Here are the parrotbench results, using the "user" field from "make time" output. There's a clear speedup of nearly 1 second in the -listopt version. During parts of these tests my system was also running nice'd distcc jobs, but since user time was measured this shouldn't matter much. "real" times were slower for python-listopt (0.56 seconds difference of median values) and more scattered (1.52 std dev vs 0.32 std dev) for this reason. Python-cvs Python-listopt 18.32 18.39 18.44 18.39 18.83 17.53 18.75 17.38 18.63 17.37 18.91 17.36 18.55 17.63 18.66 18.06 18.68 17.38 18.74 17.92 Minimum 18.32 17.36 Maximum 18.91 18.39 Median 18.67 17.58 Average 18.65 17.74 Std.Dev 0.18 0.42 T-test 0.00% =ttest(b2:b11; c2:c11; 2; 3) Difference of median values -0.91