On an Intel Celeron B820 @ 1.70Ghz laptop, it took more than 40 seconds to complete and consumed 1% of battery in the meantime. The "complex equations" you are doing will not work on low-horsepower devices like phones or low-to-medium level laptops.
Just to calibrate a little, I did it on my (midtier, six month old) phone just now and it took three to four seconds.
Granted, Google Apps are disabled, so it may have been one less thing eating up CPU cycles in the background that made others so slow?