An accumulator for sums. More...
#include <GeographicLib/Accumulator.hpp>
Public Member Functions | |
Accumulator (T y=T(0)) | |
Accumulator & | operator= (T y) |
T | operator() () const |
T | operator() (T y) const |
Accumulator & | operator+= (T y) |
Accumulator & | operator-= (T y) |
Accumulator & | operator*= (int n) |
bool | operator== (T y) const |
bool | operator!= (T y) const |
bool | operator< (T y) const |
bool | operator<= (T y) const |
bool | operator> (T y) const |
bool | operator>= (T y) const |
An accumulator for sums.
This allow many numbers of floating point type T to be added together with twice the normal precision. Thus if T is double, the effective precision of the sum is 106 bits or about 32 decimal places.
The implementation follows J. R. Shewchuk, Adaptive Precision Floating-Point Arithmetic and Fast Robust Geometric Predicates, Discrete & Computational Geometry 18(3) 305--363 (1997).
Approximate timings (summing a vector<double>)
In the documentation of the member functions, sum stands for the value currently held in the accumulator.
Example of use:
// Example of using the GeographicLib::Accumulator class #include <iostream> #include <exception> #include <GeographicLib/Accumulator.hpp> using namespace std; using namespace GeographicLib; int main() { try { // Compare using Accumulator and ordinary summation for a sum of large and // small terms. double sum = 0; Accumulator<> acc = 0; sum += 1e20; sum += 1; sum += 2; sum += 100; sum += 5000; sum += -1e20; acc += 1e20; acc += 1; acc += 2; acc += 100; acc += 5000; acc += -1e20; cout << sum << " " << acc() << "\n"; } catch (const exception& e) { cerr << "Caught exception: " << e.what() << "\n"; return 1; } return 0; }
Definition at line 40 of file Accumulator.hpp.
GeographicLib::Accumulator< T >::Accumulator | ( | T | y = T(0) |
) | [inline] |
Construct from a T. This is not declared explicit, so that you can write Accumulator<double> a = 5;
.
[in] | y | set sum = y. |
Definition at line 101 of file Accumulator.hpp.
References GEOGRAPHICLIB_STATIC_ASSERT.
Accumulator& GeographicLib::Accumulator< T >::operator= | ( | T | y | ) | [inline] |
Set the accumulator to a number.
[in] | y | set sum = y. |
Definition at line 110 of file Accumulator.hpp.
T GeographicLib::Accumulator< T >::operator() | ( | ) | const [inline] |
Return the value held in the accumulator.
Definition at line 116 of file Accumulator.hpp.
T GeographicLib::Accumulator< T >::operator() | ( | T | y | ) | const [inline] |
Return the result of adding a number to sum (but don't change sum).
[in] | y | the number to be added to the sum. |
Definition at line 123 of file Accumulator.hpp.
Accumulator& GeographicLib::Accumulator< T >::operator+= | ( | T | y | ) | [inline] |
Add a number to the accumulator.
[in] | y | set sum += y. |
Definition at line 129 of file Accumulator.hpp.
Accumulator& GeographicLib::Accumulator< T >::operator-= | ( | T | y | ) | [inline] |
Subtract a number from the accumulator.
[in] | y | set sum -= y. |
Definition at line 135 of file Accumulator.hpp.
Accumulator& GeographicLib::Accumulator< T >::operator*= | ( | int | n | ) | [inline] |
Multiply accumulator by an integer. To avoid loss of accuracy, use only integers such that n T is exactly representable as a T (i.e., powers of two). Use n = 1 to negate sum.
[in] | n | set sum *= n. |
Definition at line 143 of file Accumulator.hpp.
bool GeographicLib::Accumulator< T >::operator== | ( | T | y | ) | const [inline] |
Test equality of an Accumulator with a number.
Definition at line 147 of file Accumulator.hpp.
bool GeographicLib::Accumulator< T >::operator!= | ( | T | y | ) | const [inline] |
Test inequality of an Accumulator with a number.
Definition at line 151 of file Accumulator.hpp.
bool GeographicLib::Accumulator< T >::operator< | ( | T | y | ) | const [inline] |
Less operator on an Accumulator and a number.
Definition at line 155 of file Accumulator.hpp.
bool GeographicLib::Accumulator< T >::operator<= | ( | T | y | ) | const [inline] |
Less or equal operator on an Accumulator and a number.
Definition at line 159 of file Accumulator.hpp.
bool GeographicLib::Accumulator< T >::operator> | ( | T | y | ) | const [inline] |
Greater operator on an Accumulator and a number.
Definition at line 163 of file Accumulator.hpp.
bool GeographicLib::Accumulator< T >::operator>= | ( | T | y | ) | const [inline] |
Greater or equal operator on an Accumulator and a number.
Definition at line 167 of file Accumulator.hpp.