[MNG-6693] Various speed improvements

[gnodet]

No description provided.

[michael-o]

Can you please explain how your changes improve performance?

[gnodet]

How ? You mean why each change helps improving performance or how did I measure the effect ? or how did i find those ?
For the what, my main goal is to speed up time mvn foo when running the build on https://github.com/apache/camel, so that's easily reproducible. Currently, with 3.6.1, it takes more than 50s. I'm now slightly above 30s with all the included changes.
As for the how, I'm using YourKit profile to find out the spots that takes times. I've been spending a lot of time trying to improve the model building mechanism in various ways, but could not get any significant results, so I'm back to a bunch of smaller improvements, which is the subject of this PR.
For the specifics, it depends:

• using regexp is quite slow for simple checks, so checking if there's a '-' in a string is way faster than running the regexp in the first place, so if we can avoid it, it's better
• avoid running the full model interpolation on the parent if the version is not to be interpolated
• speed up the string search interpolator by reusing the plexus interpolator instead of adding / removing the same value sources / processors each time
• cache valid ids (they are mostly always the same)
• avoid concatenating strings which are not used (during validation, as they are only used when there's a violation)
• the second commit provides a full blown new model interpolator which does not use reflection and is much master
• the third commit does early checking before calling Validate.notBlank which proves to be quite slow when called a few million times

[gnodet]

Another point to consider for speed improvements would be to use specific Map implementations where it makes sense. In my run, I end up with 9.951.957 calls to HashMap.put taking up to 12% of the time used when running DefaultMaven.buildGraph, so it's worth investigating.

[michael-o]

Thanks, I will go through. I think the new model interpolator deserves a separate ticket. The rest seems to be spot improvements.

[gnodet]

I'll create a separate ticket on monday for the interpolator and will thus keep this PR for the other small changes.

[gnodet]

I've pushed 2 new commits. I'll create a separate JIRA issue for the one about the ManagedVersionMap which saves another couple of seconds.

[gnodet]

Closing this PR as I've opened 4 smaller ones.