lsst::meas::astrom::detail Namespace Reference

Classes
class	BinomialMatrix
	A class that computes binomial coefficients up to a certain power. More...

Functions
int	computePackedOffset (int order)
	Compute the index of the first coefficient with the given order in a packed 2-d polynomial coefficient array. More...
int	computePackedSize (int order)
	Compute this size of a packed 2-d polynomial coefficient array. More...
void	computePowers (Eigen::VectorXd &r, double x)
	Fill an array with integer powers of x, so \($r[n] == r^n\). More...
Eigen::VectorXd	computePowers (double x, int n)
	Return an array with integer powers of x, so \($r[n] == r^n\). More...

Function Documentation

computePackedOffset()

int lsst::meas::astrom::detail::computePackedOffset ( int  order )

inline

Compute the index of the first coefficient with the given order in a packed 2-d polynomial coefficient array.

This defines the ordering as

[(0,0), (0,1), (1,0), (0,2), (1,1), (2,0), ...]

(or the same with indices swapped).

Definition at line 45 of file polynomialUtils.h.

{ return (order * (order + 1)) / 2; }

computePackedSize()

int lsst::meas::astrom::detail::computePackedSize ( int  order )

inline

Compute this size of a packed 2-d polynomial coefficient array.

Definition at line 50 of file polynomialUtils.h.

{ return computePackedOffset(order + 1); }

computePowers() [1/2]

Eigen::VectorXd lsst::meas::astrom::detail::computePowers	(	double	x,
		int	n
	)

Return an array with integer powers of x, so \($r[n] == r^n\).

When multiple powers are needed, this should be signficantly faster than repeated calls to std::pow().

Definition at line 40 of file polynomialUtils.cc.

                                             {
    Eigen::VectorXd r(n + 1);
    computePowers(r, x);
    return r;
}

computePowers() [2/2]

void lsst::meas::astrom::detail::computePowers	(	Eigen::VectorXd &	r,
		double	x
	)

Fill an array with integer powers of x, so \($r[n] == r^n\).

When multiple powers are needed, this should be signficantly faster than repeated calls to std::pow().

Definition at line 33 of file polynomialUtils.cc.

                                               {
    r[0] = 1.0;
    for (int i = 1; i < r.size(); ++i) {
        r[i] = r[i - 1] * x;
    }
}