C ++ performance

[Imadatobanisa]

Please, look at the test sample :
Very simple code:
for (volatile long i = 0; i < 1000000000;i++); // A billion loop
I see it took about 5 seconds to complete...
Let's divide : 3.2 x 10⁹ / 1 x 10⁹ / 5.0 ≈ 0.64 x 100% ≈ (64 %)
(My computer speed is 3.2 GHz...)
What do you think about this result and C++ performance?

[Cubbi]

I think you need to turn up optimization settings on your compiler. This loop is supposed to take exactly zero time.

[Peter87]

I think it must have been a bad compiler that didn't manage to optimize away the loop.

[Imadatobanisa]

I rewrote it, but I forgot the word volatile... Sorry. :)

[Imadatobanisa]

But perhaps...Can this code be optimized or compressed more?

[naraku9333]

What do you think about this result and C++ performance?

I'd say it's more to do with the performance of your system memory then c++.

[Cubbi]

With volatile, let's compare computers and compilers

3.55 GHz Power 750
    IBM XL 11.1: 4.37 s
    GNU g++ 4.7.2: 3.45 s (good job this time)

2.67 GHz Intel Core i7
    GNU g++ 4.7.2: 2.44 s
    LLVM clang++ 3.1: 2.44 s
    Intel icpc 13.0: 2.43 s

I still think you need to turn up those optimization settings

(either way, this kind of loop is not exactly what CPUs are optimized for)