Run shell function in parallel over file lines

gistfile1.txt

#!/usr/bin/env bash

FILE="/tmp/file.txt"
PROC=3

echo -e "aaa bbb ccc\nddd eee fff" > "$FILE"

function do_it() {
  echo "---"
  printf "$1 $2 $3\n"
}

export -f do_it

mapfile -t "LINES" <"$FILE"

parallel -j "$PROC" ::: do_it ::: "${LINES[@]}"