RS: [Beowulf] Sempron compile optimization
award at uda.ad
Wed Nov 23 07:19:04 PST 2005
I'm running a Fedora, classicaly compiled for "i686", on the aforesaid Semperon 3000+ (actually a 1800MHz clock).
>Sorry, to be more explicit, I think that MOST people probably don't want
>to use -m features, whether or not they work. The compiler will usually
>"do the right thing" without them, unless you are cross-compiling. I
>think they are there mostly for cross-compilers.
So far, a quick series summation gave me:
* "vanilla" gcc (no switches): 19.1 s
* add -march=athlon: 9.9 s
* other FPU options (-sse, -3dnow) have no further effect, probably incorporated into athlon.
* replace with -march=x86-64: 8.3 s
* add -m64: cc1 complains, doesn't compile. Doc says it should work (yah).
No exactly rocket science, but a 130% speedup that doesn't cost anything. Disclaimer: probably depends quite a lot on your code, as usual.
The bad news is: you also get to recompile all your dynamically linked libraries, or you don't win anything. Happened to me with libgmp.
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