Benchmark: timing 1000000 iterations of p1, p2, p3, p4...
        p1:  3 wallclock secs ( 3.00 usr +  0.00 sys =  3.00 CPU)
             @ 333333.33/s (n=1000000)
        p2:  3 wallclock secs ( 2.79 usr +  0.00 sys =  2.79 CPU)
             @ 358422.94/s (n=1000000)
        p3:  3 wallclock secs ( 3.09 usr +  0.00 sys =  3.09 CPU)
             @ 323624.60/s (n=1000000)
        p4:  3 wallclock secs ( 2.82 usr +  0.00 sys =  2.82 CPU)
             @ 354609.93/s (n=1000000)