Author: Peter W. Gillgasch
Date: 05:57:14 01/26/00
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On January 26, 2000 at 03:14:11, Tom Kerrigan wrote: >On January 25, 2000 at 23:38:06, Peter W. Gillgasch wrote: > >>Ad 1: This was true for Deep Thought since the difference >> between the fast and the slow eval was noticeable >> due to the sequential properties introduced by >> the Xylinx devices looking at the position on a >> file by file basis. Since DBII is not hampered >> by issues like FPGA capacities this is the first >> bottleneck that was to be removed. As Dave Footland >> has reported they had interesting things in their >> evaluation. In the light of this and in the light >> of things Hans has said it it extremely unlikely >> that they ever take a "slow eval" in DB since there >> is (a) probably no speed gain in doing so and (b) >> things like pins and king safety can add up quite >> a bit, taking a "slow eval" makes no sense in a >> machine which knows that the queen is pinned and >> will be lost versus a bishop or that there is a >> mate in one versus your king. > >I'm not sure I follow this. It seems like both a fast eval and a slow eval would >make sense, depending on the situation. This is an assumption from the "it is a tree search problem, we need more speed and another full width ply please and the tree search will see one ply later that I am going to be checkmated, so why should I care" department. Feng did design DT for speed, DB for more speed (still with cramped pieces all over the place) and finally DBII for more evaluation. As soon as you introduce a slow evaluation you introduce the usual inaccuracies and if you have pin detection __hardware__ why should you be so idiotic and believe that since your run off the mill equivalent of a "fast eval" (say piece placement and material) is 4 pawns outside of the A-B window that it is "safe" to elect to ignore the equivalent of a software "slow eval" ? In the first DB - GK match, how many points does a run off the mill "fast eval" assign to the black rook on h8 and the black bishop on b8 ? 8 pawn units, probably. Jesus Christ ! That stuff was worth __zero__. If Feng didn´t understand that he needs to fix that for real after that game, well, I don´t know. I suspect that there are other guys reading this forum who are in a situation where there is no gain speedwise in electing to ignore the "slow" evaluation. Testing for taking the slow evaluation only is is my case more expensive than taking the full evaluation (4 clock cycles). It helps :) >I read somewhere that DB's fast eval took 3 cycles and the slow eval took 11 >cycles. I'm not 100% sure about the 11 cycles, though. It may be 12. I haven´t seen any clock cycle descriptions of DB. You are probably mixing things up with DT unless you can specify "somewhere" ;) -- Peter
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