Author: Steve Maughan
Date: 05:30:59 06/15/04
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Fabien, If I may also ask some questions about Fruit? For me Fruit 1.0 is really quite amazing! Clearly the strength comes from the search. It is able to search much deeper than many programs (including Monarch 1.0), yet it's difficult to attribute this to anything in particular. Take for example the position with the winning move Rxf6+ - (it not too difficult to solve): [D]1r3k1r/6pp/p3Qp2/P7/q1P5/8/1n4PP/1R3R1K w - - In this position on my 2 GHz P4 Fruit 1.0 searches to 14 ply in 18 secs and finds the solution much sooner. Monarch 1.0 is at least one ply behind at 18 secs and I've noticed this to be the case4 in many positions. If I may ask - what's the secret of Fruit's ability to search deeply? Can you give us some clues? What part of the search are you most proud of? Having looked at the source code you seem to be doing the following: 1) Check at the first ply - nothing new there 2) Your implementation of ETC seems somewhat different. You actually make the move (as opposed to calulate the new hash value). And then call full_leaf - what does this do - it seems to check for leaf status otherwise return nothing? What's the thinking here? Does Fruit get much of an Branching Factor improvement with ETC? 3) In the Null move verification Full_Simple is called which seems to force moves to be played i.e. no early cut-offs i.e. the opposite of Full_Simple. 4) For move ordering it looks as if Fruit has toyed with the idea of performing a QSearch to get the best move. This seems to be disabled in Fruit 1.0 and instead you rely on MVA/LVA and not SEE - was SEE worse for this? 5) Fruit seems to cut losing captures in the QSearch using SEE So what part of Fruit 1.0, in your opinion, is contributing to such a good branching factor? Regards, Steve
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