line search abstract class.
Definition: any.hpp:35
Real beta
Definition: sabr.cpp:200
Real alpha
Definition: sabr.cpp:200