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#pragma once
#include <ATen/native/DispatchStub.h>
namespace c10 {
class Scalar;
}
namespace at {
struct TensorIterator;
struct TensorIteratorBase;
namespace native {
#if defined(__CUDACC__) || defined(__HIPCC__)
#define HOST_DEVICE __host__ __device__
#else
#define HOST_DEVICE
#endif
// integral power in pytorch allows for negative exponents, giving truncated integral results.
// e.g. since 2**-1==0.5, the truncated integral result is zero. 1**negative_exponent is the
// only non-zero result.
template <class T,
typename std::enable_if<std::is_integral<T>::value, T>::type* = nullptr>
static inline HOST_DEVICE __ubsan_ignore_signed_int_overflow__ T powi_impl(T a, T b) {
T result = 1;
while (b) {
if (b & 1) {
result *= a;
}
b /= 2;
a *= a;
}
return result;
}
template <class T,
typename std::enable_if<std::is_integral<T>::value && !std::is_signed<T>::value, T>::type* = nullptr>
static inline HOST_DEVICE T powi(T a, T b) {
return powi_impl(a, b);
}
template <class T,
typename std::enable_if<std::is_integral<T>::value && std::is_signed<T>::value, T>::type* = nullptr>
static inline HOST_DEVICE T powi(T a, T b) {
if ( b < 0 ) {
if ( a == 1 ) {
return 1;
} else if ( a == -1 ) {
auto negative = (-b) % static_cast<T>(2);
return negative ? -1 : 1;
} else {
return 0;
}
}
return powi_impl(a, b);
}
using pow_tensor_tensor_fn = void (*)(TensorIteratorBase&);
using pow_tensor_scalar_fn = void (*)(TensorIteratorBase&, const c10::Scalar&);
DECLARE_DISPATCH(pow_tensor_tensor_fn, pow_tensor_tensor_stub);
DECLARE_DISPATCH(pow_tensor_scalar_fn, pow_tensor_scalar_stub);
} // namespace native
} // namespace at
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