LSST Applications  21.0.0-147-g0e635eb1+1acddb5be5,22.0.0+052faf71bd,22.0.0+1ea9a8b2b2,22.0.0+6312710a6c,22.0.0+729191ecac,22.0.0+7589c3a021,22.0.0+9f079a9461,22.0.1-1-g7d6de66+b8044ec9de,22.0.1-1-g87000a6+536b1ee016,22.0.1-1-g8e32f31+6312710a6c,22.0.1-10-gd060f87+016f7cdc03,22.0.1-12-g9c3108e+df145f6f68,22.0.1-16-g314fa6d+c825727ab8,22.0.1-19-g93a5c75+d23f2fb6d8,22.0.1-19-gb93eaa13+aab3ef7709,22.0.1-2-g8ef0a89+b8044ec9de,22.0.1-2-g92698f7+9f079a9461,22.0.1-2-ga9b0f51+052faf71bd,22.0.1-2-gac51dbf+052faf71bd,22.0.1-2-gb66926d+6312710a6c,22.0.1-2-gcb770ba+09e3807989,22.0.1-20-g32debb5+b8044ec9de,22.0.1-23-gc2439a9a+fb0756638e,22.0.1-3-g496fd5d+09117f784f,22.0.1-3-g59f966b+1e6ba2c031,22.0.1-3-g849a1b8+f8b568069f,22.0.1-3-gaaec9c0+c5c846a8b1,22.0.1-32-g5ddfab5d3+60ce4897b0,22.0.1-4-g037fbe1+64e601228d,22.0.1-4-g8623105+b8044ec9de,22.0.1-5-g096abc9+d18c45d440,22.0.1-5-g15c806e+57f5c03693,22.0.1-7-gba73697+57f5c03693,master-g6e05de7fdc+c1283a92b8,master-g72cdda8301+729191ecac,w.2021.39
LSST Data Management Base Package
SafeSum.h
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1 // -*- LSST-C++ -*-
2 /*
3  * Developed for the LSST Data Management System.
4  * This product includes software developed by the LSST Project
5  * (https://www.lsst.org).
6  * See the COPYRIGHT file at the top-level directory of this distribution
7  * for details of code ownership.
8  *
9  * This program is free software: you can redistribute it and/or modify
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13  *
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15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17  * GNU General Public License for more details.
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21  */
22 #ifndef LSST_AFW_MATH_POLYNOMIALS_SafeSum_h_INCLUDED
23 #define LSST_AFW_MATH_POLYNOMIALS_SafeSum_h_INCLUDED
24 
25 #include <cmath>
26 
27 namespace lsst { namespace geom { namespace polynomials {
28 
32 enum class SumMode {
34  FAST,
36  SAFE
37 };
38 
61 template <typename T>
62 class SafeSum {
63 public:
64 
65  explicit SafeSum(T initial=static_cast<T>(0)) noexcept :
66  _sum(initial),
67  _correction(static_cast<T>(0))
68  {}
69 
70  SafeSum & operator=(T value) noexcept {
71  _sum = value;
72  _correction = static_cast<T>(0);
73  return *this;
74  }
75 
76  SafeSum & operator+=(T value) noexcept {
77  T t = _sum + value;
78  // update _correction to account for lost low-order bits of the
79  // greater of _sum and value
80  if (std::abs(_sum) >= std::abs(value)) {
81  _correction += (_sum - t) + value;
82  } else {
83  _correction += (value - t) + _sum;
84  }
85  _sum = t;
86  return *this;
87  }
88 
89  SafeSum & operator-=(T value) noexcept {
90  return operator+=(-value);
91  }
92 
93  explicit operator T() const noexcept {
94  return _sum + _correction;
95  }
96 
97 private:
98  T _sum;
99  T _correction;
100 };
101 
102 }}} // namespace lsst::geom::polynomials
103 
104 #endif // !LSST_AFW_MATH_POLYNOMIALS_SafeSum_h_INCLUDED
A numerically stable summation algorithm for floating-point numbers.
Definition: SafeSum.h:62
SafeSum & operator-=(T value) noexcept
Definition: SafeSum.h:89
SafeSum(T initial=static_cast< T >(0)) noexcept
Definition: SafeSum.h:65
SafeSum & operator+=(T value) noexcept
Definition: SafeSum.h:76
SafeSum & operator=(T value) noexcept
Definition: SafeSum.h:70
SumMode
Enum used to control how to sum polynomial terms.
Definition: SafeSum.h:32
@ SAFE
Compensated summation using SafeSum. Involves ~4x as many floating point operations.
@ FAST
Summation using regular floating-point addition.
Angle abs(Angle const &a)
Definition: Angle.h:106
A base class for image defects.