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Subject: Re: assembly--not really that fast

Author: Ed Schröder

Date: 04:05:02 01/13/02

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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



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