Benchmark: timing 5000000 iterations of sub1, sub2, sub3...
      sub1:  8 wallclock secs  @ 664805.21/s (n=5000000)
      sub2:  6 wallclock secs  @ 988924.05/s (n=5000000)
      sub3:  4 wallclock secs  @ 1139731.02/s (n=5000000)