An R instructor provided this code to ensure that students only use half the cores on their PCs/Laptops in parallel processing. However, as shown below, the system report from my mac says I have 4 while this library seems to detect 8. To make sure at least 1 or 2 cores are free, is this code set correctly? Or should I alter the last line maybe with an ifelse() statement that tells it what to do when system specs don't agree with its detection?
R code:
# Setting Parallel processing
library(doMC)
library(parallel)
number_of_cores <- detectCores()
registerDoMC(cores = number_of_cores/2)
Output (how many cores it sees):
[1] 8
What "About this Mac" -> "System Report" reports for specs including cores:
Model Name: MacBook Pro
Model Identifier: MacBookPro14,3
Processor Name: Intel Core i7
Processor Speed: 2.8 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 16 GB
Boot ROM Version: MBP143.0160.B02
The issue here is number of threads versus number of cores. Cores are physical, while threads (more or less) split a core and are software driven. This combination of arguments should get you just the cores:
detectCores(all.tests = FALSE, logical = FALSE)