lsst::afw::math::InterpolateGsl Class Reference

Inheritance diagram for lsst::afw::math::InterpolateGsl:

Public Member Functions
virtual	~InterpolateGsl ()
virtual double	interpolate (double const x) const
Public Member Functions inherited from lsst::afw::math::Interpolate
virtual	~Interpolate ()

Private Member Functions
	InterpolateGsl (std::vector< double > const &x, std::vector< double > const &y, Interpolate::Style const style)

Private Attributes
::gsl_interp_type const *	_interpType
::gsl_interp_accel *	_acc
::gsl_interp *	_interp

Friends
boost::shared_ptr< Interpolate >	makeInterpolate (std::vector< double > const &x, std::vector< double > const &y, Interpolate::Style const style)

Additional Inherited Members
Public Types inherited from lsst::afw::math::Interpolate
enum	Style {   UNKNOWN = -1, CONSTANT = 0, LINEAR = 1, NATURAL_SPLINE = 2,   CUBIC_SPLINE = 3, CUBIC_SPLINE_PERIODIC = 4, AKIMA_SPLINE = 5, AKIMA_SPLINE_PERIODIC = 6,   NUM_STYLES }
Protected Member Functions inherited from lsst::afw::math::Interpolate
	Interpolate (std::vector< double > const &x, std::vector< double > const &y, Interpolate::Style const style=UNKNOWN)
	Interpolate (std::pair< std::vector< double >, std::vector< double > > const xy, Interpolate::Style const style=UNKNOWN)
Protected Attributes inherited from lsst::afw::math::Interpolate
std::vector< double > const	_x
std::vector< double > const	_y
Interpolate::Style const	_style

Detailed Description

Definition at line 174 of file Interpolate.cc.

Constructor & Destructor Documentation

lsst::afw::math::InterpolateGsl::~InterpolateGsl ( )

virtual

Definition at line 218 of file Interpolate.cc.

                                {
    ::gsl_interp_free(_interp);
    ::gsl_interp_accel_free(_acc);
}

lsst::afw::math::InterpolateGsl::InterpolateGsl ( std::vector< double > const &  x, std::vector< double > const &  y, Interpolate::Style const  style  )

private

Parameters

x	the x-values of points
y	the values at x[]
style	desired interpolator

Definition at line 188 of file Interpolate.cc.

                                :
    Interpolate(x, y), _interpType(styleToGslInterpType(style))
{
    _acc = ::gsl_interp_accel_alloc();
    if (!_acc) {
        throw LSST_EXCEPT(pex::exceptions::MemoryError, "gsl_interp_accel_alloc failed");
    }
    
    _interp = ::gsl_interp_alloc(_interpType, _y.size());
    if (!_interp) {
        throw LSST_EXCEPT(pex::exceptions::OutOfRangeError,
                          str(boost::format("Failed to initialise spline for type %s, length %d")
                              % _interpType->name % _y.size()));

    }
    // Note, "x" and "y" are vector<double>; gsl_inter_init requires double[].
    // The &(x[0]) here is valid because std::vector guarantees that the values are
    // stored contiguously in memory (for types other than bool); C++0X 23.3.6.1 for
    // those of you reading along.
    int const status = ::gsl_interp_init(_interp, &x[0], &y[0], _y.size());
    if (status != 0) {
        throw LSST_EXCEPT(pex::exceptions::RuntimeError,
                          str(boost::format("gsl_interp_init failed: %s [%d]")
                              % ::gsl_strerror(status) % status));
    }
}

Member Function Documentation

double lsst::afw::math::InterpolateGsl::interpolate ( double const  x ) const

virtual

Implements lsst::afw::math::Interpolate.

Definition at line 223 of file Interpolate.cc.

{
    // New GSL versions refuse to extrapolate.
    // gsl_interp_init() requires x to be ordered, so can just check
    // the array endpoints for out-of-bounds.
    if ((xInterp < _x.front() || (xInterp > _x.back()))) {
        // do our own quadratic extrapolation.
        // (GSL only provides first and second derivative functions)
        /* could also just fail via:
         throw LSST_EXCEPT(
         pex::exceptions::InvalidParameterError,
         (boost::format("Interpolation point %f outside range [%f, %f]")
         % x % _x.front() % _x.back()).str()
         );
         */
        double x0, y0;
        if (xInterp < _x.front()) {
            x0 = _x.front();
            y0 = _y.front();
        } else {
            x0 = _x.back();
            y0 = _y.back();
        }
        // first derivative at endpoint
        double d = ::gsl_interp_eval_deriv(_interp, &_x[0], &_y[0], x0, _acc);
        // second derivative at endpoint
        double d2 = ::gsl_interp_eval_deriv2(_interp, &_x[0], &_y[0], x0, _acc);
        return y0 + (xInterp - x0)*d + 0.5*(xInterp - x0)*(xInterp - x0)*d2;
    }
    assert(xInterp >= _x.front());
    assert(xInterp <= _x.back());
    return ::gsl_interp_eval(_interp, &_x[0], &_y[0], xInterp, _acc);
}

Friends And Related Function Documentation

boost::shared_ptr< Interpolate > makeInterpolate ( std::vector< double > const &  x, std::vector< double > const &  y, Interpolate::Style const  style  )

friend

A factory function to make Interpolate objects

Member Data Documentation

::gsl_interp_accel* lsst::afw::math::InterpolateGsl::_acc

private

Definition at line 184 of file Interpolate.cc.

::gsl_interp* lsst::afw::math::InterpolateGsl::_interp

private

Definition at line 185 of file Interpolate.cc.

::gsl_interp_type const* lsst::afw::math::InterpolateGsl::_interpType

private

Definition at line 183 of file Interpolate.cc.

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

• /home/lsstsw/stack/Linux64/afw/11.0-2-g04d2804/src/math/Interpolate.cc