I'm still learning about Cinder, but my initial impression is that there are many similar techniques used, and maybe one interesting difference is that with Pyston we've focused more on out-of-the-box performance while Cinder has had an opportunity to co-optimize the runtime with a particular codebase and presumably gets better results if you're able to do that.

I don't understand, can't those changes be merged upstream?

Edit: Also yesterday's HN discussion on Cinder https://news.ycombinator.com/item?id=27043217

Or better yet, why can't the two projects be combined into one?

Wouldn't it be better to have two companies working on it instead of just one? Or are the implementation details too far apart?

Wondering same, as it shows full compatibility to cpython unlike Facebook implementation

My understanding is that can is only half the question. Yes, the changes CAN be upstreamed but my understanding (through others, so take it with a grain of salt), is that the CPython doesn’t like to take optimization changes that obscure the CPython code base. As a result, they often deny merging optimizations in favor of readability in the C codebase. Again, just my understanding and may not be 100% accurate.

Cinder is fully compatible with the CPython's C-API

They are alternative solutions to the same problem.

Are they not compatible solutions? I understand if the development is very fast you want to have focus, but the goal here is performance, it seems worth to at least coordinate. I hope it happens!!

There are many ways to get to the same place. It's worth a shot to experiment with different approaches, they also don't have the same pros and cons.

I'm sure at this level of tech they are well aware of the prior art.