Merge pull request xtensor-stack#1256 from AntoinePrv/batch-constant-nttp

Add make_batch_constant from std::array in C++20

Author: JohanMabille

include/xsimd/types/xsimd_batch_constant.hpp

@@ -408,6 +408,15 @@ namespace xsimd
             return {};
         }
 
+#if __cplusplus >= 202002L
+        template <std::array Arr, class A, std::size_t... Is>
+        XSIMD_INLINE constexpr batch_constant<typename decltype(Arr)::value_type, A, Arr[Is]...>
+        make_batch_constant(std::index_sequence<Is...>) noexcept
+        {
+            return {};
+        }
+#endif
+
         template <typename T, class G, class A, std::size_t... Is>
         XSIMD_INLINE constexpr batch_bool_constant<T, A, G::get(Is, sizeof...(Is))...>
         make_batch_bool_constant(std::index_sequence<Is...>) noexcept
@@ -422,6 +431,15 @@ namespace xsimd
             return {};
         }
 
+#if __cplusplus >= 202002L
+        template <typename T, std::array Arr, class A, std::size_t... Is>
+        XSIMD_INLINE constexpr batch_bool_constant<T, A, Arr[Is]...>
+        make_batch_bool_constant(std::index_sequence<Is...>) noexcept
+        {
+            return {};
+        }
+#endif
+
     } // namespace detail
 
     /**
@@ -479,6 +497,21 @@ namespace xsimd
         return {};
     }
 
+#if __cplusplus >= 202002L
+    /**
+     * @brief Build a @c batch_constant from a std::array (C++20)
+     *
+     * @tparam Arr The std::array containing the values (non type template argument).
+     * @tparam A Architecture that will be used when converting to a regular batch.
+     */
+    template <std::array Arr, class A = default_arch>
+        requires(Arr.size() == batch<typename decltype(Arr)::value_type, A>::size)
+    XSIMD_INLINE constexpr auto make_batch_constant() noexcept
+    {
+        return detail::make_batch_constant<Arr, A>(std::make_index_sequence<Arr.size()>());
+    }
+#endif
+
     /*
      * @brief Build a @c batch_bool_constant with a single repeated value.
      *
@@ -491,6 +524,23 @@ namespace xsimd
         return {};
     }
 
+#if __cplusplus >= 202002L
+    /**
+     * @brief Build a @c batch_constant from a std::array of boolean (C++20)
+     *
+     * @tparam Arr The std::array containing the boolean values (non type template argument).
+     * @tparam A Architecture that will be used when converting to a regular batch.
+     */
+    template <typename T, std::array Arr, class A = default_arch>
+        requires(
+            (Arr.size() == batch_bool<T, A>::size)
+            && std::is_same_v<typename decltype(Arr)::value_type, bool>)
+    XSIMD_INLINE constexpr auto make_batch_bool_constant() noexcept
+    {
+        return detail::make_batch_bool_constant<T, Arr, A>(std::make_index_sequence<Arr.size()>());
+    }
+#endif
+
 #endif
 
     namespace generator

test/test_batch_constant.cpp

@@ -9,6 +9,8 @@
  * The full license is in the file LICENSE, distributed with this software. *
  ****************************************************************************/
 
+#include <numeric>
+
 #include "xsimd/xsimd.hpp"
 #ifndef XSIMD_NO_SUPPORTED_ARCHITECTURE
 
@@ -43,6 +45,22 @@ struct constant_batch_test
         CHECK_BATCH_EQ((batch_type)b, expected);
     }
 
+    void test_init_from_array() const
+    {
+#if __cplusplus >= 202002L
+        constexpr array_type expected = []()
+        {
+            array_type out = {};
+            std::iota(out.begin(), out.end(), 0);
+            return out;
+        }();
+
+        constexpr auto b = xsimd::make_batch_constant<expected, arch_type>();
+        INFO("batch(value_type)");
+        CHECK_BATCH_EQ((batch_type)b, expected);
+#endif
+    }
+
     void test_init_from_generator() const
     {
         array_type expected;
@@ -217,6 +235,8 @@ TEST_CASE_TEMPLATE("[constant batch]", B, BATCH_INT_TYPES)
     constant_batch_test<B> Test;
     SUBCASE("init_from_constant") { Test.test_init_from_constant(); }
 
+    SUBCASE("test_init_from_array") { Test.test_init_from_array(); }
+
     SUBCASE("init_from_generator") { Test.test_init_from_generator(); }
 
     SUBCASE("as_batch") { Test.test_cast(); }
@@ -263,6 +283,25 @@ struct constant_bool_batch_test
         CHECK_BATCH_EQ((batch_bool_type)b, expected);
     }
 
+    void test_init_from_array() const
+    {
+#if __cplusplus >= 202002L
+        constexpr bool_array_type expected = []()
+        {
+            bool_array_type out = {};
+            for (std::size_t k = 0; k < out.size(); ++k)
+            {
+                out[k] = k % 2 == 0;
+            }
+            return out;
+        }();
+
+        constexpr auto b = xsimd::make_batch_bool_constant<value_type, expected, arch_type>();
+        INFO("batch_bool_constant(value_type)");
+        CHECK_BATCH_EQ((batch_bool_type)b, expected);
+#endif
+    }
+
     void test_init_from_generator() const
     {
         bool_array_type expected;
@@ -357,6 +396,8 @@ TEST_CASE_TEMPLATE("[constant bool batch]", B, BATCH_INT_TYPES)
     constant_bool_batch_test<B> Test;
     SUBCASE("init_from_constant") { Test.test_init_from_constant(); }
 
+    SUBCASE("test_init_from_array") { Test.test_init_from_array(); }
+
     SUBCASE("init_from_generator") { Test.test_init_from_generator(); }
 
     SUBCASE("as_batch") { Test.test_cast(); }