functor.hpp

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/* Copyright 2025 René Widera
 * SPDX-License-Identifier: MPL-2.0
 */
 
#pragma once
 
#include "alpaka/core/common.hpp"
 
#include <type_traits>
#include <utility>
 
namespace alpaka
{
    /** Marks a functor which supports SimdPtr as arguments
     *
     * Wrapping a functor or lambda with this class to signal support for SimdPtr.
     * A stencil functor can be used to write stencil operations within a transform call.
     */
    template<typename T_Func>
    struct StencilFunc : T_Func
    {
        using Functor = T_Func;
 
        constexpr StencilFunc(auto&& func) : T_Func{ALPAKA_FORWARD(func)}
        {
        }
    };
 
    template<typename T_Func>
    ALPAKA_FN_HOST_ACC StencilFunc(T_Func&&) -> StencilFunc<T_Func>;
 
    /** Marks a functor that can only be executed with scalar types and not SIMD packages.
     *
     * The functor will be executed element wise for SIMD packages due to methods used which prevent using SIMD
     * packages directly.
     */
    template<typename T_Func>
    struct ScalarFunc : T_Func
    {
        using Functor = T_Func;
 
        constexpr ScalarFunc(auto&& func) : T_Func{ALPAKA_FORWARD(func)}
        {
        }
    };
 
    template<typename T_Func>
    ALPAKA_FN_HOST_ACC ScalarFunc(T_Func&&) -> ScalarFunc<T_Func>;
 
    /** Execute the functor with or without an accelerator as first argument
     *
     * The functor is not allowed to have both possible signatures.
     *
     * @{
     */
    template<typename T_Acc, typename T_Functor, typename... T_Args>
    requires std::invocable<T_Functor, T_Acc, T_Args...>
    inline constexpr auto callFunctor(T_Acc const& acc, T_Functor&& functor, T_Args&&... args)
    {
        return functor(acc, std::forward<T_Args>(args)...);
    }
 
    template<typename T_Acc, typename T_Functor, typename... T_Args>
    requires std::invocable<T_Functor, T_Args...>
    inline constexpr auto callFunctor(T_Acc const&, T_Functor&& functor, T_Args&&... args)
    {
        return functor(std::forward<T_Args>(args)...);
    }
 
    /** @} */
} // namespace alpaka