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Kokkos_BitOps.hpp
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Wed, Jul 17, 17:51

Kokkos_BitOps.hpp
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/*
//@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 H. Carter Edwards (hcedwar@sandia.gov)
//
// ************************************************************************
//@HEADER
*/
#ifndef KOKKOS_BITOPS_HPP
#define KOKKOS_BITOPS_HPP
#include <Kokkos_Macros.hpp>
#include <cstdint>
#include <climits>
namespace Kokkos {
namespace Impl {
/**\brief Find first zero bit.
*
* If none then return -1 ;
*/
KOKKOS_FORCEINLINE_FUNCTION
int bit_first_zero( unsigned i ) noexcept
{
enum : unsigned { full = ~0u };
#if defined( __CUDA_ARCH__ )
return full != i ? __ffs( ~i ) - 1 : -1 ;
#elif defined( KOKKOS_COMPILER_INTEL )
return full != i ? _bit_scan_forward( ~i ) : -1 ;
#elif defined( KOKKOS_COMPILER_IBM )
return full != i ? __cnttz4( ~i ) : -1 ;
#elif defined( KOKKOS_COMPILER_GNU ) || defined( __GNUC__ ) || defined( __GNUG__ )
return full != i ? __builtin_ffs( ~i ) - 1 : -1 ;
#else
int offset = -1 ;
if ( full != i ) {
for ( offset = 0 ; i & ( 1 << offset ) ; ++offset );
}
return offset ;
#endif
}
KOKKOS_FORCEINLINE_FUNCTION
int bit_scan_forward( unsigned i )
{
#if defined( __CUDA_ARCH__ )
return __ffs(i) - 1;
#elif defined( KOKKOS_COMPILER_INTEL )
return _bit_scan_forward(i);
#elif defined( KOKKOS_COMPILER_IBM )
return __cnttz4(i);
#elif defined( KOKKOS_COMPILER_GNU ) || defined( __GNUC__ ) || defined( __GNUG__ )
return __builtin_ffs(i) - 1;
#else
unsigned t = 1u;
int r = 0;
while ( i && ( i & t == 0 ) )
{
t = t << 1;
++r;
}
return r;
#endif
}
KOKKOS_FORCEINLINE_FUNCTION
int bit_scan_reverse( unsigned i )
{
enum { shift = static_cast<int>( sizeof(unsigned) * CHAR_BIT - 1 ) };
#if defined( __CUDA_ARCH__ )
return shift - __clz(i);
#elif defined( KOKKOS_COMPILER_INTEL )
return _bit_scan_reverse(i);
#elif defined( KOKKOS_COMPILER_IBM )
return shift - __cntlz4(i);
#elif defined( __GNUC__ ) || defined( __GNUG__ )
return shift - __builtin_clz(i);
#else
unsigned t = 1u << shift;
int r = 0;
while ( i && ( i & t == 0 ) )
{
t = t >> 1;
++r;
}
return r;
#endif
}
/// Count the number of bits set.
KOKKOS_FORCEINLINE_FUNCTION
int bit_count( unsigned i )
{
#if defined( __CUDA_ARCH__ )
return __popc(i);
#elif defined ( __INTEL_COMPILER )
return _popcnt32(i);
#elif defined( KOKKOS_COMPILER_IBM )
return __popcnt4(i);
#elif defined( __GNUC__ ) || defined( __GNUG__ )
return __builtin_popcount(i);
#else
// http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetNaive
i = i - ( ( i >> 1 ) & ~0u / 3u ); // temp
i = ( i & ~0u / 15u * 3u ) + ( ( i >> 2 ) & ~0u / 15u * 3u ); // temp
i = ( i + ( i >> 4 ) ) & ~0u / 255u * 15u; // temp
// count
return (int)( ( i * ( ~0u / 255u ) ) >> ( sizeof(unsigned) - 1 ) * CHAR_BIT );
#endif
}
KOKKOS_INLINE_FUNCTION
unsigned integral_power_of_two_that_contains( const unsigned N )
{
const unsigned i = Kokkos::Impl::bit_scan_reverse( N );
return ( (1u << i) < N ) ? i + 1 : i ;
}
} // namespace Impl
} // namespace Kokkos
#endif // KOKKOS_BITOPS_HPP

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