organicmaps/fast_double_parser
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Trying something else.

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Daniel Lemire 2020-03-16 16:39:19 -04:00
parent f604da42a9
commit 9549ece6fc
1 changed files with 9 additions and 2 deletions
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11
include/fast_double_parser.h
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@ -1135,7 +1135,11 @@ really_inline double compute_float_64(int64_t power, uint64_t i, bool negative,
// We expect this next branch to be rarely taken (say 1% of the time).
// When (upper & 0x1FF) == 0x1FF, it can be common for
// lower + i < lower to be true (proba. much higher than 1%).
if (unlikely((upper & 0x1FF) == 0x1FF) && (lower + i < lower)) {
//
// There are cases where we *know* that factor_mantissa is
// exact, because 5**27 < 2**64
bool exact_mantissa = (power >= 0) && (power <= 27);
if (unlikely((!exact_mantissa) && ((upper & 0x1FF) == 0x1FF) && (lower + i < lower))) {
uint64_t factor_mantissa_low =
mantissa_128[power - FASTFLOAT_SMALLEST_POWER];
// next, we compute the 64-bit x 128-bit multiplication, getting a 192-bit
@ -1149,9 +1153,12 @@ really_inline double compute_float_64(int64_t power, uint64_t i, bool negative,
if (product_middle < product_middle1) {
product_high++; // overflow carry
}
// There are cases where we *know* that factor_mantissa is
// exact, because 5**55 < 2**128
exact_mantissa = (power >= 0) && (power <= 55);
// we want to check whether mantissa *i + i would affect our result
// This does happen, e.g. with 7.3177701707893310e+15
if (((product_middle + 1 == 0) && ((product_high & 0x1FF) == 0x1FF) &&
if (((!exact_mantissa) && (product_middle + 1 == 0) && ((product_high & 0x1FF) == 0x1FF) &&
(product_low + i < product_low))) { // let us be prudent and bail out.
*success = false;
return 0;