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Subject: Re: History pruning

Author: Vasik Rajlich

Date: 05:46:32 02/28/06

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On February 27, 2006 at 11:51:09, Miguel A. Ballicora wrote:

>On February 27, 2006 at 09:41:37, Tord Romstad wrote:
>
>>On February 27, 2006 at 06:48:18, Tord Romstad wrote:
>>
>>>I'll try to write an explanation on my web page, and refer to that one
>>>in the future.  I hope to have it ready today or tomorrow.  Stay tuned!
>>
>>My first draft is ready:
>>
>>http://www.glaurungchess.com/lmr.html
>>
>>Comments, corrections and suggested additions or improvements
>>are welcome.
>
>I was away from CC 3 years and I was wondering what this technique was. Thanks
>for the explanation, it was pretty clear.
>Unfortunately, I tried this ~5 years ago in several ways and it did not work .
>It was not my idea, it was Bob Hyatt's here at CCC. I still have in my code this
>ancient lines (nodecount is moves searched):
>
>		#if 0
>		/* BH's suggestion, modified */
>		if (nodecount == 15 && depth == 1) {
>			break;
>		}
>		#endif
>
>		#if 0
>		/* BH's suggestion */
>		if (nodecount == 15 && depth == 2) {
>			depth--;
>		}
>		#endif
>
>		#if 0
>		/* BH's suggestion, modified */
>		if (nodecount == 15 && prun_cand ) {
>			break;
>		}
>		#endif
>

Note that the method Tord describes is quite a bit different. Most important is
that the late moves are reduced rather than thrown away - I see now why Tord
insisted on that term :)

Vas

>Considering that after moves 15 the order in my case is determined by history
>heuristics, one the options literally was history pruning, and I tried
>reductions too. The tree decreased but my engine (gaviota) played terrible.
>Maybe I should give it a try again. As you can see, the implementation was too
>raw.
>
>Miguel
>
>>
>>The only two engines I mention in my "Sample Code" paragraph are
>>Fruit and Glaurung.  This is because of ignorance, and not because
>>of disrespect to other authors.  If you are the author of an open source
>>engine using history pruning (or whatever you prefer to call it) and
>>wants it to be mentioned on my page, please let me know.
>>
>>Tord



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