diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h index 2272518..f99371c 100644 --- a/include/fast_float/float_common.h +++ b/include/fast_float/float_common.h @@ -220,6 +220,50 @@ constexpr static double powers_of_ten_double[] = { 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19, 1e20, 1e21, 1e22}; constexpr static float powers_of_ten_float[] = {1e0, 1e1, 1e2, 1e3, 1e4, 1e5, 1e6, 1e7, 1e8, 1e9, 1e10}; +// used for max_mantissa_double and max_mantissa_float +constexpr uint64_t constant_55555 = 5 * 5 * 5 * 5 * 5; +// Largest integer value v so that (5**index * v) <= 1<<53. +// 0x10000000000000 == 1 << 53 +constexpr static uint64_t max_mantissa_double[] = { + 0x10000000000000, + 0x10000000000000 / 5, + 0x10000000000000 / (5 * 5), + 0x10000000000000 / (5 * 5 * 5), + 0x10000000000000 / (5 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555), + 0x10000000000000 / (constant_55555 * 5), + 0x10000000000000 / (constant_55555 * 5 * 5), + 0x10000000000000 / (constant_55555 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555 * 5 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555), + 0x10000000000000 / (constant_55555 * constant_55555 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * 5 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * constant_55555), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * constant_55555 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * constant_55555 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * constant_55555 * 5 * 5 * 5), + 0x10000000000000 / (constant_55555 * constant_55555 * constant_55555 * constant_55555 * 5 * 5 * 5 * 5)}; + // Largest integer value v so that (5**index * v) <= 1<<24. + // 0x1000000 == 1<<24 + constexpr static uint64_t max_mantissa_float[] = { + 0x1000000, + 0x1000000 / 5, + 0x1000000 / (5 * 5), + 0x1000000 / (5 * 5 * 5), + 0x1000000 / (5 * 5 * 5 * 5), + 0x1000000 / (constant_55555), + 0x1000000 / (constant_55555 * 5), + 0x1000000 / (constant_55555 * 5 * 5), + 0x1000000 / (constant_55555 * 5 * 5 * 5), + 0x1000000 / (constant_55555 * 5 * 5 * 5 * 5), + 0x1000000 / (constant_55555 * constant_55555), + 0x1000000 / (constant_55555 * constant_55555 * 5)}; template struct binary_format { using equiv_uint = typename std::conditional::type; @@ -228,11 +272,10 @@ template 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(); 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(); + static inline constexpr uint64_t max_mantissa_fast_path(int64_t power); 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); @@ -282,21 +325,6 @@ template <> inline constexpr int binary_format::infinite_power() { template <> inline constexpr int binary_format::sign_index() { return 63; } template <> inline constexpr int binary_format::sign_index() { return 31; } -template <> inline constexpr int binary_format::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::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::max_exponent_fast_path() { return 22; } @@ -304,11 +332,17 @@ template <> inline constexpr int binary_format::max_exponent_fast_path() return 10; } -template <> inline constexpr uint64_t binary_format::max_mantissa_fast_path() { - return uint64_t(2) << mantissa_explicit_bits(); +template <> inline constexpr uint64_t binary_format::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::max_mantissa_fast_path() { - return uint64_t(2) << mantissa_explicit_bits(); +template <> inline constexpr uint64_t binary_format::max_mantissa_fast_path(int64_t power) { + // caller is responsible to ensure that + // power >= 0 && power <= 10 + // + return max_mantissa_float[power]; } template <> diff --git a/include/fast_float/parse_number.h b/include/fast_float/parse_number.h index 62ae3b0..8789475 100644 --- a/include/fast_float/parse_number.h +++ b/include/fast_float/parse_number.h @@ -87,11 +87,10 @@ from_chars_result from_chars_advanced(const char *first, const char *last, } answer.ec = std::errc(); // be optimistic answer.ptr = pns.lastmatch; - // Next is Clinger's fast path. - if (binary_format::min_exponent_fast_path() <= pns.exponent && pns.exponent <= binary_format::max_exponent_fast_path() && pns.mantissa <=binary_format::max_mantissa_fast_path() && !pns.too_many_digits) { + // Next is a modified Clinger's fast path, inspired by Jakub Jelínek's proposal + if (pns.exponent >= 0 && pns.exponent <= binary_format::max_exponent_fast_path() && pns.mantissa <=binary_format::max_mantissa_fast_path(pns.exponent) && !pns.too_many_digits) { value = T(pns.mantissa); - if (pns.exponent < 0) { value = value / binary_format::exact_power_of_ten(-pns.exponent); } - else { value = value * binary_format::exact_power_of_ten(pns.exponent); } + value = value * binary_format::exact_power_of_ten(pns.exponent); if (pns.negative) { value = -value; } return answer; } diff --git a/include/fast_float/simple_decimal_conversion.h b/include/fast_float/simple_decimal_conversion.h index e878014..0484d74 100644 --- a/include/fast_float/simple_decimal_conversion.h +++ b/include/fast_float/simple_decimal_conversion.h @@ -137,7 +137,7 @@ inline uint64_t round(decimal &h) { } bool round_up = false; if (dp < h.num_digits) { - round_up = h.digits[dp] >= 5; // normally, we round up + round_up = h.digits[dp] >= 5; // normally, we round up // but we may need to round to even! if ((h.digits[dp] == 5) && (dp + 1 == h.num_digits)) { round_up = h.truncated || ((dp > 0) && (1 & h.digits[dp - 1])); @@ -266,7 +266,7 @@ adjusted_mantissa compute_float(decimal &d) { return answer; } else if(d.decimal_point >= 310) { // We have something at least as large as 0.1e310 which is - // always infinite. + // always infinite. answer.power2 = binary::infinite_power(); answer.mantissa = 0; return answer; diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt index 9704aa2..dfeec75 100644 --- a/tests/CMakeLists.txt +++ b/tests/CMakeLists.txt @@ -56,6 +56,8 @@ endfunction(fast_float_add_cpp_test) fast_float_add_cpp_test(example_test) fast_float_add_cpp_test(example_comma_test) fast_float_add_cpp_test(basictest) +target_compile_features(basictest PRIVATE cxx_std_17) + fast_float_add_cpp_test(long_test) fast_float_add_cpp_test(powersoffive_hardround) fast_float_add_cpp_test(string_test)