HeunIvpOdeSolver.cpp

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//Heun's Method
//Megan Lewis, University of Saskatchewan
//January 2009
#include "HeunIvpOdeSolver.hpp"

void HeunIvpOdeSolver::CalculateNextYValue(AbstractOdeSystem* pAbstractOdeSystem,
                                                  double timeStep,
                                                  double time,
                                                  std::vector<double>& rCurrentYValues,
                                                  std::vector<double>& rNextYValues)
{
    /*
     * Apply Heun 2nd order method for each time step in AbstractOneStepIvpSolver.
     * Calculates a vector containing the next Y value from the current one for each
     * equation in the system.
     */

    const unsigned num_equations = pAbstractOdeSystem->GetNumberOfStateVariables();

    std::vector<double> k1(num_equations);
    std::vector<double> k2(num_equations);
    std::vector<double>& dy = rNextYValues; // re-use memory

    // Work out k1
    pAbstractOdeSystem->EvaluateYDerivatives(time, rCurrentYValues, k1);

    // Add current y values to k1 values
    for (unsigned i=0; i<num_equations; i++)
    {
        dy[i] = timeStep*k1[i] + rCurrentYValues[i];
    }
    //Work out k2
    pAbstractOdeSystem->EvaluateYDerivatives(time+timeStep, dy, k2);

    // New solution
    for (unsigned i=0; i<num_equations; i++)
    {
        rNextYValues[i] = rCurrentYValues[i] + timeStep*0.5*(k1[i] + k2[i]);
    }
}


// Serialization for Boost >= 1.36
#include "SerializationExportWrapperForCpp.hpp"
CHASTE_CLASS_EXPORT(HeunIvpOdeSolver)