optimizing a executable shell script with mlrMBO

runMBO.R

library(mlrMBO)
library(stringi)
library(jsonlite)

# read command line args (in a not very safe way)
# Script can be called like that:
# Rscript runMBO.R iters=20 time=10 seed=1
args = commandArgs(TRUE)
# defaults:
iters = 50
time = 30
seed = 123
# parse args (and possibly overwrite defaults)
for (arg in args) {
  eval(parse(text = arg))
}
set.seed(seed)

# write bash script
lines = '#!/bin/bash
fun ()
{
  x1=$1
  x2=$2
  command="(s($x1-1) + ($x1^2 + $x2^2))"
  result=$(bc -l <<< $command)
}
echo "Start calculation."
fun $1 $2
echo "The result is $result!" > "result.txt"
echo "Finish calculation."
'
writeLines(lines, "fun.sh")
system("chmod +x fun.sh")

# runScript function to execute bash script
runScript = function(x) {
  # console output file output_1490030005_1.1_2.4.txt
  output_file = sprintf("output_%i_%.1f_%.1f.txt", as.integer(Sys.time()), x[['x1']], x[['x2']])
  # redirect output with ./fun.sh 1.1 2.4 > output.txt
  # alternative: ./fun.sh 1.1 2.4 > /dev/null to drop it
  command = sprintf("./fun.sh %f %f > %s", x[['x1']], x[['x2']], output_file)
  error.code = system(command)
  if (error.code != 0) {
    stop("Simulation had error.code != 0!")
  }
  result = readLines("result.txt")
  # the pattern matches 12 as well as 12.34 and .34
  # the ?: makes the decimals a non-capturing group.
  result = stri_match_first_regex(result, pattern = "\\d*(?:\\.\\d+)?(?=\\!)")
  as.numeric(result)
}

# define mlrMBO optimization 
par.set = makeParamSet(
  makeNumericParam("x1", lower = -3, upper = 3),
  makeNumericParam("x2", lower = -2.5, upper = 2.5)
)
fn = makeSingleObjectiveFunction(
  id = "fun.sh", 
  fn = runScript,
  par.set = par.set,
  has.simple.signature = FALSE
)
ctrl = makeMBOControl()
ctrl = setMBOControlInfill(ctrl, crit = crit.ei)
ctrl = setMBOControlTermination(ctrl, iters = iters, time.budget = time)
configureMlr(show.info = FALSE, show.learner.output = FALSE)
run = mbo(fun = fn, control = ctrl)

# save result to json
write_json(run[c("x","y")], "mbo_res.json")