the dorbel daily

Tuesday, 31 January 2012

More Golden Point Stuff

In the last post we looked at a couple of difficult plays, where the player had an option to make his 5pt or hit. Here's the first.

Black leads 2-0 to 5. He chose to play 24/18*, but Timothy Chow in his comment pointed out all the downside to that play. Too many return shots, a staggering 30 (!), after which White may well make her bar anyway. Four blots is also more than most positions can stand when you are outboarded also. What we have to grasp here is that this is highly likely to develop into a prime/prime struggle and for that, you need a prime. 10/4 makes a very useful point and leaves no blots, but it also makes it very hard for Black to make his bar and his 5pt in the time that he has left. The best play, by a lot, is 10/5, 6/5 and leave the 4pt slotted. Anything else is a blunder. After that play, White is a favourite to make her bar or hit, but is unlikely to do both. If she hits, Black will get return shots. If she makes the prime, Black will be a favourite to make a four point board.
Making the 5pt is a world class play. Not sure I would have spotted it. I think that I would have made the 4pt, wrongly.

In this position, trailing 4-away, 3-away, Black decided to double. A doubled gammon takes him nicely to the winning post, while cube ownership and gammons are much less useful than usual for White. It's a pretty easy take and technically it's a bit short of being a double too, but I still like it. Black won't have to make any more doubling decisions and if he gets lucky he can win this match in a few rolls. A useful guide incidentally, although not infallible, is "Never double until you've made a point inboard". This is still known in London as the Dimitri Rule, after Dimitri Kourdoulas the likeable Cypriot regular at the old Double Five Club.
After doubling, Black had to play 4-1 and opted for the double hit, 8/4*/3*. This of course leaves Black with six (!) blots and no hiding place if White gets among them. XG2 will play this at all levels up to ++, but a 2592 game rollout was unable to separate the two plays. They are essentially equal. I like making the 5pt. Rather as in the first position, it gives you a position with which you can fight the upcoming battle. It also unstacks the 6pt and leaves Black nicely placed to blitz or make a five prime, or both. It also looks to me as if it will be fairly easy to play. Still, if like Paul Weaver and XG2 you like the double hit, go for it! Acording to the rollout you will do as well as me, provided you can handle the complex game that has to follow.

Tomorrow I want to look at some positions where I was trying to defend against a backgame. In the later stages, the plays are usually fairly regular, but in the first stages immediately after the Big Bang as it were, the plays are far from obvious. How well does the bot play them? How well did I play them? We'll see, but until then, enjoy the game!

Saturday, 28 January 2012

The Golden Point.

Just how important is it to make the 5pt? Often we are presented with a choice of making it or using the roll to hit somewhere else. In a different form we also sometimes have the opportunity to make either Golden Point. There are of course no definitive answers. Sometimes it's right and sometimes it's wrong, but today we can have a look at a range of positions, some commonplace, some rare.

Here's a very common one and most of you know this one.

Position One.

It's always correct to hit, money or match, any score. Hitting gains 20 pips in the race and removes the White slot. Still, many intermediate and beginner players still make their 5pt with this one, wrongly. How about with 1-1? Now making the bar and 5pts is correct and hitting is always wrong, although not by a great deal at some scores.
That was an easy one, so how about this?

Position Two

Not many people run out with 5-4 or 6-3, so you don't often see this one, but against weak players it can be a good alternate if they don't know how to play 3-1.
Hitting is clearly correct and making the 5pt is an error. What you do with the one is not so clear. I always hit and split, but 13/10*/9 is also quite good.

Much more commonplace is the response when White has made a major split.

Position Three

For money and at GammonSave, making the 5pt figures to be correct, but at GammonGo and DMP the issue is far from clearcut. I haven't rolled this out (although I will) but at lower levels of evaluation (XG2++) there is nothing to choose between them. A very common mistake here is to make the 4pt with a 4-2, but hitting is correct except at GammonSave where the two plays are very close.

Now let's move on to some more difficult stuff. Here's a position that a student faced and got wrong. What would you have done with this?

Position Four

Leading 2-0 to 5 Black had this 5-1 to play. Hit? Make the 5pt? Make the 4pt? And if you think that one is hard, try this one!

Position Five

Here Black, the renowned American expert Paul Weaver, is trailing 4-away, 3-away to Mochy.
As an extra problem, should he double this? If he does and gets a take, how should he play a 4-1?

Take your time, you have a day, possibly two to think about this one! If anybody has actually rolled out Position Three I'd like to hear from you.
Until the next time, enjoy the game!

Friday, 27 January 2012


I'm sorry that you haven't had much to look at these last few days. Sometimes inspiration dries up, sometimes I research some positions and then find that in fact they are not as interesting as I first thought, sometimes I write something and then find that even I am falling asleep while reading it! However, enthusiasm is welling up again and I have some nice themes to look at this week. Hit or make the 5 point, an ever-recurring problem, some ways of looking at race cubes for beginners and how to make the most out of playing against bots. That's all in the next few days while I sit around with my leg up after having my varicose veins stripped (recommended for masochists and anaesthesia fans).
In the meantime, I want all of my British readers to mark a date in their diaries, for the annual Scope Charity tournament at the RAC Club on 26th February. This is a superbly run (Mike Main and Peter Bennet) day out in a fabulous venue, with a champagne reception, the best brunch you will ever eat, auctions and of course backgammon. It benefits Scope, the Cerebral Palsy charity and you will have a terrific day out and may even win something. More details at this url .

My annotated matches are still available at $10 a go.
Mochy v Falafel, 13pts. The two best players in the world playing at world champion level.
Mochy v Melzi, 13pts. Mochy takes on Carlo Melzi, the world class Italian.
Mochy v Peever, 13pts, Mochy v Paul Weaver, the world class American teacher.

All the significant plays rolled out and interesting positions annotated by me, with some comments from Mochy. Specify XG, Gnu, Snowie or Word doc.
payPal to dorbel(at)gmail(dot)com.

Finally, personal lessons are always available for all levels below expert. Based on your actual matches and focussing on the areas that lose you the most equity, these are only 20 euros a lesson. Think they might suit you? Ask for a free trial!

Finally, the best online league is Fibs League . Join anytime and usually start straight away. Well run, good fun, recommended.

That's it for today, tomorrow I hope to have something for you that isn't advertising! Until then, enjoy the game!

Sunday, 15 January 2012

Last Man Standing and Friends.

Here we are again, money game, Black on roll holds the cube, White with 14 checkers off is still dancing. Can Black redouble?

Not unless he wants to be beavered! White is a small favourite here and will love to get her hands on the cube in this immensely volatile position. Basically Black isn't yet in a four roll position, as 24 of his rolls only bear one man off. He still has some danger of leaving a shot too. The same number of checkers on three points is no redouble and a take and even if you move them all down to the lowest two (or one) points, White can easily take a correct redouble.

When Black gets down to six checkers though things are very different.

Now 18 rolls bear off two or more checkers and White's chances of dancing and getting a shot are of course dramatically reduced. Now Black should redouble and White should pass, usually with a small sigh. It's awful to lose with 14 men off. We've gone from no double/beaver to redouble/pass in a roll, an indicator of the huge volatility when one side (or both) is down to a single checker. White can take if she has entered and reached her 18pt. That position looks like this.

While White was on the bar, the position was complicated by the chances of her dancing again and/or getting a shot but now that it is just a race we can use EPC to figure this out. Her task in running round is of course simple, but she will sometimes enter her home board with a roll that doesn't bear off usually meaning last roll wastage. For that reason, we have to add some pips to her pipcount and the agreed figure for a single checker is 3.5, so her EPC is 21.5. Black is a little worse than a true three roll position, as not all his doubles save a roll and he may yet roll three consecutive ones. Quite arbitrarily I add 0.5 of a pip to that to make his EPC 22.5, so redouble/take.
If you don't know what EPC is then you need to read this article.
Walter Trice invented this and it is very valuable. He expands upon this further in his articles in GammonVillage Magazine .

It is premium content, so you will need a subscription, very good value at $50 a year, huge archive of articles and matches, with new content added regularly. You could also buy Walter's wonnderful book, "Backgammon Boot Camp", arguably the most bangs for your buck on the market.

Until the next time, enjoy the game!

Thursday, 12 January 2012

Last Man Standing.

In the Christmas Quiz I emphasised the difficulty facing the player whose opponent has taken off 14 men. There are unusual checker plays that you have to make, but today I just want to look at using the cube.

Here's a position that you might face. Black hit White's's last man and closed her out and White has danced every time up to here. It's a money game, so what's the correct cube action for both sides?

Black didn't double and rolled 6-5, taking two off and White danced again leaving the position below.

Now what's the correct cube action for both sides?

I'll expand on this tomorrow, so if you want a comment, get it in now!

Enjoy the game!

Tuesday, 10 January 2012

The Answers Part Two

The answers for Numbers 6 to 10

Position 6

Money game, Black to play 3-3.
The plays that include 5/2*(2) do very badly in the rollout. Switching from priming to blitzing when you have already cubed and you don't have the ammo in position for the attack just isn't the plan. That solid 7 to 4 block is Black's big asset and shouldn't be traded away. Rather surprisingly Bill Davis and Danny Kleinman liked bar/22, 13/10, 5/2*(2) back in 1990 and so did Barclay Cooke when he showed the position as No 102 in Paradoxes and Probabilities. That's a shockingly bad play and so is hitting twice! So, what's best? It's probably one of these, either bar/22, 21/18*/15, 13/10 or bar/22, 24/18*, 13/10. The rollout hasn't split them yet. If it does I'll let you know and for now I'll allow either as the winner. Two entrants got the first of these.

Position 7.

Money game, Black to play 5-1.
All good quizes need a position like this. The answer is of course 7/2, 7/6, for minimum shots and to avoid the 6-6 disaster next when not hit.
Two entrants got this right.

Position 8.

Make the play of 6-6 that leaves the fewest shots.
Dead sneaky this one. The answer is 14/2, 10/4(2). This appears to leave 11 shots, but actually only leaves 5. You have to play the full roll if you can, so White can't hit with 6-1, 4-1 or 2-1!
Only one entrant got this right and he was honest enough to say that he had seen it before and remembered the trick.

Position 9

Money game, Black to play 1-1.

2/off(2), More wins, more gammons, more backgammons. It does leave a big mess after rolling a 1 next turn, but for that to hurt you have to roll a 1, get hit, hit back and then get hit. That's 30% x 30% x 30% x 55% = somewhere between 1 and 2% and even then you haven't lost as you own the cube. Gumpi also cleverly points out that playing 2/1(4) creates 2-1 as a blot number next turn. Only one entrant got this one right.

Position 10

Money game, Black to play 5-3.
24/21, 9/4. When you have to leave a blot, or as here blots, put them where they will do most good if not hit. This play at least puts the blots on points that Black really wants. 11/8, 9/4 is the only alternate that comes close on XG++ but I admit that I haven't rolled this one out yet. Our experts from 1990 also picked this play and 3 of the class of 2012 also nailed it.

So after all that, who won? Stiefnu scored a brilliant 7/10 just squeezing in ahead of Timothy Chow who totalled an excellent 6. Well done all of you and thank you very much for taking part. This blog is nothing without you. If Steve sends me his address I'll send him his wonderful prize, which I just know he will treasure.

Until the next time, enjoy the game!

Tuesday, 3 January 2012

The Big Quiz, the Answers

The Answers!

Position One.

Black leads 6-2 to 9. Should he redouble? If he does, should White take?
These positions are very difficult to sort out over the board, as they take us into regions where we are not used to calculating winning chances. For money this is such a monster pass that we don't need to figure White's chances, as they fall so far short of the usual take point. At this score though, a Black redouble puts the match on the line. Let's do our risk/gain analysis.
For Black, ND/WIN is Crawford, needs 7 or 91%.
D/WIN wins the match, 100%
ND/LOSE is needs 3, needs 5 or 65%
D/Lose loses the match, 0%
If Black doubles he risks 65 to gain 9, R/R+G = 65/74 = 88%.
Black's doubling window opens at 88%. Does he have that? It's easier to count White's winners than Black's. White wins when Black fails to throw 2-2 or better (31/36) and then rolls 4-4 or better (3/36). That's 3/36 x 31/36 = 93/1296 or about 7.2%. There's also a sequence when Black rolls 2-1 twice and White bears off in one or two rolls which adds about 0.1%, so we'll give White 7.3% wins and Black 92.7%. The double is clear then and as White can preserve 9% of ME by passing, she should drop. Double/Pass.
6 out of 8 contestants got this right.

Position 2.

Money game, Black to play 3-1.
By the slimmest of margins, 12/9, 11/10 is correct. Dave Kettler and Julia both explained this one very nicely for me, pointing out that 11/7 or 12/8 both waste pips after a specific roll next turn. After 11/7 you waste a pip with 3-2. After 12/8 you waste a pip with a 3-1.
4 out of 8 got this right.

Position 3.

Double match point, Black to play 1-1.
Very tough. A 2592 game rollout plumps for 10/9, 7/6, 3/1*. The answer in 1990 was 10/8, 5/4, 2/1* but the bot places that third 0.015ppg behind. The second place play only 0.004 behind is 7/6, 5/4, 3/1*. Perhaps the biggest surprise for me was that 10/7, 2/1* was only sixth best although still quite close. I assume that this is because if White enters with a 6-1, Black will actually do better to have two men sent back! Also, if White dances, Black doesn't really want his next 6 to be played to the ace point, so plays that leave the outfield spare further back do well. Black really must try to pick up all three checkers if he possibly can.
Nobody got this right, with the majority wanting to make the bar.

Position 4.

7 point match, White leads 5-2, cube action?

Double and take for money, but here no. Cube actions that take our opponent exactly to the winning post are usually suspect and this is no double/take.
Black no double/win, trails 4-away, 2-away. 33%
Black double/win, trails 3-away, 2-away. 40%
Black no double/lose, trails 5-away/Crawford. 16%
Black double/lose, loses match. 0%.
Black is risking 16% to gain 7%, R/R+G = 16/23 = 69.5%
Black needs 69.5% minimum to cube and with only 23 winners and 13 losers he only has just under 64%.
4 out of 8 got this right.

Position 5.

Money game, Black to play 1-1.
It's 2/off(2)! In 1990 they got this one wrong and a 5184 game rollout on XG proves it . Basically the safe play wins almost 100% with 99.31 gammons and 17.08 backgammons. Taking 2 off still wins 97% and although the gammons drop to 62%, backgammons jump to 53%. The difference is only 0.007 of a point and I don't think that there is any way to calculate this over the board, but you may like to consider that a considerable part of White's equity after Black takes off 2 checkers resides in White's ability to use the cube correctly. XG manages this very nicely but how confident are you that you know when to redouble against a man who has born off 14 checkers? It's pretty tough. In practice this should make the 2/off play clearly right.
5 out of 8 got this right.
Tomorrow (really!) I'll post the answers for positions 6 through 10.
After these five, Timothy Chow leads with an excellent 4/5.
Enjoy the game!