Last night I needed a square root function that would work on 64-bit unsigned integers. I have been using the standard library's sqrt, but my first thought was that an integer square root could be faster.

I looked around and found what was said to be a "fast" integer square root on Stack Overflow by Craig McQueen. I used the code as-is except that I changed it to use 64-bit unsigned ints because that was what I needed.

It seemed like a reasonably performance efficient algorithm, but I had always heard that sqrt, even in hardware, was slow. Because sqrt gets used a lot, I thought better safe than sorry, so this morning I decided to benchmark the integer algorithm against sqrt just to be sure.

• Int Elapsed 1506419us
• Float Elapsed 159330us
• Float+Cast Elapsed 182160us