Benchmark: timing 5 iterations of Atest, Btest, Ctest, Dtest...
     Atest:  4 wallclock secs ( 4.08 usr +  0.23 sys =  4.31 CPU) @  1.16/s (n=5)
     Btest:  5 wallclock secs ( 4.18 usr +  0.00 sys =  4.18 CPU) @  1.20/s (n=5)
     Ctest:  5 wallclock secs ( 4.17 usr +  0.00 sys =  4.17 CPU) @  1.20/s (n=5)
     Dtest:  5 wallclock secs ( 4.21 usr +  0.00 sys =  4.21 CPU) @  1.19/s (n=5)
        Rate Atest Dtest Btest Ctest
Atest 1.16/s    --   -2%   -3%   -3%
Dtest 1.19/s    2%    --   -1%   -1%
Btest 1.20/s    3%    1%    --   -0%
Ctest 1.20/s    3%    1%    0%    --