Tips on making regex more performant?

[1100110]

On 06/18/2013 01:53 PM, Gary Willoughby wrote:
> Below is an example snippet of code to test for performance of regex
> matches. I need to parse a large log and extract data from it and i've
> noticed a huge increase in time of the loop when reading and using regex.
>
>      ...
>      auto alert = regex(r"^Alert ([0-9]+)");
>
>      while ((line = file.readln()) !is null)
>      {
>          auto m = match(line, alert);
>
>          if (m)
>          {
>              alerts++;
>          }
>
>          counter++;
>      }
>      ...
>
> Using the above example i parse about 700K lines per second (i'm reading
> from an SSD). If i comment out the regex match function, i read at 4.5M
> lines per second. Considering i need to use about 8 regex matches and
> extract data, this figure further drops to about 100K lines per second.
>
> Is there anything i can do to speed up regex matching in such a
> scenario? Are there any tips you can share to speed things up?
>
> Thanks.

enum alert = ctRegex!r"^Alert ([0-9]+)";

And then use it the same way.