Benchmark: timing 100 iterations of granfather, usual...
granfather:  4 wallclock secs ( 3.69 usr +  0.03 sys =  3.72 CPU) @ 26.89/s (n=1
00)
     usual:  2 wallclock secs ( 2.08 usr +  0.00 sys =  2.08 CPU) @ 48.12/s (n=1
00)