organicmaps/fast_double_parser
13
Fork 0
mirror of https://github.com/lemire/fast_double_parser.git synced 2025-04-03 20:04:57 +00:00
Code Issues 1 Projects Releases Wiki Activity Actions

Adding an explanation.

Browse source
This commit is contained in:
Daniel Lemire 2020-10-02 13:40:55 -04:00
parent 3224a04edb
commit ccbc8d2e97
1 changed files with 3 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
include/fast_double_parser.h
View file

@ -955,6 +955,9 @@ really_inline double compute_float_64(int64_t power, uint64_t i, bool negative,
// know that we have an exact computed value for the leading
// 55 bits because any imprecision would play out as a +1, in
// the worst case.
// Having 55 bits is necessary because
// we need 53 bits for the mantissa but we have to have one rounding bit and
// we can waste a bit if the most significant bit of the product is zero.
// 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%).