What are some examples of loop unrolling in programming?

What are some examples of loop unrolling in programming?

Loop unrolling is an optimization technique that reduces the overhead of loop control. For example, instead of writing a loop that increments a counter and processes one element at a time, you can process multiple elements in each iteration. Here's a simple example:

Instead of:

for (int i = 0; i < 8; i++) {
    array[i] += 5;
}

You can unroll it to:

for (int i = 0; i < 8; i += 4) {
    array[i] += 5;
    array[i + 1] += 5;
    array[i + 2] += 5;
    array[i + 3] += 5;
}

What are the benefits of loop unrolling?

The main benefits of loop unrolling include reduced loop overhead, improved cache performance, and increased instruction-level parallelism. By decreasing the number of iterations, you can also minimize the number of jumps in the code, which can lead to better performance.

Are there any downsides to loop unrolling?

Yes, there are some downsides. Loop unrolling can increase the size of the binary code, which may lead to cache misses. Additionally, if the loop body is too large, it can reduce the benefits of pipelining in modern CPUs.

Can you give me another example of loop unrolling?

Sure! Here's another example:

Instead of:

for (int i = 0; i < 10; i++) {
    process(data[i]);
}

You can unroll it to:

for (int i = 0; i < 10; i += 2) {
    process(data[i]);
    process(data[i + 1]);
}