Integrate work of Sebastian from the parallel branch

[JohannesLichtenberger]

We have to integrate Sebastian's work on parallelization (probably in some parts with newer Java language possibilities).

https://github.com/sebbae/brackit/tree/parallel

[AlvinKuruvilla]

For faster reference, I think all we need to add to support Sebastian's parallelization work is:

• Block
• forkjoin

[JohannesLichtenberger]

Good point. I think as Java has majored, we can even use Java's ForkJoinPool and stuff like that :-)

[JohannesLichtenberger]

Maybe first, we can copy the stuff, add tests and then rewrite some stuff to modern Java 👍

[AlvinKuruvilla]

Yeah, that was my thinking. This is the PR that ports the primary functionality.

[JohannesLichtenberger]

@AlvinKuruvilla I've changed a couple of minor things you've changed from Sebastian's code (namely yield() and a finali threadid. yield() is an abstract class and can/should be overriden in subclasses, I guess, that's why it makes a difference :-)

[AlvinKuruvilla]

Oh, okay, that makes sense. I'll merge those changes and get started on porting the tests

[AlvinKuruvilla]

I don't think there are any test cases to port over from the branch. I think we will need to write our own

[mosheduminer]

Do we have a way of benchmarking the improvements (and potentially the cases where it might cause perf degradation)?

[AlvinKuruvilla]

I was thinking we should have a suite of benchmarks for the codebase too. It would be cool, in my opinion, to do some performance profiling.
But to answer your question I don't believe there is

[JohannesLichtenberger]

I'm not sure if he has committed everything, otherwise he's benchmarked some stuff. Have a look at his thesis :)

[JohannesLichtenberger]

The real question is also if it's working in all cases, as it was in a branch and Sebastian hasn't merged it.

[AlvinKuruvilla]

Is his thesis listed somewhere? I don’t see it as a repository on his profile or in the brackit repository

[JohannesLichtenberger]

It's listed under publications in the README: Separating Key Concerns in Query Processing - Set Orientation, Physical Data Independence, and Parallelism