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Subject: Re: Greek Gift?

Author: Dann Corbit

Date: 10:26:56 11/22/00

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On November 21, 2000 at 23:17:27, Michael Neish wrote:

>
>Hello,
>
>I know some programs have code in their evaluations to detect a possible Greek
>gift sacrifice, and avoid it.  But is there any program that can iterate through
>the moves for a more detailed search?  Is there a way to do this statically?
>
>There are probably several key factors, such as whether the Black pieces can
>come to the rescue, whether the White King is vulnerable to in-between checks
>which might allow Black to reposition.  I suspect one could analyse these
>factors in PreEval(), or earlier one could find out the potential of a Greek
>gift sacrifice arising, and possibly alter one's strategy accordingly.  Far
>fetched maybe.
>
>I thought of these questions when the following position arose in a computer v
>computer game (my program (W) v Sigma Chess (B)).  I don't know whether there is
>a forced win - maybe not - but after 12. Bxh7 Kxh7 13. Ng5+, 13. ... Kg8 seems
>to lose.  13. ... Kg6 puts up more resistance, but I don't know whether White
>will win.
>
>[D]r4rk1/pp1bnppp/1qn1p3/1NbpP3/8/3B1N2/PPPBQPPP/R3K2R w - -
>
>Hiarcs 7 seems to like 14. h4, but still gives the advantage to Black (less than
>a Pawn).  Can any program find a win?  Can any human, for that matter?

Phalanx wants to castle:

r4rk1/pp1bnppp/1qn1p3/1NbpP3/8/3B1N2/PPPBQPPP/R3K2R w - -
    -> increment adds 7.2 s to soft time limit
    -> soft time limit 127.2 s
    -> hard time limit 708 s
  5    -28    52    81442  Pa2-a4  !
  5    -15    56    89053  Pa2-a4  Nc6-b4  Bd2xb4  Bc5xb4  Pc2-c3  Bb4-c5
                           O-O
  5 ->   0:00.77   122893   1 turn
  6    -15   103   161924  Pa2-a4  ??
  6   -126   120   198977  Pa2-a4  Pa7-a6  Nb5-d6  Nc6-b4  Bd2-g5  Nb4xd3
  6   -121   126   210695  Ra1-b1  !
  6    -26   172   292179  Ra1-b1  Pa7-a6  Nb5-c3  Nc6-b4  O-O  Nb4xd3
                           Pc2xd3  Qb6-b4
  6 ->   0:03.78   620829   1 turn
  7    -27   582   997215  Ra1-b1  Ne7-g6  Pa2-a4  Nc6-b4  O-O  Nb4xd3
                           Qe2xd3
  7    -22   715  1247370  O-O  !
  7      1   800  1410900  O-O  Pa7-a6  Nb5-c3  Nc6-b4  Bd2-g5  Nb4xd3
                           Pc2xd3  Ne7-f5  Ra1-c1
  7 ->   0:11.47  1940259   1 turn
  8    -10  1620  2812785  O-O  Pa7-a6  Nb5-c3  Nc6-b4  Nf3-e1  Ra8-c8
                           Bd2-f4  Nb4xd3  Ne1xd3  Ne7-f5  Nd3xc5  Qb6xc5
  8 ->   0:29.80  4954563   0 turns
  9    -20  5554  9820667  O-O  Pf7-f6  Pe5xf6  Rf8xf6  Bd2-g5  Rf6-f8
                           Pc2-c4  Nc6-b4  Bg5xe7  Bc5xe7
  9 ->   1:56.94 19937233   0 turns
 10    -10 18233 31911313  O-O  Pa7-a6  Nb5-c3  Nc6-b4  Bd2-g5  Ra8-c8
                           Nf3-e1  Qb6-a5  Qe2-h5  Nb4xd3
 10 ->   5:16.36 52303444   0 turns
Depth=10, Value=-10, Time=316.36, Last turn=7.15, Nodes=52303444, N/s=165328
PV = O-O  Pa7-a6  Nb5-c3  Nc6-b4  Bd2-g5  Ra8-c8  Nf3-e1  Qb6-a5
     Qe2-h5  Nb4xd3

Crafty wants Nc3, but it looks very bleak.  If there is any good idea, it is
probably the castle choice.  I suspect the problem was a earlier move, leading
to this position.

White(1): setboard r4rk1/pp1bnppp/1qn1p3/1NbpP3/8/3B1N2/PPPBQPPP/R3K2R w - -
White(1): go
              time surplus   0.00  time limit 16666:39 (16666:39)
         nss  depth   time  score   variation (1)
                6     0.27  -0.27   1. c3 Na5 2. Be3 Nc4 3. Bxc5 Qxc5 4.
                                    Nbd4
                6->   0.69  -0.27   1. c3 Na5 2. Be3 Nc4 3. Bxc5 Qxc5 4.
                                    Nbd4
                7     0.96  -0.44   1. c3 a6 2. b4 Bxf2+ 3. Qxf2 Qxf2+
                                    4. Kxf2 axb5 5. Rhe1 Nd8
                7     1.84  -0.31   1. Rb1 a6 2. Nc3 Nb4 3. Bg5 Nxd3+ 4.
                                    cxd3 h6 5. Bf4
                7->   2.41  -0.31   1. Rb1 a6 2. Nc3 Nb4 3. Bg5 Nxd3+ 4.
                                    cxd3 h6 5. Bf4
                8     2.75  -0.52   1. Rb1 a6 2. Nc3 Nb4 3. Bg5 Qc7 4.
                                    Bxe7 Bxe7 5. Rd1 Nxd3+ 6. Qxd3
                8->   7.83  -0.52   1. Rb1 a6 2. Nc3 Nb4 3. Bg5 Qc7 4.
                                    Bxe7 Bxe7 5. Rd1 Nxd3+ 6. Qxd3
                9     9.30  -0.53   1. Rb1 a6 2. Nc3 Nb4 3. Bg5 Qc7 4.
                                    Rc1 Nxd3+ 5. cxd3 Rac8 6. Nd4 Bxd4
                                    7. Bxe7
                9->  16.36  -0.53   1. Rb1 a6 2. Nc3 Nb4 3. Bg5 Qc7 4.
                                    Rc1 Nxd3+ 5. cxd3 Rac8 6. Nd4 Bxd4
                                    7. Bxe7
               10    20.43  -0.61   1. Rb1 a6 2. Nc3 Nb4 3. Rc1 Rac8 4.
                                    Bg5 Qc7 5. Rf1 Nxd3+ 6. cxd3 h6 <HT>
               10->  40.18  -0.61   1. Rb1 a6 2. Nc3 Nb4 3. Rc1 Rac8 4.
                                    Bg5 Qc7 5. Rf1 Nxd3+ 6. cxd3 h6 <HT>
               11    54.45  -0.74   1. Rb1 a6 2. Nc3 Qc7 3. Ng5 h6 4. Nf3
                                    Ng6 5. Bxg6 fxg6 6. Be3 d4
               11->   2:50  -0.74   1. Rb1 a6 2. Nc3 Qc7 3. Ng5 h6 4. Nf3
                                    Ng6 5. Bxg6 fxg6 6. Be3 d4
               12     3:08  -0.80   1. Rb1 a6 2. Nc3 Qc7 3. Rd1 Ng6 4.
                                    Bxg6 fxg6 5. Be3 Bb4 6. Bd2 Rac8 7.
                                    Rf1
               12     6:59  -0.78   1. Nc3 Nb4 2. Nd1 Rac8 3. a3 Nxd3+
                                    4. cxd3 Ba4 5. Bg5 h6 6. Nc3 Bd7 7.
                                    Be3 f5 8. exf6 Rxf6 9. Bxc5 Qxc5
               12->   9:38  -0.78   1. Nc3 Nb4 2. Nd1 Rac8 3. a3 Nxd3+
                                    4. cxd3 Ba4 5. Bg5 h6 6. Nc3 Bd7 7.
                                    Be3 f5 8. exf6 Rxf6 9. Bxc5 Qxc5
               13    13:10  -0.85   1. Nc3 Nb4 2. Nd1 Rac8 3. a3 Nxd3+
                                    4. cxd3 Ba4 5. Bg5 h6 6. Nc3 Bb3 7.
                                    Bf4 f5 8. exf6 Rxf6
               13    16:43  -0.83   1. Rb1 a6 2. Nc3 Qc7 3. Rd1 Ng6 4.
                                    Bxg6 fxg6 5. Be3 Bb4 6. Bd2 Rac8 7.
                                    a3 Bc5
               13->  24:18  -0.83   1. Rb1 a6 2. Nc3 Qc7 3. Rd1 Ng6 4.
                                    Bxg6 fxg6 5. Be3 Bb4 6. Bd2 Rac8 7.
                                    a3 Bc5
               14    26:51  -0.94   1. Rb1 a6 2. Nc3 Qc7 3. Ng5 h6 4. Nf3
                                    Ng6 5. Bxg6 fxg6 6. Rc1 Nd4 7. Nxd4
                                    Bxd4 8. f4 Rac8
               14    44:20  -0.84   1. Nc3 Nb4 2. Nd1 Rac8 3. Bxb4 Qxb4+
                                    4. c3 Qf4 5. Qd2 Qxd2+ 6. Kxd2 f6 7.
                                    Re1 fxe5 8. Nxe5 Ba4 9. b3 Be8
               14->  71:59  -0.84   1. Nc3 Nb4 2. Nd1 Rac8 3. Bxb4 Qxb4+
                                    4. c3 Qf4 5. Qd2 Qxd2+ 6. Kxd2 f6 7.
                                    Re1 fxe5 8. Nxe5 Ba4 9. b3 Be8
               15    89:51  -0.86   1. Nc3 Nb4 2. Nd1 Rac8 3. Bxb4 Qxb4+
                                    4. c3 Qg4 5. Ne3 Qf4 6. Bc2 f6 7. g3
                                    Qh6 8. Kd1 Qh3
               15-> 161:13  -0.86   1. Nc3 Nb4 2. Nd1 Rac8 3. Bxb4 Qxb4+
                                    4. c3 Qg4 5. Ne3 Qf4 6. Bc2 f6 7. g3
                                    Qh6 8. Kd1 Qh3
               16   242:14  -0.87   1. Nc3 Nb4 2. Nd1 Rac8 3. Bxb4 Qxb4+
                                    4. c3 Qf4 5. Qd2 Qxd2+ 6. Kxd2 Nc6
                                    7. Re1 d4 8. Ke2 dxc3 9. Nxc3 Rfd8
                                    10. Kf1 h6
               16-> 527:34  -0.87   1. Nc3 Nb4 2. Nd1 Rac8 3. Bxb4 Qxb4+
                                    4. c3 Qf4 5. Qd2 Qxd2+ 6. Kxd2 Nc6
                                    7. Re1 d4 8. Ke2 dxc3 9. Nxc3 Rfd8
                                    10. Kf1 h6
               17   737:31  -0.89   1. Nc3 Nb4 2. Nd1 Nxd3+ 3. cxd3 Rfc8
                                    4. Rc1 Ng6 5. a3 Be7 6. Be3 <HT>
               17   792:45   3/44*  1. Rb1




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