the dorbel daily

Tuesday, 25 January 2011

Two Blots Inboard, How Bad Is That?

Here's a nice checker play problem for you, which I got wrong. It's interesting not only because it's a tough play, but also because it illustrates a much wider principle. How would you play 6-4 here? Red trails 0-3 to 5 in the match, but in this game he has already cubed and leads 125 - 138 before the roll. White is the world class player and noted theorist Rick Janowski.

Three plays stand out, the double hit, 9/3*, 8/4*, the single hit 9/3*, 7/3* and the non-hit 9/4, 8/2. Nothing else is worth a look. My thinking went like this. "I lead in the race and my position is solid, apart from the fact that my anchor is detached from the rest of my checkers. Moreover, White is completely stripped in the outfield, so will find it hard to make a damaging play next turn. I don't need to give him 22 shots to possibly turn the game around when he owns his 6, 5 and 4pts." I chose 9/4, 8/2.
Actually, this is probably the best play to win the game, but it doesn't win as many gammons as the hit plays and gammons are very valuable here. I can't lose one and winning one will get me to Crawford. Of the hit plays, the double hit is clearly best in the rollouts, illustrating a valuable guide to good play. Two on the bar is better by far. It's better here because of the match score (dead cube, one way gammon threat), even though it leaves two blots and White has a strong board. My play was a large blunder costing about 0.17ppg
Another very interesting aspect of this is that if the cube were centred, the non hit is clearly correct! Why is this? It's because after the quiet play, I can usually offer an optimal cube next turn, so the hit plays with their attendant risks aren't efficient. When they work and White can't hit from the bar, I lose my market by the length of the street. When they don't work and White hits, I haven't got a cube at all.
For money, the quiet play is much more competitive, although still an error and the single hit is on a par with the double hit. This of course is because gammon losses come into play.

The next position also illustrates the strength of putting two men on the roof.

It's a position from earlier in the match. White leads 2-0 to 5 and forced plays have led to this position. White doubles from the bar. I expect that everybody will drop this like a hot brick and I certainly did. However, Snowie 3-ply will take this! Rollouts suggest that it is actually a pass, but not by much, demonstrating how strong it is to put two men up, even when you are trapped behind a prime and have two blots inboard. Here too of course the score is a factor, as White's gammons are less valuable than usual because of overage and cube ownership is also worth a lot. The pass is clearer at "normal" scores, although still not huge.
I recommend that you play this out for a few games if you find this hard to believe, you can learn a lot. Your first problem might well be how to play your next two! Any ideas? I'll give you the answer in the next post. Until then, enjoy the game!

Saturday, 15 January 2011

Re-learning Old Lessons.

Today's position comes from a nine-point Fibs League match against Walfinho from Austria. I've already doubled on the strength of my four prime but White has anchored and is now threatening to start building a prime of his own. I have 4-2 to play. What would you do?

Red (dorbel) v. White (Walfinho), Game one, Match to 9 points. Pipcount Red 144-White 156.

My prime is front-loaded, which if you haven't come across the term means that all the spares are down the low end and of course this makes for lack of flexibility. 8/4, 6/4 makes the 4pt nicely and leaves the 8pt slotted. It leaves a shot of course, but White isn't going to hit even if he does roll a 5. This was enough for me, the play makes a valuable point, improves the spread of my builders and free slots the back of a five prime, that'll do. It's an enormous blunder.
My main priority in this position should be to get my back checkers moving, before White builds a nice prime to keep them in. I should know this without even giving it much thought, because there is a hugely powerful guide to the correct checker play in these situations and it is this.

When your opponent has a high anchor and you don't, you must respond immediately to try and equalise.

That even applies here, where White's anchor is the feeble 22pt and it is primed. Red just has to get those back checkers moving, so that they can race or anchor or hit something in the outfield as the dice dictate. Otherwise the advantage will swing slowly to White as she builds her prime and stays anchored at the edge of yours. The best play is 24/18. White will usually hit it of course, but you should get lots of returns and while she is hitting, she isn't improving her board.
I am indebted for the above rule to Paul Lamford, the British writer and teacher. I had forgotten it and needed reminding of how strong it is.
Look for Paul Lamford's books, they are very useful. 100 Backgammon Puzzles is an excellent cheap read, full of useful examples like this one and his Starting Out In Backgammon is a great beginner guide.
Until the next time, enjoy the game!

Friday, 14 January 2011

Return of the Blunder Log.

Well, the Dorbel Daily has been inactive for too long. Sometimes your brain needs a rest from analysing and studying. This is a GOOD TIP actually. Don't read about backgammon or do any studying in the run-up to a tournament. It is a well known phenomenon that learning new things has an initial bad effect on your game. This is because you will start applying them in inappropriate places. Only when you have fully grasped a new concept will it be of benefit. Think of it as remodelling a golf swing. It will pay off in the long run, but you don't want to start on it a fortnight before the Open.
So, I am going to try and post daily for a bit and these posts will be a bit of a grab bag, of blunders made by me in online play. I won't be posting those that are just oversights, partly to spare my blushes and partly because they aren't very interesting. The "Oh God, I didn't even see that I could have made a 6 prime" sort of thing isn't useful.
Here's a position from a Gamesgrid match with Chiemi. It's the first game of a 7 point match, I've been cubed and I have a 5-3 to play. What would you do?

I chose to make the board, 7/4, 6/1 and wait for a shot. I reasoned that hitting a shot would certainly save the gammon and that I might even win, but his level of thinking is much too wooly. First I should have looked at the exact number of White rolls that leave a shot next turn, which is of course all 2s except 2-2. That's 10/36 after which I hit 11/36 or 110/1296 or about 8%. White will of course take 2 off with any 2, so have 10 men off in total. So, I'll be on roll with White on the bar and holding the cube in something like the position below.

In this position I win the game just about 30% of the time holding the cube. If that seems a bit low to you, the two spares on the 3pt are the problem, for two reasons. First they give me very little choice in how I bear in the last checker and I may even have to leave a shot. The second is that I badly need to bear off as many checkers as possible before breaking my board and of course for that purpose it would be much better if they were on the high points. Move them to the 6 and 5 pts and I go up to about 36%.
So, 8% to get a shot and hit it multiplied by 30% wins after hitting comes out to about 2.4% wins if I wait. We can add a little bit for getting and hitting a shot later as well and in fact the rollout says I win 3.2% if I wait. If I had made the effort I could have come up with a figure of about 3% over the table, but I didn't which was partly laziness and partly because like everybody else I play too fast on the net. Now let's look at how many gammons I lose if I wait. None if I hit of course, but lots if I don't! When I don't get a shot and hit it, White will have somewhere between 9 and 12 checkers off and I'll be anywhere between 0% and about 70% to lose a gammon, so 35% gammons is a reasonable guess. In fact the rollout says 36%.
What if I just run the 5-3? I would have guessed 15% gammons over the board and Snowie says 14.3%, and of course I never win. So by staying I win about 3% but lose 36% gammons instead of 14%! It's not even remotely close. I should have nailed the number of my wins exactly and even if I had been way off in my estimates of gammons, I would have come up with the right answer, which is that staying is a huge blunder.
So there you go. Trying to win the game is usually good, but there comes a time to turn mother's picture to the wall and ride out! This was one of them.
Until tomorow, enjoy the game!