diff options
| author | Jonathan Wakely <jwakely@redhat.com> | 2020-10-30 15:14:33 +0000 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2020-10-30 20:58:08 +0000 |
| commit | a1343e5c74093124d7fbce6052d838f47a8eeb20 (patch) | |
| tree | e97bbf1e90e45518d94fd278478cf60bde60d08c | |
| parent | d1e5d82af819025df9d9a81e8c591690e299924a (diff) | |
| download | gcc-a1343e5c74093124d7fbce6052d838f47a8eeb20.zip gcc-a1343e5c74093124d7fbce6052d838f47a8eeb20.tar.gz gcc-a1343e5c74093124d7fbce6052d838f47a8eeb20.tar.bz2 | |
libstdc++: Use double for unordered container load factors [PR 96958]
These calculations were changed to use long double nearly ten years ago
in order to get more precision than float:
https://gcc.gnu.org/pipermail/libstdc++/2011-September/036420.html
However, double should be sufficient, whlie being potentially faster
than long double, and not requiring soft FP calculations for targets
without native long double support.
libstdc++-v3/ChangeLog:
PR libstdc++/96958
* include/bits/hashtable_policy.h (_Prime_rehash_policy)
(_Power2_rehash_policy): Use double instead of long double.
| -rw-r--r-- | libstdc++-v3/include/bits/hashtable_policy.h | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h index cea5e54..7fed87f 100644 --- a/libstdc++-v3/include/bits/hashtable_policy.h +++ b/libstdc++-v3/include/bits/hashtable_policy.h @@ -458,7 +458,7 @@ namespace __detail // Return a bucket count appropriate for n elements std::size_t _M_bkt_for_elements(std::size_t __n) const - { return __builtin_ceill(__n / (long double)_M_max_load_factor); } + { return __builtin_ceill(__n / (double)_M_max_load_factor); } // __n_bkt is current bucket count, __n_elt is current element count, // and __n_ins is number of elements to be inserted. Do we need to @@ -559,7 +559,7 @@ namespace __detail _M_next_resize = size_t(-1); else _M_next_resize - = __builtin_floorl(__res * (long double)_M_max_load_factor); + = __builtin_floorl(__res * (double)_M_max_load_factor); return __res; } @@ -567,7 +567,7 @@ namespace __detail // Return a bucket count appropriate for n elements std::size_t _M_bkt_for_elements(std::size_t __n) const noexcept - { return __builtin_ceill(__n / (long double)_M_max_load_factor); } + { return __builtin_ceill(__n / (double)_M_max_load_factor); } // __n_bkt is current bucket count, __n_elt is current element count, // and __n_ins is number of elements to be inserted. Do we need to @@ -582,16 +582,16 @@ namespace __detail // If _M_next_resize is 0 it means that we have nothing allocated so // far and that we start inserting elements. In this case we start // with an initial bucket size of 11. - long double __min_bkts + double __min_bkts = std::max<std::size_t>(__n_elt + __n_ins, _M_next_resize ? 0 : 11) - / (long double)_M_max_load_factor; + / (double)_M_max_load_factor; if (__min_bkts >= __n_bkt) return { true, _M_next_bkt(std::max<std::size_t>(__builtin_floorl(__min_bkts) + 1, __n_bkt * _S_growth_factor)) }; _M_next_resize - = __builtin_floorl(__n_bkt * (long double)_M_max_load_factor); + = __builtin_floorl(__n_bkt * (double)_M_max_load_factor); return { false, 0 }; } else |