5 ms·
She's right about squaring on each iteration, though. And granted, a square root is much more expensive, though done only once. Which method is faster would d
by borkabrak 11y ago
She's right about squaring on each iteration, though. And granted, a square root is much more expensive, though done only once. Which method is faster would depend on the number of iterations.
- uxcn 11y agoThe latency for sqrtss on broadwell is 11 cycles with a throughput of 4, where mul is a latency of 3 and throughput of 1. So, using some concrete numbers, sqrt is more expensive, but not polynomially or even an order of magnitude.
- JoeAltmaier 11y agoRight with modern floating point implementations its not the old guess-and-iterate method any more. SQRT is probably now on the order of an inverse?
- uxcn 11y agoI honestly haven't looked into it in that much detail, but if I had to guess... probably. I'm not sure what the implementation used in hardware currently is, but at very least it's constant bounded, Conversions are still somewhat expensive, but I do know compared to polynomial time or a large enough constant, it can be a better choice for an optimization. For example, computing log10 of an integer.