% improvement

For general rambling.
Post Reply
Minion to the Exalted Pooh-Bah
Posts: 2790
Joined: Fri Jul 18, 2003 2:28 pm
Location: Irvine, CA

% improvement

Post by Peijen »

if I reduce the runtime from 100s to 80s, what's my % improvement?

Grand Pooh-Bah
Posts: 6718
Joined: Tue Sep 19, 2006 8:45 pm
Location: Portland, OR

Re: % improvement

Post by Jonathan »

"Improvement" implies you are measuring performance. Performance is proportional to the inverse of wallclock time.

Therefore, if you want to quote a percentage improvement, you would calculate performance like so:
new = 1/80s = 0.0125 units of work per second
old = 1/100s = 0.0100 units of work per second

improvement = new/old = 0.0125/0.0100 = 1.25x or +25%

The 20% figure is accurate if you are quoting a reduction in wallclock time, but you would typically phrase that as -20%, because wallclock time decreased.

Post Reply