OK, I recently ( last hour) installed the C::B IDE, which uses the MINGW compiler. Now I have a question. Ive noticed that teh MINGW provides an option called 'expensive optimizations', what effect does this have on compile time and on speed of the executable?
Also, Im wondering, since I have access to several different compilers, how do various compilers rate on optimization?
Most compiler optimizations weigh speed vs size, as far as compilation speed, intuitively I would say it would be longer, but in practice, I have never notice any difference.(but then again, I've never compiled anything that takes hours to build.
Longest program ive compiled takes about 45 minutes, but its a couple million lines of computer generated code.Originally Posted by Darryl
I think the longest compilation time I've ever had was about a minute for computer-generated code and maybe 30 seconds for hand-written code. That's for my code, though. Compiling the Allegro and Boost took a few hours each.
Expensive optimizations are optimizations that could speed up your program slightly, but take a long time for the compiler to do.OK, I recently ( last hour) installed the C::B IDE, which uses the MINGW compiler. Now I have a question. Ive noticed that teh MINGW provides an option called 'expensive optimizations', what effect does this have on compile time and on speed of the executable?
Also see GCC's other optimization options: http://www.network-theory.co.uk/docs...cintro_49.html
dwk
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OK, thanks dwks. Thats sort of what i figured it was but wanted to make sure. Ill just leave it on then, since extra compile time is nothing but every last picogram of speed is important.
I didn't know this, but -O3 can actually make your program slower.
You could try -O2 and -O3 to see which works better.-O3
This option turns on more expensive optimizations, such as function inlining, in addition to all the optimizations of the lower levels -O2 and -O1. The -O3 optimization level may increase the speed of the resulting executable, but can also increase its size. Under some circumstances where these optimizations are not favorable, this option might actually make a program slower.
-O2
This option turns on further optimizations, in addition to those used by -O1. These additional optimizations include instruction scheduling. Only optimizations that do not require any speed-space tradeoffs are used, so the executable should not increase in size. The compiler will take longer to compile programs and require more memory than with -O1. This option is generally the best choice for deployment of a program, because it provides maximum optimization without increasing the executable size. It is the default optimization level for releases of GNU packages.
dwk
Seek and ye shall find. quaere et invenies.
"Simplicity does not precede complexity, but follows it." -- Alan Perlis
"Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
"The only real mistake is the one from which we learn nothing." -- John Powell
Other boards: DaniWeb, TPS
Unofficial Wiki FAQ: cpwiki.sf.net
My website: http://dwks.theprogrammingsite.com/
Projects: codeform, xuni, atlantis, nort, etc.
Yeah I saw that. Ill have to keep that in mind if my frame rate drops too low.
