Author: Vincent Diepeveen
Date: 14:46:23 02/16/05
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On February 16, 2005 at 13:09:14, Frank Phillips wrote: >Has anybody got any experience with g++ 3.4 for amd64 (x86_64) - for Linux? > >I have been using the profile generated optimisation option, but the code it >produces is no faster then with simple -O3. > >I simply compile with -fprofile-generate >then run, >then recompile with -fprofile-use. > >The relevant *.gcno, *.gcda files are produced. Must be doing something >wrong..... > >Frank First of all get the LATEST version of gcc. thats 3.4.3 now. and if when i post 3.4.4 is released get that one. like bob my experience is that the PGO in gcc is pretty buggy. icc is however such a bad optimizing compiler that gcc is far faster for diep. i guess icc is better bugfixed for 64 bits code as that mattered for specint2000, guess why :) Anyway gcc isn't that great in 64 bits perhaps, but it's scheduling better for opteron than icc is, which for diep is more important. icc of course is only good for intel hardware when your program hasn't been in specint yet. main idea is. delete all your files except source files. THEN run the fprofile generate single cpu. then delete all object files then run the profile use. never use intel c++. they will do anything to slow you down at AMD hardware. Vincent
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