Question

I read recently, in an article on game programming written in 1996, that using global variables is faster than passing parameters.

Was this ever true, and if so, is this still true today?

Answer 1

Short answer – No, good programmers make code go faster by knowing and using the appropriate tools for the job, and then optimizing in a methodical way where their code does not meet their requirements.

Longer answer – This article, which in my opinion is not especially well-written, is not in any case general advice on program speedup but ’15 ways to do faster blits’. Extrapolating this to the general case is missing the writer’s point, whatever you think of the merits of the article.

If I was looking for performance advice, I would place zero credence in an article that does not identify or show a single concrete code change to support the assertions in the sample code, and without suggesting that measuring the code might be a good idea. If you are not going to show how to make the code better, why include it?

Some of the advice is years out of date – FAR pointers stopped being an issue on the PC a long time ago.

A serious game developer (or any other professional programmer, for that matter) would have a good laugh about advice like this:

You can either take out the assert’s
completely, or you can just add a
#define NDEBUG when you compile the final version.

My advice to you, if you really wish to evaluate the merit of any of these 15 tips, and since the article is 14 years old, would be to compile the code in a modern compiler (Visual C++ 10 say) and try to identify any area where using a global variable (or any of the other tips) would make it faster.

[Just joking – my real advice would be to ignore this article completely and ask specific performance questions on Stack Overflow as you hit issues in your work that you cannot resolve. That way the answers you get will be peer reviewed, supported by example code or good external evidence, and current.]