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Subject: Re: some simple questions for the computer wizz's

Author: Gerd Isenberg

Date: 14:18:15 12/12/05

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On December 12, 2005 at 16:40:23, Joseph Ciarrochi wrote:

>sorry i am not a computer expert, so these are probably simple questions for you
>folks..
>
>Is it possibile for rybka to make use of multiple processors? Or does this
>require a complete rewrite of the program

Not a complete rewrite - for multi-threading the search should not use globals
to write search/eval related results, such as board representation or eval
stuff, to become multi-threading aware with some additional initialze/split-fork
code.

The other way of multiple processes with shared hashtable is what Vincent likes,
avoiding pointers to otherwise thread-local memory, but using globals. He has a
none-recursive search afaik - because split/fork seems easier to implement
there.

In either case - it is not the quantity of codelines - but the "quality" and the
where.


>
>Rybka functions better on 64 bit chip than 32 chip (i've heard that it is not
>hte case for fruit and fritz). Will there, or is there, a 128 bit chip. Will
>techological developments lead to an ever increasing bit capacity , or is the
>future in multiple processors (or both)?

For x86 we already have 8 (P4, amd64 32-bit mode) or 16 (amd64 64-bit mode)
128-bit xmm-register with SSE2(3)-instruction set. It is a kind of
vector-register-file for SIMD-instructions with vectors of either 2 doubles, 4
floats, or as integers 16 bytes, 8 words (short), 4 dwords (int) or 2 quadwords
(__int64, long long).

But internal busses and alus are still 64-bit (alu = arithmecical/logical unit)
on current amd64 cpus. Pure register-register, risc-like SSE2(3)-instructions
usually are double dispatch instructions with a typical latency of 2 cycles.
My guess: we will first have quad-cpus on a single-core and then 128-bit alus.

With some further prefix bytes even 256- or 512-bit register may become true
some day...

Gerd

>
>best
>Joseph



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