[PATCH] libstdc++/91223 Improve unordered containers == operator

[François Dumont]

On 1/13/20 10:53 PM, Jonathan Wakely wrote:
> On 13/01/20 22:41 +0100, François Dumont wrote:
>>
>> For the multi-keys we could still avoid redundant comparisons when 
>> _Equal is just doing == on the key type. On unordered_multiset we 
>> could just avoids the call to is_permuation and on the 
>> unordered_multimap we could check the is_permutation only on the 
>> associated value rather than on the std::pair.
>>
> I don't think that's necessary, or helpful.
>
> The idea of https://gcc.gnu.org/ml/libstdc++/2020-01/msg00070.html is
> that you shouldn't be using _Equal at all, and therefore it doesn't
> matter whether it's std::equal_to or not.
>
>
And it was indeed possible.

 Â Â Â  PR libstdc++/91223
 Â Â Â  * include/bits/hashtable.h (_Hashtable<>): Make _Equality<> friend.
 Â Â Â  * include/bits/hashtable_policy.h: Include <bits/stl_algo.h>.
 Â Â Â  (_Equality_base): Remove.
 Â Â Â  (_Equality<>::_M_equal): Review implementation. Use 
std::is_permutation.
 Â Â Â  * testsuite/23_containers/unordered_multiset/operators/1.cc
 Â Â Â  (Hash, Equal, test02, test03): New.
 Â Â Â  * testsuite/23_containers/unordered_set/operators/1.cc
 Â Â Â  (Hash, Equal, test02, test03): New.

Tested under Linux x86_64.

Ok to commit ?

François

-------------- next part --------------
A non-text attachment was scrubbed...
Name: pr91263.patch
Type: text/x-patch
Size: 10290 bytes
Desc: not available
URL: <http://gcc.gnu.org/pipermail/libstdc++/attachments/20200115/7b1b5d61/attachment.bin>