1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
/* -*- mode: c++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
Copyright (C) 2011 Klaus Spanderen
This file is part of QuantLib, a free-software/open-source library
for financial quantitative analysts and developers - http://quantlib.org/
QuantLib is free software: you can redistribute it and/or modify it
under the terms of the QuantLib license. You should have received a
copy of the license along with this program; if not, please email
<quantlib-dev@lists.sf.net>. The license is also available online at
<https://www.quantlib.org/license.shtml>.
This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the license for more details.
*/
/*! \file fdmndimsolver.hpp
*/
#ifndef quantlib_fdm_n_dim_solver_hpp
#define quantlib_fdm_n_dim_solver_hpp
#include <ql/patterns/lazyobject.hpp>
#include <ql/math/interpolations/multicubicspline.hpp>
#include <ql/methods/finitedifferences/finitedifferencemodel.hpp>
#include <ql/methods/finitedifferences/meshers/fdmmesher.hpp>
#include <ql/methods/finitedifferences/solvers/fdmsolverdesc.hpp>
#include <ql/methods/finitedifferences/operators/fdmlinearoplayout.hpp>
#include <ql/methods/finitedifferences/solvers/fdmbackwardsolver.hpp>
#include <ql/methods/finitedifferences/stepconditions/fdmsnapshotcondition.hpp>
#include <ql/methods/finitedifferences/utilities/fdminnervaluecalculator.hpp>
#include <ql/methods/finitedifferences/stepconditions/fdmstepconditioncomposite.hpp>
#include <numeric>
namespace QuantLib {
template <Size N>
class FdmNdimSolver : public LazyObject {
public:
FdmNdimSolver(const FdmSolverDesc& solverDesc,
const FdmSchemeDesc& schemeDesc,
ext::shared_ptr<FdmLinearOpComposite> op);
void performCalculations() const override;
Real interpolateAt(const std::vector<Real>& x) const;
Real thetaAt(const std::vector<Real>& x) const;
// template meta programming
typedef typename MultiCubicSpline<N>::data_table data_table;
void static setValue(data_table& f,
const std::vector<Size>& x, Real value);
private:
const FdmSolverDesc solverDesc_;
const FdmSchemeDesc schemeDesc_;
const ext::shared_ptr<FdmLinearOpComposite> op_;
const ext::shared_ptr<FdmSnapshotCondition> thetaCondition_;
const ext::shared_ptr<FdmStepConditionComposite> conditions_;
std::vector<std::vector<Real> > x_;
std::vector<Real> initialValues_;
const std::vector<bool> extrapolation_;
mutable ext::shared_ptr<data_table> f_;
mutable ext::shared_ptr<MultiCubicSpline<N> > interp_;
};
template <Size N>
inline FdmNdimSolver<N>::FdmNdimSolver(const FdmSolverDesc& solverDesc,
const FdmSchemeDesc& schemeDesc,
ext::shared_ptr<FdmLinearOpComposite> op)
: solverDesc_(solverDesc), schemeDesc_(schemeDesc), op_(std::move(op)),
thetaCondition_(new FdmSnapshotCondition(
0.99 * std::min(1.0 / 365.0,
solverDesc.condition->stoppingTimes().empty() ?
solverDesc.maturity :
solverDesc.condition->stoppingTimes().front()))),
conditions_(FdmStepConditionComposite::joinConditions(thetaCondition_, solverDesc.condition)),
x_(solverDesc.mesher->layout()->dim().size()),
initialValues_(solverDesc.mesher->layout()->size()),
extrapolation_(std::vector<bool>(N, false)) {
QL_REQUIRE(solverDesc.mesher->layout()->dim().size() == N, "solver dim " << N
<< "does not fit to layout dim " << solverDesc.mesher->layout()->size());
for (Size i=0; i < N; ++i) {
x_[i].reserve(solverDesc.mesher->layout()->dim()[i]);
}
for (const auto& iter : *solverDesc.mesher->layout()) {
initialValues_[iter.index()] = solverDesc_.calculator
->avgInnerValue(iter, solverDesc.maturity);
const std::vector<Size>& c = iter.coordinates();
for (Size i=0; i < N; ++i) {
if ((std::accumulate(c.begin(), c.end(), 0UL) - c[i]) == 0U) {
x_[i].push_back(solverDesc.mesher->location(iter, i));
}
}
}
f_ = ext::shared_ptr<data_table>(new data_table(x_));
}
template <Size N> inline
void FdmNdimSolver<N>::performCalculations() const {
Array rhs(initialValues_.size());
std::copy(initialValues_.begin(), initialValues_.end(), rhs.begin());
FdmBackwardSolver(op_, solverDesc_.bcSet, conditions_, schemeDesc_)
.rollback(rhs, solverDesc_.maturity, 0.0,
solverDesc_.timeSteps, solverDesc_.dampingSteps);
for (const auto& iter : *solverDesc_.mesher->layout()) {
setValue(*f_, iter.coordinates(), rhs[iter.index()]);
}
interp_ = ext::shared_ptr<MultiCubicSpline<N> >(
new MultiCubicSpline<N>(x_, *f_, extrapolation_));
}
template <Size N> inline
Real FdmNdimSolver<N>::thetaAt(const std::vector<Real>& x) const {
if (conditions_->stoppingTimes().front() == 0.0)
return Null<Real>();
calculate();
const Array& rhs = thetaCondition_->getValues();
data_table f(x_);
for (const auto& iter : *solverDesc_.mesher->layout()) {
setValue(f, iter.coordinates(), rhs[iter.index()]);
}
return (MultiCubicSpline<N>(x_, f)(x)
- interpolateAt(x)) / thetaCondition_->getTime();
}
template <Size N> inline
Real FdmNdimSolver<N>::interpolateAt(const std::vector<Real>& x) const {
calculate();
return (*interp_)(x);
}
template <Size N> inline
void FdmNdimSolver<N>::setValue(data_table& f,
const std::vector<Size>& x, Real value) {
FdmNdimSolver<N-1>::setValue(f[x[x.size()-N]], x, value);
}
template <> inline
void FdmNdimSolver<1>::setValue(data_table& f,
const std::vector<Size>& x, Real value) {
f[x.back()] = value;
}
}
#endif
|
