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Optimize shortest float formatting

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This commit is contained in:
Victor Zverovich 2024-08-01 18:22:09 -07:00
parent 1db2274966
commit 8a06cee826
1 changed files with 12 additions and 14 deletions
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26
include/fmt/format.h
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@ -3194,16 +3194,6 @@ FMT_CONSTEXPR20 auto format_float(Float value, int precision,
exp = static_cast<int>(e);
if (e > exp) ++exp; // Compute ceil.
dragon_flags = dragon::fixup;
} else if (precision < 0) {
// Use Dragonbox for the shortest format.
if (binary32) {
auto dec = dragonbox::to_decimal(static_cast<float>(value));
write<char>(appender(buf), dec.significand);
return dec.exponent;
}
auto dec = dragonbox::to_decimal(static_cast<double>(value));
write<char>(appender(buf), dec.significand);
return dec.exponent;
} else {
// Extract significand bits and exponent bits.
using info = dragonbox::float_info<double>;
@ -3497,9 +3487,18 @@ FMT_CONSTEXPR20 auto write_float(OutputIt out, T value, format_specs specs,
specs);
}
int precision = specs.precision >= 0 || specs.type == presentation_type::none
? specs.precision
: 6;
int precision = specs.precision;
if (precision < 0) {
if (specs.type != presentation_type::none) {
precision = 6;
} else if (is_fast_float<T>::value && !is_constant_evaluated()) {
// Use Dragonbox for the shortest format.
using floaty = conditional_t<sizeof(T) >= sizeof(double), double, float>;
auto dec = dragonbox::to_decimal(static_cast<floaty>(value));
return write_float<Char>(out, dec, specs, sign, loc);
}
}
if (specs.type == presentation_type::exp) {
if (precision == max_value<int>())
report_error("number is too big");
@ -3511,7 +3510,6 @@ FMT_CONSTEXPR20 auto write_float(OutputIt out, T value, format_specs specs,
} else if (precision == 0) {
precision = 1;
}
int exp = format_float(convert_float(value), precision, specs,
std::is_same<T, float>(), buffer);