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Subject: Re: a position for chess programs

Author: blass uri

Date: 12:46:44 10/22/98

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On October 22, 1998 at 13:01:13, Hans Havermann wrote:

>On October 20, 1998 at 20:17:00, Robert Hyatt wrote:
>
>>I thought I would give this a whirl, since I have been making minor endgame
>>scoring changes anyway, and was surprised to find this running Crafty 15.21
>>on my 4 processor machine:
>>               10    10.70  -1.17   1. ... Ke5 2. Rxb4 Rxa2+ 3. Kf3 Ra5
>>                                    4. g4 Rc5 5. Re4+ Kd5 6. Rd4+ Ke5 7.
>>                                    g5 Rc1
>>               10->  17.04  -1.17   1. ... Ke5 2. Rxb4 Rxa2+ 3. Kf3 Ra5
>>                                    4. g4 Rc5 5. Re4+ Kd5 6. Rd4+ Ke5 7.
>>                                    g5 Rc1
>>               11    28.40  -1.30   1. ... Ke5 2. Kd3 Kd5 3. e4+ Ke5 4.
>>                                    Kc4 h6 5. Kxb4 Kxe4 6. a4 Rb8+ 7. Kc3
>>                                    Rd8
>>               11     1:01  -1.26   1. ... Ra3 2. Rxb4 Rxa2+ 3. Kf3 Rc2
>>                                    4. g3 Rc6 5. Ke4 Ke6 6. h4 h6 7. g4
>>               11->   1:23  -1.26   1. ... Ra3 2. Rxb4 Rxa2+ 3. Kf3 Rc2
>>                                    4. g3 Rc6 5. Ke4 Ke6 6. h4 h6 7. g4
>>               12     1:36  -1.32   1. ... Ra3 2. Rxb4 Rxa2+ 3. Kf3 Ra6
>>                                    4. g4 h6 5. h4 Rd6 6. Rd4 Rc6 7. Ke4
>>                                    Ke6
>>               12->   2:19  -1.32   1. ... Ra3 2. Rxb4 Rxa2+ 3. Kf3 Ra6
>>                                    4. g4 h6 5. h4 Rd6 6. Rd4 Rc6 7. Ke4
>>                                    Ke6
>
>(Old) Crafty 14.6 (running on a G3) finds the ...Ra3 at 8-ply already:
>
> 8  -1.27 Ke5 Kd3 Kd5 e4+ Kc5 Rc2+ Kd6 Kc4 Rc8+ Kb3 Rb8
> 8  -1.09 Ra3 Kf3 Ke5 Rxb4 Rxa2 g4 h6 e4
> 8->-1.09 Ra3 Kf3 Ke5 Rxb4 Rxa2 g4 h6 e4
> 9  -1.11 Ra3 Kf3 Ra4 g4 Ke5 Rc2 h5 gxh5 gxh5 e4
> 9->-1.11 Ra3 Kf3 Ra4 g4 Ke5 Rc2 h5 gxh5 gxh5 e4
>10  -1.11 Ra3 Rxb4 Rxa2+ Kf3 h5 g4 Kg5 gxh5 gxh5 Rb5+ Kh4 Ke4 Rd2
>10->-1.11 Ra3 Rxb4 Rxa2+ Kf3 h5 g4 Kg5 gxh5 gxh5 Rb5+ Kh4 Ke4 Rd2
>11  -1.12 Ra3 Rxb4 Rxa2+ Kf3 Ra3 Kf4 g5+ Ke4 h5 g4 hxg4 hxg4 Rc3 Rd4
>11->-1.12 Ra3 Rxb4 Rxa2+ Kf3 Ra3 Kf4 g5+ Ke4 h5 g4 hxg4 hxg4 Rc3 Rd4
>12  -1.11 Ra3 Rxb4 Rxa2+ Kf3 h5 Rb6+ Kg5 g3 Ra3 Rb5+ Kf6 Ke4 Ra4+ Kd5 Kf5 h4
>12->-1.11 Ra3 Rxb4 Rxa2+ Kf3 h5 Rb6+ Kg5 g3 Ra3 Rb5+ Kf6 Ke4 Ra4+ Kd5 Kf5 h4
>13  -1.14 Ra3 Rxb4 Rxa2+ Kf3 Ra5 g4 h5 h4 hxg4+ Rxg4 Ra3 Kf4 Ra1 e4 Rf1+ Ke3 Rd1
>           Rg5 Rd6
>13->-1.14 Ra3 Rxb4 Rxa2+ Kf3 Ra5 g4 h5 h4 hxg4+ Rxg4 Ra3 Kf4 Ra1 e4 Rf1+ Ke3 Rd1
>           Rg5 Rd6
>14  -1.13 Ra3 Rxb4 Rxa2+ Kf3 Ra5 Rb6+ Kg5 g3 Rf5+ Ke4 Rf1 Rd6 Rc1 Rd5+ Kf6 g4
>           Ke6 g5
>14->-1.13 Ra3 Rxb4 Rxa2+ Kf3 Ra5 Rb6+ Kg5 g3 Rf5+ Ke4 Rf1 Rd6 Rc1 Rd5+ Kf6 g4
>           Ke6 g5
>15  -1.17 Ra3 Rxb4 Rxa2+ Kf3 Ra6 h4 h6 Rb5 Ra3 g4 g5 Rf5+ Kg6 h5+ Kg7 Rd5
>           Kf6 Ke4
>15->-1.17 Ra3 Rxb4 Rxa2+ Kf3 Ra6 h4 h6 Rb5 Ra3 g4 g5 Rf5+ Kg6 h5+ Kg7 Rd5
>           Kf6 Ke4
>
>By contrast, MacChess (5.0b3) refuses to relinquish ...Ra4:
>
>07/01| -125| Ke5 Rxb4 Rxa2+ Kf3 Rd2 Rb5+ Kf6 Rb6+ Ke5 e4
>07/11| -124| Ra4 Kf3 h5 Re2 Ra3 g4 Rc3
>08/01| -125| Ra4 Kf3 h5 g4 hxg4+ hxg4 Ke5 Re2 g5
>09/01| -125| Ra4 Kf3 h5 g4 Ke5 Re2 Ra3 gxh5 gxh5 h4
>10/01| -125| Ra4 Kf3 h5 g3 g5 g4 hxg4+ hxg4 Ke6 Re2 Kd5
>11/01| -124| Ra4 g4 h5 gxh5 gxh5 Kf3 Ke5 h4 b3 Rxb3 Rxh4 Rb5+ Kd6 e4 Rh3+ Kf4
>12/01| -123| Ra4 Kf3 h5 g3 g5 g4 h4 Rc2 Ke5 Rc5+ Kf6 Rc6+ Ke7 Rc4
>13/01| -123| Ra4 Kf3 h5 g3 g5 g4 h4 Rc2 Ke5 Rc6 Ra7 Rc5+ Kf6 Rf5+ Kg6
>14/01| -124| Ra4 h4 Ke5 Kf3 h6 Rb3 Kd6 g4 Ke5 Rb1 Kd6 Rb2 g5 h5
>15/01| -124| Ra4 h4 Ke5 Kf3 h6 g4 h5 gxh5 gxh5 Rc2 Ra5 Re2 Ra3 Rg2 Kd6 Rf2
>
>Never suggests ...Ra3: Subtle scoring differences, I suppose. With a losing
>position such as this, I'm not sure it amounts to anything, anyhow.

Is it a losing position after Ra3?
The game continued Ra3 Rxb4 Rxa2+ Kf3 h5 and I do not see how white can win.

I have no practical chances to win a drawn KRP V KR because my opponent has
perfect tablebases and I did not find how I can do better than it.

Uri



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