Power of Two Utilities

template <typename T>
[[nodiscard]] __host__ __device__ inline constexpr
bool is_power_of_two(T value) noexcept;

template <typename T>
[[nodiscard]] __host__ __device__ inline constexpr
T next_power_of_two(T value) noexcept;

template <typename T>
[[nodiscard]] __host__ __device__ inline constexpr
T prev_power_of_two(T value) noexcept;

The functions provide utilities to determine if an integer value is a power of two, and to compute the next and previous power of two.

Parameters

• value: The input value.

Return value

• is_power_of_two: Return true if value is a power of two, false otherwise.

• next_power_of_two: Return the smallest power of two greater than or equal to value.

• prev_power_of_two: Return the largest power of two less than or equal to value.

Constraints

• T is an integer types. Contrary to cuda::std::has_single_bit, cuda::bit_floor, and cuda::bit_ceil, T can be both signed and unsigned.

Preconditions

• value > 0

Performance considerations

See <cuda/std/bit> performance considerations

Example

#include <cuda/cmath>
#include <cuda/std/cassert>

__global__ void pow2_kernel() {
    assert(!cuda::is_power_of_two(20));
    assert(cuda::next_power_of_two(20) == 32);
    assert(cuda::prev_power_of_two(20) == 16);
}

int main() {
    pow2_kernel<<<1, 1>>>();
    cudaDeviceSynchronize();
    return 0;
}

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