the dorbel daily

Wednesday, 29 February 2012

Learning To Love The Cube. part 3

A Reader writes, "It's all very well saying that you think that we should double as soon as we think that it might be a double, but what should our winning chances be to make it right? When should we first think about doubling?"
This is a very good question. Let's take the second part first. When should we first think about doubling? I would say, whenever something good happens. You hit and they dance, you roll a great number to make a vital point, you escape, you roll a useful double. All of these represent a big leap forward. If one of these things happens, it's a great indicator that the cube is hot. If you are a beginner, just using this as your wake up call will work well, but the real trick is to get your double in before the good roll! If you can anticipate the likelihood of a big swing next turn, then you'll be doubling like a pro.
Now the first part, what winning chances do we need? Usually of course, you need to at least be the favourite, but there is no set threshold where it becomes right to cube. Your chances might as little as 53% and it be clearly right to redouble, or as much as 70% and still not have a initial cube. The key factor usually is the volatility. If it's a race or you are bearing in against a holding game, then things aren't usually very volatile and you don't need to make the take too easy. A correct cube will probably be in excess of 70% wins. If on the other hand it's a blitz or a position where the next roll will decide things one way or the other, then something much less can be enough, particularly if there are some gammons about.
So, what sort of thing are we looking for in order to anticipate our good roll and get the cube in before the party starts? Look at this position.

Position One

Black is on roll and leads 1-0 to 5. This isn't an immediately obvious cube, but it's actually quite strong. What are we looking for? Black leads in the race 140-158, more than two average rolls. He's made his 5pt, while White has no points yet and Black has also escaped a checker. White too has one loose checker and her back men haven't moved yet. Black is already very strong, winning about 68% if the game is played to the end, with around 17% gammons, but crucially this is actually quite volatile. Black has a range of threats. He can hit the blot or make the bar or another inboard point, or escape to the midpoint. When he can't do any of these things, he can just make a safe quiet play. After that it will be White's roll and on her turn, she has almost no threats and some difficult rolls of her own with those awkward stacks. This recipe, a variety of threats and no really bad rolls, is always the basis of a cube.
In the match, Black didn't double and ran out with a 5-4, then White rolled 5-2 and made her 4pt.

Position Two.

Nothing much has happened but Black has lost his market and this is now a clear double and pass. The race has got shorter, Black has increased his lead and White now has to try and win with an ace point holding game. In real terms, Black's wins have jumped to 73%, but his gammons have dropped to about 11%, although I wouldn't attempt to calculate that over the board. I just know that an ace point game and nothing else is a pass!
If boldness is our guide when doubling, should we be bold takers too? We'll look at that tomorrow.

A new site to me is WarpGammon but it comes well recommended. They have regular tournaments, mostly free entry, but there is one that costs $11 to enter which should be fun.
You can play your matches on various servers, including SafeHarbourGames , a nice friendly site where I have played once or twice. Venture out!

Fibsleagammon season 55 has now finished. Provisonal result. From Master A perennial rivals dorbel and BushSucks will cross swords with stukatz and Mason_Verger from Master B in the playoffs.
These should be terrific matches with a high standard of play, so I'll try to tell you when they are scheduled.
Until tomorrow, enjoy the game!

Friday, 24 February 2012

Learning To Love The Cube Part 2

More Fibsleague news. In Master A dorbel and BushSucks will be going into the playoffs, where they will be joined from Master B by stukatz who produced a late burst to finish 9-4. The second place there will go down to tie points between the players who finished on 8 wins and as it stands Mason_Verger leads that pack. The Gold, Silver and Bronze divisions have thrown up some rising stars who will be looking to do some damage when promoted. _loak from France has compiled an 8-2 record in Gold A and MISS_IRAN has topped that with 9-2 in Silver A. pilogen (Italy) has had an outstanding season in Silver C with an 8-3 record and it's great to see that perennial Fibs favourite MacMom topping the Bronze division on 8-3, just ahead of fellow American twist on the same score. Last but not least, the Sesame division has seen lots of action with players from 9 different countries, including Ukraine and Hungary and all these players will of course be in Bronze next season. Mention must be made here of Alexander from the UK, currently on 7-0!

I'd like to expand a bit more on what I said about doubling in the last post, in the light of several very interesting comments. I think, in fact I am sure, that players below expert level are too cautious with their doubles. I don't think that this is because they under-estimate their winning chances, because they don't really think of positions in that way. Part of it is just pessimism. "What if she turns this one round, I'll be losing two points instead of one". Weaker players don't win as often, so they do tend to have a pessimistic outlook!
Here's a position that illustrates this, from a match with a student.

White is on roll and on the bar, and it's 0-0 to 5. Cube action?
This is in fact not a commonplace position and if you said, "I have thought about this and I don't think that it is a cube", that's fair enough. It's a huge blunder not to cube and we all make huge blunders from time to time, but what the student said to me was, "All I could think was, 'What if I dance?'" All he could see was the dark side, the 16 rolls where White danced and not the 20 rolls where White entered. This pessimism stopped him from even considering a cube.
In practice, if White does dance, Black is probably a very small favourite, certainly not good enough to recube, whereas he will be a huge underdog if hit and struggling even if White just enters. Very volatile positions like this are often cubes. I like to ask myself, "If I roll my worst, can he redouble?" If, as here, the answer is no, then that is a very strong pointer towards doubling. Still struggling to see this as a cube? Set up the board and play it 50 times with the cube in the middle and 50 times with Black owning the cube. You can actually do this simultaneously using 2 cubes. You'll learn something about the position, which is nice, but much more importantly, it will do wonders for your attitude in the future.
There is too a natural human tendency to want the match to last as long as possible. I don't know what the reason for this is, but it is very common. I saw this position passed recently.

It's 2-2 to 5 and Black redoubled to 4. White passed. It's pretty easy to work this one out, White wins the match every time Black throws a one, so White will win 30.5% of the time from here. If she passes, White will have to win the next two games, so her match winning chances are 25%. Passing hands over 5.5% of the match equity. How bad a mistake is that? It is the equivalent of resigning the first game of a nine point match before you roll the first die!
I asked White why she passed. She said, "I didn't want to put it all on the dice." This remark is actually fair enough if she considered herself to be much the stronger player of the two, but no she didnt think that, she would just rather play than end the match right here.
How much stronger do you need to be to consider passing this? If you think that you can win a cubeless game against this Black player 55% of the time, that's probably good enough to make this a marginal take/pass.
What if it is Black who is the 55% better player? This is by the way a very big skill advantage. Should Black even be doubling? No, if he is that much of a favourite, redoubling here is a big mistake.
We've digressed a bit here, because whenever I discuss cube actions you should always assume that the players are equal, but for the player trying hard to be more aggressive, if you are distinctly the weaker player, positions like these where the dice decide should be meat and drink to you. In these positions, both players are momentarily equal and you should be delighted to see the cube rising.
One more interesting sideline on the subject of escalating the cube and of course shortening matches. At one time the GBots on Fibs used to play 25 point matches. The reason that they don't do that any more is that some players worked out that their chances of winning a 25 pointer against a GBot were better, considerably better, if they could finish the match in one or two games than if they battled it out playing properly. The tactic was to cube immediately, take any recube and immediately recube to the next level, ideally getting the cube to 32. Against a bot, this is a brilliant and entirely legitimate tactic, increasing your wins in a 25 pointer from about 5% to about 18%! This doesn't work against a strong human, because he won't treat you as an equal, but the bot does and this flaw is what you are exploiting.

We've by no means covered all that there is to say on this subject of becoming a more aggressive cuber, so I'll go on with it again tomorrow. Until then, as ever, enjoy the game!

Thursday, 23 February 2012

Learning To Love The Cube

There are several ways to approach improving one’s checker play but for me, the most important feature is your attitude to the cube. How do you view it? I want to divide this into Doubling and Taking, because the two skills are actually quite different. I see doubling as being much more important. This is because we typically face many more doubling decisions than taking decisions, as obviously we only consider a take when we get cubed, but have to consider doubling several times in every game.

World Class players, without exception, are eager to turn the cube at the first reasonable opportunity. They actively look for chances to double very early, as early as the bots and much earlier than players below expert level. There attitude is, “I think that this might be a cube, it’s certainly very close, so even if it is a small mistake, I’ll turn it now.”

If you are not actively looking for these opportunities as soon as you think that you have an advantage in the game, you are certain to miss them. Bear in mind that they adopt this policy even when they are playing another player of their own standard, so they have worked out that this attitude is technically correct. For the rest of us playing opponents that are anything but World Class, it is even more likely to be the right policy. Why? Look at it like this.

Doubling on the first roll that you think that you may have a double has some hidden benefits. The first is that it allows your opponent the chance to make a mistake. Choosing not to double does not do this. “But”, I hear you say, “If I double very early then there is no chance that she will make a mistake and wrongly pass”. There is less chance certainly, but there will be some wrong passes and when they do come along, they will be huge blunders. One blunder that gives away 0.3 or 0.4 of a point (and these do happen) will pay for a lot of slightly early cubes. There is more. Once you have cubed, you can’t then make subsequent cube errors in that game, unless of course you get recubed later. There is more too. Part of the equity of the player taking the cube resides in her ability to use it efficiently later, but only very, very strong players do this. If your opponent isn’t an expert, the chances are that she will miss her chance to redouble you in later and/or cash when she is too good to double. By giving her the cube it’s true that you give her some theoretical equity, but that will only help her if she uses it well and the chances are that she won’t. By cubing early then, you not only kill your own chances to make a later cube error, but you open up the possibility that she will do so!

“If I wait until I am stronger, then there is much more chance that she will make a bad pass”. This is absolutely true, but there are two things to consider here. The first is that you risk losing your market. The second is that the possible mistake that she can make is much smaller. If for example you wait until your equity is say 0.95 of a point after a double and take, then it is true that her take/pass decision will be very difficult, but if she makes the wrong decision, it only costs her 0.05 of a point.

The second kind of doubling decision is, “Am I too good to double?” This is one of the nicest decisions that we face of course, difficult to get right but always meaning that we are in a very strong position. I have a very simple rule for this. I only play on for a gammon if I am 100% certain that I am too good and if I do, I make sure that I keep reviewing that decision on every roll. How does this work in practice? It means that I make some small errors when I am technically too good (i.e. worth more than a point a game on this roll). However there are two compensating factors that more than make up for these errors. The first is the possibility of wrong takes, which are always huge blunders. Not very likely? Show me the player who has never taken a cube that was actually too good. I have and Iam quite sure that I will do again. They come up a lot and it only takes one of these every now and then to pay for a lot of small errors when they correctly pass.

The second is that when they correctly pass, it puts a concrete point on to the scoresheet. It isn’t theoretical equity, it’s a real point and I don’t have to play to get it!

So, we need an aggressive attitude that actively wants to double and we need a way of approaching each roll that gives us the time to consider a cube. Now of course we get to the difficult part, which is trying to figure out our winning chances so that we can see if we should be doubling. I’ll digress for a moment though, to say that experts never think to themselves, “What if he takes and turns it round and I lose?” They only think, “Is it a double?” However, looking at the position from our opponent’s point of view can paradoxically lead us to the correct cube action. This is the legendary Woolsey Rule. Invented by the great theoretician and player Kit, it simply states, “Are you 100% sure that this is a take?” If not, it must be a double.” Even easier, you can simplify it further to the dorbel rule. “If I was him, would I want to be doubled here?” No? Ship it in!

Food for thought? I hope so. Let me know what you think of this and please, ask questions.

Tomorrow we'll look at taking and passing and actually look at some real positions.

Until then, enjoy the game and get that cube moving!

Tuesday, 21 February 2012

Backwoods v zyxtcba, The Last Cubes

Fibs League updates. In Master A, BushSucks has finished his campaign with 8-4 and only jackdaddy (7-4) and roadkillbooks (4-4) can equal this score in the race for second place behind dorbel (9-3). Over in Master B where they are playing 13 matches in this session, MasonVerger, runnerup and blotsalot are all completed on 8-5 and looking nervously at the final matches of stukatz (7-4) and Backwoods (6-3). Sunday is the last day for play. Looking down through the Gold, Silver, Bronze and Sesame divisions, the league looks very healthy with a further 97 players spread over the four lower divisions. This is a good week to sign up if you want to try league play, with the new season starting in March.

In the last post we left you looking at this position from Backwoods v. zyxtcba. White is on roll trailing 5-9 to 13.

Both Timothy and Clem nailed this one in the comments section, clear double for White and at this score, Black should pass. The cube is worth next to nothing for Black and although gammon wins work well for him, taking him to exactly 13, he isn't going to win many of those with White owning the 20pt anchor. White actually wins this game about 69% of the time, including 24 gammons, while Black's gammons are down in the backround noise range at about 5%.
It didn't work like that in the game. White didn't double and Black, who has become more and more wary of turning the cube as the match progresses, eventually cashed after missing a string of correct doubles. Match leaders often freeze up like this and for positions with a lot of gammons that's a fairly good policy, but in races and holding games, the double and take points are not very much different than normal and you do need to keep the pressure on.
If you are the trailer and you see the leader missing opportunities to turn the cube, this often means that they are going to be nervous takers as well, so look for opportunities to double anything with a gammon threat.

This next one is from Game 12 with White now trailing 5-10.

Actually White should double this even for money, but there Black would have a simple take. At 3-away, 8-away, Black has to let this one go. The cube is just about dead after a take and his own gammons will include overage, so it's a very close pass. In the match Backwoods turned the cube and Black correctly passed. Trailing 6-10 to 13, White then had this one in the next game.

Not immediately obvious that this one is a cube, but note again White's high anchor, just like the position at the start of this post. The old-timers hated to embark on a blitz without a high anchor and they knew a thing or two. It keeps the gammon losses down and provides a nice point from which to recirculate if hits are exchanged. Note too Black's dead checkers on the ace point. He'll have to play the rest of this game with 13 checkers, always much more difficult than when you have the full set to use. White has one out of play as well, but if his blitz works he'll make it and if it doesn't, he may be able to recirculate it. Double and take, but in the match a missed opportunity. Black won an undoubled gammon to go to Crawford and eventually won the match 13-12 for his first Master's Title.

This 13 pointer lasted 18 games, unusually long and down to a lot of missed doubles. Missing doubling opportunities is one of the things that separates us lesser mortals from the demi-gods who play at the very top level. The only way that I can see to cure this tendency is to double earlier and earlier until you start to see some wrong doubles creeping in. That's what I'm trying to do in my matches and in the next post I'll try to show you some examples, of the sort of position that I am doubling (or failing to double) these days.

Until then, enjoy the game!

Monday, 20 February 2012

Backwoods v. zyxtcba part 6

More news from Fibsleague. Your correspondent will top Master A with a 9-3 record, but the battle for the second play-off place is very strong. PHunter, BluNick and Zbyszko are already in the clubhouse with 7-5, but BushSucks and jackdaddy are on 7-4 and roadkillbooks and Prae can also get to 8 wins if they complete and win all their remaining matches.
Over in Master B, MasonVerger, runnerup and blotsalot are all done with an 8-5 record, but wordman and Magic_One can still also reach this figure, while stukatz (currently 6-4) and Backwoods (6-3) can even reach 9 or 10 wins, so anybody's guess who will make the play-offs here. Six days to go! If you don't already play in the league and would like regular tough matches, this is a good time to join with the new season starting at the beginning of March.

In the master's top 12 play off for 2011, Schigolch (Germany) has eliminated Mano, the last Frenchman standing, 2-0 and now meets PHunter (Switzerland) in the quarter-finals. In the only other tie started, BushSucks leads fellow-German masselkopp 1-0.
Thanks and much kudos to Franck del Rio (Tomawaky) for ten years running the best league on the Internet.

Now some more cube action from zyxtcba v Backwoods. We're in Game Nine with zyxtcba leading 7-5. Neither side has had a correct double up until now, but a double hit from the bar and a partial fan has left zyx in this position.

It's hard to imagine anybody taking this and looking at it now, I suspect that all of us would vote to play on here. Zyxtcba (Black) chose to double and White gratefully passed. It's easy to be critical with hindsight. The pressure of the match is something we can't factor in and this sort of panicky cube afflicts a lot of us after a game where the the pressure has been on for some time and we've suddenly leapt ahead. Maintaining a dispassionate and objective view at all times is a key skill, although easier said than done!

In the next game Black made a similar, although less clearcut mistake.

Black has a very solid position here, while White is in complete disarray. Again, nobody takes this as White and although Black often has to cash this later he should certainly play on for now. Should I double or should I play on for the gammon? Rather like "Shall I have Moet or would I prefer Veuve Clicquot?", this question is a pleasant one for a bg player, although it's often a tough call. Take your time over it. Savour the moment. Try to view it from the opponent's point of view. As White, you really want to give this one up I think. Hopelessly outgunned for race and position, you have to be pleased to escape from here only losing a point.

Now Backwoods (White) trails 5-9 to 13 and he should be very alert to any cube opportunities. He badly needs to win 2 or 4 points to get back into this and if he cubes aggressively, his chances of being recubed are of course very remote. One consolation for Black is that if he can take and win a gammon, that neatly wins the match, but White must take that chance. This position looks like just such an opportunity. On roll should White be doubling and if he does, can Black take?

We'll look closely at this one in the next post, which should come rolling out of the shop tomorrow with any luck. Until then, enjoy the game!

Wednesday, 15 February 2012

More Backwoods v. Zyxtcba, part 5.

Today I received the results of David Escoffery's Fibs Fall Open, 2011. This long running tourney attracted 91 entrants at $50 a time and the results were as follows.

David McAllister (rastaman) from Australia defeated Matthias Krings (sita) from Germany in the final and the losing semi-finalists were Klaus Evers (Phoenix) from Germany and Roberto Litzenberger (roadkillbooks) from Argentina. Also in the money after reaching the last eight were the Americans Eddie Branch (eddiebranch), Scott Simpson (notverylucky), John Graas (jdg) and Chuck Bower (c_ray).
You can enter twice in this tournament and there is a consolation event as well. Thomas Lusk (USA) won this defeating Klaus Evers in the final and Michael Schoppmeyer (stoerchle) from Germany and Joe Potts (mrjoe) from the USA also cashed.
Entries are now being taken for the Spring Open, so go in the first instance to the rules page .
The draw is on March 25th. Lets give this excellent international tourney a full bracket of 128.

Two more cube positions from zyxtcba v. Backwoods. In this first one, Black (zyxtcba) is on roll leading 6-5 to 13. White is on the bar.

This is a very good reference position. Any time that you have made the 6-5-4 block, you should be alert to the possibilities of a double. I like to put a mental flag on it, saying "Cube Hot!" With a White checker on the bar Black should definitely be doubling this one. A lot of people would pass this, me included, but White has just enough going for him to eke out a highly marginal take. White's 5pt is made and Black has no active builders with which to press home the attack. His awkward stack on the midpoint will provide those, but that's a turn or two away yet. Does Black think that he is too good to double? We don't know, but there are two ways to approach this when you are not sure about that. The first is to play on and see what happens next, the second is just to double it anyway and I very definitely like the second approach. If it is slightly too good, well at least cashing puts a point on the scoresheet, but sometimes they take! If it isn't too good, then the double must be right. I guarantee that the last thing White wants to see here is the cube, so put it to him. I only play on when it is clearly right to do so.
A few turns later the game has progressed to something much more static. Black is on roll again.

A 22pt anchor behind a five prime is usually a pass, particularly when as here, the doubler has one man back against three back for White. Either of these factors can make for a double on their own, together they are very strong. Worth remembering, this is quite a common situation. Black failed to double this though and cashed next turn when he was even stronger.
Bold cube action wins matches. The first thing that you will notice if you watch world class players in action is that they double very aggressively, more so than at any time in the past. The first thing that you notice about beginners (not that either of these players is a beginner, I don't mean that) is that they miss lots of doubling opportunities. Use dorbel's rule. "If I was him, would I want to be doubled? If the answer is no, turn it!"

More from this match tomorrow. Until then, as ever, enjoy the game!

Monday, 13 February 2012

Backwoods v. zyxtcba part 4

Two questions left over from the last post and here's the first, with Black leading 6-4 to 13.

Black (zyxtcba) went for 20/10, encouraged by those two blots that White has in his homeboard no doubt. Some knowledgeable commenters also liked this, but it's a blunder. At present, this is a positional struggle, with Black holding a clear advantage. He has much the better anchor and all his checkers are in play. White on the other hand has four checkers already behind Black's 20pt anchor. These are useless for priming but can suddenly become useful if this turns into a hitting contest. Abandoning the anchor initiates exactly that sort of game. My own personal rule is, if it isn't obviously right to run, choose something else! So, what else? Some commenters and also XG++ like 13/7, 13/9, an ambitious attempt to build a winning prime at the cost of two blots. Old Skool masters liked this sort of play a lot, reasoning that if you own the 20pt, you can put your checkers where you want them and damn the torpedoes. It's actually still a very sound guideline and I can imagine a world class player making this play. The other contender is 13/3, less ambitious but it retains the midpoint and the anchor and forces White to quit his anchor if he wants to hit. Subtly it also activates the two spares on Black's 6pt to do something useful. I like this a lot, moving steadily towards a winning prime with little risk. A 2592 game 3-ply rollout also makes this a small but not definitive favourite. It's hard to spot like so many quiet strong plays. Humans are hard-wired to take positive action to deal with a problem now, but in backgammon, keeping all your options open and adopting a quieter approach is often as good or better. Erroll Flynn had the big style, much preferring to swing in to the banqueting hall on the chandelier, but one wonders whether walking quietly down the stairs wouldn't have served as well. An interesting and instructive position.

White (Backwoods) also had a roll that is commonly mishandled by beginners. Here it is.

Sadly Backwoods chose the beginner play, 23/22, 13/7 but hitting on the ace is absolutely clear. White must take advantage of his stronger board and go for the gammonish closeout. This is not an isolated case. It's worth taking a bigger risk than this to try for a closeout and here it is so important to stop Black making an anchor on the ace that White should probably hit there even if he knows that Black is about to roll a one! This also comes up a lot, well worth remembering.

Other news. We're into the last two weeks of Fibs League session 55 and both Master A and Master B are coming nicely to the boil. In Master A your correspondent has 8-3 with one match to play, but everybody else has played fewer matches and nine other players can still put a run together and equal or surpass this score. In Master B Germany's runnerup is 8-4, also with one match to play (Master B has 14 players in this session) but again, most of the division will still be hoping for a burst of form to catch or pass that.
The 2011 Master Playoffs kicked off, with Schigolch (Germany) winning his first match with Mano (France). All these ties are best of three 9 pointers.

A word about rollouts. This blog attracts some mild criticism because I don't post the results of rollouts. It may be useful for you to know that I use XG for this, with 3-ply checker play. It's possible, likely even, that a higher level of play can produce a different result, but you do have to remember that players who can play as well as XG 3-ply are few and far between, so by using more advanced settings, you move into areas where no human can play well enough to achieve the theoretical equity. As the differences usually amount to a few hundreths of a point of equity, the value of a more accurate answer is limited anyway. I've also found that posting rollout results is boring and counter-productive, as they stifle debate. I would rather listen to our correspondents discussing why they would make a play any day, even if they are wrong!! Backgammon isn't about knowing what the right answer is, it's about knowing why the right answer is right, so that when in future we meet something like it, we have something to base a play on.
Anybody can do rollouts and I am always pleased to hear from somebody who has rolled out a position from here and got a different answer, but I won't be posting mine.

I'll have some more action from Backwoods v. zyxtcba tomorrow, perhaps even later today, so stay tuned. Until then, enjoy the game!

Friday, 10 February 2012

Backwoods v zyxtcba Part 3

It's Game Six now and zyxtcba (Black) has built a comfortable 6-2 lead. It's Backwoods (White) who is on roll here though, with one of those juicy late game positions so volatile that the cube is red hot on almost every roll.

Position One

The pipcount favours Black 75-105, but that shouldn't stop White from doubling here. Hit and dance is a market loser and he has lots of rolls that hit two checkers. He can actually be too good after this next sequence. Black has the stronger board of course and that 30 pip lead, so he can take. White's play isn't always straightforward though and after the take he rolled 2-1, playing 17-14*. This is not a big error, but the double hit is clearly right. Always do what the enemy does not want you to do. If you were playing Black here, do you want White to put two men on the roof? Emphatically not. The double hit clearly wins more gammons and trailing 2-6 Black has to select that option. Anyway, he played 17/14*, Black rolled 2-6 and we got to this position.

Position Two

White only has one number that misses and here it is, 5-5. Worse still, he crucially misplays it with 15/5, 14/9, 6/1. The best play is 14/4, 9/4(2), leaving a checker on the 15pt to cover the outfield as best it can. There was no more hitting after this and in the end White staggered over the line and won the race.

Game Seven started with Black now leading 6-4 to 13. There were no interesting cube opportunities for either side in this game, but there were two checker plays that clearly illuminate themes that recur over and over again, so it will be valuable to look at these.

Position Three. Black leads 6-4 to 13 and has to play a 6-4.

What's your play?

Later in the same game, it's White on roll. Black is on the bar.

Position 4

White correctly decided that he was now too good to double and rolled 6-1. What's your play?

We'll take a look at these tomorrow. Until then, enjoy the game!

Wednesday, 8 February 2012

Backwoods v. zyxtcba Part 2.

We pick up the match in Game Four, with Backwoods (White) leading 2-1.

Neither side has had a correct double up until now, but White is on roll here after Black (zyxtcba) has just run off his 20pt anchor with a 6-5.


White leads 72-79 and I think most of us will recognise this as a double. Backwoods certainly did and turned the cube. Can Black take? You do need to have a methodology for race doubles, as they occur often and guesswork will lead to a lot of mistakes in commonplace positions. The simplest, which works well enough for a straightforward race like this is 8-9-12. Compare your pipcount to the opponent. If you lead by 8% you have enough for an initial double. If you lead by 9% you have a redouble and if you lead by 12%, then that is the first point at which the opponent should correctly pass. Here Black leads by 7 in a 72 pip race. 7/72 is 10% approximately, a clear double and a straightforward take. Do not worry about the fact that Black needs five cross-overs to White's three. Crossovers do matter, but not very much and they can usually be safely ignored. White's stack on the 6pt and gap on the 5pt would also be taken into account by perfectionists, but just knowing the length of the race and the size of the lead gives us the correct answer, double/take. Those of you who want to refine your racing cube play can search the Internet for Walter Trice's Rule 62, The Keith Count, The Ward Count and others!

In Position One, Black only wins about 23% of the games if they are played out to the end cubeless, but owning the cube in a race with a lot of mileage left has enough value to give Black a take and later on we got down to this delightful position with Black on roll.

Position Two

What's the correct cube action for both sides? In very short races like this, with only a few checkers left and uneven distribution, just using 8-9-12 is often misleading, but it actually gets this one right. Black leads by 2 pips with 16 to go and 2/16 is 12.5% indicating double/pass, which is the right answer! We can also look at this as a three roll position, i.e. one where both sides are likely to be off in three rolls. TIP. An equal three roll position is double/pass.
That is to say that if White's position was the mirror image of Black's, it's double and pass so clearly White must drop here where he is worse than that.
As above, you can further refine your technique in these short races with unequal distribution with one of the counting methods mentioned above. I would add to this the Thorp formula, old and easy to use, but for most of us, keeping it simple is good!

White blundered and took and so went into game Five trailing 2-5 to 13. Black built a strong position and arrived at this next position on roll.

Position Three

Any time that you have a five prime with an enemy checker behind it, you have to think about doubling, if only because to see a cube in this position is not what White wants! Always do what the other player does not want you to do. White emphatically doesn't want to be doubled, so it's a cube. Perhaps Black is inclined to be cautious because he is the match leader and feels that that is his best strategy. Perhaps he think that if things go well he might win a gammon, we don't know. At all events he didn't double, White breathed a sigh of relief and the next exchange (Black 6-1, 24/17*, White 5-3, bar/22, 13/8* got us to Position Four.

Position Four

Don't you just hate to double from the bar? Join the club, but when there are blots to be hit and you have a five prime with two enemy checkers behind it, it is right and actually Position 4 is a marginal take/pass. TIP. A 22 pt anchor behind a five prime is usually a pass. Here, even though Black is on the bar a double is correct with 15 hitting numbers to get among White's three blots. Even if Black dances, White will still be struggling to tidy up and note that awkward stack on the 6pt too. A doubling opportunity missed and next turn Black had a big cash after hitting from the bar.

Zyxtcba's victory in the play-off's at the end of Fibs League season 54 was just sufficient to propel him into the top 12 in the Master's list for 2011. These players now go into a knock-out contest to decide the supreme champion for the year. All ties are best-of-three 9 point matches. The first round features the players who finished in the 5th to 12th spots. An all-German tie matches BushSucks with masselkopp, Mason_Verger (Germany) plays zyxtcba (California, USA), roadkillbooks (Argentina) plays otto (Canada) and Schigolch (Germany) plays mano (France). The winners of these ties will advance to the quarter-finals, where the seeded players, jarma (Hawaii, USA), dorbel (UK), BluNick (Italy) and PHunter (Switzerland) wait for them. 12 players from 8 countries demonstrates the wide appeal of this excellent league, smoothly run for us by Tomawaky, so if you don't play in it and want some good action, sign up today at Fibsleague .

Until tomorrow, enjoy the game!

Monday, 6 February 2012

Fibs League 54 Play-off

In my last post I promised you some riveting "defending against a back-game" stuff. The game turned out to be even more difficult than I thought, with very long rollouts needed and a lot of thinking time, so rather than present you with something half-baked and not thought out, I'll postpone that for a bit.
Not much use trying to explain it to you if I don't know what's going on in the first place!

Instead, some reporting. Fibsleague, Franck del Rio's long running contest reached the end of session 54 with a 13 pt play-off between zyxtcba (USA) and Backwoods (Finland). Zyx had never won the title, while BW was going for his record setting sixth crown and was the favourite in most eyes. Zyxtcba was the winner in a thriller, 13-12 so let's take a look at some of the major decisions.

Game 1. 0-0 to 13. White (Backwoods) on roll.

White has caught Black cold and put two checkers on the bar and correctly doubles this. Can Black take it? Zyxtcba passed and you can hardly blame him. Nobody likes to take with two men on the bar, but it's a fairly clear take and the pass is a blunder. What are the features that might lead us to the right decision? White only has a two point board as yet and still has only eight checkers in the zone. The midpoint is still stacked and the back checkers haven't moved. The point that White has made is the 3pt, useful but not a killer and the point that White has slotted is the 2pt, not ideal.
How can we add all this up and get "take" at the end? If only there was some nice formula that took all these factors into account, but that is the Holy Grail of backgammon theorists. Keep this one in mind next time you get caught out by an early blitz. Improvements for White, a better point made, a better point slotted, split back checkers, another builder in the outfield, any of these can push this one into the drop box.

One of the biggest equity sinks for all of us is the missed double. There are a number of reasons for this. First and foremost, doubling any position gives your opponent the chance to make a mistake, passing when he should take or vice versa. Also, if taken you can't then make subsequent missed double mistakes! A string of four or five missed doubles hurts a lot. A third subtle feature is that most players below expert level handle redoubles poorly, often missing a chance for a correct 4 cube. Handing the cube to an opponent of this type eliminates your chance of a doubling error and opens the opportunity for your opponent to make a big mistake or two.

Game 2. Black 0 White 1 to 13. Black on roll.

Zyxtcba (Black) misses a chance to double here. He has a small lead (128-136), he has escaped his back checkers and his front position should develop nicely, giving him winning chances racing, priming or even blitzing in some variations. White can still take. His own front position is OK, so if he can hit a shot he can turn it round quickly and he might jump out and win the race too. Nevertheless, Black should double this and let White have a problem, even though he probably knows that White, a bold taker and redoubler, will make good use of the cube if he can.
Black missed two more chances to double this one before eventually cashing to level the scores.

Game 3. 1-1 to 13. White on roll.

Backwoods (White) missed a very rare doubling opportunity here. Usually doubling while you are still anchored like this is a no-no, race lead (127-148) or not. Here though Black is going to have a lot of difficulty unloading that grossly obese midpoint and building a board. White's plan is to run the blot off the 20pt and then wait for a double or a 5-x to clear his anchor. After that, the race should be easy to win. I can't see that I would have doubled here either though. I am just being wise after the event.
In the match Backwoods ran the blot with a 6-2, zyxtcba eschewed the hit after rolling 2-1 and we got to this position.

Game 3. 1-1 to 13. White on roll.

Here's why it was correct for White to double last turn. He has escaped his blot and gained in the race and this is now a pass! This is really exactly the same as when you double with the midpoint to clear against a bar anchor. White has plenty of time to roll the double that does the job and should only face one single shot when he doesn't. In the match he again chose to roll and rolled a 5-5 for mega market loss. Two very unusual positions and we'll go on and look at Game Four tomorrow. I do mean tomorrow I promise.
Until then, enjoy the game!