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G++ Compiler -O (Optimization) Tag

Posted on 1998-12-29
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Last Modified: 2012-05-12
What's the benefeits of using this tag?

I'm compiling a MUD engine, right now using g++ -c, and am wondering if there's any benefeit (and if, then what specifically) -O optimization will give me, in terms of space, memory, speed, etc. And if I should use it.

Thanks!

Matt-
matt@anji.smhall.org
 
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Question by:tribal9
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sosedada earned 0 total points
ID: 1181272
-O is equivalent to -O1, or the first optimization level.  g++ also has -O2, -O3, and -Os.  The downside of these is compilation time.  However, they will speed up your program, definitely.  I believe in most cases executable size is decreased, but this is not guaranteed.

-O1, -O2, -O3 perform increasing amounts of optimization, require increasing amounts of time and also have a higher chance of breaking.  Optimization usually only breaks if your code is really complex.  

-Os is an options that performs no optimizations that increase executable size.  This means less speed optimization but a greater decrease in size.

As far as memory usage goes, optimization should decrease it.  Variables may be eliminated and optimization should decrease the number of lines of code necessary.

I would recommend using -O1 (or -O) for sure.  Perhaps before distribution, you could play with the higher optimization options to see how they would benefit you.
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by:jkr
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sosedada - wow, great elaboration! (indeed  - hard to improve...  ;-)
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by:tribal9
ID: 1181274
By far the best answer I have recieved on here in awhile.

You earned your 5 points. =)


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