Quote:Original post by dpadam450
Well 26 seconds vs 1/2 second is a problem. So in a respectful way, I as the developer have a problem (26 seconds), that I as the developer see because I see debug mode :(

If its a game, you have a problem whether its 26 seconds or 1/2 second. That would imply a very bad algorithm that should be the focus of your efforts rather than swapping out std::vector for an array, or possibly using std::vector in a sane manner, since your benchmark doesn't do so.

Again, you're 1) optimizing for a special case (debug mode) not the general case (release mode), 2) focusing on the wrong thing (trying to out-think the compiler rather than using data structures intelligently), 3) using an artificial benchmark to prematurely make performance decisions. If your game is spending 1/2 of a second in vector/array code, then there are larger problems afoot.

The single thing you can rightfully blame std::vector of is the fact that every vector must do at least one heap allocation and if you have more than a dozen or so elements, it must at least do two heap allocations (and will do log(N) allocations if you keep pushing_back without reserving).
On the other hand, declaring int array[10000000]; like in your example takes about 40 MB of stack space, which honestly is a number that very well justifies a heap allocation. In fact, I'm surprised your program doesn't crash, because with default options, you only have a 1 MB stack size, if I remember correctly.

Other than for the allocations, it isn't worth to worry about overhead. While I can't say much about MSVC (since I'm not using it), chances are that it is not optimizing much worse than gcc (this can be safely assumed).
And gcc on the other hand, optimizes most of STL and TR1 into the exact same (and sometimes better) code as carefully hand-tuned specialized code. It is a total waste of time to try and do any better.

Moving to General Programming so we can stop distracting beginners with potentially dangerous and/or wrong ideas, and take off the kid gloves and tell people when they're wrong.

It's funny, C++ is probably the last language that still has arrays.

All others have either collections or dictionaries.

&#106avascript doesn't even have ints.<br><br>And somehow, the world hasn't come to standstill.