RK4NumericalMethod.cpp

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#include "RK4NumericalMethod.hpp"
 
template<unsigned ELEMENT_DIM, unsigned SPACE_DIM>
RK4NumericalMethod<ELEMENT_DIM,SPACE_DIM>::RK4NumericalMethod()
    : AbstractNumericalMethod<ELEMENT_DIM,SPACE_DIM>()
{
}
 
template<unsigned ELEMENT_DIM, unsigned SPACE_DIM>
RK4NumericalMethod<ELEMENT_DIM,SPACE_DIM>::~RK4NumericalMethod()
{
}
 
template<unsigned ELEMENT_DIM, unsigned SPACE_DIM>
void RK4NumericalMethod<ELEMENT_DIM,SPACE_DIM>::UpdateAllNodePositions(double dt)
{
    // Store initial node locations
    auto old_node_locations = this->SaveCurrentNodeLocations();
 
    // Apply boundary conditions to the initial positions, then resave
    this->ImposeBoundaryConditions(old_node_locations);
    old_node_locations = this->SaveCurrentNodeLocations();
 
    // Compute k1 = F(r^t) / nu
    auto k1 = this->ComputeForcesIncludingDamping();
 
    // Update to r^t + dt*k1/2 and compute k2
    unsigned index = 0;
    for (auto node_iter = this->mpCellPopulation->rGetMesh().GetNodeIteratorBegin();
         node_iter != this->mpCellPopulation->rGetMesh().GetNodeIteratorEnd();
         ++node_iter, ++index)
    {
        c_vector<double, SPACE_DIM> new_location = node_iter->rGetLocation() + (dt/2.0) * k1[index];
        this->SafeNodePositionUpdate(node_iter->GetIndex(), new_location);
    }
    this->ImposeBoundaryConditions(old_node_locations);
 
    // Compute k2 = F(r^t + dt*k1/2) / nu
    auto k2 = this->ComputeForcesIncludingDamping();
 
    // Update to r^t + dt*k2/2 (from old locations) and compute k3
    index = 0;
    for (auto node_iter = this->mpCellPopulation->rGetMesh().GetNodeIteratorBegin();
         node_iter != this->mpCellPopulation->rGetMesh().GetNodeIteratorEnd();
         ++node_iter, ++index)
    {
        c_vector<double, SPACE_DIM> old_location = old_node_locations.find(&(*node_iter))->second;
        c_vector<double, SPACE_DIM> new_location = old_location + (dt/2.0) * k2[index];
        this->SafeNodePositionUpdate(node_iter->GetIndex(), new_location);
    }
    this->ImposeBoundaryConditions(old_node_locations);
 
    // Compute k3 = F(r^t + dt*k2/2) / nu
    auto k3 = this->ComputeForcesIncludingDamping();
 
    // Update to r^t + dt*k3 (from old locations) and compute k4
    index = 0;
    for (auto node_iter = this->mpCellPopulation->rGetMesh().GetNodeIteratorBegin();
         node_iter != this->mpCellPopulation->rGetMesh().GetNodeIteratorEnd();
         ++node_iter, ++index)
    {
        c_vector<double, SPACE_DIM> old_location = old_node_locations.find(&(*node_iter))->second;
        c_vector<double, SPACE_DIM> new_location = old_location + dt * k3[index];
        this->SafeNodePositionUpdate(node_iter->GetIndex(), new_location);
    }
    this->ImposeBoundaryConditions(old_node_locations);
 
    // Compute k4 = F(r^t + dt*k3) / nu
    auto k4 = this->ComputeForcesIncludingDamping();
 
    // Final RK4 position update: r^(t+1) = r^t + (dt/6)*(k1 + 2*k2 + 2*k3 + k4)
    index = 0;
    for (auto node_iter = this->mpCellPopulation->rGetMesh().GetNodeIteratorBegin();
         node_iter != this->mpCellPopulation->rGetMesh().GetNodeIteratorEnd();
         ++node_iter, ++index)
    {
        c_vector<double, SPACE_DIM> effective_force = (k1[index] + 2.0*k2[index] + 2.0*k3[index] + k4[index]) / 6.0;
        c_vector<double, SPACE_DIM> old_location = old_node_locations.find(&(*node_iter))->second;
        c_vector<double, SPACE_DIM> displacement = dt * effective_force;
 
        this->DetectStepSizeExceptions(node_iter->GetIndex(), displacement, dt);
 
        c_vector<double, SPACE_DIM> new_location = old_location + displacement;
        this->SafeNodePositionUpdate(node_iter->GetIndex(), new_location);
    }
}
 
template<unsigned ELEMENT_DIM, unsigned SPACE_DIM>
void RK4NumericalMethod<ELEMENT_DIM, SPACE_DIM>::OutputNumericalMethodParameters(out_stream& rParamsFile)
{
    // No new parameters to output, so just call method on direct parent class
    AbstractNumericalMethod<ELEMENT_DIM,SPACE_DIM>::OutputNumericalMethodParameters(rParamsFile);
}
 
// Explicit instantiation
template class RK4NumericalMethod<1,1>;
template class RK4NumericalMethod<1,2>;
template class RK4NumericalMethod<2,2>;
template class RK4NumericalMethod<1,3>;
template class RK4NumericalMethod<2,3>;
template class RK4NumericalMethod<3,3>;
 
// Serialization for Boost >= 1.36
#include "SerializationExportWrapperForCpp.hpp"
EXPORT_TEMPLATE_CLASS_ALL_DIMS(RK4NumericalMethod)