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

[Marco Scheurer]

On Tuesday, September 3, 2002, at 05:10  pm, Arend Bayer wrote:

> On 3 Sep 2002, Dave Denholm wrote:
>
> > Unrolling the loop
> > reduced the time from 6 minutes to 5 minutes 37 seconds. (I had been
> > wondering whether the measured speedup had been due to it doing less
> > work, rather than due to the unrolling.)
>
> What I've been wondering: Shouldn't we expect a modern compiler do do 
> the
> loop unrolling himself?

Aren't there also cases where loop unrolling has a negative effect?

Speaking of micro optimizations and speed/space trade offs, I've been 
wondering about these:

- There are many bi-dimensional arrays. Would it make sense to replace 
them by pointers to pointers? Two indirections are supposed to be faster 
than the arithmetic needed to access elements in a bi-directional array. 
The syntax to read an element is the same, but some initialization code 
is needed.

- Replace floats with doubles? The net effect probably depends on the 
processor and the compiler, and is not likely to make a huge difference. 
But maybe these floats could be declared as ggfloat, with an option to 
typedef this as float or double.


Marco Scheurer
Sen:te, Lausanne, Switzerland    http://www.sente.ch