HeunIvpOdeSolver.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 //Heun's Method
00030 //Megan Lewis, University of Saskatchewan
00031 //January 2009
00032 #include "HeunIvpOdeSolver.hpp"
00033 
00034 void HeunIvpOdeSolver::CalculateNextYValue(AbstractOdeSystem* pAbstractOdeSystem,
00035                                                   double timeStep,
00036                                                   double time,
00037                                                   std::vector<double>& rCurrentYValues,
00038                                                   std::vector<double>& rNextYValues)
00039 {
00040     /*
00041      * Apply Heun 2nd order method for each time step in AbstractOneStepIvpSolver.
00042      * Calculates a vector containing the next Y value from the current one for each
00043      * equation in the system.
00044      */
00045 
00046     const unsigned num_equations = pAbstractOdeSystem->GetNumberOfStateVariables();
00047 
00048     std::vector<double> k1(num_equations);
00049     std::vector<double> k2(num_equations);
00050     std::vector<double>& dy = rNextYValues; // re-use memory
00051 
00052     // Work out k1
00053     pAbstractOdeSystem->EvaluateYDerivatives(time, rCurrentYValues, k1);
00054 
00055     // Add current y values to k1 values
00056     for (unsigned i=0; i<num_equations; i++)
00057     {
00058         dy[i] = timeStep*k1[i] + rCurrentYValues[i];
00059     }
00060     //Work out k2
00061     pAbstractOdeSystem->EvaluateYDerivatives(time+timeStep, dy, k2);
00062 
00063     // New solution
00064     for (unsigned i=0; i<num_equations; i++)
00065     {
00066         rNextYValues[i] = rCurrentYValues[i] + timeStep*0.5*(k1[i] + k2[i]);
00067     }
00068 }
00069 
00070 
00071 // Serialization for Boost >= 1.36
00072 #include "SerializationExportWrapperForCpp.hpp"
00073 CHASTE_CLASS_EXPORT(HeunIvpOdeSolver)

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