From fa9a7a6766de0319960f6166c64e5590e613c478 Mon Sep 17 00:00:00 2001
From: Frederick Roy <froy@lnrobo.com>
Date: Mon, 2 Feb 2026 07:52:51 +0900
Subject: [PATCH 1/3] rewrite for better cache accesses

---
 Sofa/framework/Type/src/sofa/type/Mat.h | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/Sofa/framework/Type/src/sofa/type/Mat.h b/Sofa/framework/Type/src/sofa/type/Mat.h
index 3067a701727..1989bebf971 100644
--- a/Sofa/framework/Type/src/sofa/type/Mat.h
+++ b/Sofa/framework/Type/src/sofa/type/Mat.h
@@ -1299,15 +1299,13 @@ template <sofa::Size L, sofa::Size C, sofa::Size P, class real>
 constexpr Mat<L,P,real> operator*(const Mat<L,C,real>& m1, const Mat<C,P,real>& m2) noexcept
 {
     Mat<L,P,real> r(NOINIT);
-    for (Size i = 0; i<L; i++)
+    for (Size i = 0; i < L; ++i)
     {
-        for (Size j = 0; j<P; j++)
+        for (Size k = 0; k < C; ++k)
         {
-            r(i,j) = m1(i,0) * m2(0,j);
-            for (Size k = 1; k<C; k++)
-            {
-                r(i,j) += m1(i,k) * m2(k,j);
-            }
+            const auto aik = m1(i,k);
+            for (Size j = 0; j < P; ++j)
+                r(i,j) += aik * m2(k,j);
         }
     }
     return r;

From eb57d55fe64006e0f992a13a1ead2b96f855ea1a Mon Sep 17 00:00:00 2001
From: Frederick Roy <froy@lnrobo.com>
Date: Wed, 4 Feb 2026 10:10:59 +0900
Subject: [PATCH 2/3] zero-initialize the result matrix

---
 Sofa/framework/Type/src/sofa/type/Mat.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sofa/framework/Type/src/sofa/type/Mat.h b/Sofa/framework/Type/src/sofa/type/Mat.h
index 1989bebf971..ff855ba72b7 100644
--- a/Sofa/framework/Type/src/sofa/type/Mat.h
+++ b/Sofa/framework/Type/src/sofa/type/Mat.h
@@ -1298,7 +1298,7 @@ constexpr Mat<L,L,Real> tensorProduct(const Vec<L,Real>& a, const Vec<L,Real>& b
 template <sofa::Size L, sofa::Size C, sofa::Size P, class real>
 constexpr Mat<L,P,real> operator*(const Mat<L,C,real>& m1, const Mat<C,P,real>& m2) noexcept
 {
-    Mat<L,P,real> r(NOINIT);
+    Mat<L,P,real> r;
     for (Size i = 0; i < L; ++i)
     {
         for (Size k = 0; k < C; ++k)

From 5672af4b841ca3ffa1830202666f65bbd8156413 Mon Sep 17 00:00:00 2001
From: Frederick Roy <froy@lnrobo.com>
Date: Thu, 5 Feb 2026 07:49:26 +0900
Subject: [PATCH 3/3] really zero-init'ed

---
 Sofa/framework/Type/src/sofa/type/Mat.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sofa/framework/Type/src/sofa/type/Mat.h b/Sofa/framework/Type/src/sofa/type/Mat.h
index ff855ba72b7..33051223e7f 100644
--- a/Sofa/framework/Type/src/sofa/type/Mat.h
+++ b/Sofa/framework/Type/src/sofa/type/Mat.h
@@ -1298,7 +1298,7 @@ constexpr Mat<L,L,Real> tensorProduct(const Vec<L,Real>& a, const Vec<L,Real>& b
 template <sofa::Size L, sofa::Size C, sofa::Size P, class real>
 constexpr Mat<L,P,real> operator*(const Mat<L,C,real>& m1, const Mat<C,P,real>& m2) noexcept
 {
-    Mat<L,P,real> r;
+    Mat<L,P,real> r(static_cast<real>(0));
     for (Size i = 0; i < L; ++i)
     {
         for (Size k = 0; k < C; ++k)