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Subject: Re: Mate in 1 - but Fritz 6 needs 1 hour!!!

Author: Ed Schröder

Date: 22:03:49 08/10/00

Go up one level in this thread


On August 10, 2000 at 21:36:23, Robert Hyatt wrote:

>On August 10, 2000 at 17:22:17, Dann Corbit wrote:
>
>>On August 10, 2000 at 16:17:47, Christoph Fieberg wrote:
>>
>>>Unbelievable, but true:
>>>I composed a position which is mate in 1 and can easily found, but Fritz6 on
>>>Pentium III, 500 Mhz and 32 MB Hash needs more than 1 hour to show it (excatly
>>>1:03:17)!!!
>>>How do other computers react?
>>>
>>>The position is
>>>FEN: 8/8/pppppppK/NBBR1NRp/nbbrqnrP/PPPPPPPk/8/Q7 w - - 0 1
>>>
>>>It is possible to reach this position from starting position:
>>>1.Sa3 Sa6 2.Sc4 Sc5 3.Sa5 Sa4 4.b3 b6 5.La3 La6 6.Lc5 Lc4 7.h4 h5 8.Th3 Th6
>>>9.Td3 Te6 10.Td5 Te4 11.Sh3 Sh6 12.e3 e6 13.Le2 Le7 14.Lf3 Lf6 15.d3 d6 16.Ke2
>>>Ke7 17.Dd2 Lc3 18.Te5 Lb4 19.Th1 Td4 20.Lc6 Dd7 21.Lb5 Th8 22.Td5 Kf6 23.Sg1 Sg4
>>>24.Th3 Se5 25.Tg3 Kf5 26.Tf3+ Kg4 27.Tf5 a6 28.g3 c6 29.Sf3 Kh3 30.Sg5+ Kh2
>>>31.Se4 Sg6 32.Kf3 Se5+ 33.Kf4 Sg6+ 34.Kg5 Se5 35.a3 Th6 36.c3 Tf6 37.De2 g6
>>>38.Kh6 Sg4+ 39.Kh7 De7 40.Tf4 Tf5 41.Sg5 Df6 42.Df3 De5 43.Kg8 De4 44.Sh3 Tg5
>>>45.Tf6 Sh6+ 46.Kh7 Sg4 47.Df5 Kg2 48.Kg7 Sh2 49.De5 Tg4 50.Sg5 Sf3 51.Sh7 Sg1
>>>52.Df4 [52.Tf5 Se2 53.Sf6 Sf4 54.Se8 Kh2 55.Tg5 Kg2 56.Kh7 Kh2 57.Sg7 Kg2 58.Sf5
>>>f6 59.f3 Kh2 60.Kh6 Kh3 Test it! What time do computers need to reach a certain
>>>search depths?] 52...Se2 53.Df3+ Kh2 54.Tff5 Sf4 55.Dd1 Kg2 56.Tg5 Kh2 57.Sf6
>>>Kg2 58.Sg8 Kh2 59.Se7 Kg2 60.Sf5 Kh2 61.Da1 Kg2 62.f3 f6 63.Kh6 Kh3 Mate in 1!
>>>(64. Dh1#). What time do different programms need to show it in the display? 1-0
>>>
>>>52.Tf5 leads to a position with White Queen on e5 (instead on a1).
>>>FEN: 8/8/pppppppK/NBBRQNRp/nbbrqnrP/PPPPPPPk/8/8 w - - 0 61
>>>
>>>How long do computers need to reach for example depth 9?
>>>Fritz 6 reached depth 5 after 9 hours!! (on Pentium III, 500 MHz, 32 MB Hash) He
>>>showed 61. Dxe4 Txe4 62. dxe4 Lxc5 3. Txg4 hxg4 as best moves (+1.56 for White).
>>>What is the best move?
>>
>>chest finds the solution after examination of exactly one position (the first
>>one it tried):
>>
>>E:\chest-3.19>chest319 -b epd.epd
>>[D] 8/8/pppppppK/NBBR1NRp/nbbrqnrP/PPPPPPPk/8/Q7 w - - acn 1; acs 0; bm Qh1#; ce
>>32766; dm 1; pv Qh1#;
>>
>>
>>Crafty found it at ply 2:
>>E:\PROGRA~2\winboard\Crafty>crafty
>>EPD Kit revision date: 1996.04.21
>>found computer opening book file [e:/crafty/release/bookc.bin].
>>hash table memory = 24M bytes.
>>pawn hash table memory = 4M bytes.
>>EGTB cache memory = 2M bytes.
>>draw score set to    0.00 pawns.
>>choose from book moves randomly (using weights.)
>>choose from 5 best moves.
>>book learning enabled
>>result learning enabled
>>position learning enabled
>>threshold set to 9 pawns.
>>4 piece tablebase files found
>>1302kb of RAM used for TB indices and decompression tables
>>
>>Crafty v17.11
>>
>>White(1): epdpfga epd.epd epd.out
>>PFGA: EPD record: 1
>>middle-game phase
>>              clearing hash tables
>>              time surplus   0.00  time limit 30.00 (3:00)
>>         nss  depth   time  score   variation (1)
>>                1    43.87   7.19   1. dxe4 Rxd5 2. Rxg4 hxg4 3. exd5 Bxa5
>>                                    4. Bxa4 dxc5 5. gxf4 gxf5 6. bxc4 cxd5
>>                                    7. cxd5 exd5
>>                1    50.87     ++   1. Qh1#!!
>>                1    50.87   Mate   1. Qh1#
>>                1->  50.87   Mate   1. Qh1#
>>                2    50.87   Mate   1. Qh1#
>>                2->  50.89   Mate   1. Qh1#
>>              time=51.17  cpu=99%  mat=0  n=5928139  fh=100%  nps=115851
>>              ext-> checks=11 recaps=0 pawns=0 1rep=1 thrt:0
>>              predicted=0  nodes=5928139  evals=4531128
>>              endgame tablebase-> probes done=0  successful=0
>>              hashing-> trans/ref=1%  pawn=92%  used=0%
>>
>>I had a lot of stuff in memory, so it took crafty a long time to start up.
>
>
>That wasn't the problem.  the first move searched (the one a simple eval/
>material ordering suggests) takes forever, and millions of nodes to search.
>
>Programs that like the check first will solve it instantly.  programs that
>look at something else first may well get lost in a huge tree of captures,
>and take a lot of time to get off the captures and onto the simple mating
>move.

Here is another one that might blow up the tree on the first ply (and next
iterations) in case you don't limit q-search.

[d]4K3/PPPPPPPP/8/8/8/8/pppppppp/4k3 w - -

Lots of fun.

Ed




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