diff --git a/libsrc/core/simd_generic.hpp b/libsrc/core/simd_generic.hpp
index e6fdb68b..5186784b 100644
--- a/libsrc/core/simd_generic.hpp
+++ b/libsrc/core/simd_generic.hpp
@@ -726,6 +726,57 @@ namespace ngcore
       }
   }
 
+  // TODO: specialize for AVX, ... 
+  template<int N>
+  NETGEN_INLINE auto SwapPairs (SIMD<double,N> a)
+  {
+    if constexpr(N==1) {
+        // static_assert(false);
+        return a;
+      }
+    else if constexpr(N==2) {
+        return SIMD<double,N> (a.Hi(), a.Lo());
+      }
+    else {
+      return SIMD<double,N> (SwapPairs(a.Lo()), SwapPairs(a.Hi()));
+    }
+  }
+
+
+  template<int N>
+  NETGEN_INLINE auto HSum128 (SIMD<double,N> a)
+  {
+    if constexpr(N==1) {
+        // static_assert(false);
+        return a;
+      }
+    else if constexpr(N==2) {
+        return a;
+      }
+    else {
+      return HSum128(a.Lo()) + HSum128(a.Hi());
+    }
+  }
+
+  
+  // TODO: specialize for AVX, ... 
+  // a*b+-c   (even: -, odd: +)
+  template<int N>
+  NETGEN_INLINE auto FMAddSub (SIMD<double,N> a, SIMD<double,N> b, SIMD<double,N> c)
+  {
+    if constexpr(N==1) {
+        // static_assert(false);
+        return a*b-c;
+      }
+    else if constexpr(N==2) {
+        return SIMD<double,N> (a.Lo()*b.Lo()-c.Lo(),
+                               a.Hi()*b.Hi()+c.Hi());
+      }
+    else {
+      return SIMD<double,N> (FMAddSub(a.Lo(), b.Lo(), c.Lo()),
+                             FMAddSub(a.Hi(), b.Hi(), c.Hi()));
+    }
+  }
 }