I’m sharing a poster Bill Gillespie and I (Charles Margossian) presented at the American Conference on Pharmacometrics 8, last month. The poster presents a trick for solving certain kinds of ODEs, in order to gain an appreciable speed-up.
I implemented a routine using this method in Torsten, our open-source extension of Stan for Pharmacometrics (https://github.com/metrumresearchgroup/example-models).
A manuscript on the subject is (almost) done.