mirror of
https://github.com/pytorch/pytorch.git
synced 2025-10-20 21:14:14 +08:00
110339a310
Introduced by #113276. I've added a test to catch future regressions. Pull Request resolved: https://github.com/pytorch/pytorch/pull/115647 Approved by: https://github.com/desertfire, https://github.com/vfdev-5
73 lines
2.1 KiB
C++
73 lines
2.1 KiB
C++
#pragma once
|
|
|
|
#include <c10/macros/Macros.h>
|
|
#include <c10/util/TypeSafeSignMath.h>
|
|
#include <cmath>
|
|
|
|
#if defined(__CUDA_ARCH__)
|
|
#include <c10/cuda/CUDAMathCompat.h>
|
|
#define C10_COMPAT_COPYSIGN c10::cuda::compat::copysign
|
|
#elif defined(__HIPCC__)
|
|
#include <c10/hip/HIPMathCompat.h>
|
|
#define C10_COMPAT_COPYSIGN c10::hip::compat::copysign
|
|
#else
|
|
#include <c10/util/copysign.h>
|
|
#define C10_COMPAT_COPYSIGN c10::copysign
|
|
#endif
|
|
|
|
// The functions in this file should be header-only as it is used under
|
|
// ABI-compatibility mode.
|
|
|
|
namespace c10 {
|
|
|
|
// NOTE: [Floor Division in Python]
|
|
// Python's __floordiv__ operator is more complicated than just floor(a / b).
|
|
// It aims to maintain the property: a == (a // b) * b + remainder(a, b)
|
|
// which can otherwise fail due to rounding errors in the remainder.
|
|
// So, instead it is calculated as: a // b = (a - remainder(a, b)) / b
|
|
// With some additional fix-ups added to the result.
|
|
//
|
|
// For reference, see CPython's implementation:
|
|
// https://github.com/python/cpython/blob/ace008c531dd685a30c1dd68f9b5ba35f20171cf/Objects/floatobject.c#L636
|
|
|
|
template <typename scalar_t>
|
|
inline C10_HOST_DEVICE scalar_t div_floor_floating(scalar_t a, scalar_t b)
|
|
__ubsan_ignore_float_divide_by_zero__ {
|
|
if (C10_UNLIKELY(b == 0)) {
|
|
// Divide by zero: return standard IEEE result
|
|
return a / b;
|
|
}
|
|
|
|
auto mod = std::fmod(a, b);
|
|
auto div = (a - mod) / b;
|
|
if ((mod != 0) && (b < 0) != (mod < 0)) {
|
|
div -= scalar_t(1);
|
|
}
|
|
|
|
scalar_t floordiv;
|
|
if (div != 0) {
|
|
floordiv = std::floor(div);
|
|
if (div - floordiv > scalar_t(0.5)) {
|
|
floordiv += scalar_t(1.0);
|
|
}
|
|
} else {
|
|
floordiv = C10_COMPAT_COPYSIGN(scalar_t(0), a / b);
|
|
}
|
|
return floordiv;
|
|
}
|
|
|
|
template <typename scalar_t>
|
|
inline C10_HOST_DEVICE scalar_t div_floor_integer(scalar_t a, scalar_t b) {
|
|
if (c10::signs_differ(a, b)) {
|
|
// Subtracts one from the results of truncation division if the
|
|
// divisor and dividend have different sign(bit)s and the remainder of
|
|
// the division is nonzero
|
|
const auto quot = a / b;
|
|
const auto rem = a % b;
|
|
return rem ? quot - 1 : quot;
|
|
}
|
|
return a / b;
|
|
}
|
|
|
|
} // namespace c10
|