Why is it faster to process a sorted array than an unsorted array in C++?

In C++, it is faster to process a sorted array than an unsorted array because of branch prediction. In computer architecture, a branch prediction determines whether a conditional branch (jump) in the instruction flow of a program is likely to be taken or not.

Let’s take an example −

if(arr[i] > 50) {
   Do some operation B
} else {
   Do some operation A
}

If we run this code for 100 elements in unsorted and sorted order below things will be happened −

For sorted array −

1, 2, 3, 4, 5, …… 50, 51………100
A, A, A, A, A A, B B

It will load the correct branch in the pipeline and correct sequence

A, A, A, A, A, A, A, A A, B B

For unsorted array −

5, 51, 6, 90, 4, 49, 60…
A, B, A, B, A, A, A, B

Branch prediction doesn’t play a significant role here. It is very difficult to predict the right operation between A and B.