D std.regex is so slow

[Dmitry Olshansky]

On Tuesday, 19 September 2017 at 16:27:51 UTC, jmh530 wrote:
> On Tuesday, 19 September 2017 at 07:53:27 UTC, Daniel Kozak 
> wrote:
>> https://github.com/mariomka/regex-benchmark#performance
>>
>> Do you know why?
>>
>> Here is a code:
>> https://github.com/mariomka/regex-benchmark/blob/master/d/benchmark.d
>>
>> I have try it with ldc too, but is still much slower (10x) 
>> than PHP
>
> Looks like they added ldc to it. I'm seeing 3x slower than PHP 
> on Email and URI, but roughly par on IP. It really stands out 
> on the DMD one how much better it does on the IP one than the 
> Email/URI ones.

IP is detected to be "semi-fixed" thus hitting a nice fast path.

Others would have worked with BitNFA, a patch that we had to 
revert because auto-tester run out of memory.