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Re: [gnugo-devel] engine/influence.c (and DFA)

From: Gunnar Farneback
Subject: Re: [gnugo-devel] engine/influence.c (and DFA)
Date: Tue, 03 Sep 2002 20:23:41 +0200
User-agent: EMH/1.14.1 SEMI/1.14.3 (Ushinoya) FLIM/1.14.2 (Yagi-Nishiguchi) APEL/10.3 Emacs/20.7 (sparc-sun-solaris2.7) (with unibyte mode)

Marco wrote:
> > I think in all performance relevant spots (maybe with the exception of
> > influence.c), we are using one-dimensional arrays since the
> > 1D-transition by Gunnar and Inge early in 3.1.x.
> influence.c still has bidimensional arrays, I think, and even with the 
> 1D transition you still have a multiplication, don't you? Based on what 
> I read a (probably too long) while ago in Numerical Recipes in C, double 
> indirection was faster than multiply, at least on Pentium.

The influence code is a special case. Otherwise everything that's time
critical is done with one-dimensional arrays. There is very little
need for multiplications in the addressing. Neither traversal of the
board, nor moving around between vertices require that.


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