unroll search

[DenisYaroshevskiy]

unrolling search while also putting the "check for match" in an isolated place to make the codegen smaller.

I need to add more tests for iteration but other than that should be revieable.

The benchmarks for this also need improvements, the simplest (and not a very good one) is find for one char.

Here is the numbers for that (you should look at the best one always).

This is timing for find (baseline)

/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:0      55.5 ns         55.5 ns     12491744
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:8      55.8 ns         55.8 ns     12606370
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:16     89.2 ns         89.2 ns      7866881
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:24     87.9 ns         87.9 ns      7962216
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:32     62.9 ns         62.9 ns     11197921
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:40     60.6 ns         60.6 ns     11972006
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:48     75.7 ns         75.7 ns      9416124
/name:find 0/size:10000/type:char/algorithm:eve::algo::find_if/percentage:100/padding:56     73.2 ns         73.2 ns      9590033

This is the performance for search for a single char now:

/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:0         166 ns          166 ns      4209565
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:8         129 ns          129 ns      5348094
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:16        126 ns          126 ns      5584025
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:24        152 ns          152 ns      4592188
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:32        150 ns          150 ns      4663308
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:40        129 ns          129 ns      5412031
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:48        125 ns          125 ns      5611149
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:56        166 ns          166 ns      4205887

This is the performance for search for a single char before:

----------------------------------------------------------------------------------------------------------------------------------
Benchmark                                                                                        Time             CPU   Iterations
----------------------------------------------------------------------------------------------------------------------------------
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:0         140 ns          140 ns      4937022
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:8         200 ns          200 ns      3499883
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:16        200 ns          200 ns      3511696
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:24        138 ns          138 ns      5085738
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:32        137 ns          137 ns      5099563
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:40        167 ns          167 ns      4232450
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:48        167 ns          167 ns      4253506
/name:find 0/size:10000/type:char/algorithm:eve::algo::search/percentage:100/padding:56        138 ns          138 ns      5061660

[jfalcou]

You can mark the paramter [[maybe_unused]], it is better than random cast to void IMO.

EVE_FORCEINLINE bool main_loop(Traits tr, I& f, [[maybe_unused]] auto unroll_l, S l, Delegate& delegate) const

[jfalcou]

Any update ont hsi samll details ?
The PR is fine once fixed and can be merged

[DenisYaroshevskiy]

1. I don't have time to fix this until the weekend.
2. I still want to add more testing for iteration.

It's good if everything else seems ok.