[R] parallel number of cores according to memory?

[ivo welch]

ugghhh---apologies.  although in 2020, it would be nice if the mailing
list had an automatic html filter (or even bouncer!)

I am using macos.  alas, my experiments suggest that `mclapply()` on a
32-core intel system with 64GB of RAM, where the input data frame is
8GB and the output is about 500MB per core (to be stitched together
into about 16GB), the system starts swapping like crazy, comes to a
halt, and then usually crashes.

/iaw