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Public Member Functions | List of all members
lsst::geom::polynomials::SafeSum< T > Class Template Reference

A numerically stable summation algorithm for floating-point numbers. More...

#include <SafeSum.h>

Public Member Functions

 SafeSum (T initial=static_cast< T >(0)) noexcept
 
SafeSumoperator= (T value) noexcept
 
SafeSumoperator+= (T value) noexcept
 
SafeSumoperator-= (T value) noexcept
 
 operator T () const noexcept
 

Detailed Description

template<typename T>
class lsst::geom::polynomials::SafeSum< T >

A numerically stable summation algorithm for floating-point numbers.

SafeSum implements += and -= operators that can be used to accumulate floating point numbers with very different magnitudes, with accuracy limited only by the usual floating-point inaccuracy in represented the final sum.

SafeSum is explicitly convertible to and from its underlying floating-point type and only supports in-place addition and subtraction, in order to avoid cases where a combination of implicit conversion and multiple overloaded operators could lead to accidental use of regular floating-point operations.

SafeSum uses the Kahan-Neumaier algorithm (though this should be considered an implementation detail by callers), which maintains a lower-order-bit correction that compensates for the loss of precision in the main sum. Particularly aggressive compiler optimizations that do not preserve IEEE floating point behavior (e.g. gcc's -fassociative-math) may optimize away the correction and reduce SafeSum's behavior to a standard unsafe sum.

Definition at line 62 of file SafeSum.h.

Constructor & Destructor Documentation

◆ SafeSum()

template<typename T >
lsst::geom::polynomials::SafeSum< T >::SafeSum ( T initial = static_cast<T>(0))
inlineexplicitnoexcept

Definition at line 65 of file SafeSum.h.

Member Function Documentation

◆ operator T()

template<typename T >
lsst::geom::polynomials::SafeSum< T >::operator T ( ) const
inlineexplicitnoexcept

Definition at line 93 of file SafeSum.h.

◆ operator+=()

template<typename T >
SafeSum & lsst::geom::polynomials::SafeSum< T >::operator+= ( T value)
inlinenoexcept

Definition at line 76 of file SafeSum.h.

◆ operator-=()

template<typename T >
SafeSum & lsst::geom::polynomials::SafeSum< T >::operator-= ( T value)
inlinenoexcept

Definition at line 89 of file SafeSum.h.

◆ operator=()

template<typename T >
SafeSum & lsst::geom::polynomials::SafeSum< T >::operator= ( T value)
inlinenoexcept

Definition at line 70 of file SafeSum.h.


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