How do you create a progress bar when using the “foreach()” function in R?

Question

there are some informative posts on how to create a counter for loops in an R program. However, how do you create a similar function when using the parallelized version wit

Answer 1

This code implements a progress bar tracking a parallelized foreach loop using the doMC backend, and using the excellent progress package in R. It assumes that all cores, specified by numCores, do an approximately equal amount of work.

library(foreach)
library(doMC)
library(progress)

iterations <- 100
numCores <- 8

registerDoMC(cores=numCores)

pbTracker <- function(pb,i,numCores) {
    if (i %% numCores == 0) {
        pb$tick()
    }
}

pb <- progress_bar$new(
  format <- " progress [:bar] :percent eta: :eta",
  total <- iterations / numCores, clear = FALSE, width= 60)


output = foreach(i=1:iterations) %dopar% {
    pbTracker(pb,i,numCores)
    Sys.sleep(1/20)
}