Implementation of arange algorithm

Author: vvish

include/xsimd_algorithm/stl/arange.hpp

@@ -0,0 +1,77 @@
+/***************************************************************************
+ * Copyright (c) Johan Mabille, Sylvain Corlay, Wolf Vollprecht and         *
+ * Martin Renou                                                             *
+ * Copyright (c) QuantStack                                                 *
+ * Copyright (c) Serge Guelton                                              *
+ *                                                                          *
+ * Distributed under the terms of the BSD 3-Clause License.                 *
+ *                                                                          *
+ * The full license is in the file LICENSE, distributed with this software. *
+ ****************************************************************************/
+
+#ifndef XSIMD_ALGORITHMS_ARANGE_HPP
+#define XSIMD_ALGORITHMS_ARANGE_HPP
+
+#include "xsimd/xsimd.hpp"
+
+#include <iterator>
+
+namespace xsimd
+{
+    namespace detail
+    {
+        template <class Arch = default_arch, class ForwardIterator, class T>
+        T sequential_arange(ForwardIterator first, ForwardIterator last, T value, T step) noexcept
+        {
+            for (; first != last; ++first, value += step)
+            {
+                *first = value;
+            }
+
+            return value;
+        }
+    }
+
+    template <class Arch = default_arch, class ContiguousIterator, class T>
+    void arange(ContiguousIterator first, ContiguousIterator last, T value, T step) noexcept
+    {
+        using value_type = typename std::decay<decltype(*first)>::type;
+        using batch_type = batch<value_type, Arch>;
+
+        const std::size_t size = static_cast<std::size_t>(std::distance(first, last));
+        constexpr std::size_t simd_size = batch_type::size;
+
+        if (size < simd_size)
+        {
+            detail::sequential_arange(first, last, value, step);
+            return;
+        }
+
+        const auto* const ptr_begin = &(*first);
+        const std::size_t align_begin = xsimd::get_alignment_offset(ptr_begin, size, simd_size);
+        const std::size_t align_end = align_begin + ((size - align_begin) & ~(simd_size - 1));
+
+        const auto align_begin_it = std::next(first, align_begin);
+        const auto align_end_it = std::next(first, align_end);
+
+        value = detail::sequential_arange(first, align_begin_it, value, step);
+
+        alignas(batch_type::arch_type::alignment()) value_type init_tmp[simd_size];
+        detail::sequential_arange(init_tmp, init_tmp + simd_size, value, step);
+        batch_type batch_val = batch_type::load_aligned(init_tmp);
+
+        const batch_type step_batch(static_cast<value_type>(simd_size));
+        for (auto current = align_begin_it; current != align_end_it; std::advance(current, simd_size))
+        {
+            batch_val.store_aligned(&(*current));
+            batch_val = batch_val + (step_batch * step);
+        }
+
+        value = *std::next(align_end_it, -1) + step;
+
+        detail::sequential_arange(align_end_it, last, value, step);
+    }
+
+} // namespace xsimd
+
+#endif // XSIMD_ALGORITHMS_ARANGE_HPP

test/CMakeLists.txt

@@ -47,6 +47,7 @@ endif()
 
 set(XSIMD_ALGORITHM_TESTS
     main.cpp
+    test_arange.cpp
     test_iterator.cpp
     test_reduce.cpp
     test_transform.cpp

test/test_arange.cpp

@@ -0,0 +1,114 @@
+/***************************************************************************
+ * Copyright (c) Johan Mabille, Sylvain Corlay, Wolf Vollprecht and         *
+ * Martin Renou                                                             *
+ * Copyright (c) QuantStack                                                 *
+ * Copyright (c) Serge Guelton                                              *
+ *                                                                          *
+ * Distributed under the terms of the BSD 3-Clause License.                 *
+ *                                                                          *
+ * The full license is in the file LICENSE, distributed with this software. *
+ ****************************************************************************/
+
+#include "xsimd_algorithm/stl/arange.hpp"
+
+#ifndef XSIMD_NO_SUPPORTED_ARCHITECTURE
+
+#include "doctest/doctest.h"
+
+#include <cstddef>
+#include <vector>
+
+#if XSIMD_WITH_NEON && !XSIMD_WITH_NEON64
+#define ARANGE_TYPES int, float
+#else
+#define ARANGE_TYPES int, long, float, double
+#endif
+
+template <typename Type>
+struct arange_test
+{
+    using vector = std::vector<Type>;
+    static constexpr std::size_t simd_size = xsimd::batch<Type>::size;
+
+    static vector fill_expected(Type start, size_t size, Type step = Type { 1 })
+    {
+        vector result(size);
+
+        for (size_t i = 0; i < size; ++i)
+        {
+            result[i] = start + (i * step);
+        }
+
+        return result;
+    }
+
+    void test_arange_aligned(Type init_value, size_t size, Type step) const
+    {
+        vector c(size);
+        xsimd::arange(c.begin(), c.end(), init_value, step);
+        const vector expected = fill_expected(init_value, size, step);
+
+        CHECK(std::equal(expected.begin(), expected.end(), c.begin()));
+        CHECK(expected.size() == c.size());
+    }
+
+    void test_arange_misaligned(Type init_value, size_t size, Type step) const
+    {
+        const size_t missalignment = 1;
+        vector c(size + missalignment * 2);
+        auto first = c.begin() + missalignment;
+        auto last = first + size;
+
+        xsimd::arange(first, last, init_value, step);
+
+        const vector expected = fill_expected(init_value, size, step);
+        CHECK(std::equal(expected.begin(), expected.end(), first));
+        CHECK(expected.size() == static_cast<size_t>(std::distance(first, last)));
+    }
+};
+
+TEST_CASE_TEMPLATE("arange test", T, ARANGE_TYPES)
+{
+    using Test = arange_test<T>;
+
+    const std::array test_sizes {
+        size_t { 0 },
+        size_t { 1 },
+        Test::simd_size - 1,
+        Test::simd_size,
+        Test ::simd_size + 1,
+    };
+
+    const std::array init_values {
+        T { -1 },
+        T { 0 },
+        T { 1 },
+    };
+
+    const std::array steps { -2, -1, 0, 1, 2 };
+
+    Test test;
+
+    size_t sub_case_id = 0;
+    for (const auto size : test_sizes)
+    {
+        for (const auto init_value : init_values)
+        {
+            for (const auto step : steps)
+            {
+                const std::string aligned_subcase_name = "Aligned" + std::to_string(sub_case_id++) + ", size: " + std::to_string(size) + ", init_value: " + std::to_string(init_value) + ", step: " + std::to_string(step);
+                SUBCASE(aligned_subcase_name.c_str())
+                {
+                    test.test_arange_aligned(init_value, size, step);
+                }
+                const std::string misaligned_subcase_name = "Misaligned" + std::to_string(sub_case_id++) + ", size: " + std::to_string(size) + ", init_value: " + std::to_string(init_value) + ", step: " + std::to_string(step);
+                SUBCASE(misaligned_subcase_name.c_str())
+                {
+                    test.test_arange_misaligned(init_value, size, step);
+                }
+            }
+        }
+    }
+}
+
+#endif