Author: Thorsten Czub
Date: 15:04:54 12/29/97
Please, my analysis have been done on a k6/200 with giving Genius5 3968
KByte for hash.
For point 1 use pgn1, for point2 use pgn2:
[Event "PGN1"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "Karpov"]
[Black "Topalov"]
[Result "1-0"]
[SetUp "1"]
[FEN "rqr3k1/3Qbp2/p1n1p1p1/1pp5/2P2P2/2N3P1/PP3PB1/R3R1K1 w - -"]
1. *
[Event "PGN2"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "Karpov"]
[Black "Topalov"]
[Result "*"]
[SetUp "1"]
[FEN "rq3rk1/3Qbp2/p1n1p1p1/1pp5/2P2P2/2N3P1/PP3PB1/R3R1K1 b - -"]
1. *
1.
Set up the position PGN1 in Genius5/WIN (import it as PGN or setup
manually).
Put level on infinite.
Let Genius5 compute on the whites move.
It considers Bxc6 in the 8/20 search.
Changes to cxb5 in this search.
It runs through the 9/21 search without changes until (arround 51' !!)
it computes in the 34th
branch (that is Rxe6), but did not see the point and starts the next
iteration (10/22) with main-line
(since 18'58") cxb5 Ra7 Qd3 Nd4 bxa6 Qxb2 Rab1 +0.60.
2.
Now set up again the position but take the rook from c to f8 !
Or import PGN2, that is the old position but with the rook-move taken
back.
Let Genius5 compute about THIS position that is ONE ply before the
unique key-move Rxe6 with
following Rxg6.
After 1'23 in only search 8/20 Genius5 finds the key move Rxe6 , but
here of course as the 2nd
ply of the main-line !
The main line is:
Rc8 Rxe6 Ra7 Rxg6+ fxg6 Qxe6+ Kg7 Bxc6 with an evaluation of -1.15.
It will still play Rc8 in the 9/21 search with -1.15 evaluation.
Conclusions:
This is what I call the asymmetric-search. It is the reason Genius5 is
that strong and plays that
"Levy"-like ("do nothing, but do it well").
The reason it finds the key moves FASTER although you go back (!!) one
ply shows that it
computes more brute-force (less pruning) in the plies 2,4,6,8,... !
The reason it has not found Rxe6 in the position with the rook on c8 is,
that is had to find the key
move with the plies that prune much and have pruned it away !!
ALL Lang program have this search-technique.
From the first dedicated machine Mephisto Amsterdam to the latest
Genius5 engine.
Lang has changed the knowledge and the tactical abilities, but never has
he changed the search-
strategy.
I will further (when I have some time) show you a position where Genius5
decides to choose the
boring (also weaker) moves/main-lines with having 1,3,5,7...
plies-search, and if you take one
ply back, it plays for the same color better, more active moves that
would lead to a more
powerful game. It IS the search that makes genius play "boring" since
1985 Amsterdam-module.
Thanks.
P.S.: Take care about those effects when analysing your own games with
Genius5. Especially
your email-chess-games ! You cannot trust Genius' analysis even if you
let it compute 12 hours
per move. The effect seen in the position above will not disappear
whatever time you give it. All
your analysis time invested could be WASTED because the FIRST move in
the main-line is NOT
the best one in the position you analyse.
Never trust genius5's 1,3,5,7... iteration-moves from the main-line !
They could be completely
overseeing STRONG moves.
Use Genius as an instrument. But use it not blind trusting. Remember the
asymmetric search
and take care of it.
I remember a very old "argument" with Thomas Mally or Andreas Mader
(both writers) from PC-
SCHACH/MODUL in the past. He said that he cannot understand my sceptical
position
concerning using the dedicated mephisto-machines (with Lang program) for
analysis. In fact it
was the Mephisto Lyon or Almeria or something like this.
He told me that he even bought a second machine for analysis !!
I was very shocked. I still remember this episode, although it is years
ago.
Sitting with Genius5 about the above position, having much faster
hardware than the old
Motorola 68000 or 68020 CPU, I am still convinced that my decision NOT
to trust those machines
due to their lack of "accuracy" that results from the highly contrast
between the 2 pruning-levels
was reasonable.
If a program is not able to find such an important move although it runs
on such a fast machine,
how much would it would have overseen on a (how many times?) slower
Motorola 68020 ??!!
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