Author: Robert Hyatt
Date: 08:55:18 06/11/02
Go up one level in this thread
On June 10, 2002 at 11:18:25, Les Fernandez wrote: >On June 10, 2002 at 11:01:50, Robert Hyatt wrote: > >>On June 10, 2002 at 03:22:55, Andrew Williams wrote: >> >>>On June 10, 2002 at 00:18:51, Les Fernandez wrote: >>> >>>>On June 10, 2002 at 00:02:39, Robert Hyatt wrote: >>>> >>>>>On June 09, 2002 at 23:45:38, Les Fernandez wrote: >>>>> >>>>>>I rarely come across strange output using Crafty but this position doesnt seem >>>>>>to work right. The ce after analysis I think should be -32765 but in fact it is >>>>>>reporting a "0"??? Either I am dead tired or something is screwy. Would >>>>>>somebody using Crafty run this epd string? It is a very simple mate and I cant >>>>>>seem to find the problem. Its probably just late <S>. >>>>>> >>>>>>Here is Crafty analysis: >>>>>> >>>>>>rnb4k/5r2/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/7R b - - acd 1; acn 1; acs 1; ce 0; >>>>>>pv Rh7; >>>>>> >>>>>>The pv appears to be right but the ce value is dead wrong!! >>>>>> >>>>>>If you find the same results can someone please explain the nature of this? >>>>>> >>>>>>[D]rnb4k/5r2/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/7R b - - >>>>>> >>>>>> >>>>>>Thanks >>>>> >>>>>Can you describe _exactly_ how you produced that? IE post the epd file >>>>>you used, etc... >>>>> >>>> >>>>EPD Kit revision date: 1996.04.21 >>>>unable to open book file [./book.bin]. >>>>book is disabled >>>>unable to open book file [./books.bin]. >>>>search time set to 180.00. >>>>hash table memory = 48M bytes. >>>>pawn hash table memory = 10M bytes. >>>>Crafty 18.9 vs ferret >>>>kibitz Hello from Crafty v18.9! >>>>pondering enabled. >>>>play best book line after search. >>>>EGTB access enabled >>>>using tbpath=./TB >>>>4 piece tablebase files found >>>>1406kb of RAM used for TB indices and decompression tables >>>>PFGA: EPD record: 1 >>>> >>>>The exact epd string that was in epd.epd was: >>>> >>>>rnb4k/5r2/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/7R b - - >>>> >>>>And the epd.out file was: >>>> >>>>rnb4k/5r2/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/7R b - - acd 1; acn 1; acs 1; ce 0; >>>>pv Rh7; >>>> >>>> >>>>The analysis report can be found in my original post here. This one puzzles me >>>>too Bob but I could not rule out that its late <S>. If you need any additional >>>>info let me know. >>>> >>>>Thanks >>> >>>Is this because Black has only one move? In my program, if there's only one move >>>available *during a game* it only searches to depth 4. For testing epd >>>positions, it searches normally, even if there is only one move. >>> >>>Andrew >> >> >>That might be the reason. With only one move, the epd code in Crafty might >>not do a search at all, and that would leave the score unchanged from the last >>epd position perhaps... > >Um I am not sure that is what is going on here, let me explain. What I did was >I took an epd position that reported a mate sequence and then made the pv moves >and then created all the following epd positions that eventually led to the >reported mate based on the pv sequence from the first position. Following is >the results of Crafty which ran the epd's that I created based on the pv line >from the first position: > >rnb4k/5r2/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/R7 w - - acd 4; acn 10909; acs 1; ce >32764; pv Rh1+ Rh7 Rxh7#; >rnb4k/5r2/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/7R b - - acd 1; acn 10909; acs 1; ce >0; pv Rh7; >rnb4k/7r/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/7R w - - acd 4; acn 7328; acs 1; ce >32766; pv Rxh7#; >rnb4k/7R/2p1p1Q1/pp3pP1/3P4/b2B1KP1/1PPB4/8 b - - acd 1; acn 1; acs 1; ce >-32767; pv; > >As you can see the second epd string reports a "0" but the one before it and >after it are in fact reporting a value. If your thought "With only one move, >the epd ..... " is correct then why would the last epd position which is the >actual final move show a ce of -32767 ??? Any other thoughts Bob? > >Thanks The issue is this: "if one side has exactly one move to make at the root, then there is no reason to do a search there since the search _must_ return that one move as best." It is possible that the epd implementation (I did not write it) doesn't handle this reasonably and gets the score wrong by avoiding a search completely...
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