RungeKutta4IvpOdeSolver.cpp

00001 /*
00002 
00003 Copyright (C) University of Oxford, 2005-2011
00004 
00005 University of Oxford means the Chancellor, Masters and Scholars of the
00006 University of Oxford, having an administrative office at Wellington
00007 Square, Oxford OX1 2JD, UK.
00008 
00009 This file is part of Chaste.
00010 
00011 Chaste is free software: you can redistribute it and/or modify it
00012 under the terms of the GNU Lesser General Public License as published
00013 by the Free Software Foundation, either version 2.1 of the License, or
00014 (at your option) any later version.
00015 
00016 Chaste is distributed in the hope that it will be useful, but WITHOUT
00017 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
00018 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
00019 License for more details. The offer of Chaste under the terms of the
00020 License is subject to the License being interpreted in accordance with
00021 English Law and subject to any action against the University of Oxford
00022 being under the jurisdiction of the English Courts.
00023 
00024 You should have received a copy of the GNU Lesser General Public License
00025 along with Chaste. If not, see <http://www.gnu.org/licenses/>.
00026 
00027 */
00028 
00029 #include "RungeKutta4IvpOdeSolver.hpp"
00030 
00031 void RungeKutta4IvpOdeSolver::CalculateNextYValue(AbstractOdeSystem* pAbstractOdeSystem,
00032                                                   double timeStep,
00033                                                   double time,
00034                                                   std::vector<double>& rCurrentYValues,
00035                                                   std::vector<double>& rNextYValues)
00036 {
00037     /*
00038      * Apply Runge-Kutta 4th order method for each timestep in AbstractOneStepIvpSolver.
00039      * Calculates a vector containing the next Y value from the current one for each
00040      * equation in the system.
00041      */
00042 
00043     const unsigned num_equations = pAbstractOdeSystem->GetNumberOfStateVariables();
00044 
00045     if (num_equations != k1.size())
00046     {
00047         k1.resize(num_equations);
00048         k2.resize(num_equations);
00049         k3.resize(num_equations);
00050         k4.resize(num_equations);
00051         yki.resize(num_equations);
00052     }
00053 
00054     std::vector<double>& dy = rNextYValues; // re-use memory
00055 
00056     pAbstractOdeSystem->EvaluateYDerivatives(time, rCurrentYValues, dy);
00057     for (unsigned i=0; i<num_equations; i++)
00058     {
00059         k1[i] = timeStep*dy[i];
00060         yki[i] = rCurrentYValues[i] + 0.5*k1[i];
00061     }
00062 
00063     pAbstractOdeSystem->EvaluateYDerivatives(time+0.5*timeStep, yki, dy);
00064     for (unsigned i=0; i<num_equations; i++)
00065     {
00066         k2[i] = timeStep*dy[i];
00067         yki[i] = rCurrentYValues[i] + 0.5*k2[i];
00068     }
00069 
00070     pAbstractOdeSystem->EvaluateYDerivatives(time+0.5*timeStep, yki, dy);
00071     for (unsigned i=0; i<num_equations; i++)
00072     {
00073         k3[i] = timeStep*dy[i];
00074         yki[i] = rCurrentYValues[i] + k3[i];
00075     }
00076 
00077     pAbstractOdeSystem->EvaluateYDerivatives(time+timeStep, yki, dy);
00078     for (unsigned i=0; i<num_equations; i++)
00079     {
00080         k4[i] = timeStep*dy[i];
00081         rNextYValues[i] = rCurrentYValues[i] + (k1[i]+2*k2[i]+2*k3[i]+k4[i])/6.0;
00082     }
00083 }
00084 
00085 
00086 // Serialization for Boost >= 1.36
00087 #include "SerializationExportWrapperForCpp.hpp"
00088 CHASTE_CLASS_EXPORT(RungeKutta4IvpOdeSolver)

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