  We consider the first, and most well studied, speed scaling problem in the
algorithmic literature: where the scheduling quality of service measure is a
deadline feasibility constraint, and where the power objective is to minimize
the total energy used. Four online algorithms for this problem have been
proposed in the algorithmic literature. Based on the best upper bound that can
be proved on the competitive ratio, the ranking of the online algorithms from
best to worst is: $\qOA$, $\OA$, $\AVR$, $\BKP$. As a test case on the
effectiveness of competitive analysis to predict the best online algorithm, we
report on an experimental "horse race" between these algorithms using instances
based on web server traces. Our main conclusion is that the ranking of our
algorithms based on their performance in our experiments is identical to the
order predicted by competitive analysis. This ranking holds over a large range
of possible power functions, and even if the power objective is temperature.
