What kind of knowledge is present?

[Eraserheads]

Black to move...

[D]r1b2rk1/ppp2ppp/2n2n2/3q4/3P4/3BPP2/P2B2PP/R2QK1NR b KQ - 0 10

What kind of knowledge is present in a chess engine, when it chooses to sacrifice his Knight by playing ...Nxd4 ? This is the type of sacrifice which has no immediate, concrete returns. I do not do chess programming, but I'm curious as to what knowledge is needed for an engine to make such a move.

Among the engines available today,

Glaurung 1.2.1 likes ...Nxd4 and gives a small advantage for Black.
Rybka 2.3.2a likes the move too, as does Fritz 11. Deep Junior 8 likes the move as well. So does Gandalf 6.

Old engines like Junior 6, Fritz 6 and HIARCS 7.32 do not like it at all. Surprisingly even Gambit Tiger 2.0 does not want to play it.

This type of move was unthinkable in the previous decade, but now more and more engines seem to be 'catching up/maturing'. Can these types of moves be used as benchmarks for 'chess understanding'?












PS

Black often needs to play à la Morozevich and sharpen the game, relying upon an initiative to offset his material sacrifice. Here is Rychagov – Morozevich, Moscow 2001 (blitz): 1.d4 d5 2.c4 Nc6 3.e3 e5 4.cxd5 Qxd5 5.Nc3 Bb4 6.Bd2 Bxc3 7.bxc3 Nf6 8.f3 0–0 9.Bd3 exd4 10.cxd4 (note Black’s thematic exchange of his Bishops for White’s Knights, White’s large pawn center, and Black’s delay of …exd4)

[pedrox]

When an engine play Nxd4, he has to find compensation for the lost material and because the white possess a pair of bishops.

325+50-100-100 = 175 cp, this is the white material advantage.

The pieces squares of the black pieces seem better, the king castled, good structure pawns, Kgnith pointing to the center, the rooks can go to the diagonals of the center, this may be 35 points ahead for black.

175-35 = 140 cp (White)

With the change will have a black pawn on c7 passed, as we are still in the middle game is not valued much this pawn, it must be appreciated as +10 for black.

140-10 = 130 cp (White)

The White King has not castling, he has not good protection of pawns who cover and can be attacked by the black rook on e8 and the kgnith f6, it must be appreciated as +50 for black.

130-50 = 80 cp (White)

The mobility of the black pieces, along with the columns open and queen at the centre can be an advantage for black 40 points. In addition, the rook will be locked in h1 giving another 50 points to the black.

80-40-50 = -10 cp Black now with slight advantage

White will have an isolated pawn on a2 and the black candidate in b7.

-10- 10- 10 = -30 cp for Black

Here is an explanation why the program can sacrifice Nxd4 and valued as 0.30 points even better.

[pedrox]

Even after the change DanaSah has a slight advantage, if she does not make the sacrifice is because it is believed that the move 10.. Bf5 is best for the black and that the same happens to many other engines.

[d]r1b2rk1/ppp2ppp/5n2/8/3q4/3B1P2/P2B2PP/R2QK1NR w KQ - 0 10

Code: Select all

DanaSah v.3.13:
   2	00:00	         604	604	-0,45	Db1 Ad7
   2	00:00	         867	867	-0,35	Ab5 Td8
   3	00:00	       1.994	1.994	-0,34	Ab5 De5+ Ae2 Td8
   3	00:00	       3.276	3.276	-0,31	Db1 Te8+ Ce2 Ad7
   4	00:00	       9.096	909.600	-0,04	Ab5 De5+ Ae2 Td8 Ch3 Axh3 gxh3
   5	00:00	      16.233	1.623.300	-0,34	Ab5 De5+ Ae2 Td8 Tc1 Ad7
   5	00:00	      61.545	1.025.750	-0,18	Ac2 Dh4+ g3 Dd4 Ce2 Te8
   6	00:00	      82.611	917.900	-0,16	Ac2 Te8+ Ce2 Dc4 Ag5 Dc3+ Ad2 Dd4
   7	00:00	     115.365	961.375	-0,10	Ac2 Te8+ Ce2 Dh4+ g3 Dh5 f4 Df3 Tf1
   8	00:00	     216.104	939.582	-0,10	Ac2 Te8+ Ce2 Dh4+ g3 Dh5 f4 Df3 Tf1 Dg2
   9	00:00	     510.705	911.973	-0,22	Ac2 Dh4+ g3 Dh5 Db1 Te8+ Rd1 Dd5 Ce2 Dxf3 Te1
  10	00:00	     935.993	926.725	-0,20	Ac2 Dh4+ g3 Dh5 Rf2 Te8 Tb1 Dd5 Aa4 c6 Dc2
  11	00:03	   3.670.823	871.929	-0,06	Ac2 Dh4+ Rf1 Ae6 Ce2 Tad8 g3 Dc4 Rg2 Dd5 Ae3 Dh5
  12	00:07	   6.600.608	882.434	-0,10	Ac2 Dh4+ g3 Dh5 Rf2 Te8 Rg2 Ad7 Ad3 Tad8 h3 Dc5 Tb1
  13	00:41	  37.324.961	910.364	-1,69	Ac2 Te8+ Ce2 Cg4 Tf1 Txe2+ Rxe2 Af5 fxg4 Te8+ Rf3 Axg4+ Rg3 Axd1 Taxd1 Te2 Tf4 Db2
  13	00:46	  42.198.014	917.348	-0,30	Ab5 De5+ Ae2 Te8 Rf2 Af5 Tc1 Tad8 Re1 Cd5 Tc5 Ad3 h4 Axe2 Cxe2
  13	00:51	  47.800.154	937.257	-0,21	Ae2 Cd5 Tc1 Te8 Ag5 De5 Dd2 h6 Tc5 Ae6 Af4 Dxf4 Txd5
  14	01:10	  65.351.125	933.587	-0,16	Ae2 Cd5 Tc1 Te8 Ag5 De5 Dd2 h6 Tc5 Ae6 Af4 Dxf4 Txd5 Da4
  15	02:19	 130.045.340	935.577	-0,14	Ae2 c6 Tb1 Te8 Tb4 Dc5 Dc1 Dd6 Dc2 b5 Ch3 a5 Th4 Axh3 Txh3 c5
  16	04:54	 265.177.145	901.963	-0,30	Ae2 Te8 Tc1 Cd5 Ag5 De5 Dd2 Af5 f4 Dd6 Tc4 c6 Cf3 b5 Td4 Tab8

[Eraserheads]

thanks for the very informative reply!