On my machine and debug mode `i == 7` takes 12 seconds to run and `i * i == 49` takes 20 seconds. With release mode it was like 1.3 for `i * i == 49` and 0.8 for the other. A little faster than double the speed, which means it's at least faster than `i == -7 or i == 7`.
Based on [this online benchmark](http://quick-bench.com/iue_glaKKJOSvKdgeUtmHRhNapA), you'll see multiplication is more than 2 times slower in C++
