extended.h File Reference

This files containts definitions for the extended precision class that allows for high precision reductions using Kahan-Babushka-Klein summation. More...

#include "plumbing/defs.h"

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Namespaces
namespace	hila
	Implement hila::swap for gauge fields.

Functions
template<typename T , std::enable_if_t< std::is_arithmetic< T >::value, int > = 0>
ExtendedPrecision	operator+ (ExtendedPrecision a, const T b)
	ExtendedPrecision precision operators + - * / – also ext * arithm.
template<typename A , typename B , std::enable_if_t< hila::AorB_extended< A, B >::value, int > = 0>
bool	operator== (const A &a, const B &b)
	comparison operators

Detailed Description

This files containts definitions for the extended precision class that allows for high precision reductions using Kahan-Babushka-Klein summation.

Uses internally three double precision variables to store the value and compensation. Precision can be > 15 orders of magnitude better than plain doble.

Use:

ExtendedPrecision s1 = 0, s2 = 0;
onsites(ALL) {
    s1 += <double/float/int -valued expression>;
    s2 += <some other expression>
}
 
// below subtraction and comparison is done in extended precision
if (s1 == s2)
    hila::out0 << "s1 equals s2\n";
else
    hila::out0 << "s1 is " << (s1 > s2) ? "greater" : "less"
               << " than s2, with difference " << s1 - s2 << '\n';

Class implements basic arithmetics ( + - * / ), assignments (= += *=) and comparison ops for ExtendedPrecision types. ExtendedPrecision is not automatically downgraded to double in order to avoid accidental loss of accuracy.

To get a double approximation of the value use

s1.to_double()
// or equvalently explicit casting
static_cast<double>(s1)

Definition in file extended.h.