The benchmark section ("But is it fast?") contains a common error when trying to represent ratios as percentages. For the "Tweets" case, it reports a speedup o

The benchmark section ("But is it fast?") contains a common error when trying to represent ratios as percentages. For the "Tweets" case, it reports a speedup of 229%. The old value is 11.73 and the new is 5.108. That is a speedup of 2.293 (i.e. the new measurement is 2.293 times faster), but that is a difference of -56%, not 229%, so it's 129% faster, if you really want to use a comparative percentage. Because using percentages to express ratio of change can be confusing or misleading, I always recommend using speedup instead, which is a simple ratio. A speedup of 2 is twice as fast. A speedup of 1 is the same. 0.5 is half as fast. Formulas: speedup(old, new) = old / new relativePercent(old, new) = ((new / old) - 1) * 100 differenceInPercent(old, new) = (new - old) / old * 100