Merge reduction into one

src/targets/gpu/kernels/include/migraphx/kernels/array.hpp

@@ -134,6 +134,15 @@ struct array
         return result;
     }
 
+    template<class F>
+    constexpr auto apply(F f) const
+    {
+        array<decltype(f(d[0])), N> result;
+        for(index_int i = 0; i < N; i++)
+            result[i] = f(d[i]);
+        return result;
+    }
+
     MIGRAPHX_DEVICE_ARRAY_OP(+=, +)
     MIGRAPHX_DEVICE_ARRAY_OP(-=, -)
     MIGRAPHX_DEVICE_ARRAY_OP(*=, *)
@@ -201,6 +210,11 @@ struct array
     }
 };
 
+template<class T, class... Ts>
+constexpr array<T, sizeof...(Ts)+1> make_array(T x, Ts... xs)
+{
+    return {x, static_cast<T>(xs)...};
+}
 template <class T, T... Xs>
 struct integral_const_array : array<T, sizeof...(Xs)>
 {

src/targets/gpu/kernels/include/migraphx/kernels/layernorm.hpp

@@ -6,6 +6,14 @@
 
 namespace migraphx {
 
+template <class T, index_int N, class Op>
+constexpr auto vec_reduce(const array<T, N>& a, Op op)
+{
+    return a.apply([&](auto x) {
+        return vec_reduce(x, op);
+    });
+}
+
 template <index_int Axis,
           class F,
           class BinOp,
@@ -22,23 +30,19 @@ __device__ void generic_binary_layernorm(
     MIGRAPHX_ASSERT(relements > 0);
     reduce::block::run<reduce_output>([&](auto, auto r) {
         using value_type = typename Input1::type;
-        auto mean        = [&](auto f) {
-            return r.reduce(op::sum{}, 0, [&](auto x1, auto x2) {
-                return f(x1, x2) / value_type{relements};
+        auto means = r.reduce(op::sum{}, make_array<value_type>(0, 0), [&](auto x1, auto x2) {
+            auto x = op(x1, x2);
+            return make_array(x, x*x) / value_type{relements};
         })(input1, input2);
-        };
-        // mean(x)
-        auto mean_x = mean(op);
-        // mean(m ^ 2)
-        auto mean_m2 = mean([&](auto x1, auto x2) {
-            auto m = op(x1, x2) - mean_x;
-            return m * m;
-        });
+
+        auto mean_x = means[0];
+        auto mean_x2 = means[1];
 
         r.inner([&](auto& y, auto x1, auto x2, auto... xs) {
-            auto m = op(x1, x2) - mean_x;
+            auto x = op(x1, x2);
+            auto m = x - mean_x;
             // m * rsqrt(mean(m ^ 2) + 1e-12)
-            y = compute(m * rsqrt(mean_m2 + value_type{1e-12}), xs...);
+            y = compute(m * rsqrt(mean_x2 - mean_x + value_type{1e-12}), xs...);
         })(output, input1, input2, inputs...);
     });
 }