If I travel 25 miles in 1 hour, my speed was 25mph. If I go 100% faster, I'm going 50mph and get there in 30 minutes. If I go 200% faster, I'm going 75mph and get there in 20 minutes.
However, the original statement of "We have reduced the time for the computation by ~119%!" is still wrong-seeming, I agree. It should be "We have increased the speed for the computation by 119%" or "We have reduced the time for the computation by <WHATEVER>" :)
> We have reduced the time for the computation by ~119%!
You can say 100% faster when you are talking about speed. You can't say 100% faster when you are talking about duration. "Reduced the time" is talking about duration.
However, the original statement of "We have reduced the time for the computation by ~119%!" is still wrong-seeming, I agree. It should be "We have increased the speed for the computation by 119%" or "We have reduced the time for the computation by <WHATEVER>" :)