Which is faster/more efficient?

[Nickolas]

Is assigning a value to a variable using another variable faster than the normal way? I mean is this:

Code: Select all

const a = 1;
int b = a;

faster than this:

Code: Select all

int b = 1;

?

P.S. I only care about using the variable. The "loading" of the constant isn't my concern. I probably didn't express this very well. I mean that I don't care about the time that "loading" the constant takes.

P.S. 2 It's C# but I believe it is the exact same code in C/C++.

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[Xian Nox]

The second one I think. And anyway, the speed difference is so low (ns), that you won't notice it.

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[codestation]

You have 4 answers for that:

1) The second one is more efficient because the first one involves 2 memory accesses and the other one doesn't since the constant value is probably embedded in the asm opcode (this is dependent of the target architecture).

2) Your compiler will optimize that code to your 2nd case so it doesn't matter.

3) It depends on the language so C#, C and C++ compilers can have different output for the same code depending on the type and optimization levels.

4) Why do you care for that? the compiler knows better than you. Also don't optimize prematurely, you can lose precious time on things that the compiler will be doing anyway. If you feel that this piece of code is the bottleneck of your app then use a profiler to find it out.

P.S.: i'll go with the 4th.

[Nickolas]

I asked just out of curiosity but this could really affect large scale programs... (Maybe games...) Thanks for answering though!

[m0skit0]

this could really affect large scale programs...

No. Read codestation's 4th answer again

[Nickolas]

this could really affect large scale programs...

No. Read codestation's 4th answer again

Oops. Must have missed that. Anyway, thanks for answering.