GRL1IvpOdeSolver.cpp

/*

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*/

/*
Megan E. Marsh, Raymond J. Spiteri
Numerical Simulation Laboratory
University of Saskatchewan
December 2011
Partial support provided by research grants from the National
Science and Engineering Research Council (NSERC) of Canada
and the MITACS/Mprime Canadian Network of Centres of Excellence.
*/
#include <cmath>
#include "GRL1IvpOdeSolver.hpp"

void GRL1IvpOdeSolver::CalculateNextYValue(AbstractOdeSystem* pAbstractOdeSystem,
                                           double timeStep,
                                           double time,
                                           std::vector<double>& rCurrentYValues,
                                           std::vector<double>& rNextYValues)
{
    /*
     * Apply GRL1 first-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 double delta = 1.0e-8; // The step for numerical Jacobian calculation

    const unsigned num_equations = pAbstractOdeSystem->GetNumberOfStateVariables();

    if (mEvalF.size() != num_equations)
    {
        mEvalF.resize(num_equations);
        mPartialF.resize(num_equations);
        mTemp.resize(num_equations);
    }

    double tempY;

    pAbstractOdeSystem->EvaluateYDerivatives(time, rCurrentYValues, mEvalF);
    for (unsigned i=0; i<num_equations; i++)
    {
        tempY= rCurrentYValues[i];
        rCurrentYValues[i]=tempY+delta;
        pAbstractOdeSystem->EvaluateYDerivatives(time, rCurrentYValues, mTemp);
        mPartialF[i]=(mTemp[i]-mEvalF[i])/delta;
        rCurrentYValues[i]=tempY;
    }
    // New solution
    for (unsigned i=0; i<num_equations; i++)
    {
        // std::cout<<"Partial F"<< mPartialF[i]<<std::endl;
        if(fabs(mPartialF[i])<delta)
        {
            rNextYValues[i]=rCurrentYValues[i]+mEvalF[i]*timeStep;
        }
        else
        {
            rNextYValues[i]=rCurrentYValues[i]+(mEvalF[i]/mPartialF[i])*(exp(mPartialF[i]*timeStep)-1);
        }

    }
}


// Serialization for Boost >= 1.36
#include "SerializationExportWrapperForCpp.hpp"
CHASTE_CLASS_EXPORT(GRL1IvpOdeSolver)