Cabana_Index.hpp

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/****************************************************************************
 * Copyright (c) 2018-2023 by the Cabana authors                            *
 * All rights reserved.                                                     *
 *                                                                          *
 * This file is part of the Cabana library. Cabana is distributed under a   *
 * BSD 3-clause license. For the licensing terms see the LICENSE file in    *
 * the top-level directory.                                                 *
 *                                                                          *
 * SPDX-License-Identifier: BSD-3-Clause                                    *
 ****************************************************************************/

#ifndef CABANA_INDEX_HPP
#define CABANA_INDEX_HPP
 
#include <impl/Cabana_TypeTraits.hpp>
 
#include <Kokkos_Core.hpp>
 
#include <type_traits>
 
namespace Cabana
{
namespace Impl
{
 
//---------------------------------------------------------------------------//
template <int VectorLength>
class Index
{
  public:
    // Validate the inner array size.
    static_assert( Impl::IsVectorLengthValid<VectorLength>::value,
                   "Invalid vector length" );

    static constexpr int vector_length = VectorLength;

    static constexpr int vector_length_offset = ( vector_length - 1 );

    static constexpr int vector_length_binary_bits =
        Impl::LogBase2<vector_length>::value;

    KOKKOS_FORCEINLINE_FUNCTION
    static constexpr std::size_t s( const std::size_t i )
    {
        return ( i - ( i & vector_length_offset ) ) >>
               vector_length_binary_bits;
    }

    KOKKOS_FORCEINLINE_FUNCTION
    static constexpr std::size_t a( const std::size_t i )
    {
        return i & vector_length_offset;
    }

    KOKKOS_FORCEINLINE_FUNCTION
    static constexpr std::size_t i( const std::size_t s, const std::size_t a )
    {
        return ( s << vector_length_binary_bits ) + a;
    }
};
 
//---------------------------------------------------------------------------//
 
} // end namespace Impl
 
} // end namespace Cabana
 
#endif // end CABANA_INDEX_HPP