text: /*
  //@HEADER
  // ************************************************************************
  //
  //                        Kokkos v. 2.0
  //              Copyright (2014) Sandia Corporation
  //
  // Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
  // the U.S. Government retains certain rights in this software.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  // 1. Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //
  // 2. Redistributions in binary form must reproduce the above copyright
  // notice, this list of conditions and the following disclaimer in the
  // documentation and/or other materials provided with the distribution.
  //
  // 3. Neither the name of the Corporation nor the names of the
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "AS IS" AND ANY
  // EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  // PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SANDIA CORPORATION OR THE
  // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // Questions? Contact Christian R. Trott (crtrott@sandia.gov)
  //
  // ************************************************************************
  //@HEADER
  */
  
  #ifndef KOKKOS_CUDA_UNIQUE_TOKEN_HPP
  #define KOKKOS_CUDA_UNIQUE_TOKEN_HPP
  
  #include <Kokkos_Macros.hpp>
  #ifdef KOKKOS_ENABLE_CUDA
  
  #include <Kokkos_CudaSpace.hpp>
  #include <Kokkos_UniqueToken.hpp>
  #include <impl/Kokkos_SharedAlloc.hpp>
  #include <impl/Kokkos_ConcurrentBitset.hpp>
  
  namespace Kokkos {
  namespace Experimental {
  
  // both global and instance Unique Tokens are implemented in the same way
  template <>
  class UniqueToken<Cuda, UniqueTokenScope::Global> {
   private:
    uint32_t volatile* m_buffer;
    uint32_t m_count;
  
   public:
    using execution_space = Cuda;
    using size_type       = int32_t;
  
  #if defined(KOKKOS_ENABLE_DEPRECATED_CODE)
    explicit UniqueToken(execution_space const&);
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken() : m_buffer(0), m_count(0) {}
  #else
    explicit UniqueToken(execution_space const& = execution_space());
  #endif
  
  #ifdef KOKKOS_CUDA_9_DEFAULTED_BUG_WORKAROUND
    KOKKOS_INLINE_FUNCTION
    UniqueToken(const UniqueToken& rhs)
        : m_buffer(rhs.m_buffer), m_count(rhs.m_count) {}
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken(UniqueToken&& rhs)
        : m_buffer(std::move(rhs.m_buffer)), m_count(std::move(rhs.m_count)) {}
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken& operator=(const UniqueToken& rhs) {
      m_buffer = rhs.m_buffer;
      m_count  = rhs.m_count;
      return *this;
    }
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken& operator=(UniqueToken&& rhs) {
      m_buffer = std::move(rhs.m_buffer);
      m_count  = std::move(rhs.m_count);
      return *this;
    }
  #else
    KOKKOS_INLINE_FUNCTION
    UniqueToken(const UniqueToken&) = default;
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken(UniqueToken&&) = default;
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken& operator=(const UniqueToken&) = default;
  
    KOKKOS_INLINE_FUNCTION
    UniqueToken& operator=(UniqueToken&&) = default;
  #endif
  
    /// \brief upper bound for acquired values, i.e. 0 <= value < size()
    KOKKOS_INLINE_FUNCTION
    size_type size() const noexcept { return m_count; }
  
    /// \brief acquire value such that 0 <= value < size()
    KOKKOS_INLINE_FUNCTION
    size_type acquire() const {
      const Kokkos::pair<int, int> result =
          Kokkos::Impl::concurrent_bitset::acquire_bounded(
              m_buffer, m_count, Kokkos::Impl::clock_tic() % m_count);
  
      if (result.first < 0) {
        Kokkos::abort(
            "UniqueToken<Cuda> failure to release tokens, no tokens available");
      }
  
      return result.first;
    }
  
    /// \brief release an acquired value
    KOKKOS_INLINE_FUNCTION
    void release(size_type i) const noexcept {
      Kokkos::Impl::concurrent_bitset::release(m_buffer, i);
    }
  };
  
  template <>
  class UniqueToken<Cuda, UniqueTokenScope::Instance>
      : public UniqueToken<Cuda, UniqueTokenScope::Global> {
   public:
  #ifdef KOKKOS_ENABLE_DEPRECATED_CODE
    explicit UniqueToken(execution_space const& arg)
        : UniqueToken<Cuda, UniqueTokenScope::Global>(arg) {}
  #else
    explicit UniqueToken(execution_space const& arg = execution_space())
        : UniqueToken<Cuda, UniqueTokenScope::Global>(arg) {}
  #endif
  };
  
  }  // namespace Experimental
  }  // namespace Kokkos
  
  #endif  // KOKKOS_ENABLE_CUDA
  #endif  // KOKKOS_CUDA_UNIQUE_TOKEN_HPP
  