Author: Robert Hyatt
Date: 07:22:52 01/13/02
Go up one level in this thread
On January 13, 2002 at 07:05:02, Ed Schröder wrote: >On January 13, 2002 at 05:35:06, Tom Kerrigan wrote: > >>On January 13, 2002 at 05:10:44, David Dory wrote: >> >>>On January 13, 2002 at 01:53:02, emerson tan wrote: >>> >>>>What's the best computer language to program a chess software in terms of speed >>>>of execution? Is it FORTRAN? C++? C? or any other language I dont know? What are >>>>the advantages and disadvantages of each language? What languages does FRITZ, >>>>SHREDDER, REBEL, TIGER, JUNIOR, HIARCS, CRAFTY, CHESSMATER AND OTHER FAMOUS >>>>PROGRAMS USE? >>>> >>>>Thanks >>> >>>Most of the top amateur and pro programs are written in C. Many sprinkle in some >>>assembly language in very time-critical sections. Some very good programs have >>>been written in assembly - which is blazingly fast. Unfortunately when the >> >>Assembly used to be blazingly fast, back when compilers weren't very good and >>microprocessors were simpler, but it has lost a lot of its advantages. >> >>It is now extremely difficult to write assembly that's faster than compiled C. >>There are so many rules about how to schedule instructions and align data for >>good performance that only a computer can keep up with them all. I've >>participated in contests with highly regarded assembly language programmers and >>Visual C++ usually outperforms their hand-written code by ~20%. This is often >>because the humans forget or aren't aware of some obscure rule about aligning >>data or instructions. >> >>Another problem with assembly is that it's hard to keep current. Assembly that >>ran well on Pentiums does not necessarily run well on Pentium Pros. I know that >>Fritz was bitten by this problem--the engine was written in assembly and >>optimized for the Pentium when the PPro came out, and it actually ran slower on >>an equally-clocked PPro. A C program can just be recompiled with a PPro-suited >>compiler and get performance gains from the new processor. >> >>-Tom > > >I have to disagree, I have a MSVC6 version of Rebel and it runs 30% slower than >the ASM version. > >Ed I've always sais that the people that say that C is just as fast as assembly simply don't know "how to do it right". Cray has the _best_ optimizing FORTRAN compiler on the planet, _bar_ _none_. Yet the assembly version of Cray Blitz was roughly 5x faster when we started and even at the end of the project it was still 3x faster. There are several reasons: 1. You know more about the program than the compiler. No bounds-checking on "switch" type statements is necessary. 2. you know whether a value can be positive, negative, or both. The compiler can't. 3. you know whether a value can exceed (say) 127 or not. The compiler can't. 4. You know how many registers the CPU has and can design code around that, while C doesn't give you such control. 5. you know exactly which registers procedure "x" will destroy, so you don't have to save everything before calling it. If you are careful, you don't have to save _anything_. the list goes on and on. In the case of the Cray, we could do some tricky things in assembly that the compiler simply couldn't do, particularly dealing with vectors and the vector hardware. IE we could use vector values as temporary registers. We didn't have to continually save/restore stuff as procedure calls were made because we didn't use _any_ "library functions" whatsoever in the search itself. I would be more than happy to take on _any_ compiler, given a program as complex as a chess engine. And the compiler simply won't have a chance. Of course, there _are_ good reasons for using C. Portability and ease of change to name just two... But for absolutely max speed, there is only one answer...
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