Create a tclktk progressbar to provide feedback when running a parallel job

foreach-progressbar.R

library(foreach)
library(iterators)
library(doParallel)
library(tcltk)

# Choose number of iterations
n <- 250

# In sequence, without progress bar ---------------------------------------

print("Running sequential task")

time1 <- system.time({
  k <- foreach(i = icount(n), .packages = "tcltk", .combine = c) %do% {
    Sys.sleep(0.01)
    log2(i)
  }
})

print(time1)

# In sequence, with progress bar ------------------------------------------

print("Running sequential task with progress bar")

pb <- tkProgressBar("Sequential task", min=1, max=n)

time2 <- system.time({
  k <- foreach(i = icount(n), .packages = "tcltk", .combine = c) %do% {
    if(!exists("pb")) pb <- tkProgressBar("Sequential task", min=1, max=n)
    setTkProgressBar(pb, i)
    Sys.sleep(0.01)
    log2(i)
  }
})

close(pb)
rm(pb)

print(time2)


# Run the loop in parallel ------------------------------------------------

print("Running parallel task with progress bar")

cl <- makeCluster(8)

registerDoParallel(cl)

time3 <- system.time({
  clusterExport(cl, c("n"))
  k <- foreach(i = icount(n), .packages = "tcltk", .combine = c) %dopar% {
    if(!exists("pb")) pb <- tkProgressBar("Parallel task", min=1, max=n)
    setTkProgressBar(pb, i)
    Sys.sleep(0.01)
    log2(i)
  }
})

#Stop the cluster
stopCluster(cl)

print(time3)