Will multi threading provide any performance boost?

Question

I am new to programming in general so please keep that in mind when you answer my question.

I have a program that takes a large 3D array (1 billion elements) and sums up

Answer 1

It's a matrix problem?

Both Intel and AMD have super-optimized libraries for all sorts of heavy math problems. These libraries use threading, arrange the data for best cache use, cache prefetch, SSE vector instructions. Everything.

I believe you have to pay for the libraries, but they are well worth the money.