BufCpuTraits.hpp

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/* Copyright 2025 Anton Reinhard
 * SPDX-License-Identifier: MPL-2.0
 */
#pragma once
 
#include "alpaka/dev/DevCpu.hpp"
#include "alpaka/mem/buf/Traits.hpp"
#include "alpaka/mem/buf/cpu/BufCpu.hpp"
 
namespace alpaka::trait
{
    //! The CPU device memory buffer type trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct BufType<DevCpu, TElem, TDim, TIdx>
    {
        using type = BufCpu<TElem, TDim, TIdx>;
    };
 
    //!  The BufCpu device type trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct DevType<BufCpu<TElem, TDim, TIdx>>
    {
        using type = DevCpu;
    };
 
    //! The BufCpu device get trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct GetDev<BufCpu<TElem, TDim, TIdx>>
    {
        ALPAKA_FN_HOST static auto getDev(BufCpu<TElem, TDim, TIdx> const& buf) -> DevCpu
        {
            return buf.m_spBufImpl->m_dev;
        }
    };
 
    //! The BufCpu dimension getter trait.
    template<typename TElem, typename TDim, typename TIdx>
    struct DimType<BufCpu<TElem, TDim, TIdx>>
    {
        using type = TDim;
    };
 
    //! The BufCpu memory element type get trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct ElemType<BufCpu<TElem, TDim, TIdx>>
    {
        using type = TElem;
    };
 
    //! The BufCpu width get trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct GetExtents<BufCpu<TElem, TDim, TIdx>>
    {
        ALPAKA_FN_HOST auto operator()(BufCpu<TElem, TDim, TIdx> const& buf)
        {
            return buf.m_spBufImpl->m_extentElements;
        }
    };
 
    //! The BufCpu native pointer get trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct GetPtrNative<BufCpu<TElem, TDim, TIdx>>
    {
        ALPAKA_FN_HOST static auto getPtrNative(BufCpu<TElem, TDim, TIdx> const& buf) -> TElem const*
        {
            return buf.m_spBufImpl->m_pMem;
        }
 
        ALPAKA_FN_HOST static auto getPtrNative(BufCpu<TElem, TDim, TIdx>& buf) -> TElem*
        {
            return buf.m_spBufImpl->m_pMem;
        }
    };
 
    //! The BufCpu pointer on device get trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct GetPtrDev<BufCpu<TElem, TDim, TIdx>, DevCpu>
    {
        ALPAKA_FN_HOST static auto getPtrDev(BufCpu<TElem, TDim, TIdx> const& buf, DevCpu const& dev) -> TElem const*
        {
            if(dev == getDev(buf))
            {
                return buf.m_spBufImpl->m_pMem;
            }
            else
            {
                throw std::runtime_error("The buffer is not accessible from the given device!");
            }
        }
 
        ALPAKA_FN_HOST static auto getPtrDev(BufCpu<TElem, TDim, TIdx>& buf, DevCpu const& dev) -> TElem*
        {
            if(dev == getDev(buf))
            {
                return buf.m_spBufImpl->m_pMem;
            }
            else
            {
                throw std::runtime_error("The buffer is not accessible from the given device!");
            }
        }
    };
 
    //! The BufCpu offset get trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct GetOffsets<BufCpu<TElem, TDim, TIdx>>
    {
        ALPAKA_FN_HOST auto operator()(BufCpu<TElem, TDim, TIdx> const& /*buf*/) const -> Vec<TDim, TIdx>
        {
            return Vec<TDim, TIdx>::zeros();
        }
    };
 
    //! The BufCpu idx type trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct IdxType<BufCpu<TElem, TDim, TIdx>>
    {
        using type = TIdx;
    };
 
    //! The MakeConstBuf trait for CPU buffers.
    template<typename TElem, typename TDim, typename TIdx>
    struct MakeConstBuf<BufCpu<TElem, TDim, TIdx>>
    {
        ALPAKA_FN_HOST static auto makeConstBuf(BufCpu<TElem, TDim, TIdx> const& buf) -> ConstBufCpu<TElem, TDim, TIdx>
        {
            return ConstBufCpu<TElem, TDim, TIdx>(buf);
        }
 
        ALPAKA_FN_HOST static auto makeConstBuf(BufCpu<TElem, TDim, TIdx>&& buf) -> ConstBufCpu<TElem, TDim, TIdx>
        {
            return ConstBufCpu<TElem, TDim, TIdx>(std::move(buf));
        }
    };
 
    //! The BufCpu memory allocation trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct BufAlloc<TElem, TDim, TIdx, DevCpu>
    {
        template<typename TExtent>
        ALPAKA_FN_HOST static auto allocBuf(DevCpu const& dev, TExtent const& extent) -> BufCpu<TElem, TDim, TIdx>
        {
            ALPAKA_DEBUG_MINIMAL_LOG_SCOPE;
 
            // If ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT is defined, positive, and a power of 2, use it as the
            // default alignment for host memory allocations. Otherwise, the alignment is chosen to enable
            // optimal performance dependant on the target architecture.
#if defined(ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT)
            static_assert(
                ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT > 0
                    && ((ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT & (ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT - 1)) == 0),
                "If defined, ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT must be a power of 2.");
            constexpr std::size_t alignment = static_cast<std::size_t>(ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT);
#else
            constexpr std::size_t alignment = core::vectorization::defaultAlignment;
#endif
            // alpaka::AllocCpuAligned is stateless
            using Allocator = AllocCpuAligned<std::integral_constant<std::size_t, alignment>>;
            static_assert(std::is_empty_v<Allocator>, "AllocCpuAligned is expected to be stateless");
            auto* memPtr = alpaka::malloc<TElem>(Allocator{}, static_cast<std::size_t>(getExtentProduct(extent)));
            auto deleter = [](TElem* ptr) { alpaka::free(Allocator{}, ptr); };
 
            return BufCpu<TElem, TDim, TIdx>(dev, memPtr, std::move(deleter), extent);
        }
    };
 
    //! The ConstBufCpu stream-ordered memory allocation capability trait specialization.
    template<typename TDim>
    struct HasAsyncBufSupport<TDim, DevCpu> : public std::true_type
    {
    };
 
    //! The BufCpu stream-ordered memory allocation trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct AsyncBufAlloc<TElem, TDim, TIdx, DevCpu>
    {
        template<typename TQueue, typename TExtent>
        ALPAKA_FN_HOST static auto allocAsyncBuf(TQueue queue, TExtent const& extent) -> BufCpu<TElem, TDim, TIdx>
        {
            ALPAKA_DEBUG_MINIMAL_LOG_SCOPE;
 
            static_assert(
                std::is_same_v<Dev<TQueue>, DevCpu>,
                "The BufCpu buffer can only be used with a queue on a DevCpu device!");
            DevCpu const& dev = getDev(queue);
 
            // If ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT is defined, positive, and a power of 2, use it as the
            // default alignment for host memory allocations. Otherwise, the alignment is chosen to enable
            // optimal performance dependant on the target architecture.
#if defined(ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT)
            static_assert(
                ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT > 0
                    && ((ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT & (ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT - 1)) == 0),
                "If defined, ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT must be a power of 2.");
            constexpr std::size_t alignment = static_cast<std::size_t>(ALPAKA_DEFAULT_HOST_MEMORY_ALIGNMENT);
#else
            constexpr std::size_t alignment = core::vectorization::defaultAlignment;
#endif
            // alpaka::AllocCpuAligned is stateless
            using Allocator = AllocCpuAligned<std::integral_constant<std::size_t, alignment>>;
            static_assert(std::is_empty_v<Allocator>, "AllocCpuAligned is expected to be stateless");
            auto* memPtr = alpaka::malloc<TElem>(Allocator{}, static_cast<std::size_t>(getExtentProduct(extent)));
            auto deleter = [l_queue = std::move(queue)](TElem* ptr) mutable
            {
                alpaka::enqueue(
                    l_queue,
                    [ptr]()
                    {
                        // free the memory
                        alpaka::free(Allocator{}, ptr);
                    });
            };
 
            return BufCpu<TElem, TDim, TIdx>(dev, memPtr, std::move(deleter), extent);
        }
    };
 
    //! The pinned/mapped memory allocation capability trait specialization.
    template<>
    struct HasMappedBufSupport<PlatformCpu> : public std::true_type
    {
    };
 
    //! The pinned/mapped memory allocation trait specialization.
    template<typename TElem, typename TDim, typename TIdx>
    struct BufAllocMapped<PlatformCpu, TElem, TDim, TIdx>
    {
        template<typename TExtent>
        ALPAKA_FN_HOST static auto allocMappedBuf(
            DevCpu const& host,
            PlatformCpu const& /*platform*/,
            TExtent const& extent) -> BufCpu<TElem, TDim, TIdx>
        {
            // Allocate standard host memory.
            return allocBuf<TElem, TIdx>(host, extent);
        }
    };
 
} // namespace alpaka::trait