From 53eba7524f2d47b3a54c3aa947f988314288c06a Mon Sep 17 00:00:00 2001
From: Bernhard Manfred Gruber <bernhardmgruber@gmail.com>
Date: Fri, 25 Feb 2022 18:06:35 +0100
Subject: [PATCH] add dot product for Array

---
 include/llama/Array.hpp | 10 ++++++++++
 tests/array.cpp         |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/include/llama/Array.hpp b/include/llama/Array.hpp
index af12abc052..0c76ab2326 100644
--- a/include/llama/Array.hpp
+++ b/include/llama/Array.hpp
@@ -208,6 +208,16 @@ namespace llama
             prod *= s;
         return prod;
     }
+
+    template<typename T, std::size_t N>
+    LLAMA_FN_HOST_ACC_INLINE constexpr auto dot(Array<T, N> a, Array<T, N> b) -> T
+    {
+        T r = 0;
+        if constexpr(N > 0)
+            for(std::size_t i = 0; i < N; i++)
+                r += a[i] * b[i];
+        return r;
+    }
 } // namespace llama
 
 namespace std
diff --git a/tests/array.cpp b/tests/array.cpp
index 05bfab83fc..7f4335351d 100644
--- a/tests/array.cpp
+++ b/tests/array.cpp
@@ -52,3 +52,11 @@ TEST_CASE("Array.product")
     STATIC_REQUIRE(product(llama::Array{1, 2}) == 2);
     STATIC_REQUIRE(product(llama::Array{3, 2, 1}) == 6);
 }
+
+TEST_CASE("Array.dot")
+{
+    STATIC_REQUIRE(llama::dot(llama::Array<int, 0>{}, llama::Array<int, 0>{}) == 0);
+    STATIC_REQUIRE(llama::dot(llama::Array{2}, llama::Array{3}) == 6);
+    STATIC_REQUIRE(llama::dot(llama::Array{4, 5}, llama::Array{6, 7}) == 59);
+    STATIC_REQUIRE(llama::dot(llama::Array{1, 2, 3, 4}, llama::Array{-5, 6, -7, 0}) == -14);
+}