From 1b8ded4702a9e4352e13235d3f646299750bb2b1 Mon Sep 17 00:00:00 2001
From: Thomas Fischer <thomas.fischer@ufz.de>
Date: Thu, 25 Jul 2024 14:31:58 +0200
Subject: [PATCH] [MaL] Implement KahanSum algorithm
---
MathLib/KahanSum.h | 49 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
create mode 100644 MathLib/KahanSum.h
diff --git a/MathLib/KahanSum.h b/MathLib/KahanSum.h
new file mode 100644
index 00000000000..0a360f355dd
--- /dev/null
+++ b/MathLib/KahanSum.h
@@ -0,0 +1,49 @@
+/**
+ * \file
+ * \copyright
+ * Copyright (c) 2012-2024, OpenGeoSys Community (http://www.opengeosys.org)
+ * Distributed under a Modified BSD License.
+ * See accompanying file LICENSE.txt or
+ * http://www.opengeosys.org/project/license
+ */
+
+#pragma once
+
+#include <iomanip>
+#include <ostream>
+
+namespace MathLib
+{
+
+class KahanSum
+{
+public:
+ explicit constexpr KahanSum(double const value = 0) : value_(value) {}
+
+ constexpr KahanSum& operator+=(double const increment)
+ {
+ double const y = increment - correction_;
+ double const t = value_ + y;
+ correction_ = (t - value_) - y;
+ value_ = t;
+ return *this;
+ }
+
+ constexpr double value() const { return value_; }
+ constexpr double operator()() const { return value_; }
+
+ friend inline std::ostream& operator<<(std::ostream& os, KahanSum const& x)
+ {
+ auto const precision = os.precision();
+ return os << std::setprecision(
+ std::numeric_limits<double>::max_digits10)
+ << x.value() << " (± " << x.correction_ << ')'
+ << std::setprecision(precision);
+ }
+
+private:
+ double value_;
+ double correction_ = 0.;
+};
+
+} // namespace MathLib
--
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