IWOCL / SYCLcon is a workshop on OpenCL, SYCL (an attempt to single source heterogeneous computing - kind of close to what we are doing with the Stan Math OpenCL backend) and everything related to parallel C++.
This isnt really a Stan related conference but enough people here are interested in OpenCL and the future of parallel C++ that I thought I gave a heads up since its online, on-demand and free.
@tadej is going to present our (honestly - mostly his) work on the kernel generator - which is awesome by the way. There are many other interesting talks and panels: https://www.iwocl.org/iwocl-2020/conference-program/
Me and Tadej were planning on going anyways but Covid-19 has changed the plans to something more conveniant.
Not sure if registration has an upper limit or not, its all free.