RungeKutta2< IntegrandClass > Class Template Reference

Collaboration diagram for RungeKutta2< IntegrandClass >:

Public Member Functions
void	Integrate (const Grid &grid, int startPoint, int endPoint, Array< double, 2 > &result)
	RungeKutta2 (IntegrandClass &integrand)

Private Member Functions
void	IntegrateForw (const Grid &grid, int startPoint, int endPoint, Array< double, 2 > &result)
void	IntegrateRev (const Grid &grid, int startPoint, int endPoint, Array< double, 2 > &result)

Private Attributes
IntegrandClass &	Integrand

Detailed Description

template<class IntegrandClass>
class RungeKutta2< IntegrandClass >

Definition at line 109 of file RungeKutta.h.

Constructor & Destructor Documentation

RungeKutta2()

RungeKutta2 ( IntegrandClass &  integrand )

inline

Definition at line 177 of file RungeKutta.h.

                                         : Integrand(integrand)
  {
    // Do nothing
  }

Member Function Documentation

Integrate()

void Integrate ( const Grid &  grid, int  startPoint, int  endPoint, Array< double, 2 > &  result  )

inline

Definition at line 169 of file RungeKutta.h.

References RungeKutta2< IntegrandClass >::IntegrateForw(), and RungeKutta2< IntegrandClass >::IntegrateRev().

  {
    if (endPoint > startPoint)
      IntegrateForw(grid, startPoint, endPoint, result);
    else
      IntegrateRev(grid, startPoint, endPoint, result);
  }

IntegrateForw()

void IntegrateForw ( const Grid &  grid, int  startPoint, int  endPoint, Array< double, 2 > &  result  )

inlineprivate

Definition at line 115 of file RungeKutta.h.

References Range::all(), Array< T, D, ALLOC >::cols(), and RungeKutta2< IntegrandClass >::Integrand.

Referenced by RungeKutta2< IntegrandClass >::Integrate().

  {
    int numVars = result.cols();
    Array<double, 1> k1(numVars), k2(numVars), k3(numVars), k4(numVars);
    Array<double, 1> y(numVars), yplus(numVars);
    double h, x;

    const static double OneSixth = 1.0 / 6.0;
    const static double OneThird = 1.0 / 3.0;

    for (int i = startPoint; i < endPoint; i++)
    {
      x                           = grid(i);
      h                           = grid(i + 1) - x;
      y                           = result(i, Range::all());
      k1                          = h * Integrand(x, y);
      yplus                       = y + 0.5 * k1;
      k2                          = h * Integrand(x + 0.5 * h, yplus);
      yplus                       = y + 0.5 * k2;
      k3                          = h * Integrand(x + 0.5 * h, yplus);
      yplus                       = y + k3;
      k4                          = h * Integrand(x + h, yplus);
      result(i + 1, Range::all()) = y + (OneSixth * (k1 + k4) + OneThird * (k2 + k3));
    }
  }

IntegrateRev()

void IntegrateRev ( const Grid &  grid, int  startPoint, int  endPoint, Array< double, 2 > &  result  )

inlineprivate

Definition at line 141 of file RungeKutta.h.

References Range::all(), Array< T, D, ALLOC >::cols(), and RungeKutta2< IntegrandClass >::Integrand.

Referenced by RungeKutta2< IntegrandClass >::Integrate().

  {
    int numVars = result.cols();
    Array<double, 1> k1(numVars), k2(numVars), k3(numVars), k4(numVars);
    Array<double, 1> y(numVars), yplus(numVars);
    double h, x;

    const static double OneSixth = 1.0 / 6.0;
    const static double OneThird = 1.0 / 3.0;

    for (int i = startPoint; i > endPoint; i--)
    {
      x                           = grid(i);
      h                           = grid(i - 1) - x;
      y                           = result(i, Range::all());
      k1                          = h * Integrand(x, y);
      yplus                       = y + 0.5 * k1;
      k2                          = h * Integrand(x + 0.5 * h, yplus);
      yplus                       = y + 0.5 * k2;
      k3                          = h * Integrand(x + 0.5 * h, yplus);
      yplus                       = y + k3;
      k4                          = h * Integrand(x + h, yplus);
      result(i - 1)/*, Range::all())*/ = y + (OneSixth * (k1 + k4) + OneThird * (k2 + k3));
    }
  }

Member Data Documentation

Integrand

IntegrandClass& Integrand

private

Definition at line 112 of file RungeKutta.h.

Referenced by RungeKutta2< IntegrandClass >::IntegrateForw(), and RungeKutta2< IntegrandClass >::IntegrateRev().

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The documentation for this class was generated from the following file:

• /home/pk7/projects/qmc/for_cron_doxygen/qmcpack/src/QMCTools/ppconvert/src/common/RungeKutta.h