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Simplify float_info

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This commit is contained in:
Victor Zverovich 2022-03-14 13:15:30 -07:00
parent f91f61cd13
commit 72f487562d
3 changed files with 18 additions and 31 deletions
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15
include/fmt/format-inl.h
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@ -1788,11 +1788,10 @@ template <> struct cache_accessor<double> {
// Various integer checks
template <class T>
bool is_left_endpoint_integer_shorter_interval(int exponent) noexcept {
return exponent >=
float_info<
T>::case_shorter_interval_left_endpoint_lower_threshold &&
exponent <=
float_info<T>::case_shorter_interval_left_endpoint_upper_threshold;
const int case_shorter_interval_left_endpoint_lower_threshold = 2;
const int case_shorter_interval_left_endpoint_upper_threshold = 3;
return exponent >= case_shorter_interval_left_endpoint_lower_threshold &&
exponent <= case_shorter_interval_left_endpoint_upper_threshold;
}
// Remove trailing zeros from n and return the number of zeros removed (float)
@ -1933,7 +1932,8 @@ template <typename T> decimal_fp<T> to_decimal(T x) noexcept {
static_cast<int>((br & exponent_mask<T>()) >> num_significand_bits<T>());
if (exponent != 0) { // Check if normal.
exponent += float_info<T>::exponent_bias - num_significand_bits<T>();
const int exponent_bias = std::numeric_limits<T>::max_exponent - 1;
exponent -= exponent_bias + num_significand_bits<T>();
// Shorter interval case; proceed like Schubfach.
// In fact, when exponent == 1 and significand == 0, the interval is
@ -1944,7 +1944,8 @@ template <typename T> decimal_fp<T> to_decimal(T x) noexcept {
} else {
// Subnormal case; the interval is always regular.
if (significand == 0) return {0, 0};
exponent = float_info<T>::min_exponent - num_significand_bits<T>();
exponent =
std::numeric_limits<T>::min_exponent - num_significand_bits<T>() - 1;
}
const bool include_left_endpoint = (significand % 2 == 0);

16
include/fmt/format.h
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@ -1227,45 +1227,29 @@ template <typename T, typename Enable = void> struct float_info;
template <> struct float_info<float> {
using carrier_uint = uint32_t;
static const int exponent_bits = 8;
static const int min_exponent = -126;
static const int max_exponent = 127;
static const int exponent_bias = -127;
static const int decimal_digits = 9;
static const int kappa = 1;
static const int big_divisor = 100;
static const int small_divisor = 10;
static const int min_k = -31;
static const int max_k = 46;
static const int cache_bits = 64;
static const int divisibility_check_by_5_threshold = 39;
static const int case_fc_pm_half_lower_threshold = -1;
static const int case_shorter_interval_left_endpoint_lower_threshold = 2;
static const int case_shorter_interval_left_endpoint_upper_threshold = 3;
static const int shorter_interval_tie_lower_threshold = -35;
static const int shorter_interval_tie_upper_threshold = -35;
static const int max_trailing_zeros = 7;
};
template <> struct float_info<double> {
using carrier_uint = uint64_t;
static const int exponent_bits = 11;
static const int min_exponent = -1022;
static const int max_exponent = 1023;
static const int exponent_bias = -1023;
static const int decimal_digits = 17;
static const int kappa = 2;
static const int big_divisor = 1000;
static const int small_divisor = 100;
static const int min_k = -292;
static const int max_k = 326;
static const int cache_bits = 128;
static const int divisibility_check_by_5_threshold = 86;
static const int case_fc_pm_half_lower_threshold = -2;
static const int case_shorter_interval_left_endpoint_lower_threshold = 2;
static const int case_shorter_interval_left_endpoint_upper_threshold = 3;
static const int shorter_interval_tie_lower_threshold = -77;
static const int shorter_interval_tie_upper_threshold = -77;
static const int max_trailing_zeros = 16;
};
// 80-bit extended precision long double.

18
test/format-impl-test.cc
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@ -226,15 +226,17 @@ TEST(fp_test, get_cached_power) {
TEST(fp_test, dragonbox_max_k) {
using fmt::detail::dragonbox::floor_log10_pow2;
using float_info = fmt::detail::dragonbox::float_info<float>;
EXPECT_EQ(fmt::detail::const_check(float_info::max_k),
float_info::kappa -
floor_log10_pow2(float_info::min_exponent -
fmt::detail::num_significand_bits<float>()));
EXPECT_EQ(
fmt::detail::const_check(float_info::max_k),
float_info::kappa -
floor_log10_pow2(std::numeric_limits<float>::min_exponent -
fmt::detail::num_significand_bits<float>() - 1));
using double_info = fmt::detail::dragonbox::float_info<double>;
EXPECT_EQ(fmt::detail::const_check(double_info::max_k),
double_info::kappa -
floor_log10_pow2(double_info::min_exponent -
fmt::detail::num_significand_bits<double>()));
EXPECT_EQ(
fmt::detail::const_check(double_info::max_k),
double_info::kappa -
floor_log10_pow2(std::numeric_limits<double>::min_exponent -
fmt::detail::num_significand_bits<double>() - 1));
}
TEST(fp_test, get_round_direction) {