[triangleman83]

I'm having trouble with your post. You said the right way to calculate it is (t1 - t0)/t0, but said later that the actual amount is (157 - 98)/157, which is (t1 - t0)/t1.

Also I believe the author is referring to speed improvements, whereas you are referring to time improvements. Let's say I take 200 operations to perform a task, then I optimize code to perform the same task in 100 operations. The program runs at 20 operations per second regardless of how many operations there are.

The task which took 10 seconds before will now take 5 seconds, or a 50% time reduction, which is how you calculate it. However, the program is now running twice as fast, because in 20 seconds, the program can run twice, which is how the author calculated it.

Both of you are correct, just depending on what your context is.