[jpf0]

A bunch of questions: Is multi-threading happening at the level of user-defined functions? How are threads scheduled? What's the underlying method or library for enabling multi-threading (Cilk, openMP, some LWT library...)? To what extent has this level of granularity been tested against other levels of nested parallelism (e.g. SIMD or otherwise parallel operators)? Have you tested performance by OS, and if so, have you noted any necessary OS-level modifications related to thread management? Is this part of a broader roadmap for accelerator integration?

[sadiq]

1. Domains are the unit of parallelism. A domain is essentially an OS thread with a bunch of extra runtime book-keeping data. You can use Domain.spawn (https://github.com/ocaml-multicore/ocaml-multicore/blob/5.00...) to spawn off a new domain which will run the supplied function and terminate when it finishes. This is heavyweight though, domains are expected to be long-running.

2. Domainslib is the library developed alongside multicore to aid users in exploiting parallelism. It supports nested parallelism and is pretty highly optimised (https://github.com/ocaml-multicore/domainslib/pull/29 for some graphs/numbers). The domainslib repo has some good examples: https://github.com/ocaml-multicore/domainslib/tree/master/te...

3. We've not tested against other forms of parallelism. There isn't anything stopping you exploiting SIMD in addition to parallelism from domains.

4. No, we've not compared performance by OS.

5. No plans for the multicore team to look at accelerator integration at the moment.