Author: Christophe Theron
Date: 20:20:43 01/17/01
Go up one level in this thread
On January 17, 2001 at 11:22:49, Bas Hamstra wrote:
>On January 16, 2001 at 20:59:43, Christophe Theron wrote:
>
>>On January 16, 2001 at 20:25:53, Bas Hamstra wrote:
>>
>>>On January 15, 2001 at 21:33:02, Christophe Theron wrote:
>>>
>>>>On January 15, 2001 at 18:24:23, Bas Hamstra wrote:
>>>>
>>>>>On January 14, 2001 at 10:18:08, Robert Hyatt wrote:
>>>>>
>>>>>>On January 14, 2001 at 00:37:12, Christophe Theron wrote:
>>>>>>
>>>>>>>On January 14, 2001 at 00:22:17, Robert Hyatt wrote:
>>>>>>>
>>>>>>>>On January 14, 2001 at 00:05:08, Christophe Theron wrote:
>>>>>>>>
>>>>>>>>>On January 13, 2001 at 17:19:19, Robert Hyatt wrote:
>>>>>>>>>
>>>>>>>>>>On January 13, 2001 at 17:13:13, Gian-Carlo Pascutto wrote:
>>>>>>>>>>
>>>>>>>>>>>Hi all,
>>>>>>>>>>>
>>>>>>>>>>>I just added code to my program to handle fractional extensions
>>>>>>>>>>>and recapture extensions.
>>>>>>>>>>>
>>>>>>>>>>>My problem now is: how do I test & tune these? I did what I
>>>>>>>>>>>normally do and ran it through WAC. It did worse. Probably not
>>>>>>>>>>>so surprising as they are nearly all rather simple tactical
>>>>>>>>>>>positions, so extending more (on checks...not so much on
>>>>>>>>>>>recaptures) is nearly always a win.
>>>>>>>>>>>
>>>>>>>>>>>Does anybody here have a testcase? Maybe a set of positions
>>>>>>>>>>>where it _really_ matters how you do your extensions?
>>>>>>>>>>>
>>>>>>>>>>>If you added frac. extensions you your program, what made you
>>>>>>>>>>>decide to do so?
>>>>>>>>>>>
>>>>>>>>>>>--
>>>>>>>>>>>GCP
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>Do as I did. Make the extension amount something you can set via command.
>>>>>>>>>>Then run a potload of tests. I ran WAC with all the extensions set to
>>>>>>>>>>values between .5 and 1.0, in increments of .25. That is 3 cases for
>>>>>>>>>>each extension and I varied 4 different extensions. 81 tests and you then
>>>>>>>>>>look at which ones needed the fewest total nodes to solve _all_ the test
>>>>>>>>>>positions...
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>So Crafty is cooked for WAC!? ;)
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Christophe
>>>>>>>>
>>>>>>>>
>>>>>>>>:)
>>>>>>>>
>>>>>>>>actually not, as I used a lot of other positions as well (IE I used some of
>>>>>>>>the "crafty goes deep" positions that were not tactical at all....)
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>I am still using full ply extensions.
>>>>>>>
>>>>>>>I think I should try fractional extensions. Actually I did in the past. My 16
>>>>>>>bits version used fractional extensions (in 1/100th of ply), but I was also
>>>>>>>doing much more extensions. I mean I had more reasons to do extensions.
>>>>>>>
>>>>>>>As for now, I prefer to be extremely "selective" in my extensions. There are a
>>>>>>>lot of conditions to meet before Tiger triggers an extension.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Christophe
>>>>>>
>>>>>>
>>>>>>Fractional ply extensions give a chance for better control. IE you can say
>>>>>>"OK, I want to extend 3 checks, then not extend 1, then extend the next three,
>>>>>>but not the next... then you use a 3/4 ply extension... it is also useful
>>>>>>for controlling the one-legal-reply extension since that is really a double
>>>>>>extension on one ply and extending _two_ plies is potentially catastrophic.
>>>>>
>>>>>They can also be very powerful, see Genius. It sees amazing things in 0 sec. So
>>>>>it can be done.
>>>>
>>>>
>>>>
>>>>Unfortunately this has nothing to do with fractional extensions.
>>>
>>>I was referring to extending more than 1 ply.
>>
>>
>>
>>What Genius does is not achieved by extensions. That's what I meant.
>
>Are you sure? I am pretty sure it uses some kind of threat detection that
>detects a mate if one side passes, and follow lines based on the result. Sort of
>nullmove mate extension, only it wasn't named that way then.
>
>If it does NOT do this (as you say) then explain to me how it sees MATE06 in 1
>second for WAC141. I can make my program do the same and see a mate in just over
>30.000 nodes, while NOT choking at all on other positions. In fact it can see
>many other deep mates instantly. Like Genius.
>
>I therefore assumed Genius does the same sort of thing, though it might be
>achieved differently. Singular extensions. Or by a super qsearch. But even then
>I believe in fact the same happens: follow lines based on threats.
>
>Bas.
It does a kind of super QSearch based on detecting threats, but this has a very
high cost.
The basic principle has nothing to do with extensions. It is just a different
definition of what "quiescence" is. BTW this has been explained by Shanon in his
early papers about computer chess, nothing really new here.
It is sometimes spectacular, but as I said it is very expensive. Maybe it's
efficient at low ply depths, because it helps to find deep tactics in a
reasonnable amount of time, but I doubt it is as efficient when you are able to
reach higher depths
Christophe
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