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Subject: questions about WAC

Author: Uri Blass

Date: 00:51:22 12/27/01


I downloaded WAC.epd from Dann corbit's site
in order to test my program and I see that there are some cases
when there is more than one solution and
at least in the first 2 cases the solutions are not correct


[D]r1bqk2r/ppp1nppp/4p3/n5N1/2BPp3/P1P5/2P2PPP/R1BQK2R w KQkq -
bm Ba2 Nxf7; id "WAC.022";

I am not sure if Nxf7 wins the game
I see that Ba2 is one of the solutions and
I do not understand it
Nxf7 seems clearly better for positional reasons but
I am not sure if it is winning for white

Is Ba2 clearly better than other posiiible moves like Nxe6?

Here is Deep Fritz's analysis after Ba2 and after Nxe6
and After Ba2(I give only depth 13 because smaller
depthes are not interesting)

New position
r1bqk2r/ppp1nppp/4p3/n5N1/3Pp3/P1P5/B1P2PPP/R1BQK2R b KQkq - 0 1

Analysis by Deep Fritz:

1...b6 2.Qh5 Ng6 3.0-0 Bb7 4.Bxe6 fxe6 5.Nxh7 Kf7 6.Ng5+
  =  (0.00)   Depth: 13/41   00:01:35  52878kN

(Blass, Tel-aviv 27.12.2001)

After Nxe6
New position
r1bqk2r/ppp1nppp/4N3/n7/2BPp3/P1P5/2P2PPP/R1BQK2R b KQkq - 0 1

Analysis by Deep Fritz:

1...Bxe6 2.Bxe6 0-0 3.Ba2 c5 4.Bg5 h6 5.Bh4 cxd4 6.cxd4 Qc7 7.Bxe7
  =  (-0.03)   Depth: 13/37   00:01:20  46390kN

(Blass, Tel-aviv 27.12.2001)


second example is WAC 31

[D]rb3qk1/pQ3ppp/4p3/3P4/8/1P3N2/1P3PPP/3R2K1 w - -
bm Qxa8 d6 dxe6; id "WAC.031

Qxa8 is a bad move and I do not understand how it is one of
the solutions

d6 dxe6 are good moves and g3 is also a winning move that does not appear in the
solutions

I already tested my program in the first
31 problems of WAC and it could solve almost all of them
in less than a second.

The only problem that it could not solve in a reasonable time
is WAC 2
I guess that it needs depth 13 in order to solve it
and the estimated time that
it needs to get this depth is at least some hours.

The hardest problem for it
(from the problems that it solved) was WAC 22
but I consider it as a positional problem because
there are many moves that win a pawn for white to get equality
in material.

Qh5 is one of them and my program found Nxf7 at depth 4
but changed it's mind at depth 6 to Qh5 only to change
it's mind later again to Nxf7 at depth 7.

The search techniques are similiar to TSCP except
limiting the qsearch to 7 plies

I believe that it is illogical to let the qsearch to explode
and it is also illogical to let it to explode only when the
program search deeper.

Qsearch is selective search and if you search many plies
forward then you cannot trust your score and
if you cannot trust your score there is no logical reason
to waste more nodes in order to find a score and
it seems better to me to save time and to
return static evaluation.

Uri



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