From 71bafff64d65c233b1138aa3110989c0764a295c Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sat, 16 Jan 2021 22:43:22 +0300
Subject: [PATCH] Implement matrix Frobenius (L2) norm

---
 libs/geom/include/psemek/geom/matrix.hpp | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/libs/geom/include/psemek/geom/matrix.hpp b/libs/geom/include/psemek/geom/matrix.hpp
index 2d99fb70..235d9709 100644
--- a/libs/geom/include/psemek/geom/matrix.hpp
+++ b/libs/geom/include/psemek/geom/matrix.hpp
@@ -2,6 +2,7 @@
 
 #include <psemek/geom/detail/array.hpp>
 #include <psemek/geom/vector.hpp>
+#include <psemek/geom/math.hpp>
 
 #include <algorithm>
 
@@ -39,7 +40,6 @@ namespace psemek::geom
 		static matrix scalar(T const & s);
 	};
 
-
 	template <typename T, std::size_t R, std::size_t C>
 	matrix<T, R, C> matrix<T, R, C>::zero()
 	{
@@ -269,6 +269,22 @@ namespace psemek::geom
 		return result;
 	}
 
+	template <typename T, std::size_t R, std::size_t C>
+	T frobenius_norm_sqr(matrix<T, R, C> const & m)
+	{
+		T r{0};
+		for (std::size_t i = 0; i < R; ++i)
+			for (std::size_t j = 0; j < C; ++j)
+				r += sqr(m[i][j]);
+		return r;
+	}
+
+	template <typename T, std::size_t R, std::size_t C>
+	T frobenius_norm(matrix<T, R, C> const & m)
+	{
+		return std::sqrt(frobenius_norm_sqr(m));
+	}
+
 	template <typename Stream, typename T, std::size_t R, std::size_t C>
 	Stream & operator << (Stream & os, matrix<T, R, C> const & m)
 	{