Yeah, going to spend a lot of tomorrow with it and talking this through with @Matthijs. Want to make sure I’m not crazy about this particular optimization though - here’s the PR: https://github.com/stan-dev/math/pull/801. I think only the changes on lines 349 and 352 were necessary (changing the declaration of adjB to auto from VectorXd adjB(size_)), but wanted to change the rest as much as I easily could for symmetry.
Here’s a screenshot of Instruments reading the trace generated with the above command:
The really crucial thing with Instruments is to hit this checkbox on the Call Tree menu at the bottom:
Inverting the Call Tree lets you find the hotspots much more easily.
I’m still trying to figure out how to actually count method invocations, because that’s super useful sometimes. But Instruments crashes on my Mac when I try to do that, haha.