copy/copy_backward/fill/fill_n/equal rework

[François Dumont]

Ping ?

On 9/9/19 8:34 PM, François Dumont wrote:
> Hi
>
> Â Â Â  This patch improves stl_algobase.h 
> copy/copy_backward/fill/fill_n/equal implementations. The improvements 
> are:
>
> - activation of algo specialization for __gnu_debug::_Safe_iterator 
> (w/o _GLIBCXX_DEBUG mode)
>
> - activation of algo specialization for _Deque_iterator even if mixed 
> with another kind of iterator.
>
> - activation of algo specializations __copy_move_a2 for something else 
> than pointers. For example this code:
>
> std::vector<char> v { 'a', 'b', .... };
>
> ostreambuf_iterator out(std::cout);
>
> std::copy(v.begin(), v.end(), out);
>
> is not calling the specialization __copy_move_a2(const char*, const 
> char*, ostreambuf_iterator<>);
>
> It also fix a _GLIBCXX_DEBUG issue where the __niter_base 
> specialization was wrongly removing the _Safe_iterator<> layer. The 
> testsuite/25_algorithms/copy/debug/1_neg.cc test case was failing on a 
> debug assertion because _after_ the copy we were trying to increment 
> the vector iterator after past-the-end. Of course the problem is the 
> _after_, Debug mode should detect this _before_ it takes place which 
> it does now.
>
> Note that std::fill_n is now making use of std::fill for some 
> optimizations dealing with random access iterators.
>
> Performances are very good:
>
> Before:
>
> copy_backward_deque_iterators.cc    deque 2 deque 1084r 1084u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    deque 2 vector 3373r 3372u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    vector 2 deque 3316r 3316u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    int deque 2 char vector 3610r 
> 3609u    0s         0mem    0pf
> copy_backward_deque_iterators.cc    char vector 2 int deque 3552r 
> 3552u    0s         0mem    0pf
> copy_backward_deque_iterators.cc    deque 2 list 10528r 10528u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    list 2 deque 2161r 2162u 
> 0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 deque                 752r 
> 751u    0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 vector               3300r 
> 3299u    0s         0mem    0pf
> copy_deque_iterators.cc      vector 2 deque               3144r 
> 3140u    0s         0mem    0pf
> copy_deque_iterators.cc      int deque 2 char vector      3340r 
> 3338u    1s         0mem    0pf
> copy_deque_iterators.cc      char vector 2 int deque      3132r 
> 3132u    0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 list                 10013r 
> 10012u    0s         0mem    0pf
> copy_deque_iterators.cc      list 2 deque                 2274r 
> 2275u    0s         0mem    0pf
> equal_deque_iterators.cc     deque vs deque               8676r 
> 8675u    0s         0mem    0pf
> equal_deque_iterators.cc     deque vs vector              5870r 
> 5870u    0s         0mem    0pf
> equal_deque_iterators.cc     vector vs deque              3163r 
> 3163u    0s         0mem    0pf
> equal_deque_iterators.cc     int deque vs char vector     5845r 
> 5845u    0s         0mem    0pf
> equal_deque_iterators.cc     char vector vs int deque     3307r 
> 3307u    0s         0mem    0pf
>
> After:
>
> copy_backward_deque_iterators.cc    deque 2 deque  697r  697u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    deque 2 vector  219r  218u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    vector 2 deque  453r  453u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    int deque 2 char vector 1914r 
> 1915u    0s         0mem    0pf
> copy_backward_deque_iterators.cc    char vector 2 int deque 2112r 
> 2111u    0s         0mem    0pf
> copy_backward_deque_iterators.cc    deque 2 list 7770r 7771u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    list 2 deque 2194r 2193u 
> 0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 deque                 505r 
> 504u    0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 vector                221r 
> 221u    0s         0mem    0pf
> copy_deque_iterators.cc      vector 2 deque                398r 
> 397u    0s         0mem    0pf
> copy_deque_iterators.cc      int deque 2 char vector      1770r 
> 1767u    0s         0mem    0pf
> copy_deque_iterators.cc      char vector 2 int deque      1995r 
> 1993u    0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 list                 7650r 
> 7641u    2s         0mem    0pf
> copy_deque_iterators.cc      list 2 deque                 2270r 
> 2270u    0s         0mem    0pf
> equal_deque_iterators.cc     deque vs deque                769r 
> 768u    0s         0mem    0pf
> equal_deque_iterators.cc     deque vs vector               231r 
> 230u    0s         0mem    0pf
> equal_deque_iterators.cc     vector vs deque               397r 
> 397u    0s         0mem    0pf
> equal_deque_iterators.cc     int deque vs char vector     1541r 
> 1541u    0s         0mem    0pf
> equal_deque_iterators.cc     char vector vs int deque     1623r 
> 1623u    0s         0mem    0pf
>
> In Debug Mode it is of course even better. I haven't had the patience 
> to run the benches before the patch, it just takes hours to run. So 
> here is just the After part:
>
> copy_backward_deque_iterators.cc    deque 2 deque 1128r 1128u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    deque 2 vector  616r  616u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    vector 2 deque  856r  855u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    int deque 2 char vector 2277r 
> 2277u    0s         0mem    0pf
> copy_backward_deque_iterators.cc    char vector 2 int deque 2518r 
> 2519u    0s         0mem    0pf
> copy_backward_deque_iterators.cc    deque 2 list 8029r 8028u 
> 0s         0mem    0pf
> copy_backward_deque_iterators.cc    list 2 deque 10418r 10416u 
> 0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 deque                 931r 
> 930u    0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 vector                613r 
> 613u    0s         0mem    0pf
> copy_deque_iterators.cc      vector 2 deque                794r 
> 795u    0s         0mem    0pf
> copy_deque_iterators.cc      int deque 2 char vector      2192r 
> 2192u    0s         0mem    0pf
> copy_deque_iterators.cc      char vector 2 int deque      2365r 
> 2364u    0s         0mem    0pf
> copy_deque_iterators.cc      deque 2 list                 8009r 
> 8010u    0s         0mem    0pf
> copy_deque_iterators.cc      list 2 deque                 10979r 
> 10970u    1s         0mem    0pf
> equal_deque_iterators.cc     deque vs deque               1034r 
> 1032u    0s         0mem    0pf
> equal_deque_iterators.cc     deque vs vector               481r 
> 482u    0s         0mem    0pf
> equal_deque_iterators.cc     vector vs deque               646r 
> 646u    0s         0mem    0pf
> equal_deque_iterators.cc     int deque vs char vector     1802r 
> 1802u    0s         0mem    0pf
> equal_deque_iterators.cc     char vector vs int deque     1867r 
> 1865u    0s         0mem    0pf
>
> Note that copy/copy_backward 'list 2 deque' is still much slower 
> because for the moment we can't remove the debug layer. I plan to do a 
> refinement to also cover this use case.
>
> In Debug implementations I have duplicated the Debug checks because 
> those algo specialization will also be used when users are directly 
> using <debug/vector> for instance without defining _GLIBCXX_DEBUG.
>
> All algos tests passed except the constexpr ones in Debug mode, I've 
> put this on my todo list.
>
> Ok to commit once I completed all the other tests ?
>
> François
>