| Message ID | 88d3aa39-2146-3ea5-8bb2-a4d9b70accbd@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | None | expand |
On 17/11/19 22:31 +0100, François Dumont wrote: >This is an implementation of PR 68303. > >I try to use this idea as much as possible to avoid computation of >hash codes. > >Note that tests are not showing any gain. I guess hash computation >must be quite bad to get a benefit from it. So I am only activating it >when hash code is not cached and/or when computation is not fast. If the tests don't show any benefit, why bother making the change? Does it help the example in the PR? >   PR libstdc++/68303 >   * include/bits/hashtable_policy.h >   (_Small_size_threshold<_Hash>): New. >   (_Hashtable_traits<>): Add _Small_size_threshold std::size_t template >   parameter, default to 0. >   (_Hashtable_traits<>::__small_size_threshold): New. >   (_Hash_code_base<>::_M_hash_code(const __node_type*)): New. >   (_Equal_helper<>::_S_node_equals): New. >   * include/bits/hashtable.h: >   (__small_size_threshold_default<>): New template alias. >   (_Hashtable<>::find): Add linear lookup when size is lower or equal to >   _Small_size_threshold. >   (_Hashtable<>::_M_emplace<_Args>(true_type, _Args&&...)): Add linear >   lookup when size is lower or equal to _Small_size_threshold. >   (_Hashtable<>::_M_insert<>(_Arg&&, const _NodeGenerator&, true_type, >   size_type)): Likewise. >   (_Hashtable<>::_M_compute_hash_code(const_iterator, const key_type&)): >   New. >   (_Hashtable<>::_M_emplace<_Args>(false_type, _Args&&...)): Use latter. >   (_Hashtable<>::_M_insert(const_iterator, _Arg&&, const _NodeGenerator&, >   false_type)): Likewise. >   (_Hashtable<>::_M_find_before_node(const key_type&)): New. >   (_Hashtable<>::_M_erase(true_type, const key_type&)): Use latter >if size >   is lower or equal to _Small_size_threshold. >   (_Hashtable<>::_M_erase(false_type, const key_type&)): Likewise. >   * include/bits/unordered_map.h (__umaps_traits): Adapt using small size >   threshold set to 20. >   (__ummap_traits): Likewise. >   * include/bits/unordered_set.h (__uset_traits, __ummset_traits): >Likewise. >   * src/c++11/hashtable_c++0x.cc: Add <bits/functional_hash.h> include. The implementation of this seems unnecessarily complicated, and it changes the mangled name of the _Hashtable_traits type, which changes the mangled name of _Hashtable too. It seems to me that instead of __traits_type::__small_size_threshold being a typedef inside the traits class, we could just use a constexpr function, maybe as a member of the _Hashtable_traits class template: --- a/libstdc++-v3/include/bits/hashtable_policy.h +++ b/libstdc++-v3/include/bits/hashtable_policy.h @@ -201,6 +201,14 @@ namespace __detail using __hash_cached = __bool_constant<_Cache_hash_code>; using __constant_iterators = __bool_constant<_Constant_iterators>; using __unique_keys = __bool_constant<_Unique_keys>; + + template<typename _Hash> + static constexpr size_t + __small_size_threshold() + { + return _Cache_hash_code ? 0 + : __detail::_Small_size_threshold<_Hash>::value; + } }; Regarding the new _Small_size_threshold class template, do we really need yet another customization point? Can't we just use __is_fast_hash? e.g. return _Cache_hash_code || __is_fast_hash ? 0 : 20; As an aside, it seems like a terrible design that _Hashtable_traits doesn't actually depend on the hash function, so any time we want to extend it to detect some other property of the hash function we need to add extra template parameters. Far too late to fix now, but we can extend it by adding members, not by changing its type.
On 17/07/20 2:58 pm, Jonathan Wakely wrote: > On 17/11/19 22:31 +0100, François Dumont wrote: >> This is an implementation of PR 68303. >> >> I try to use this idea as much as possible to avoid computation of >> hash codes. >> >> Note that tests are not showing any gain. I guess hash computation >> must be quite bad to get a benefit from it. So I am only activating >> it when hash code is not cached and/or when computation is not fast. > > If the tests don't show any benefit, why bother making the change? I eventually managed to demonstrate this optimization through a performance test case. > > Does it help the example in the PR? No, the code attached to the PR just show what the user has done to put in place this optim on his side. What I needed was a slow hash code computation compared to the equal operation. I realized that I had to use longer string to achieve this. Moreover making this optim dependant on _Hashtable_traits::__hash_cached was just wrong as we cannot use the cached hash code here as the input is a key instance, not a node. I introduce _Hashtable_hash_traits<_Hash> to offer a single customization point as this optim depends highly on the difference between a hash code computation and a comparison. Maybe I should put it at std namespace scope to ease partial specialization ? Performance test results before the patch: unordered_small_size.cc std::unordered_set<int>: 1st insert 40r 32u 8s 264000112mem 0pf unordered_small_size.cc std::unordered_set<int>: find/erase 22r 22u 0s -191999808mem 0pf unordered_small_size.cc std::unordered_set<int>: 2nd insert 36r 36u 0s 191999776mem 0pf unordered_small_size.cc std::unordered_set<int>: erase key 25r 25u 0s -191999808mem 0pf unordered_small_size.cc std::unordered_set<string>: 1st insert 404r 244u 156s -1989936256mem 0pf unordered_small_size.cc std::unordered_set<string>: find/erase 315r 315u 0s 2061942272mem 0pf unordered_small_size.cc std::unordered_set<string>: 2nd insert 233r 233u 0s -2061942208mem 0pf unordered_small_size.cc std::unordered_set<string>: erase key 299r 298u 0s 2061942208mem 0pf after the patch: unordered_small_size.cc std::unordered_set<int>: 1st insert 41r 33u 7s 264000112mem 0pf unordered_small_size.cc std::unordered_set<int>: find/erase 24r 25u 1s -191999808mem 0pf unordered_small_size.cc std::unordered_set<int>: 2nd insert 34r 34u 0s 191999776mem 0pf unordered_small_size.cc std::unordered_set<int>: erase key 25r 25u 0s -191999808mem 0pf unordered_small_size.cc std::unordered_set<string>: 1st insert 399r 232u 165s -1989936256mem 0pf unordered_small_size.cc std::unordered_set<string>: find/erase 196r 197u 0s 2061942272mem 0pf unordered_small_size.cc std::unordered_set<string>: 2nd insert 221r 222u 0s -2061942208mem 0pf unordered_small_size.cc std::unordered_set<string>: erase key 178r 178u 0s 2061942208mem 0pf libstdc++: Optimize operations on small size hashtable [PR 68303] When hasher is identified as slow and the number of elements is limited in the container use a brute-force loop on those elements to look for a given key using the key_equal functor. For the moment the default threshold below which the container is considered as small is 20. libstdc++-v3/ChangeLog: PR libstdc++/68303 * include/bits/hashtable_policy.h (_Hashtable_hash_traits<_Hash>): New. (_Hash_code_base<>::_M_hash_code(const _Hash_node_value<>&)): New. (_Hashtable_base<>::_M_key_equals): New. (_Hashtable_base<>::_M_equals): Use latter. (_Hashtable_base<>::_M_key_equals_tr): New. (_Hashtable_base<>::_M_equals_tr): Use latter. * include/bits/hashtable.h (_Hashtable<>::__small_size_threshold()): New, use _Hashtable_hash_traits. (_Hashtable<>::find): Loop through elements to look for key if size is lower than __small_size_threshold(). (_Hashtable<>::_M_emplace(true_type, _Args&&...)): Likewise. (_Hashtable<>::_M_insert_unique(_Kt&&, _Args&&, const _NodeGenerator&)): Likewise. (_Hashtable<>::_M_compute_hash_code(const_iterator, const key_type&)): New. (_Hashtable<>::_M_emplace(const_iterator, false_type, _Args&&...)): Use latter. (_Hashtable<>::_M_find_before_node(const key_type&)): New. (_Hashtable<>::_M_erase(true_type, const key_type&)): Use latter. (_Hashtable<>::_M_erase(false_type, const key_type&)): Likewise. * src/c++11/hashtable_c++0x.cc: Include <bits/functional_hash.h>. * testsuite/util/testsuite_performane.h (report_performance): Use 9 width to display memory. * testsuite/performance/23_containers/insert_erase/unordered_small_size.cc: New performance test case. Tested under Linux x86_64. Ok to commit ? François
Ping ? On 16/08/21 9:03 pm, François Dumont wrote: > On 17/07/20 2:58 pm, Jonathan Wakely wrote: >> On 17/11/19 22:31 +0100, François Dumont wrote: >>> This is an implementation of PR 68303. >>> >>> I try to use this idea as much as possible to avoid computation of >>> hash codes. >>> >>> Note that tests are not showing any gain. I guess hash computation >>> must be quite bad to get a benefit from it. So I am only activating >>> it when hash code is not cached and/or when computation is not fast. >> >> If the tests don't show any benefit, why bother making the change? > > I eventually managed to demonstrate this optimization through a > performance test case. > >> >> Does it help the example in the PR? > > No, the code attached to the PR just show what the user has done to > put in place this optim on his side. > > What I needed was a slow hash code computation compared to the equal > operation. I realized that I had to use longer string to achieve this. > > Moreover making this optim dependant on > _Hashtable_traits::__hash_cached was just wrong as we cannot use the > cached hash code here as the input is a key instance, not a node. > > I introduce _Hashtable_hash_traits<_Hash> to offer a single > customization point as this optim depends highly on the difference > between a hash code computation and a comparison. Maybe I should put > it at std namespace scope to ease partial specialization ? > > Performance test results before the patch: > > unordered_small_size.cc std::unordered_set<int>: 1st insert > 40r 32u 8s 264000112mem 0pf > unordered_small_size.cc std::unordered_set<int>: find/erase > 22r 22u 0s -191999808mem 0pf > unordered_small_size.cc std::unordered_set<int>: 2nd insert > 36r 36u 0s 191999776mem 0pf > unordered_small_size.cc std::unordered_set<int>: erase key > 25r 25u 0s -191999808mem 0pf > unordered_small_size.cc std::unordered_set<string>: 1st insert > 404r 244u 156s -1989936256mem 0pf > unordered_small_size.cc std::unordered_set<string>: find/erase > 315r 315u 0s 2061942272mem 0pf > unordered_small_size.cc std::unordered_set<string>: 2nd insert > 233r 233u 0s -2061942208mem 0pf > unordered_small_size.cc std::unordered_set<string>: erase key > 299r 298u 0s 2061942208mem 0pf > > after the patch: > > unordered_small_size.cc std::unordered_set<int>: 1st insert > 41r 33u 7s 264000112mem 0pf > unordered_small_size.cc std::unordered_set<int>: find/erase > 24r 25u 1s -191999808mem 0pf > unordered_small_size.cc std::unordered_set<int>: 2nd insert > 34r 34u 0s 191999776mem 0pf > unordered_small_size.cc std::unordered_set<int>: erase key > 25r 25u 0s -191999808mem 0pf > unordered_small_size.cc std::unordered_set<string>: 1st insert > 399r 232u 165s -1989936256mem 0pf > unordered_small_size.cc std::unordered_set<string>: find/erase > 196r 197u 0s 2061942272mem 0pf > unordered_small_size.cc std::unordered_set<string>: 2nd insert > 221r 222u 0s -2061942208mem 0pf > unordered_small_size.cc std::unordered_set<string>: erase key > 178r 178u 0s 2061942208mem 0pf > > libstdc++: Optimize operations on small size hashtable [PR 68303] > > When hasher is identified as slow and the number of elements is > limited in the > container use a brute-force loop on those elements to look for a > given key using > the key_equal functor. For the moment the default threshold below > which the > container is considered as small is 20. > > libstdc++-v3/ChangeLog: > > PR libstdc++/68303 > * include/bits/hashtable_policy.h > (_Hashtable_hash_traits<_Hash>): New. > (_Hash_code_base<>::_M_hash_code(const > _Hash_node_value<>&)): New. > (_Hashtable_base<>::_M_key_equals): New. > (_Hashtable_base<>::_M_equals): Use latter. > (_Hashtable_base<>::_M_key_equals_tr): New. > (_Hashtable_base<>::_M_equals_tr): Use latter. > * include/bits/hashtable.h > (_Hashtable<>::__small_size_threshold()): New, use > _Hashtable_hash_traits. > (_Hashtable<>::find): Loop through elements to look for > key if size is lower > than __small_size_threshold(). > (_Hashtable<>::_M_emplace(true_type, _Args&&...)): Likewise. > (_Hashtable<>::_M_insert_unique(_Kt&&, _Args&&, const > _NodeGenerator&)): Likewise. > (_Hashtable<>::_M_compute_hash_code(const_iterator, const key_type&)): > New. > (_Hashtable<>::_M_emplace(const_iterator, false_type, > _Args&&...)): Use latter. > (_Hashtable<>::_M_find_before_node(const key_type&)): New. > (_Hashtable<>::_M_erase(true_type, const key_type&)): Use > latter. > (_Hashtable<>::_M_erase(false_type, const key_type&)): > Likewise. > * src/c++11/hashtable_c++0x.cc: Include > <bits/functional_hash.h>. > * testsuite/util/testsuite_performane.h > (report_performance): Use 9 width to display memory. > * > testsuite/performance/23_containers/insert_erase/unordered_small_size.cc: > New performance test case. > > Tested under Linux x86_64. > > Ok to commit ? > > François >
Hi Is there a chance for this patch to be integrated for next gcc release ? François On 23/09/21 6:36 am, François Dumont wrote: > Ping ? > > On 16/08/21 9:03 pm, François Dumont wrote: >> On 17/07/20 2:58 pm, Jonathan Wakely wrote: >>> On 17/11/19 22:31 +0100, François Dumont wrote: >>>> This is an implementation of PR 68303. >>>> >>>> I try to use this idea as much as possible to avoid computation of >>>> hash codes. >>>> >>>> Note that tests are not showing any gain. I guess hash computation >>>> must be quite bad to get a benefit from it. So I am only activating >>>> it when hash code is not cached and/or when computation is not fast. >>> >>> If the tests don't show any benefit, why bother making the change? >> >> I eventually managed to demonstrate this optimization through a >> performance test case. >> >>> >>> Does it help the example in the PR? >> >> No, the code attached to the PR just show what the user has done to >> put in place this optim on his side. >> >> What I needed was a slow hash code computation compared to the equal >> operation. I realized that I had to use longer string to achieve this. >> >> Moreover making this optim dependant on >> _Hashtable_traits::__hash_cached was just wrong as we cannot use the >> cached hash code here as the input is a key instance, not a node. >> >> I introduce _Hashtable_hash_traits<_Hash> to offer a single >> customization point as this optim depends highly on the difference >> between a hash code computation and a comparison. Maybe I should put >> it at std namespace scope to ease partial specialization ? >> >> Performance test results before the patch: >> >> unordered_small_size.cc std::unordered_set<int>: 1st insert >> 40r 32u 8s 264000112mem 0pf >> unordered_small_size.cc std::unordered_set<int>: find/erase >> 22r 22u 0s -191999808mem 0pf >> unordered_small_size.cc std::unordered_set<int>: 2nd insert >> 36r 36u 0s 191999776mem 0pf >> unordered_small_size.cc std::unordered_set<int>: erase key >> 25r 25u 0s -191999808mem 0pf >> unordered_small_size.cc std::unordered_set<string>: 1st >> insert 404r 244u 156s -1989936256mem 0pf >> unordered_small_size.cc std::unordered_set<string>: >> find/erase 315r 315u 0s 2061942272mem 0pf >> unordered_small_size.cc std::unordered_set<string>: 2nd >> insert 233r 233u 0s -2061942208mem 0pf >> unordered_small_size.cc std::unordered_set<string>: erase key >> 299r 298u 0s 2061942208mem 0pf >> >> after the patch: >> >> unordered_small_size.cc std::unordered_set<int>: 1st insert >> 41r 33u 7s 264000112mem 0pf >> unordered_small_size.cc std::unordered_set<int>: find/erase >> 24r 25u 1s -191999808mem 0pf >> unordered_small_size.cc std::unordered_set<int>: 2nd insert >> 34r 34u 0s 191999776mem 0pf >> unordered_small_size.cc std::unordered_set<int>: erase key >> 25r 25u 0s -191999808mem 0pf >> unordered_small_size.cc std::unordered_set<string>: 1st >> insert 399r 232u 165s -1989936256mem 0pf >> unordered_small_size.cc std::unordered_set<string>: >> find/erase 196r 197u 0s 2061942272mem 0pf >> unordered_small_size.cc std::unordered_set<string>: 2nd >> insert 221r 222u 0s -2061942208mem 0pf >> unordered_small_size.cc std::unordered_set<string>: erase key >> 178r 178u 0s 2061942208mem 0pf >> >> libstdc++: Optimize operations on small size hashtable [PR 68303] >> >> When hasher is identified as slow and the number of elements is >> limited in the >> container use a brute-force loop on those elements to look for a >> given key using >> the key_equal functor. For the moment the default threshold below >> which the >> container is considered as small is 20. >> >> libstdc++-v3/ChangeLog: >> >> PR libstdc++/68303 >> * include/bits/hashtable_policy.h >> (_Hashtable_hash_traits<_Hash>): New. >> (_Hash_code_base<>::_M_hash_code(const >> _Hash_node_value<>&)): New. >> (_Hashtable_base<>::_M_key_equals): New. >> (_Hashtable_base<>::_M_equals): Use latter. >> (_Hashtable_base<>::_M_key_equals_tr): New. >> (_Hashtable_base<>::_M_equals_tr): Use latter. >> * include/bits/hashtable.h >> (_Hashtable<>::__small_size_threshold()): New, use >> _Hashtable_hash_traits. >> (_Hashtable<>::find): Loop through elements to look for >> key if size is lower >> than __small_size_threshold(). >> (_Hashtable<>::_M_emplace(true_type, _Args&&...)): Likewise. >> (_Hashtable<>::_M_insert_unique(_Kt&&, _Args&&, const >> _NodeGenerator&)): Likewise. >> (_Hashtable<>::_M_compute_hash_code(const_iterator, const >> key_type&)): New. >> (_Hashtable<>::_M_emplace(const_iterator, false_type, >> _Args&&...)): Use latter. >> (_Hashtable<>::_M_find_before_node(const key_type&)): New. >> (_Hashtable<>::_M_erase(true_type, const key_type&)): Use >> latter. >> (_Hashtable<>::_M_erase(false_type, const key_type&)): >> Likewise. >> * src/c++11/hashtable_c++0x.cc: Include >> <bits/functional_hash.h>. >> * testsuite/util/testsuite_performane.h >> (report_performance): Use 9 width to display memory. >> * >> testsuite/performance/23_containers/insert_erase/unordered_small_size.cc: >> New performance test case. >> >> Tested under Linux x86_64. >> >> Ok to commit ? >> >> François >> >
Am Di., 21. Dez. 2021 um 07:08 Uhr schrieb François Dumont via Libstdc++ <libstdc++@gcc.gnu.org>: > > Hi > > Is there a chance for this patch to be integrated for next gcc > release ? > > François > No counterargument for the acceptance, but: Shouldn't __small_size_threshold() be a noexcept function? - Daniel
On 21/12/21 7:28 am, Daniel Krügler wrote: > Am Di., 21. Dez. 2021 um 07:08 Uhr schrieb François Dumont via > Libstdc++ <libstdc++@gcc.gnu.org>: >> Hi >> >> Is there a chance for this patch to be integrated for next gcc >> release ? >> >> François >> > No counterargument for the acceptance, but: Shouldn't > __small_size_threshold() be a noexcept function? > > - Daniel Could it enhance code generation ? I could make it depends on _Hashtable_hash_traits<>::__small_size_threshold() noexcept qualification if so. But I was hoping that the compiler to detect all that itself. Otherwise no, it do not have to be noexcept as it is used to avoid hasher invocation in some situations and hasher is not noexcept constraint. At least I do not need to static_assert this.
On Tue, 21 Dec 2021 at 17:56, François Dumont via Libstdc++ < libstdc++@gcc.gnu.org> wrote: > On 21/12/21 7:28 am, Daniel Krügler wrote: > > Am Di., 21. Dez. 2021 um 07:08 Uhr schrieb François Dumont via > > Libstdc++ <libstdc++@gcc.gnu.org>: > >> Hi > >> > >> Is there a chance for this patch to be integrated for next gcc > >> release ? > >> > >> François > >> > > No counterargument for the acceptance, but: Shouldn't > > __small_size_threshold() be a noexcept function? > > > > - Daniel > > Could it enhance code generation ? I could make it depends on > _Hashtable_hash_traits<>::__small_size_threshold() noexcept > qualification if so. But I was hoping that the compiler to detect all > that itself. > > Otherwise no, it do not have to be noexcept as it is used to avoid > hasher invocation in some situations and hasher is not noexcept > constraint. At least I do not need to static_assert this. > > But why not make it noexcept? It just returns a constant integer. It can be noexcept.
On 23/12/21 2:03 pm, Jonathan Wakely wrote: > On 21/12/21 07:07 +0100, François Dumont wrote: >> Hi >> >> ??? Is there a chance for this patch to be integrated for next gcc >> release ? > > Yes, I think this can still make it for GCC 12 (the patch was first > posted long ago in stage 1 and it's just me being slow to review it). > > But I have some questions and comments ... > > >> diff --git a/libstdc++-v3/include/bits/hashtable.h >> b/libstdc++-v3/include/bits/hashtable.h >> index 6e2d4c10cfe..6b2c6b99fef 100644 >> --- a/libstdc++-v3/include/bits/hashtable.h >> +++ b/libstdc++-v3/include/bits/hashtable.h >> @@ -419,6 +419,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> _M_uses_single_bucket() const >> { return _M_uses_single_bucket(_M_buckets); } >> >> + static constexpr size_t >> + __small_size_threshold() >> + { >> + return >> + __detail::_Hashtable_hash_traits<_Hash>::__small_size_threshold(); >> + } >> + I've added the noexcept qualification as you asked. >> __hashtable_alloc& >> _M_base_alloc() { return *this; } >> >> @@ -788,6 +795,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> _M_bucket_index(__hash_code __c) const >> { return __hash_code_base::_M_bucket_index(__c, >> _M_bucket_count); } >> >> + __node_base_ptr >> + _M_find_before_node(const key_type&); >> + >> // Find and insert helper functions and types >> // Find the node before the one matching the criteria. >> __node_base_ptr >> @@ -831,6 +841,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> __node_base_ptr >> _M_get_previous_node(size_type __bkt, __node_ptr __n); >> >> + pair<const_iterator, __hash_code> >> + _M_compute_hash_code(const_iterator __hint, const key_type& >> __k) const; >> + >> // Insert node __n with hash code __code, in bucket __bkt if no >> // rehash (assumes no element with same key already present). >> // Takes ownership of __n if insertion succeeds, throws otherwise. >> @@ -1126,7 +1139,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> void _M_rehash(size_type __bkt_count, const __rehash_state& >> __state); >> }; >> >> - >> // Definitions of class template _Hashtable's out-of-line member >> functions. >> template<typename _Key, typename _Value, typename _Alloc, >> typename _ExtractKey, typename _Equal, >> @@ -1628,6 +1640,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> find(const key_type& __k) >> -> iterator >> { >> + if (size() <= __small_size_threshold()) >> + { >> + for (auto __it = begin(); __it != end(); ++__it) >> + if (this->_M_key_equals(__k, *__it._M_cur)) >> + return __it; >> + return end(); >> + } > > This loop is repeated a few times, would it be better factored out > into its own function? _M_find_loop or something? The return type is > different in some cases, so maybe it's OK like this. Yes, I also thought about that but there is often small changes from one loop to another as you noticed. > > > >> + >> __hash_code __code = this->_M_hash_code(__k); >> std::size_t __bkt = _M_bucket_index(__code); >> return iterator(_M_find_node(__bkt, __k, __code)); >> @@ -1643,6 +1663,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> find(const key_type& __k) const >> -> const_iterator >> { >> + if (size() <= __small_size_threshold()) >> + { >> + for (auto __it = begin(); __it != end(); ++__it) >> + if (this->_M_key_equals(__k, *__it._M_cur)) >> + return __it; >> + return end(); >> + } >> + >> __hash_code __code = this->_M_hash_code(__k); >> std::size_t __bkt = _M_bucket_index(__code); >> return const_iterator(_M_find_node(__bkt, __k, __code)); >> @@ -1855,6 +1883,35 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION >> } >> #endif >> >> + // Find the node before the one whose key compares equal to k. >> + // Return nullptr if no node is found. >> + template<typename _Key, typename _Value, typename _Alloc, >> + typename _ExtractKey, typename _Equal, >> + typename _Hash, typename _RangeHash, typename _Unused, >> + typename _RehashPolicy, typename _Traits> >> + auto >> + _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, >> + _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>:: >> + _M_find_before_node(const key_type& __k) >> + -> __node_base_ptr >> + { >> + __node_base_ptr __prev_p = &_M_before_begin; > > This is OK now, but would need to be std::__addressof(_M_before_begin) > if/when the _Hash_code_base type becomes dependent on the allocator's > pointer. Yes, maybe after gcc release we will talk about those fancy pointer types again. > > __n_last = __n_last->_M_next(); >> diff --git a/libstdc++-v3/include/bits/hashtable_policy.h >> b/libstdc++-v3/include/bits/hashtable_policy.h >> index 0b5443fc187..b4a8af081ce 100644 >> --- a/libstdc++-v3/include/bits/hashtable_policy.h >> +++ b/libstdc++-v3/include/bits/hashtable_policy.h >> @@ -246,6 +246,20 @@ namespace __detail >> using __unique_keys = __bool_constant<_Unique_keys>; >> }; >> >> + /** >> + * struct _Hashtable_hash_traits >> + * >> + * Important traits for hash tables depending on associated hasher. >> + * >> + */ >> + template<typename _Hash> >> + struct _Hashtable_hash_traits >> + { >> + static constexpr std::size_t >> + __small_size_threshold() >> + { return std::__is_fast_hash<_Hash>::value ? 0 : 20; } >> + }; > > Yet another trait that nobody is ever going to specialize make me sad. > I don't have a better idea though. Sure, but maybe I can document it ? I also wonder why you did not propose to make it a constant rather than requesting to add the noexcept. > > { >> @@ -1263,6 +1279,14 @@ namespace __detail >> const _Hash_node_value<_Value, __cache_hash_code>& __n) const >> { return _M_hash_code(_ExtractKey{}(__n._M_v())); } >> >> + __hash_code >> + _M_hash_code(const _Hash_node_value<_Value, false>& __n) const >> + { return _M_hash_code(_ExtractKey{}(__n._M_v())); } >> + >> + __hash_code >> + _M_hash_code(const _Hash_node_value<_Value, true>& __n) const >> + { return __n._M_hash_code; } >> + >> std::size_t >> _M_bucket_index(__hash_code __c, std::size_t __bkt_count) const >> { return _RangeHash{}(__c, __bkt_count); } >> @@ -1273,17 +1297,14 @@ namespace __detail >> noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>())) >> && noexcept(declval<const _RangeHash&>()((__hash_code)0, >> (std::size_t)0)) ) >> - { >> - return _RangeHash{}(_M_hash_code(_ExtractKey{}(__n._M_v())), >> - __bkt_count); >> - } >> + { return _M_bucket_index(_M_hash_code(__n), __bkt_count); } > > Why add this extra level of indirection (and overload resolution)? > > We know this is a _Hash_node_value<V, false>, why call _M_hash_code to > decide how to get the hash code for it? Just to avoid code duplication but indeed it introduces overload resolution so I reverted it. > > >> diff --git a/libstdc++-v3/testsuite/util/testsuite_performance.h >> b/libstdc++-v3/testsuite/util/testsuite_performance.h >> index cba3a0d4b17..4ca15ab0e71 100644 >> --- a/libstdc++-v3/testsuite/util/testsuite_performance.h >> +++ b/libstdc++-v3/testsuite/util/testsuite_performance.h >> @@ -239,7 +239,7 @@ namespace __gnu_test >> out << std::setw(4) << t.real_time() << "r" << space; >> out << std::setw(4) << t.user_time() << "u" << space; >> out << std::setw(4) << t.system_time() << "s" << space; >> - out << std::setw(8) << r.allocated_memory() << "mem" << space; >> + out << std::setw(9) << r.allocated_memory() << "mem" << space; > > One day I need to figure out why the reported memory is garbage so > often Ok with those changes ? François
On Sat, 25 Dec 2021 at 21:39, François Dumont <frs.dumont@gmail.com> wrote: > On 23/12/21 2:03 pm, Jonathan Wakely wrote: > > On 21/12/21 07:07 +0100, François Dumont wrote: > >> Hi > >> > >> ??? Is there a chance for this patch to be integrated for next gcc > >> release ? > > > > Yes, I think this can still make it for GCC 12 (the patch was first > > posted long ago in stage 1 and it's just me being slow to review it). > > > > But I have some questions and comments ... > > > > > >> diff --git a/libstdc++-v3/include/bits/hashtable.h > >> b/libstdc++-v3/include/bits/hashtable.h > >> index 6e2d4c10cfe..6b2c6b99fef 100644 > >> --- a/libstdc++-v3/include/bits/hashtable.h > >> +++ b/libstdc++-v3/include/bits/hashtable.h > >> @@ -419,6 +419,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> _M_uses_single_bucket() const > >> { return _M_uses_single_bucket(_M_buckets); } > >> > >> + static constexpr size_t > >> + __small_size_threshold() > >> + { > >> + return > >> + __detail::_Hashtable_hash_traits<_Hash>::__small_size_threshold(); > >> + } > >> + > I've added the noexcept qualification as you asked. > >> __hashtable_alloc& > >> _M_base_alloc() { return *this; } > >> > >> @@ -788,6 +795,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> _M_bucket_index(__hash_code __c) const > >> { return __hash_code_base::_M_bucket_index(__c, > >> _M_bucket_count); } > >> > >> + __node_base_ptr > >> + _M_find_before_node(const key_type&); > >> + > >> // Find and insert helper functions and types > >> // Find the node before the one matching the criteria. > >> __node_base_ptr > >> @@ -831,6 +841,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> __node_base_ptr > >> _M_get_previous_node(size_type __bkt, __node_ptr __n); > >> > >> + pair<const_iterator, __hash_code> > >> + _M_compute_hash_code(const_iterator __hint, const key_type& > >> __k) const; > >> + > >> // Insert node __n with hash code __code, in bucket __bkt if no > >> // rehash (assumes no element with same key already present). > >> // Takes ownership of __n if insertion succeeds, throws otherwise. > >> @@ -1126,7 +1139,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> void _M_rehash(size_type __bkt_count, const __rehash_state& > >> __state); > >> }; > >> > >> - > >> // Definitions of class template _Hashtable's out-of-line member > >> functions. > >> template<typename _Key, typename _Value, typename _Alloc, > >> typename _ExtractKey, typename _Equal, > >> @@ -1628,6 +1640,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> find(const key_type& __k) > >> -> iterator > >> { > >> + if (size() <= __small_size_threshold()) > >> + { > >> + for (auto __it = begin(); __it != end(); ++__it) > >> + if (this->_M_key_equals(__k, *__it._M_cur)) > >> + return __it; > >> + return end(); > >> + } > > > > This loop is repeated a few times, would it be better factored out > > into its own function? _M_find_loop or something? The return type is > > different in some cases, so maybe it's OK like this. > Yes, I also thought about that but there is often small changes from one > loop to another as you noticed. > > > > > > > >> + > >> __hash_code __code = this->_M_hash_code(__k); > >> std::size_t __bkt = _M_bucket_index(__code); > >> return iterator(_M_find_node(__bkt, __k, __code)); > >> @@ -1643,6 +1663,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> find(const key_type& __k) const > >> -> const_iterator > >> { > >> + if (size() <= __small_size_threshold()) > >> + { > >> + for (auto __it = begin(); __it != end(); ++__it) > >> + if (this->_M_key_equals(__k, *__it._M_cur)) > >> + return __it; > >> + return end(); > >> + } > >> + > >> __hash_code __code = this->_M_hash_code(__k); > >> std::size_t __bkt = _M_bucket_index(__code); > >> return const_iterator(_M_find_node(__bkt, __k, __code)); > >> @@ -1855,6 +1883,35 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > >> } > >> #endif > >> > >> + // Find the node before the one whose key compares equal to k. > >> + // Return nullptr if no node is found. > >> + template<typename _Key, typename _Value, typename _Alloc, > >> + typename _ExtractKey, typename _Equal, > >> + typename _Hash, typename _RangeHash, typename _Unused, > >> + typename _RehashPolicy, typename _Traits> > >> + auto > >> + _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, > >> + _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>:: > >> + _M_find_before_node(const key_type& __k) > >> + -> __node_base_ptr > >> + { > >> + __node_base_ptr __prev_p = &_M_before_begin; > > > > This is OK now, but would need to be std::__addressof(_M_before_begin) > > if/when the _Hash_code_base type becomes dependent on the allocator's > > pointer. > Yes, maybe after gcc release we will talk about those fancy pointer > types again. > > > > __n_last = __n_last->_M_next(); > >> diff --git a/libstdc++-v3/include/bits/hashtable_policy.h > >> b/libstdc++-v3/include/bits/hashtable_policy.h > >> index 0b5443fc187..b4a8af081ce 100644 > >> --- a/libstdc++-v3/include/bits/hashtable_policy.h > >> +++ b/libstdc++-v3/include/bits/hashtable_policy.h > >> @@ -246,6 +246,20 @@ namespace __detail > >> using __unique_keys = __bool_constant<_Unique_keys>; > >> }; > >> > >> + /** > >> + * struct _Hashtable_hash_traits > >> + * > >> + * Important traits for hash tables depending on associated hasher. > >> + * > >> + */ > >> + template<typename _Hash> > >> + struct _Hashtable_hash_traits > >> + { > >> + static constexpr std::size_t > >> + __small_size_threshold() > >> + { return std::__is_fast_hash<_Hash>::value ? 0 : 20; } > >> + }; > > > > Yet another trait that nobody is ever going to specialize make me sad. > > I don't have a better idea though. > > Sure, but maybe I can document it ? > > I also wonder why you did not propose to make it a constant rather than > requesting to add the noexcept. > > > > > { > >> @@ -1263,6 +1279,14 @@ namespace __detail > >> const _Hash_node_value<_Value, __cache_hash_code>& __n) const > >> { return _M_hash_code(_ExtractKey{}(__n._M_v())); } > >> > >> + __hash_code > >> + _M_hash_code(const _Hash_node_value<_Value, false>& __n) const > >> + { return _M_hash_code(_ExtractKey{}(__n._M_v())); } > >> + > >> + __hash_code > >> + _M_hash_code(const _Hash_node_value<_Value, true>& __n) const > >> + { return __n._M_hash_code; } > >> + > >> std::size_t > >> _M_bucket_index(__hash_code __c, std::size_t __bkt_count) const > >> { return _RangeHash{}(__c, __bkt_count); } > >> @@ -1273,17 +1297,14 @@ namespace __detail > >> noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>())) > >> && noexcept(declval<const _RangeHash&>()((__hash_code)0, > >> (std::size_t)0)) ) > >> - { > >> - return _RangeHash{}(_M_hash_code(_ExtractKey{}(__n._M_v())), > >> - __bkt_count); > >> - } > >> + { return _M_bucket_index(_M_hash_code(__n), __bkt_count); } > > > > Why add this extra level of indirection (and overload resolution)? > > > > We know this is a _Hash_node_value<V, false>, why call _M_hash_code to > > decide how to get the hash code for it? > > Just to avoid code duplication but indeed it introduces overload > resolution so I reverted it. > > > > > > >> diff --git a/libstdc++-v3/testsuite/util/testsuite_performance.h > >> b/libstdc++-v3/testsuite/util/testsuite_performance.h > >> index cba3a0d4b17..4ca15ab0e71 100644 > >> --- a/libstdc++-v3/testsuite/util/testsuite_performance.h > >> +++ b/libstdc++-v3/testsuite/util/testsuite_performance.h > >> @@ -239,7 +239,7 @@ namespace __gnu_test > >> out << std::setw(4) << t.real_time() << "r" << space; > >> out << std::setw(4) << t.user_time() << "u" << space; > >> out << std::setw(4) << t.system_time() << "s" << space; > >> - out << std::setw(8) << r.allocated_memory() << "mem" << space; > >> + out << std::setw(9) << r.allocated_memory() << "mem" << space; > > > > One day I need to figure out why the reported memory is garbage so > > often > > > Ok with those changes ? > > Yes, thanks very much (and bonne année).
diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h index 9dadc62e328..460f25affe4 100644 --- a/libstdc++-v3/include/bits/hashtable.h +++ b/libstdc++-v3/include/bits/hashtable.h @@ -48,6 +48,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Mandatory to have erase not throwing. __is_nothrow_invocable<const _Hash&, const _Tp&>>>; + template<bool __cache, typename _Hash> + using __small_size_threshold_default + = typename conditional<__cache, + // No small size optimization if hash code is cached... + integral_constant<int, 0>, + _Small_size_threshold<_Hash>>::type; /** * Primary class template _Hashtable. * @@ -743,6 +749,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __node_base* _M_find_before_node(size_type, const key_type&, __hash_code) const; + __node_base* + _M_find_before_node(const key_type&); + __node_type* _M_find_node(size_type __bkt, const key_type& __key, __hash_code __c) const @@ -766,6 +775,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __node_base* _M_get_previous_node(size_type __bkt, __node_base* __n); + pair<const_iterator, __hash_code> + _M_compute_hash_code(const_iterator __hint, const key_type& __k) const; + // Insert node __n with hash code __code, in bucket __bkt if no // rehash (assumes no element with same key already present). // Takes ownership of __n if insertion succeeds, throws otherwise. @@ -1490,6 +1502,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION find(const key_type& __k) -> iterator { + if (size() <= __traits_type::__small_size_threshold::value) + { + for (auto __it = begin(); __it != end(); ++__it) + if (this->_M_key_equals(__k, __it._M_cur)) + return __it; + return end(); + } + __hash_code __code = this->_M_hash_code(__k); std::size_t __bkt = _M_bucket_index(__code); return iterator(_M_find_node(__bkt, __k, __code)); @@ -1504,6 +1524,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION find(const key_type& __k) const -> const_iterator { + if (size() <= __traits_type::__small_size_threshold::value) + { + for (auto __it = begin(); __it != end(); ++__it) + if (this->_M_key_equals(__k, __it._M_cur)) + return __it; + return end(); + } + __hash_code __code = this->_M_hash_code(__k); std::size_t __bkt = _M_bucket_index(__code); return const_iterator(_M_find_node(__bkt, __k, __code)); @@ -1619,6 +1647,34 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION return nullptr; } + // Find the node before the one whose key compares equal to k. + // Return nullptr if no node is found. + template<typename _Key, typename _Value, + typename _Alloc, typename _ExtractKey, typename _Equal, + typename _Hash, typename _RehashPolicy, typename _Traits> + auto + _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, + _Hash, _RehashPolicy, _Traits>:: + _M_find_before_node(const key_type& __k) + -> __node_base* + { + __node_base* __prev_p = &_M_before_begin; + if (!__prev_p->_M_nxt) + return nullptr; + + for (__node_type* __p = static_cast<__node_type*>(__prev_p->_M_nxt); + __p != nullptr; + __p = __p->_M_next()) + { + if (this->_M_key_equals(__k, __p)) + return __prev_p; + + __prev_p = __p; + } + + return nullptr; + } + template<typename _Key, typename _Value, typename _Alloc, typename _ExtractKey, typename _Equal, typename _Hash, typename _RehashPolicy, typename _Traits> @@ -1702,11 +1758,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // First build the node to get access to the hash code _Scoped_node __node { this, std::forward<_Args>(__args)... }; const key_type& __k = this->_M_extract()(__node._M_node->_M_v()); + if (size() <= __traits_type::__small_size_threshold::value) + { + for (auto __it = begin(); __it != end(); ++__it) + if (this->_M_key_equals(__k, __it._M_cur)) + // There is already an equivalent node, no insertion + return { __it, false }; + } + __hash_code __code = this->_M_hash_code(__k); size_type __bkt = _M_bucket_index(__code); - if (__node_type* __p = _M_find_node(__bkt, __k, __code)) - // There is already an equivalent node, no insertion - return std::make_pair(iterator(__p), false); + if (size() > __traits_type::__small_size_threshold::value) + if (__node_type* __p = _M_find_node(__bkt, __k, __code)) + // There is already an equivalent node, no insertion + return { iterator(__p), false }; // Insert the node auto __pos = _M_insert_node(__uks, __bkt, __code, __node._M_node); @@ -1728,13 +1793,40 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _Scoped_node __node { this, std::forward<_Args>(__args)... }; const key_type& __k = this->_M_extract()(__node._M_node->_M_v()); - __hash_code __code = this->_M_hash_code(__k); + auto __res = this->_M_compute_hash_code(__hint, __k); auto __pos - = _M_insert_node(__mks, __hint._M_cur, __code, __node._M_node); + = _M_insert_node(__mks, __res.first._M_cur, __res.second, + __node._M_node); __node._M_node = nullptr; return __pos; } + template<typename _Key, typename _Value, + typename _Alloc, typename _ExtractKey, typename _Equal, + typename _Hash, typename _RehashPolicy, typename _Traits> + auto + _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, + _Hash, _RehashPolicy, _Traits>:: + _M_compute_hash_code(const_iterator __hint, const key_type& __k) const + -> pair<const_iterator, __hash_code> + { + if (size() <= __traits_type::__small_size_threshold::value) + { + if (__hint != cend()) + { + for (auto __it = __hint; __it != cend(); ++__it) + if (this->_M_key_equals(__k, __it._M_cur)) + return { __it, this->_M_hash_code(__it._M_cur) }; + } + + for (auto __it = cbegin(); __it != __hint; ++__it) + if (this->_M_key_equals(__k, __it._M_cur)) + return { __it, this->_M_hash_code(__it._M_cur) }; + } + + return { __hint, this->_M_hash_code(__k) }; + } + template<typename _Key, typename _Value, typename _Alloc, typename _ExtractKey, typename _Equal, typename _Hash, typename _RehashPolicy, typename _Traits> @@ -1830,11 +1922,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION -> pair<iterator, bool> { const key_type& __k = this->_M_extract()(__v); + + if (size() <= __traits_type::__small_size_threshold::value) + for (auto __it = begin(); __it != end(); ++__it) + if (this->_M_key_equals(__k, __it._M_cur)) + return { __it, false }; + __hash_code __code = this->_M_hash_code(__k); size_type __bkt = _M_bucket_index(__code); - if (__node_type* __node = _M_find_node(__bkt, __k, __code)) - return { iterator(__node), false }; + if (size() > __traits_type::__small_size_threshold::value) + if (__node_type* __node = _M_find_node(__bkt, __k, __code)) + return { iterator(__node), false }; _Scoped_node __node{ __node_gen(std::forward<_Arg>(__v)), this }; auto __pos = _M_insert_node(__uks, __bkt, __code, __node._M_node); @@ -1856,13 +1955,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { // First compute the hash code so that we don't do anything if it // throws. - __hash_code __code = this->_M_hash_code(this->_M_extract()(__v)); + auto __res + = this->_M_compute_hash_code(__hint, this->_M_extract()(__v)); // Second allocate new node so that we don't rehash if it throws. _Scoped_node __node{ __node_gen(std::forward<_Arg>(__v)), this }; - const key_type& __k = this->_M_extract()(__node._M_node->_M_v()); auto __pos - = _M_insert_node(__mks, __hint._M_cur, __code, __node._M_node); + = _M_insert_node(__mks, __res.first._M_cur, __res.second, + __node._M_node); __node._M_node = nullptr; return __pos; } @@ -1922,16 +2022,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _M_erase(__unique_keys_t, const key_type& __k) -> size_type { - __hash_code __code = this->_M_hash_code(__k); - std::size_t __bkt = _M_bucket_index(__code); + __node_base* __prev_n; + __node_type* __n; + std::size_t __bkt; + if (size() <= __traits_type::__small_size_threshold::value) + { + __prev_n = _M_find_before_node(__k); + if (!__prev_n) + return 0; - // Look for the node before the first matching node. - __node_base* __prev_n = _M_find_before_node(__bkt, __k, __code); - if (!__prev_n) - return 0; + // We found a matching node, erase it. + __n = static_cast<__node_type*>(__prev_n->_M_nxt); + __bkt = _M_bucket_index(__n); + } + else + { + __hash_code __code = this->_M_hash_code(__k); + __bkt = _M_bucket_index(__code); + + // Look for the node before the first matching node. + __prev_n = _M_find_before_node(__bkt, __k, __code); + if (!__prev_n) + return 0; + + // We found a matching node, erase it. + __n = static_cast<__node_type*>(__prev_n->_M_nxt); + } - // We found a matching node, erase it. - __node_type* __n = static_cast<__node_type*>(__prev_n->_M_nxt); _M_erase(__bkt, __prev_n, __n); return 1; } @@ -1945,13 +2062,31 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _M_erase(__multi_keys_t, const key_type& __k) -> size_type { - __hash_code __code = this->_M_hash_code(__k); - std::size_t __bkt = _M_bucket_index(__code); + std::size_t __bkt; + __node_base* __prev_n; + __node_type* __n; + if (size() <= __traits_type::__small_size_threshold::value) + { + __prev_n = _M_find_before_node(__k); + if (!__prev_n) + return 0; - // Look for the node before the first matching node. - __node_base* __prev_n = _M_find_before_node(__bkt, __k, __code); - if (!__prev_n) - return 0; + // We found a matching node, erase it. + __n = static_cast<__node_type*>(__prev_n->_M_nxt); + __bkt = _M_bucket_index(__n); + } + else + { + __hash_code __code = this->_M_hash_code(__k); + __bkt = _M_bucket_index(__code); + + // Look for the node before the first matching node. + __prev_n = _M_find_before_node(__bkt, __k, __code); + if (!__prev_n) + return 0; + + __n = static_cast<__node_type*>(__prev_n->_M_nxt); + } // _GLIBCXX_RESOLVE_LIB_DEFECTS // 526. Is it undefined if a function in the standard changes @@ -1959,7 +2094,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // We use one loop to find all matching nodes and another to deallocate // them so that the key stays valid during the first loop. It might be // invalidated indirectly when destroying nodes. - __node_type* __n = static_cast<__node_type*>(__prev_n->_M_nxt); __node_type* __n_last = __n->_M_next(); while (__n_last && this->_M_node_equals(__n, __n_last)) __n_last = __n_last->_M_next(); diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h index 11ea47b322e..6f329c82335 100644 --- a/libstdc++-v3/include/bits/hashtable_policy.h +++ b/libstdc++-v3/include/bits/hashtable_policy.h @@ -45,6 +45,19 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION typename _Traits> class _Hashtable; + /** + * struct _Small_size_threshold + * + * Traits like type giving the threshold below which the hashtable will be + * considered as small. + * + * @tparam _Hash The hash functor. + */ + template<typename _Hash> + struct _Small_size_threshold + : public std::integral_constant<int, __is_fast_hash<_Hash>::value ? 0 : 20> + { }; + namespace __detail { /** @@ -203,13 +216,22 @@ namespace __detail * be an arbitrary number. This is true for unordered_set and * unordered_map, false for unordered_multiset and * unordered_multimap. + * + * @tparam _Small_size_threshold Integer value. Threshold below which + * hashtable will be considered as small enough to perform linear + * lookup. */ - template<bool _Cache_hash_code, bool _Constant_iterators, bool _Unique_keys> + template<bool _Cache_hash_code, + bool _Constant_iterators, + bool _Unique_keys, + int _Small_size_threshold = 0> struct _Hashtable_traits { using __hash_cached = __bool_constant<_Cache_hash_code>; using __constant_iterators = __bool_constant<_Constant_iterators>; using __unique_keys = __bool_constant<_Unique_keys>; + using __small_size_threshold + = integral_constant<int, _Small_size_threshold>; }; /** @@ -1039,9 +1061,11 @@ namespace __detail struct _Rehash_base<_Key, _Value, _Alloc, _ExtractKey, _Equal, _Hash, _RehashPolicy, _Traits, true_type> { + private: using __hashtable = _Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, _Hash, _RehashPolicy, _Traits>; + public: float max_load_factor() const noexcept { @@ -1189,6 +1213,10 @@ namespace __detail return _M_hash()(__k); } + __hash_code + _M_hash_code(const __node_type* __n) const + { return _M_hash_code(_M_extract()(__n->_M_v())); } + std::size_t _M_bucket_index(__hash_code __c, std::size_t __bkt_count) const { return _RangedHash{}(__c, __bkt_count); } @@ -1198,9 +1226,7 @@ namespace __detail noexcept( noexcept(declval<const _Hash&>()(declval<const _Key&>())) && noexcept(declval<const _RangedHash&>()((__hash_code)0, (std::size_t)0)) ) - { - return _RangedHash{}(_M_hash()(_M_extract()(__p->_M_v())), __bkt_count); - } + { return _RangedHash{}(_M_hash_code(__p), __bkt_count); } void _M_store_code(__node_type*, __hash_code) const @@ -1268,6 +1294,10 @@ namespace __detail return _M_hash()(__k); } + __hash_code + _M_hash_code(const __node_type* __n) const + { return __n->_M_hash_code; } + std::size_t _M_bucket_index(__hash_code __c, std::size_t __bkt_count) const { return _RangedHash{}(__c, __bkt_count); } @@ -1669,21 +1699,26 @@ namespace __detail { } bool - _M_equals(const _Key& __k, __hash_code __c, const __node_type* __n) const + _M_key_equals(const _Key& __k, const __node_type* __n) const { static_assert(__is_invocable<const _Equal&, const _Key&, const _Key&>{}, "key equality predicate must be invocable with two arguments of " "key type"); + return _M_eq()(__k, this->_M_extract()(__n->_M_v())); + } + + bool + _M_equals(const _Key& __k, __hash_code __c, const __node_type* __n) const + { return _Equal_hash_code<__node_type>::_S_equals(__c, *__n) - && _M_eq()(__k, this->_M_extract()(__n->_M_v())); + && _M_key_equals(__k, __n); } bool _M_node_equals(const __node_type* __lhn, const __node_type* __rhn) const { return _Equal_hash_code<__node_type>::_S_node_equals(*__lhn, *__rhn) - && _M_eq()(this->_M_extract()(__lhn->_M_v()), - this->_M_extract()(__rhn->_M_v())); + && _M_key_equals(this->_M_extract()(__lhn->_M_v()), __rhn); } void diff --git a/libstdc++-v3/include/bits/unordered_map.h b/libstdc++-v3/include/bits/unordered_map.h index 310cfd39d79..5265020f608 100644 --- a/libstdc++-v3/include/bits/unordered_map.h +++ b/libstdc++-v3/include/bits/unordered_map.h @@ -36,30 +36,36 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _GLIBCXX_BEGIN_NAMESPACE_CONTAINER /// Base types for unordered_map. - template<bool _Cache> - using __umap_traits = __detail::_Hashtable_traits<_Cache, false, true>; + template<bool _Cache, typename _Hash> + using __umap_traits + = __detail::_Hashtable_traits<_Cache, false, true, + __small_size_threshold_default<_Cache, _Hash>::value>; template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = std::equal_to<_Key>, typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >, - typename _Tr = __umap_traits<__cache_default<_Key, _Hash>::value>> + typename _Tr = __umap_traits<__cache_default<_Key, _Hash>::value, + _Hash>> using __umap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>, _Alloc, __detail::_Select1st, _Pred, _Hash, __detail::_Prime_rehash_policy, _Tr>; /// Base types for unordered_multimap. - template<bool _Cache> - using __ummap_traits = __detail::_Hashtable_traits<_Cache, false, false>; + template<bool _Cache, typename _Hash> + using __ummap_traits + = __detail::_Hashtable_traits<_Cache, false, false, + __small_size_threshold_default<_Cache, _Hash>::value>; template<typename _Key, typename _Tp, typename _Hash = hash<_Key>, typename _Pred = std::equal_to<_Key>, typename _Alloc = std::allocator<std::pair<const _Key, _Tp> >, - typename _Tr = __ummap_traits<__cache_default<_Key, _Hash>::value>> + typename _Tr = __ummap_traits<__cache_default<_Key, _Hash>::value, + _Hash>> using __ummap_hashtable = _Hashtable<_Key, std::pair<const _Key, _Tp>, _Alloc, __detail::_Select1st, _Pred, _Hash, diff --git a/libstdc++-v3/include/bits/unordered_set.h b/libstdc++-v3/include/bits/unordered_set.h index 4319495f18b..9bfa8639faf 100644 --- a/libstdc++-v3/include/bits/unordered_set.h +++ b/libstdc++-v3/include/bits/unordered_set.h @@ -36,27 +36,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _GLIBCXX_BEGIN_NAMESPACE_CONTAINER /// Base types for unordered_set. - template<bool _Cache> - using __uset_traits = __detail::_Hashtable_traits<_Cache, true, true>; + template<bool _Cache, typename _Hash> + using __uset_traits + = __detail::_Hashtable_traits<_Cache, true, true, + __small_size_threshold_default<_Cache, _Hash>::value>; template<typename _Value, typename _Hash = hash<_Value>, typename _Pred = std::equal_to<_Value>, typename _Alloc = std::allocator<_Value>, - typename _Tr = __uset_traits<__cache_default<_Value, _Hash>::value>> + typename _Tr = __uset_traits<__cache_default<_Value, _Hash>::value, + _Hash>> using __uset_hashtable = _Hashtable<_Value, _Value, _Alloc, __detail::_Identity, _Pred, _Hash, __detail::_Prime_rehash_policy, _Tr>; /// Base types for unordered_multiset. - template<bool _Cache> - using __umset_traits = __detail::_Hashtable_traits<_Cache, true, false>; + template<bool _Cache, typename _Hash> + using __umset_traits + = __detail::_Hashtable_traits<_Cache, true, false, + __small_size_threshold_default<_Cache, _Hash>::value>; template<typename _Value, typename _Hash = hash<_Value>, typename _Pred = std::equal_to<_Value>, typename _Alloc = std::allocator<_Value>, - typename _Tr = __umset_traits<__cache_default<_Value, _Hash>::value>> + typename _Tr = __umset_traits<__cache_default<_Value, _Hash>::value, + _Hash>> using __umset_hashtable = _Hashtable<_Value, _Value, _Alloc, __detail::_Identity, _Pred, _Hash, diff --git a/libstdc++-v3/src/c++11/hashtable_c++0x.cc b/libstdc++-v3/src/c++11/hashtable_c++0x.cc index de437d00b56..dcf8a81fc5e 100644 --- a/libstdc++-v3/src/c++11/hashtable_c++0x.cc +++ b/libstdc++-v3/src/c++11/hashtable_c++0x.cc @@ -30,6 +30,7 @@ #include <tuple> #include <ext/aligned_buffer.h> #include <ext/alloc_traits.h> +#include <bits/functional_hash.h> #include <bits/hashtable_policy.h> namespace std _GLIBCXX_VISIBILITY(default)