From ce4e561cac845cbb35a9e7958aa3bc9cd45cabbd Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Fri, 4 Dec 2020 13:09:41 +0300
Subject: [PATCH] Support merging two util::statistics

---
 libs/util/include/psemek/util/statistics.hpp | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/libs/util/include/psemek/util/statistics.hpp b/libs/util/include/psemek/util/statistics.hpp
index 9172804c..4c63a89c 100644
--- a/libs/util/include/psemek/util/statistics.hpp
+++ b/libs/util/include/psemek/util/statistics.hpp
@@ -48,6 +48,9 @@ namespace psemek::util
 		T min() const { return min_; }
 		T max() const { return max_; }
 
+		template <typename H>
+		friend statistics<H> merge(statistics<H> const & s1, statistics<H> const & s2);
+
 	private:
 		std::size_t count_ = 0;
 		T sum_ = T{0};
@@ -86,4 +89,16 @@ namespace psemek::util
 		return os;
 	}
 
+	template <typename T>
+	statistics<T> merge(statistics<T> const & s1, statistics<T> const & s2)
+	{
+		statistics<T> result;
+		result.count_ = s1.count_ + s2.count_;
+		result.sum_ = s1.sum_ + s2.sum_;
+		result.sum_sqr_ = s1.sum_sqr_ + s2.sum_sqr_;
+		result.min_ = std::min(s1.min_, s2.min_);
+		result.max_ = std::max(s1.max_, s2.max_);
+		return result;
+	}
+
 }