Feature: Parallel Building

[Cregrant]

Here are my performance optimizations that aim to minimize changes to the codebase and do not use any external libraries (although Apache Compress seems like a nice one).

• There is some duplicated code, such as the ApkBuilder and ApkDecoder new fields, which can be extracted to a "global" context created somewhere in the Main class. However, I do not want to make significant changes for just one pull request.
• I did not find any changes in the decompiled code, compression type issues, or any other problems.
• Further performance optimizations can be done by changing the zip compressing library and refactoring the backsmali code (specifically, the synchronized method inside the library).

Best numbers (30mb apk, 3 dex files, 4 CPU cores) for a 10-minute benchmark:
25% means one core load

Task	Configuration	Time (s)	CPU load
decode	original	18.05	34%
decode	1thread	18.05	34%
decode	2threads	15.00	40%
decode	4threads	13.40	46%
decode	4th with 2nd commit	12.60	48%
encode	original	27.50	25%
encode	4threads	15.55	49%
encode	mergeZip	11.45	53%

[iBotPeaches]

Interesting in timing how we got 1 PR doing ParallelStreams and this one doing an executor service. It what I was basically responding to in this other pr: #3411 (comment)

In short - thanks, let me review this.

[iBotPeaches]

Took a quick static look. I have time this weekend to pull it down and do some testing.

[Cregrant]

Another suggestion is to change the Gradle distribution from all to bin if you didn't choose all intentionally.

[iBotPeaches]

Another suggestion is to change the Gradle distribution from all to bin if you didn't choose all intentionally.

We did swap from bin -> all a few years ago for some reason. Forgot why.

[iBotPeaches]

I ran some tests and I like it. I'll put in another PR shortly to:

• Make jobs configurable
• Explain how many jobs are running in info message at start of build
• Remove unused method in ZipUtils

[Cregrant]

Thanks! I thought about defining the thread count and found that setting the number in the Main class (or setting it to 1 if a debug flag is set) via a public field is the best solution. This is because you probably won't have any reason to change it in the middle of decompiling.