kokkos_allocator.hpp

// Copyright (C) The DDC development team, see COPYRIGHT.md file
//
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <cstddef>
#include <string>
#include <type_traits>
 
#include <Kokkos_Core.hpp>
 
namespace ddc {
 
template <class T, class MemorySpace>
class KokkosAllocator
{
    // Kokkos natively supports alignment for any scalar type and `Kokkos::complex<T>`
    static_assert(
            alignof(T)
                    <= std::max(alignof(std::max_align_t), alignof(Kokkos::complex<long double>)),
            "Alignment not supported");
 
public:
    using value_type = T;
 
    using memory_space = MemorySpace;
 
    template <class U>
    struct rebind
    {
        using other = KokkosAllocator<U, MemorySpace>;
    };
 
    constexpr KokkosAllocator() = default;
 
    constexpr KokkosAllocator(KokkosAllocator const& x) = default;
 
    constexpr KokkosAllocator(KokkosAllocator&& x) noexcept = default;
 
    template <class U>
    constexpr explicit KokkosAllocator(KokkosAllocator<U, MemorySpace> const&) noexcept
    {
    }
 
    ~KokkosAllocator() = default;
 
    constexpr KokkosAllocator& operator=(KokkosAllocator const& x) = default;
 
    constexpr KokkosAllocator& operator=(KokkosAllocator&& x) noexcept = default;
 
    template <class U>
    constexpr KokkosAllocator& operator=(KokkosAllocator<U, MemorySpace> const&) noexcept
    {
    }
 
    [[nodiscard]] T* allocate(std::size_t n) const
    {
        return static_cast<T*>(Kokkos::kokkos_malloc<MemorySpace>(sizeof(T) * n));
    }
 
    [[nodiscard]] T* allocate(std::string const& label, std::size_t n) const
    {
        return static_cast<T*>(Kokkos::kokkos_malloc<MemorySpace>(label, sizeof(T) * n));
    }
 
    void deallocate(T* p, std::size_t) const
    {
        Kokkos::kokkos_free(p);
    }
};
 
template <class T, class MST, class U, class MSU>
constexpr bool operator==(KokkosAllocator<T, MST> const&, KokkosAllocator<U, MSU> const&) noexcept
{
    return std::is_same_v<KokkosAllocator<T, MST>, KokkosAllocator<U, MSU>>;
}
 
#if !defined(__cpp_impl_three_way_comparison) || __cpp_impl_three_way_comparison < 201902L
// In C++20, `a!=b` shall be automatically translated by the compiler to `!(a==b)`
template <class T, class MST, class U, class MSU>
constexpr bool operator!=(KokkosAllocator<T, MST> const&, KokkosAllocator<U, MSU> const&) noexcept
{
    return !std::is_same_v<KokkosAllocator<T, MST>, KokkosAllocator<U, MSU>>;
}
#endif
 
template <class T>
using DeviceAllocator = KokkosAllocator<T, Kokkos::DefaultExecutionSpace::memory_space>;
 
template <class T>
using HostAllocator = KokkosAllocator<T, Kokkos::HostSpace>;
 
} // namespace ddc