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#pragma once
#include <c10/macros/Macros.h>
#include <c10/util/floating_point_utils.h>
#include <cstring>
#include <limits>
// TODO(#146647): Can we remove the below warning?
C10_CLANG_DIAGNOSTIC_PUSH()
#if C10_CLANG_HAS_WARNING("-Wimplicit-int-float-conversion")
C10_CLANG_DIAGNOSTIC_IGNORE("-Wimplicit-int-float-conversion")
#endif
namespace c10 {
/// Constructors
inline C10_HOST_DEVICE Float8_e8m0fnu::Float8_e8m0fnu(float value)
: x(detail::fp8e8m0fnu_from_fp32_value(value)) {}
/// Implicit conversions
inline C10_HOST_DEVICE Float8_e8m0fnu::operator float() const {
// TODO(#146647): maybe rewrite without control flow
// if exponent is zero, need to special case to return 2^-127 instead of zero
if (x == 0) {
return c10::detail::fp32_from_bits(0x00400000);
}
// if exponent is NaN, need to special case to return properly encoded NaN
if (isnan()) {
return c10::detail::fp32_from_bits(0x7f800001);
}
// leave sign at 0, set the exponent bits, leave stored mantissa at 0
uint32_t res = x << 23;
return c10::detail::fp32_from_bits(res);
}
/// Special values helper
inline C10_HOST_DEVICE bool Float8_e8m0fnu::isnan() const {
return x == 0b11111111;
}
/// NOTE: we do not define comparisons directly and instead rely on the implicit
/// conversion from c10::Float8_e8m0fnu to float.
} // namespace c10
namespace std {
template <>
class numeric_limits<c10::Float8_e8m0fnu> {
public:
static constexpr bool is_specialized = true;
static constexpr bool is_signed = false;
static constexpr bool is_integer = false;
static constexpr bool is_exact = false;
static constexpr bool has_infinity = false;
static constexpr bool has_quiet_NaN = true;
static constexpr bool has_signaling_NaN = false;
static constexpr auto has_denorm = false;
static constexpr auto has_denorm_loss = false;
static constexpr auto round_style = numeric_limits<float>::round_style;
static constexpr bool is_iec559 = false;
static constexpr bool is_bounded = true;
static constexpr bool is_modulo = false;
static constexpr int digits = 1;
static constexpr int digits10 = 0;
static constexpr int max_digits10 = 1; // just a 2!
static constexpr int radix = 2;
static constexpr int min_exponent = -126;
static constexpr int min_exponent10 = -38;
static constexpr int max_exponent = 128;
static constexpr int max_exponent10 = 38;
static constexpr auto traps = numeric_limits<float>::traps;
static constexpr auto tinyness_before = false;
static constexpr c10::Float8_e8m0fnu min() {
// 2^-127
return c10::Float8_e8m0fnu(0b00000000, c10::Float8_e8m0fnu::from_bits());
}
static constexpr c10::Float8_e8m0fnu lowest() {
// 2^-127
return c10::Float8_e8m0fnu(0b00000000, c10::Float8_e8m0fnu::from_bits());
}
static constexpr c10::Float8_e8m0fnu max() {
// 254 biased, which is 127 unbiased, so 2^127
return c10::Float8_e8m0fnu(0b11111110, c10::Float8_e8m0fnu::from_bits());
}
static constexpr c10::Float8_e8m0fnu epsilon() {
// according to https://en.cppreference.com/w/cpp/types/numeric_limits, this
// is "the difference between 1.0 and the next representable value of the
// given floating-point type". The next representable value is 2.0, so the
// difference is 1.0 which is 2^0. 0 unbiased is 127 biased.
return c10::Float8_e8m0fnu(0b01111111, c10::Float8_e8m0fnu::from_bits());
}
static constexpr c10::Float8_e8m0fnu round_error() {
// 0.5 in float, which is 2^-1, and -1 + 127 = 126
return c10::Float8_e8m0fnu(0b01111110, c10::Float8_e8m0fnu::from_bits());
}
static constexpr c10::Float8_e8m0fnu quiet_NaN() {
return c10::Float8_e8m0fnu(0b11111111, c10::Float8_e8m0fnu::from_bits());
}
};
} // namespace std
C10_CLANG_DIAGNOSTIC_POP()
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