1. Is single threaded 2. Takes a lot of CPU 3. Is a task that everyone can understand and relate to and which is close to a real world scenario
I have loads of examples meeting requirement 1+2. It is 3 that is the hard part.
Post them to parallel@gnu.org
$ ls *.png |wc -l
3580
$ time ls|sed 's/\(.*\)\..*/\1/'|parallel convert {}.png {}.ppm
ls --color 0.00s user 0.01s system 63% cpu 0.016 total
sed 's/\(.*\)\..*/\1/' 0.01s user 0.00s system 39% cpu 0.025 total
parallel convert {}.png {}.ppm 97.39s user 61.87s system 890% cpu 17.883 total
$ time ls|sed 's/\(.*\)\..*/\1/'|xargs -I {} convert {}.png {}.ppm
ls --color 0.01s user 0.00s system 63% cpu 0.016 total
sed 's/\(.*\)\..*/\1/' 0.01s user 0.00s system 39% cpu 0.025 total
xargs -I {} convert {}.png {}.ppm 93.08s user 47.88s system 38% cpu 6:10.88 total