When should I use loop unrolling?

What is loop unrolling and when should I use it?

Loop unrolling is an optimization technique that reduces the overhead of loop control. You should use it when performance is critical, and the loop has a small, fixed number of iterations.

Can you give me an example of loop unrolling in code?

Sure! Instead of writing a loop that increments an array element by one in each iteration, you can unroll it like this:

for (int i = 0; i < 8; i += 4) {
    array[i] += 1;
    array[i + 1] += 1;
    array[i + 2] += 1;
    array[i + 3] += 1;
}

Are there any downsides to loop unrolling?

Yes, loop unrolling can increase code size and may lead to cache inefficiencies. It's important to balance performance gains with these potential drawbacks.

How do I decide the optimal unrolling factor?

The optimal unrolling factor depends on the specific loop and the architecture. Generally, you should test different factors to find the best performance for your case.