Author: Albert Silver
Date: 10:10:24 12/18/99
Go up one level in this thread
On December 18, 1999 at 11:25:34, Chessfun wrote:
>On December 18, 1999 at 05:51:30, allan johnson wrote:
>
>>On December 17, 1999 at 17:10:12, Albert Silver wrote:
>>
>>>I seem to have run across a bizarre problem and wonder if this might not be a
>>>bug in Fritz (5 or 6) or one of the infamous null-move problems. I was analyzing
>>>the following position which was part of some analysis done on
>>>Yakovich-Stefanova, Sevilla op, 1999:
>>>
>>>r4rk1/p3bppp/nn6/1N6/Ppp1P3/1P2BP2/N3K1PP/R2R4 w - - 0 18
>>>
>>>In this position the indicated move is 18.Nxa7! Fritz never finds this (at least
>>>up to 14 plies) and I decided to check the lines which follow: 18...cxb3 and
>>>here again, Fritz sees nothing for White and the eval drops with each ply; yet
>>>as soon as I feed it the next move 19.Bxb6 its eval shoots up in White's favour.
>>>What gives?
>>>
>>> Albert Silver
>>
>>Albert Rebel C on my Celeron 433 plays Nxa7 within 4 seconds with a score of
>>0.80.The score, however, goes down over the next few moves.(Nxa7 Rxa7
>>Bxb6 Rb7 Bd4 c3 Rac1 Rc8 f4 Rd7 0.24)
>
>Fritz sees this line as + 1.0 depth 11/11.
I am amazed. What version of Fritz? I ran this through Fritz 5/16bit, Fritz
5.32, and Fritz 6 and they all prefer 18.bxc4. They never choose 18.Nxa7 at
that depth.
>
>>CM6000 plays Nxa7 also but with an initial eval of 0.53.It,too,drops after
>>Nxa7 cxb3 BxB6 bxa2 Rxa2.
>
>This appears the critical line.
>
>>Is it supposed to be a win for white? Fritz 5.32
>
>Win !! I think not...
>
>>doesn't consider Nxa7 but maybe the move, as Paul says, is not winning.
>>Cheers Allan
>
>Fritz: A bug?. This is a strong heading for this thread. Why not "look at this
>position".
>
>Anyway...clearly Nxa7 is not the best move. Further Fritz's eval after move 19.
>Bxb6 "shoot's up" hmmm that's not what I get after playing the next two moves,
That is two moves later. I'm talking about after 19.Bxb6. The point is that if
it thinks the position here is at +1.22 after 8 plies, +0.94 after 9 plies, and
+1.09 after 10 plies then it should have said this prior to 18.Nxa7 after 11,
12, and 13 plies respectively, but it doesn't.
>that it sees in the line. 19.....bxa2. 20. Rxa2 Bc5. where 21. a5...Rxa7 22.
>Bxa7...Bxa7 when Fritz sees Rd7 as +0.34.
>
>If you let Fritz at 18. Look at a couple of lines you will see it considers Nxa7
>but sees this as inferior to bxc4 which I believe is the best move in this
>position.
Possible but what is your line?
Albert Silver
>
>No engine I use will play Nxa7 at tounament time controls. I have looked at
>endless variations.
>Thanks.
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