Does STAN with opencl use GPU for the Cholesky decomposition for computing multivariate normal density?

[Bob_Carpenter]

Now I see why this doc is so confusing. We’re using OpenCL for some of the distribution code. There’s also GPU code under some of our matrix functions that aren’t documented here. I’m not sure where the doc is for those

There’s a cryptic comment from @rok_cesnovar here on the forums a couple of years ago:

How to enable GPU acceleration for Cholesky decomposition in the latent variable GP model?

Hi, the OpenCL backend was revamped a bit, and because of that, the GPU implementation of the cholesky_decompose is currently not exposed at the language level. We plan on re-enabling that in the near future, hopefully in this release cycle.

Looks like it used to exist but was removed? @stevebronder or @rok_cesnovar should know the current status. I’m not even sure where the doc is to turn on GPU execution of matrix functions.