Stan 2.20.0 is out, thanks to everyone who contributed!
There are a lot of exciting changes that I’ll save for the release notes (Math, Stan, CmdStan), but one thing I want to call out is a huge usability improvement in 2.20.0 - @Bob_Carpenter figured out a way to factor out much of the Stan algorithms and service code and pre-compile it, meaning each Stan model now compiles something like 5x faster (on Bob’s machine I believe it was 35s down to 7s). This should be a huge improvement in the feedback loop for iterative model development and testing speed and I’m really excited about it.
@wds15 also lead a heroic effort starting in January of this year to revamp how our autodiff handles threading and going through 6 different iterations (with lots of help from @rok_cesnovar and thorough reviews by @syclik) that leads to a very nice speedup when using map_rect with threading, as well as the ability to finally using map_rect with threading on Windows machines.
 I have also discovered a bug in Linux CmdStan for some models using cvodes., but a fix should be available in develop shortly.
Here’s a list of everyone who contributed something via git to this release in CmdStan, Stan, or Math (
git log --pretty=format:"%an" v2.19.1..v2.20.0 | sort | uniq):