Bit manipulation#

Defined in header <Kokkos_BitManipulation.hpp> which is included from <Kokkos_Core.hpp>

Provides function templates from the standard library header <bit> (since C++20).

Bit manipulation function templates are defined in the Kokkos:: namespace since Kokkos 4.1

bit_cast

reinterpret the object representation of one type as that of another (see note below)

byteswap

reverses the bytes in the given integer value

has_single_bit

checks if a number is an integral power of two

bit_ceil

finds the smallest integral power of two not less than the given value

bit_floor

finds the largest integral power of two not greater than the given value

bit_width

finds the smallest number of bits needed to represent the given value

rotl

computes the result of bitwise left-rotation

rotr

computes the result of bitwise right-rotation

countl_zero

counts the number of consecutive 0 bits, starting from the most significant bit

countl_one

counts the number of consecutive 1 bits, starting from the most significant bit

countr_zero

counts the number of consecutive 0 bits, starting from the least significant bit

countr_one

counts the number of consecutive 1 bits, starting from the least significant bit

popcount

counts the number of 1 bits in an unsigned integer

Notes#

  • For all the above template functions, a non-constexpr counterpart ending with the *_builtin suffix is provided in the Kokkos::Experimental:: namespace to make up for some compiler intrinsics that cannot appear in constant expressions.

  • In contrast to its counterpart in the C++ standard library, Kokkos::bit_cast is not usable in constant expressions (not a constexpr function) as it is not implementable as a library facility and requires compiler magic which is not available to us.