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Subject: Re: Floating point VS Integer Math.

Author: Ivan Tirado

Date: 18:35:52 05/14/98

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On May 14, 1998 at 20:40:59, Robert Hyatt wrote:

>On May 14, 1998 at 19:15:24, Bruce Moreland wrote:
>
>>
>>On May 14, 1998 at 18:32:26, Ivan Tirado wrote:
>>
>>>   In contemporary chess programs, what gets more use:
>>>floating point math or integer math? If integer math is preferred, how
>>>do different processors handle it ( ie perform )? Can a chess program be
>>>optimized to use MMX if integer math is used? In the case floating point
>>>is preferred, why this is so?
>>
>>There is probably some guy out there working furiously on a program, and
>>his big angle is that he does floating point math in just the right
>>spots, or so he thinks.
>>
>>On all the micros that I know of, you should use integers if you can.
>>Most chess programs are extreme examples of optimization, so they'll
>>tend to not use floating point at all.
>>
>>If there is a processor where floating point is faster, or some
>>combination of floating point and integer is fastest, there is some
>>lunatic out there right now writing floating point chess program code in
>>assembly language.
>>
>>And if the assembler doesn't do exactly what he wants, he'll input the
>>op-codes by hand into a hex editor.
>>
>>bruce
>
>
>I know such a lunatic.  :)  On the Cray floating point math is *fast*.
>because it was designed for floating point...  so we did mostly fp stuff
>as it gave us another degree of parallelism in that on that machine, we
>can do 1 32bit integer op, 1 64bit integer op, and one 64bit fp op, all
>in one cycle (on one cpu)...
>
>not in crafty of course...

  Ok. So in *normal* micros integer math dominates. Is this necessarily
so? Are you SURE? I do some programming myself, and I remember that the
Glide reference manual ( 3DFX graphics ) states that it uses floating
point math in its library: ( I paraphrase now ) "...because it is MUCH
faster in pentiums..". Was 3DFX wrong when it wrote this? Or am I
confusing something here? ( i.e. is FIXED POINT math == integer math ??
) Also, Mr. Hyatt, what about MMX? Do you ever wonder if it could help
crafty? ( 4 integer ops in parallel ? ) Are you planning an MMX
optimized crafty, or would that be useless? ( I think maybe you're
waiting for automatic compiler optimizations ;) )



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