In C, accessing my array index is faster or accessing by pointer is faster?

Question

In C, accessing an array index is faster or accessing by pointer is faster? By faster I mean, which one would take less clock cycle. The array is not an constant array.

Answer 1

It's completely system-dependent which one is faster, but the two are functionally equivalent to one another and I'd be really surprised if one actually was faster. That is, the code

myArr[index]

Is completely equivalent to

*(&myArr[0] + index)

Similarly, writing

*ptr

Is equivalent to writing

ptr[0]

Most compilers are smart enough to figure this out, so I'd be amazed if one was faster than another.

More importantly, though, you probably shouldn't be too worried about this. Worry about optimizations after you have everything else working. If you find that array accesses really are killing you, then consider finding a faster alternative. Otherwise, don't worry about it; it's infinitely more valuable to have clean, readable, maintainable code than it is to have optimized code unless you have a pressing need for optimization.