coffee/fast_float
1
0
Fork 0
mirror of https://github.com/fastfloat/fast_float.git synced 2026-01-01 03:12:18 +08:00
Code Issues Packages Projects Releases Wiki Activity

We might reenable clinger.

Browse Source
This commit is contained in:
Daniel Lemire 2022-11-16 16:21:34 +00:00
parent dac641ee13
commit 6ceb29a7e4
2 changed files with 52 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
include/fast_float/float_common.h
View File

@ -272,10 +272,12 @@ template <typename T> struct binary_format {
static inline constexpr int minimum_exponent();
static inline constexpr int infinite_power();
static inline constexpr int sign_index();
static inline constexpr int min_exponent_fast_path(); // used when fegetround() == FE_TONEAREST
static inline constexpr int max_exponent_fast_path();
static inline constexpr int max_exponent_round_to_even();
static inline constexpr int min_exponent_round_to_even();
static inline constexpr uint64_t max_mantissa_fast_path(int64_t power);
static inline constexpr uint64_t max_mantissa_fast_path(); // used when fegetround() == FE_TONEAREST
static inline constexpr int largest_power_of_ten();
static inline constexpr int smallest_power_of_ten();
static inline constexpr T exact_power_of_ten(int64_t power);
@ -285,6 +287,22 @@ template <typename T> struct binary_format {
static inline constexpr equiv_uint hidden_bit_mask();
};
template <> inline constexpr int binary_format<double>::min_exponent_fast_path() {
#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
return 0;
#else
return -22;
#endif
}
template <> inline constexpr int binary_format<float>::min_exponent_fast_path() {
#if (FLT_EVAL_METHOD != 1) && (FLT_EVAL_METHOD != 0)
return 0;
#else
return -10;
#endif
}
template <> inline constexpr int binary_format<double>::mantissa_explicit_bits() {
return 52;
}
@ -331,13 +349,18 @@ template <> inline constexpr int binary_format<double>::max_exponent_fast_path()
template <> inline constexpr int binary_format<float>::max_exponent_fast_path() {
return 10;
}
template <> inline constexpr uint64_t binary_format<double>::max_mantissa_fast_path() {
return uint64_t(2) << mantissa_explicit_bits();
}
template <> inline constexpr uint64_t binary_format<double>::max_mantissa_fast_path(int64_t power) {
// caller is responsible to ensure that
// power >= 0 && power <= 22
//
return max_mantissa_double[power];
}
template <> inline constexpr uint64_t binary_format<float>::max_mantissa_fast_path() {
return uint64_t(2) << mantissa_explicit_bits();
}
template <> inline constexpr uint64_t binary_format<float>::max_mantissa_fast_path(int64_t power) {
// caller is responsible to ensure that
// power >= 0 && power <= 10

34
include/fast_float/parse_number.h
View File

@ -60,6 +60,15 @@ from_chars_result parse_infnan(const char *first, const char *last, T &value) n
return answer;
}
fastfloat_really_inline bool rounds_nearest() {
// This function is meant to be equivalent to :
// prior: #include <cfenv>
// return fegetround() == FE_TONEAREST;
// volatile prevents the compiler from computing the function at compile-time
static volatile float fmin = std::numeric_limits<float>::min();
return (fmin + 1.0f == 1.0f - fmin);
}
} // namespace detail
template<typename T>
@ -87,12 +96,25 @@ from_chars_result from_chars_advanced(const char *first, const char *last,
}
answer.ec = std::errc(); // be optimistic
answer.ptr = pns.lastmatch;
// Next is a modified Clinger's fast path, inspired by Jakub Jelínek's proposal
if (pns.exponent >= 0 && pns.exponent <= binary_format<T>::max_exponent_fast_path() && pns.mantissa <=binary_format<T>::max_mantissa_fast_path(pns.exponent) && !pns.too_many_digits) {
value = T(pns.mantissa);
value = value * binary_format<T>::exact_power_of_ten(pns.exponent);
if (pns.negative) { value = -value; }
return answer;
if(detail::rounds_nearest()) {
// We have that fegetround() == FE_TONEAREST.
// Next is Clinger's fast path.
if (binary_format<T>::min_exponent_fast_path() <= pns.exponent && pns.exponent <= binary_format<T>::max_exponent_fast_path() && pns.mantissa <=binary_format<T>::max_mantissa_fast_path() && !pns.too_many_digits) {
value = T(pns.mantissa);
if (pns.exponent < 0) { value = value / binary_format<T>::exact_power_of_ten(-pns.exponent); }
else { value = value * binary_format<T>::exact_power_of_ten(pns.exponent); }
if (pns.negative) { value = -value; }
return answer;
}
} else {
// We do not have that fegetround() == FE_TONEAREST.
// Next is a modified Clinger's fast path, inspired by Jakub Jelínek's proposal
if (pns.exponent >= 0 && pns.exponent <= binary_format<T>::max_exponent_fast_path() && pns.mantissa <=binary_format<T>::max_mantissa_fast_path(pns.exponent) && !pns.too_many_digits) {
value = T(pns.mantissa);
value = value * binary_format<T>::exact_power_of_ten(pns.exponent);
if (pns.negative) { value = -value; }
return answer;
}
}
adjusted_mantissa am = compute_float<binary_format<T>>(pns.exponent, pns.mantissa);
if(pns.too_many_digits && am.power2 >= 0) {