Comparison Formulae

Collecting performance metrics, I needed a way to compare before/after numbers from optimizations into some meaningful value that would impress the brass.

I don’t recall where I found these except that my Google-fu shone a light to help me get to the formulae below. I’ve had them in my notes at work for ages and today I thought to add them here for reference.

Find savings

Formula: (newValue - oldValue) / oldValue * 100 = percent

E.g.: the amount of time it took to run an operation is 2348 milliseconds (oldValue). After an optimization, the operation executes in 842 milliseconds (newValue).

(842 - 2348) / 2348 * 100 = -64.139693356% reduction in execution time

Find gains

Formula: (oldValue / newValue) - 1 = x times improvement

Think of this result as the number of times the improved performance (newValue=842) will run above and beyond the amount of time it took the old implementation (oldValue=2348). Using the values from the previous example:

(2348 / 842) - 1 = 1.7885985748x performance gain

Pretty good, almost a 2x gain. That means the new operation can almost run three times in the same amount of time it took the old operation. Good job! Now write a report and ask for a raise.

Leave a Reply

Your email address will not be published. Required fields are marked *