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This item is a game information page
It belongs to categories: Orthodox chess, 
It was last modified on: 2010-01-10
 By Joe  Joyce. Great Shatranj. Great Shatranj. (10x8, Cells: 80) [All Comments] [Add Comment or Rating]
H.G.Muller wrote on 2008-04-27 UTC
OK, final report of the pilot tests (~100 games in a Chess context). The re-run of M vs HP with HP set at 650 did not make the HP mre valuable compared to when the engines thought they were equal. On the contrary, the result was 45.4% (51+ 64- 26=) for the Ministers, against 42% earlier. The 4.6% excess score for the High Priestesses corresponds to about 35 cP, or 17 cP a piece. That confirms the value 650 (against 633 for the Minister). Perhaps the first time the High Priestesses were partly lucky. Note that the standard error is 31 cP. Then I tried the 'Elephant' (F+A, or Elepherz, really) and 'Dababbah' (W+D, Wazibabbah), in pairs against a pair of Knights (so that the opponent actually had 4 Knights in the array RNNBQKBNNR against RNEBQKBENR or RYNBQKBNYR). Note that I started the Wazibabbahs at b1 and i1, because the on c1 and h1 there was a terrible development conflict with the Knights. EE vs NN was practically equal (I had already anticipated that, and programmed the value at 290 against the Knight's 300, for a slight discouragement of trading the imbalance away for no reason): 49.5% (39+ 40- 21=). So a _pair_ of E is worth 600. But, being color-bound pieces, I have no doubt that part of this is for the pair bonus, and that an unpaired E is worth less than half of it due to the inability to access the other color. Fairy-Max is not really a good system to test this, as it has no pair bonusses in its evaluation. As the piece itself is less valuable than the Bishop, (a pair of those isworth 750 on 10x8), my educated guess would be that the pair bonus is also smaller, about 30. That would make the E base value 285. YY vs NN gave a clear win for the Knights: 45.5% (37+, 46-, 18=). The 4.5% excess score translates to only 30cP for the YY pair, though. Thus each Wazibabbah comes out at 285. It seems an isolated F+A and D+B are equal in value, and that the F+A achieves its higher value only through the pair bonus. Finally the Commoner, which I already tested before once on 8x8. Again I tested a pair of them against two Knights. As expected, also on 10x8 a very clear win for the Knights: 40% (35+ 46- 14=). That corresponds to 70cP, or 35cP per Commoner, which thus comes out at 265 (very close to the preset of 260 I gave it, so no need for a second iteration). Note that this low Commoner value falsifies about every speculation that has been made about it (usually presented as 'King end-game value'), which all put it above the Bishop, around 400. It is not an effect of the bigger board, as I found nearly the same value on 8x8. This is opening value, though, and Betza has mentioned that the opening value of the Commoner is indeed very low, but that it gets very strong in the end-game. So I am testing that now, By setting up varies Pawn chains of 7 or 8 Pawns on 2nd and 7th rank (making sure each side plays each Pawn setup equally often in both directions), plus Kings on i1/i8, and then giving one side Knights on b1 and f1, and the other Commoners on b8 and f8. No other pieces are on the board, and I would say this definitely qualifies as end-game. 13 games is a bit early, but the Commoners are not doing very well here either (61.5% for the Knights, so far). So the preliminary conclusion of the piece values in a Chess context is: HP=650 M=630 N=300 E=285 (pair bonus=30) Y=285 G=265 P=85 It seems that all pieces with 8 targets cluster around 290, and those with 16 targets around 640, with very litle spread. (I measured an F+D earlier, and it came out at 580 for a pair, also fitting this pattern). For the Commoner this is a surprise (although it is not completely clear why others over-estimated it so much, as it is simply another piece with 8 targets, like the Knight, and much slower at that...).