Benchmark: timing 100 iterations of granfather, usual...
granfather:  4 wallclock secs ( 3.58 usr +  0.00 sys =  3.58 CPU) @ 27.95/s (n=1
00)
     usual:  4 wallclock secs ( 4.13 usr +  0.00 sys =  4.13 CPU) @ 24.24/s (n=1
00)