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========= |
\\ / F ield | OpenFOAM: The Open Source CFD Toolbox
\\ / O peration | Website: https://openfoam.org
\\ / A nd | Copyright (C) 2011-2019 OpenFOAM Foundation
\\/ M anipulation |
-------------------------------------------------------------------------------
License
This file is part of OpenFOAM.
OpenFOAM is free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
OpenFOAM 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 GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with OpenFOAM. If not, see <http://www.gnu.org/licenses/>.
\*---------------------------------------------------------------------------*/
#include "adaptiveSolver.H"
#include "addToRunTimeSelectionTable.H"
// * * * * * * * * * * * * * * * * Constructors * * * * * * * * * * * * * * //
Foam::adaptiveSolver::adaptiveSolver
(
const ODESystem& ode,
const dictionary& dict
)
:
safeScale_(dict.lookupOrDefault<scalar>("safeScale", 0.9)),
alphaInc_(dict.lookupOrDefault<scalar>("alphaIncrease", 0.2)),
alphaDec_(dict.lookupOrDefault<scalar>("alphaDecrease", 0.25)),
minScale_(dict.lookupOrDefault<scalar>("minScale", 0.2)),
maxScale_(dict.lookupOrDefault<scalar>("maxScale", 10)),
dydx0_(ode.nEqns()),
yTemp_(ode.nEqns())
{}
// * * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * //
bool Foam::adaptiveSolver::resize(const label n)
{
ODESolver::resizeField(dydx0_, n);
ODESolver::resizeField(yTemp_, n);
return true;
}
void Foam::adaptiveSolver::solve
(
const ODESystem& odes,
scalar& x,
scalarField& y,
const label li,
scalar& dxTry
) const
{
scalar dx = dxTry;
scalar err = 0.0;
odes.derivatives(x, y, li, dydx0_);
// Loop over solver and adjust step-size as necessary
// to achieve desired error
do
{
// Solve step and provide error estimate
err = solve(x, y, li, dydx0_, dx, yTemp_);
// If error is large reduce dx
if (err > 1)
{
scalar scale = max(safeScale_*pow(err, -alphaDec_), minScale_);
dx *= scale;
if (dx < vSmall)
{
FatalErrorInFunction
<< "stepsize underflow"
<< exit(FatalError);
}
}
} while (err > 1);
// Update the state
x += dx;
y = yTemp_;
// If the error is small increase the step-size
if (err > pow(maxScale_/safeScale_, -1.0/alphaInc_))
{
dxTry =
min(max(safeScale_*pow(err, -alphaInc_), minScale_), maxScale_)*dx;
}
else
{
dxTry = safeScale_*maxScale_*dx;
}
}
// ************************************************************************* //
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