Author: José Carlos
Date: 15:41:49 10/26/01
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On October 26, 2001 at 17:05:06, Tom Kerrigan wrote: >On October 26, 2001 at 16:56:19, Derek Mauro wrote: > >>As far as I can tell, static and global variables seem to be equally efficient, >>the only difference being that statics have a limited scope. Am I right, or is >>one actually more efficient than the other? Is there any advantage to passing >>around a static or a global? I've always read that globals should be avoided. >>Is there any performance reason why? >> >>Thanks for your help in advance. > >I assume you mean static -> local. (?) Nope. Static are local variables that last after the function has ended, and are still there when the function is called again. Anyway, static and global variables' performance must be equivalent, AFAIK. José C. >In the olden days, local vars were allocated on the stack (usually fast) and >globals were in the heap somewhere, possibly other segments (very slow). >Registers were also not allocated for globals (extra slow). > >These days, it doesn't really matter where your variables are located in memory >(caches are great!) and registers are allocated for anything. So it shouldn't >make a difference. Realize that there may be overhead for passing variables >between functions; most compilers can do fast calls, where arguments are put in >registers instead of the stack, so this is often a wash, too. > >Basically, program in the way that seems the most straightforward to you and >it's a safe bet that it will be fast. No harm in trying things multiple ways, >though, of course. :) > >-Tom
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