Hey all,

I post over in the poker forums occasionally, but have just recently been teaching myself backgammon. I read a few articles to get the basics, then have been playing vs gnubg at grandmaster with tutor set to 'bad'. I generally get through games being notified of 0-2 bad moves or so at the point. Until now, I've basically always been able to understand why the suggested move is better, but this one has me stumped:



I can see why 6/2*(2) is a good move, but 14/8*/6 seems better and safer. You hit a more advanced blot, and you bring your last checker home. 6/2 establishes the 2 point, but gives up the 6.

As I write this, I think the logic just dawned on me. If you leave the 2 there, any 2 lets the opponent make a point in your house. I still don't see why that makes such a difference this late though. There are plenty of open points for him to come in on regardless, and having the 2 blocked doesn't seem to hurt me much at this point.

Can anyone confirm that I'm on the right track here (that it's a better move because you limit the chances of the opponent making a point in your house), and maybe give me some more general basis to understand why that's important at this point in the game? Or of course if I'm off base, set me straight!

Hi,

the play suggested by gnu is called a switch play and there are a few reasons why this play is good.
First of all the chance of a gammon is increased, especially since you can pick up another checker.
Now here in this position that's not a strong argument since you will probably win a gammon anyway when you're not hit.
Now for the second argument. Look at it this way:
After your play 14*8/6, you have to clear the 6 point and the 5 point in bearing-off,
the 6 point plays safe with a 1 a 5 and a 6, the 5-point with a 4 and a 5, so 2's and 3'are potential trouble.
And that for a total of 6 checkers, meaning 3 throws with 2 troubled numbers
After the switch play you will only have to clear the 5 point, with 1 and 2 as troubled numbers (the 3 is no trouble since the 2-point now became a landing point)
There will be 3 or 4 checkers on the 5 point, meaning 2 throws with 2 troubled numbers, so thats less trouble.
And now for a small third argument, after the switch play the chance of picking up a third checker is increased, this might safe you when he hits you,
because then you will have more time to enter with a 2 and escape before he is able to threaten you,

greetings k.

Thanks for the input! The second point is definitely what I was missing. 14/8*/6 is safe for this move, but makes for a much more dicey situation when bearing off. (I lucked out and rolled 66 the next turn in this particular game, but I can definitely see what you're saying about there being far more dangerous rolls in that case.)

Ha, just noticed the pun in my second sentence there. Nice.

Yes, how much will you learn with your tutor set to bad?

greetings k.

More than with it set to 'very bad', but less than with it set to 'doubtful'?

I'm not planning to play seriously or anything - just wanted to learn the game for fun. Figured once I got to the point of making no or very few bad moves I'd crank it up.

Edit: Plus, you still see the doubtful moves in the history, it just doesn't warn you about them before you make them.

What's the best play if we put the red man on the bar onto the 15 point?


@MrStretchie:

If your tutor is set on "bad", then doesn't it give you bad advice? You could propably set your tutor on a better setting without changing your opponent strenght.

Setting the tutor to 'bad' (or the equivalent with other bots) has both good and bad features.

The Good: You win more games and feel better about backgammon.

The Bad: You can't tell the difference between the tutor's genuinely good moves and its bad moves, so your development as a player slows up markedly. You're going to assume that all the bot's moves will be the correct idea, but some of them will just be blunders.

I don't think that's what OP meant by "setting the tutor to bad." Gnubg marks moves as "doubtful," "bad," or "very bad" based on how you lose by making them. I think OP is playing vs. grandmaster (2-ply?), but gets warned when he tries to make a move that is going to be classified as bad (or very bad).

Didn't realize that. In that case the 'bad' setting could still be very useful.

Correct. (Except grandmaster is 3-ply.) The tutor setting is a threshold for when it will warn you about questionable moves - it has nothing to do with the strength of the AI opponent. Sorry I wasn't clear about that.

This is exactly how I learned to play backgammon. First, I set the tutor to "very bad" (meaning it only alerts when I make a move considered "very bad"). My plan was to move the filter down to "bad" after I eliminated all my "very bad" moves then down to "doubtful" after I eliminated all my "bad" moves. That never happened. I moved the filter down to "bad" long ago, but I still make at least one or two "very bad" plays per 5-point match.

One thing I would recommend: Don't just play against the computer. I started playing online, and the way the games play out and the types of situations I find myself in are completely different than what I became used to playing GNU. I just play on MSN or FIBS, but on both I can download the game history into GNU and analyse the entire game then take a look back at the bad moves. For "bad" and "very bad" moves, I can almost always see why my play was wrong. For "doubtful", it is often very subtle and I don't always know why GNU's suggested move is better...

Hi ted,

I tried to copy log on msn, and then I did a ctrl-V paste on gnu but I only got an error, can you tell me how i can download the game history into gnu?

greetings k.

Gnu has the "Import" option which allows you to search for game history files from your hard drive.

Basically, ctrl-v the log into Notepad and save. (I always save as the date then -n for the nth game I've played that day so I can track my progress later) Anyways, then open GNU and File->Open that text file.

If you ever want to manipulate the games in GNU (e.g. play the computer from a certain point after correcting a move, etc) you will want to do Game -> Swap Players before you do the analysis.

It is always a bit satisfying after losing to do the GNU analysis and see that you actually had a lower error rate but he got lucky. This, of course, can work the other way when you're the one getting lucky

Hi Ted,

your trick works. I always play at gamecolony and I e-mail the games afterwards, now i just copy the mailtext to a notepad, save it, and open it in gnu, thanks very much,

greetings k.