Tuesday, January 29, 2008

Fritz 11 - Strange Infinite Analysis Behaviour

I was very excited yesterday.

I got a chance to give Fritz 11 a whirl on a family member's computer. He got Fritz 11. So I grabbed one of my old games and fired up Fritz 11.

Now in this position, I let Fritz 11 do an infinite analysis on this position (see diagram on left). After letting this position run for over 3 minutes, Fritz threw up the surprising line:

Analysis by Fritz 11: 1. -+ (-1.62): 36.Rxf6 Re1 37.Rxh6 Rxe5 38.dxe5 d4 ... (see 2nd diagram on left)

..... what the... ? 36. Rxf6??

Fritz is kidding, right? No.

Even more surprising is that after the move 36. Rxf6 was played, Fritz now throws up the following evaluation (see 3rd diagram on left) after analysing for about 3 minutes...

1. -+ (-7.17): 36...Qxg3+ 37.Kxg3 Rxe6 38.Rf5 Rd6 39.Rf3 Rd1 ....

What? After taking the first move, Fritz now decides that the position has swung from a -1 evaluation to a -7!

If you look at the first evaluation in the 2nd diagram, for some strange reason, Fritz didn't analyse or see the line 36. Rxf6 Qxg3+ 37.Kxg3 Rxe6.

This is very odd.

If anyone is interested to give this a whirl, I've copied the FEN position below.

4r1k1/2q3p1/4bp1p/3pR3/3P4/5RQP/5PPK/2r5 w - - 0 36



  1. I'll be happy to give this position a try, if and when I get my Fritz 11 up and running. My stepson believes that some of the security measures he has in place are preventing the downloading of the database. He has not yet, however, been able to come home to have a look at the system

  2. Hippo,

    Thanks for leaving the comment on my Blog. Not taking the draw was probably a bigger mistake than dropping my queen.

    Although I am dissapointed that I let my rating slip from 1890-1856 in the long run it will make me tougher.

    I have a lot of fimily living in Sydney and also Melbourne. I hopt visit some time in 2008. I will keep you posted. I would like to check out the local chess scene.

    Getting to 2000

  3. Greg,

    Thank! That's very much appreciated. Best of luck to getting Fritz 11 running.


    No worries abt it.

    If I were in your position, I would have fought on as well. Hindsight is always 20/20.

    I've very certain you'll bounce back soon enough. That's a very good attitude to have!

    I'll post the followup comments in your blog.


  4. interesting. i am running it now, but a lot slower on fritz 8, which, despite running on a dual core, must not be optimized for faster machines?

    i wonder what rybka says?

    still hoping that you will mention my game collection?

    seen it yet?

    warm regards, dk

  5. I can explain this odd behavior!

    You mistakenly entered the move 36.Rxe6 rather than Fritz's 36.Rxf6. After 36.Rxf6, neither 36...Qxg3 nor 36...Rxe6 would be possible as the rook on e5 prevents Qg3 and Black cannot capture his own bishop on e6.

  6. drunkenite, you're absolutely right. Gosh, what was I thinking?! D'oh!
    Apologies all round.

    dk, having arrived in Sydney on Sat morn, I was working on Sunday so I still didn't have the chance to look through your database and will do so at the earliest opportunities.

  7. Defiitely Qxg3 is not possible coz of the Rook on e5! What were you thinking buddy!

  8. My only explanation was that I was still disoriented after being kidnapped by aliens ala Kirsan. :)