Author: Christophe Theron
Date: 23:10:57 10/23/00
Go up one level in this thread
On October 23, 2000 at 22:48:12, Robert Hyatt wrote:
>On October 23, 2000 at 20:50:35, Ratko V Tomic wrote:
>
>>>>> GT has larger-than-life king safety scores. That
>>>>> is all. No different search paradigm or anything else.
>>>...
>>> Christophe specifically said that the search is the same for both
>>> programs. I took that as being true,as it seemed to match my
>>> impression after watching games. It speculates more. But it
>>> isn't searching _differently_ at all.
>>
>>
>>There is quite a bit of space in between, to paraphrase your earlier comment,
>>'large safety score and nothing else' and your current one 'is not searching
>>differently'. The hypothesis I sketched in the previous note is just one of many
>>conceivable ways in between, where one can say 'the search is the same' (i.e. it
>>is using the same iterative alpha-beta & support routines), yet the novelty
>>cannot be said to be merely in a new leaf evaluator (or its weight) but it would
>>be in a way how the inputs and outputs of the search are interacting across
>>iterations via pre/post-processors, as well as how much information is
>>transferred that way (is it just score, hash, history entries & killer moves, as
>>in most programs, or something extra which helps GT make fewer mistakes in
>>deciding to undertake apparently open ended king-side attack).
>>
>>While Christophe did say the search is the same (and one can parse that to mean
>>many things; even Botvinnik's program had alpha-beta search in the lower layer),
>>he also suggested, in response to dismissive comments about the GT style as
>>being just another king safety tweak, that you're welcome to go ahead and
>>increase the king-safety scores in Crafty and see how far that gets it.
>
>
>How do you think I arrived at the _present_ king safety scores? Here is the
>point:
>
>if you have a good search (and CT certainly appears to meet that criterion)
>so that you don't get out-searched very often, then you can be more speculative.
>If you do get out-searched, then you will have massive problems, as CSTal did
>in every group of games I watched it play vs Crafty.
>
>I'd be willing to bet that I can tune my aggressiveness way up, _and_ play that
>version using a big alpha machine (to be sure I don't get out-searched anywhere
>along the way) and the aggressive version would do fine. But as hardware
>becomes more equal, then the 'speculation' had better be right. Else the
>more accurate search will find the holes in the speculation and blow through
>them.
In many cases we are talking about refutations that can only be found with a
20+ plies search (see 43.Rc6 in the Gambit Tiger - Nimzo 8 game). This is above
the current computers/programs abilities anyway (including mine).
So it works also when my program is outsearched (which indeed does not happen
often).
Christophe
>We actually played tuned like this in several ACM events using Cray Blitz. And
>it worked quite well since we were out-searching all the micros by huge margins.
>But against more equal opponents like deep thought and hitech (and belle in the
>early 80's) this was not a wise thing to try.
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