Author: Robert Hyatt
Date: 08:57:44 12/23/02
Go up one level in this thread
On December 23, 2002 at 04:43:18, Nolan Denson wrote: >What is meant by this statement. > > >You then run a set of what you think are "representative positions" >thru the compiler. > >How do you do the above. I have neve don't such a think and was wondering how do >i. I run a set of positions where there are opening, middlegame, endgame, and king and pawn only endgames, so that all the code hopefully gets executed and the branch profiles stored. For crafty, use the FEN-type positions, stuff one into it and say "move". Do this several times. I have a unix shell script that runs about 20 positions... > > >On December 22, 2002 at 21:21:54, Robert Hyatt wrote: > >>On December 22, 2002 at 08:42:23, Joel wrote: >> >>>Hey all, >>> >>>Was reading some of the previous threads where the general consensus seemed to >>>be that the Intel C++ 7.0 compiler did a much better job at optimising than the >>>VC 6.0 Sp4 compiler did. >>> >>>My compiler knowledge is very limited - I have written a C compiler before (uni >>>assignment), but optimisation wasn't an issue. I have no real idea how an >>>optimising compiler goes about it's work. >>> >>>For the record I have an Athlon XP 2100+, and my engine is bitboard based. >>> >>>Having said that, I installed the Intel compiler, and tried compiling my latest >>>version of Bodo, and then ran my dodgy little speed benchmark on it. It was >>>actually slower than the VC 6.0 compiler, though I have reason to suspect my >>>incompetence is the issue, largely due to statements like: >>> >>>"Did you use the intel C++ 7.0? Of course not. Did you do the profile-feedback >>>optimizations? Probably not." >>> >>>What I am asking is how do I do this profile-feedback optimisations, and or any >>>other optimisations which you guys do? >>> >>>What would be particularly helpful is other people could give me the compiler >>>command line parameters they use to generate fast code. >>> >>>I really need to buy a book on optimising compilers so I understand what the >>>hell is happening here. :| >>> >>>Any help greatly appreciated, >>> >>>Joel Veness >> >> >>You need to compile with the options -prof_gen and -prof_dir <dirpath> >>options. You then run a set of what you think are "representative positions" >>thru the compiler. After you finish running whatever you want, you then >>recompile, but this time you replace the -prof_gen option with the -prof_use >>option and away it goes. After this compile, it will probably be 10% faster >>than compiling without this profiling approach.
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