From 8832700e25f2ed6507454e22d8f61fd027c8a59a Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 4 Dec 2025 18:11:11 +0300
Subject: [PATCH] Optimize math::length(vector) to prevent allocations for
 runtime-sized vectors

---
 libs/math/include/psemek/math/vector.hpp | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/libs/math/include/psemek/math/vector.hpp b/libs/math/include/psemek/math/vector.hpp
index dc067e0f..fa017bb8 100644
--- a/libs/math/include/psemek/math/vector.hpp
+++ b/libs/math/include/psemek/math/vector.hpp
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <psemek/math/detail/array.hpp>
+#include <psemek/math/math.hpp>
 #include <psemek/util/hash.hpp>
 #include <psemek/util/span.hpp>
 
@@ -286,17 +287,22 @@ namespace psemek::math
 		using std::max;
 		T r = abs(v[0]);
 		for (std::size_t i = 1; i < v.dimension(); ++i)
-			r = max(r, abs(v[i]));
+			make_max(r, abs(v[i]));
 		return r;
 	}
 
 	template <typename T, std::size_t N>
 	T length(vector<T, N> const & v)
 	{
-		T const m = linf_norm(v);
-		if (m == T(0)) return m;
+		T const max = linf_norm(v);
+		if (max == T(0)) return max;
+
+		T sum{};
+		for (auto const & value : v.values())
+			sum += sqr(value / max);
+
 		using std::sqrt;
-		return m * sqrt(length_sqr(v / m));
+		return max * sqrt(sum);
 	}
 
 	template <typename T, std::size_t N>