Bird/Anthias books on opening leads

[uday]

What am I missing?

 

Let's say partner is on opening lead, and I'm just minding my own business over there.

 

All else being equal, I would prefer him to lead a card that, double dummy, will beat the contract rather than a card that, double dummy, allows the contract to make.

 

Wouldn't/Shouldn't we all?

 

I have some stats on DD-lead-efficiency of human beings. It is difficult to interpret. My original thinking was along the lines of measuring skill by assuming that - all else being equal -

 

A stronger player (leader, i suppose) is more likely to find a DD winning lead than a weaker player on any given hand

 

Think that's true?

 

What was interesting also was that since each hand has 1-12 "best" leads (discarding hands where all leads are best) , and that this number varies from hand to hand, that I had to normalize the aggregated data somehow. That is, my statistic for each player looks something like this

 

"On any hand from the set of N hands where this player was on lead, assume there was exactly 1 best lead. How often did he find it?" and also

"What % of the time over N boards with varying numbers of DD-perfect leads did this player find one of the winning leads?"

 

I don't know if this is a rating or a partial rating, but I'll say this - cheaters seem to cluster at the high end of this statistic. I'll also say that this is quite computationally intensive, and slow as heck.

I ran it over one month's hands in the MBC or something, and it took forever, or at least about a week. I suppose I could find a way to speed it up if I cared enough.

 

I'll present my data in more detail if anyone cares, at least in aggregate with names removed.

[GreenMan]

What was interesting also was that since each hand has 0-13 "best" leads

 

Seems as if this should be either 1-13 or 0-12 depending on whether you classify the case where all leads are DD equal as "all best" or "none best". Or am I misreading?

[uday]

My typo - it is 1-12 ( i discarded hands where all leads were equal from a DD POV)

[GreenMan]

I see, thanks. The study looks interesting.

[gnasher]

Let's say partner is on opening lead, and I'm just minding my own business over there.

 

All else being equal, I would prefer him to lead a card that, double dummy, will beat the contract rather than a card that, double dummy, allows the contract to make.

 

Wouldn't/Shouldn't we all?

I would prefer him to lead a card that, single dummy, will beat the contract rather than a card that, single dummy, allows the contract to make. Putting it another way, all else isn't always equal.

[rhm]

deleted

[rhm]

I would prefer him to lead a card that, single dummy, will beat the contract rather than a card that, single dummy, allows the contract to make. Putting it another way, all else isn't always equal.

This is a banality, irrefutable true and entirely worthless. Uday's comment is different, subject to arguments maybe, but not worthless.

DD acts as a proxy for single dummy and of course when in doubt you prefer the real thing to the proxy.

Nevertheless there are reasons why sometimes a proxy is used, because some uses can only or better be done with proxies.

Single dummy lead and play more often than not means a comedy of errors, bad guesses or failures without errors, which can hardly be simulated nor predicted.

After all there is one declarer and two defenders and everyone of them is not confined to a single mistake.

 

I am a long term subscriber to the Bridgeworld and for decades every month there is in the MSC an opening lead problem.

Quite frequently all suits find backers and sometimes even the vote is quite evenly split.

The arguments for each and every card is interesting, sometimes illuminating, but in the end leaves you none the wiser. Quite often some comment everything could be right

You simply do not know how often, which lead would work. How to decide? Does majority vote convince you?

 

Some scenarios can be simulated double dummy. Bird/Anthias uses 5000 deals per hand.

 

I still have to see the single dummy simulation over a meaningful sample, which would be workable and where the "single dummy analysis", whatever that is, is robust and you can trust.

I do not know how to predict errors, even though I understand the art of making opponents guess or uncertain.

 

Note, I am not claiming or arguing DD simulation should be your only source of inspiration for opening leads.

 

Rainer Herrmann

[PhilKing]

I assume Andy's point is that the best double dummy lead will not necessarily work because it may require subsequent DD play.

 

In broad terms, a more passive style may be DD best, but make the subsequent defence harder.

[rhm]

I assume Andy's point is that the best double dummy lead will not necessarily work because it may require subsequent DD play.

 

In broad terms, a more passive style may be DD best, but make the subsequent defence harder.

I understand that but where is the evidence for this claim?

It can not be the lead in itself, since many lead high when leading passive.

The view that an attacking lead is often a hit and miss affair is a bit simplistic. If true, play and defense would be boring after an attacking lead.

Even if there would be evidence I would tend to argue finding the killing defense is often hard.

What is even tougher is changing lifelong habits.

As you say DD does not argue for a passive style, just for a more passive tendency in some scenarios and it is my impression that at least some successful pairs from Italy have this approach.

I would need a lot of persuasion to use a sub-optimal strategy just because the defense will be simpler to execute if it worked.

It is a bit like claiming you should never lead an unsupported honor including an ace, because the defense for partner is tougher if he can not assume you have led from a honor sequence.

(Arguing not to do so because it is a general loosing strategy would be a very different matter.)

 

Rainer Herrmann

[helene_t]

If my lead of the king against notrumps promises KQTx(x) then partner knows it is usually safe to encourage with the jack from Jx(x). If I might have lead from KQxx(x) it could easily cost a trick to do so. So when I actually have KQTxx and partner plays low I won't know whether continuing will help declarer complete his Bath Coup.

 

DD the king from KQxx(x) is superior while standard is x against notrump.

[rhm]

If my lead of the king against notrumps promises KQTx(x) then partner knows it is usually safe to encourage with the jack from Jx(x). If I might have lead from KQxx(x) it could easily cost a trick to do so. So when I actually have KQTxx and partner plays low I won't know whether continuing will help declarer complete his Bath Coup.

 

DD the king from KQxx(x) is superior while standard is x against notrump.

This is running in circles.

 

The typical argument against DD goes time and again:

 

The defense has a guess single dummy DD would not have or declarer has no guess DD he would have single dummy. It comes in different guises like here or declarer has a two way finesse for the queen etc.

 

Even the DD proponents do not doubt that. DD is not single dummy play, but the argument of the proponents is that these effects cancel each other.

Otherwise DD results would not be a close proxy for single dummy results.

 

With regard to your example I am pretty sure that if you encourage with the jack, unless you can see a switch is urgently required, will usually be best whether partner has led from KQTx(x) or KQxx(x).

(By the way some play that the king asks for an unblock and the queen would be the right card if you do not have the ten. I like this method)

 

The main DD argument was that it seems more often better to secure at least one trick in the suit and the tempo and avoiding giving declarer a cheap trick rather than what you gain by taking your slightly better all out chance establishing this suit by starting low.

We humans are impressed by deals when we find leading low would have been the only chance to beat the contract and jump to conclusions.

Evolution has not made judging statistical trade-offs a top priority.

Human experience is known to be biased, far more obvious and also easier to show than that DD simulation is biased.

 

Rainer Herrmann

[NickRW]

I would like to know exactly what "DD" means in this context.

 

It could mean (and I suspect it does mean) the computer chose the best lead for this exact deal (i.e. it knows the layout of all 4 hands). Or, it could mean that the computer chose the average best lead with a range of possible layouts consistent with some sort of bidding sequence and what that was supposed to show (i.e. a single dummy solution is found by repeated DD analyses - which is, I think, what robots actually do when playing for real).

 

The former would, for example, favour an ace lead from Ax where partner has Kxxxx and the declarer and dummy are distributed 3-3. But, obviously, that layout won't happen on all deals that are reasonable for a particular contract/bidding sequence.

 

Nick

[rhm]

I would like to know exactly what "DD" means in this context.

 

It could mean (and I suspect it does mean) the computer chose the best lead for this exact deal (i.e. it knows the layout of all 4 hands). Or, it could mean that the computer chose the average best lead with a range of possible layouts consistent with some sort of bidding sequence and what that was supposed to show (i.e. a single dummy solution is found by repeated DD analyses - which is, I think, what robots actually do when playing for real).

 

The former would, for example, favour an ace lead from Ax where partner has Kxxxx and the declarer and dummy are distributed 3-3. But, obviously, that layout won't happen on all deals that are reasonable for a particular contract/bidding sequence.

 

Nick

The book takes hands as lead problems and for each hand samples the remaining 39 cards with constraints consistent with the bidding. Sample size: 5000 deals.

On the 5000 deals it is then checked how often which cards as opening leads will defeat the contract double dummy or for matchpoints will generate the most tricks for the defense.

 

Rainer Herrmann

[whereagles]

I've seen a claim somewhere on DD that went something like this: (sorry Rainer, can't give you the exact reference :) )

 

1. DD is more helpful for declarer at slam level since you always take the right finesse and/or get the endplay right.

 

2. At partscore level DD is more helpful for the defence, as they always get the shifts right. Declarer doesn't have much of a choice of plays at this level.

 

3. At game level, stuff sort of evens out.

[NickRW]

The book takes hands as lead problems and for each hand samples the remaining 39 cards with constraints consistent with the bidding. Sample size: 5000 deals.

On the 5000 deals it is then checked how often which cards as opening leads will defeat the contract double dummy or for matchpoints will generate the most tricks for the defense.

 

Rainer Herrmann

 

Thanks. That lends more credibility to it then.

[helene_t]

I am not saying that DD analysis is irelevant. Surely, absent other evidence, one should take the advice from the DD results when chosing opening lead strategies.

 

As for how strongly DD research should be weighted against possible contrary evidence, I don't really have a qualified opinion about it.

 

All I am saying: I simply don't see any relevance at all to the fact that average DD results are similar to average SD results for game-level contracts. Would it mean that, given that declarer has an advantage SD over DD in low-level contracts while the opposite is true for slams, the DD research would be less relevant for choosing opening leads against slams and partscores? I don't see why, as far as I am concerned the DD research, as far as opening leads is concerned, would be equally relevant regardless of how good DD research was at predicting other things.

 

If (I do say "if") it is so that passive leads work better DD than SD, I can see why that might be so: a passive lead can help the SD declarer locate a queen in partner's hand but it won't help the DD declarer. Compare that to a lead from KJxx. If it costs a trick SD it probably also costs a trick DD. Also, a passive lead works better when partner always can recognize it as such, and even find the right switch.

 

OTOH, that the lead of an unsupported ace works so well DD is intriguing. The argument that it works well because DD it is always followed by the right switch, doesn't sound credible to me. Often the right switch will be found SD as well. The strategy to lead an ace in order to get a look at dummy (and at partner's signal) is something that makes sense SD but not DD so if anything I would expect unsupported aces to work even better SD than DD.

 

I was just looking at a hand from this month's EBU magazine. You are in 3NT with AJ9 of hearts in dummy and 8 sec in your hand. You receive a small heart lead. You play opening leader for the 10 so you play the 9. If he made a standard lead from KQxx(x) you are down. DD you would have made it regardless of lead. And if he had made the (DD-research-favored) lead of the king you would have made it SD as well.

[mike777]

I am not saying that DD analysis is irelevant. Surely, absent other evidence, one should take the advice from the DD results when chosing opening lead strategies.

 

 

ok and?

 

ok I put you on the stop...you don't know....

 

perhaps I don't understand ...you answer is you don't know?

 

May I assume I never or almost never have said evidence?

 

In other words should I always take the advice of DD to win?

[helene_t]

In other words should I always take the advice of DD to win?

What about agreeing with p to play top-of-nothing against both suit and notrump so that p can recognise a passive lead? And K from suits headed by AK so that he can recognise an unsupported ace? And agree with p that you lead an honour from HHxx(x) so that he doesn't necessarily expect three honours? Give it a try and see if you like the results. And share your experience with us.

[dake50]

Bounce around as much as you like.

DD simulators SHOULD tabulate opening leads

-- agreeing Goren, Journalist, Rusinow, Combine, etc OR disagreeing each.

Then tabulate those scores.

Who has done that??

It's been computationally available for decades -- just not done.!

[PhilKing]

Bounce around as much as you like.

DD simulators SHOULD tabulate opening leads

-- agreeing Goren, Journalist, Rusinow, Combine, etc OR disagreeing each.

Then tabulate those scores.

Who has done that??

It's been computationally available for decades -- just not done.!

 

I might be being a bit thick, but in a DD simulation I think the result would be an exact tie.

[awm]

Having now read these books, I think they are in fact very good.

 

The authors have several ways to deal with the objections to double dummy:

 

1. They run sims to determine the frequency of the common "double dummy" positions people complain about where the lead solves a guess for declarer. All indications are that these positions are pretty infrequent and do not greatly change the results.

 

2. They attempt to infer logical reasons for the leads that succeed. For example, they observe that if the auction goes 1NT-3NT and I have a five-card minor, partner is very likely to be extremely short in that minor. This justifies the poor showing of the "lead from length" in this situation (leading from two or three small in a major is often better).

 

3. They compute the chance of partner having specific cards, opposite my lead from a given hand and a given auction. When opponents have most of the strength and most of the outstanding cards in a particular suit, your chance of hitting partner with the "magic" holding is really quite poor.

 

In general I find the objections to double dummy simulation unconvincing. The sims have a lot of data on their side. The objections have only anecdotal evidence, with no serious attempts at producing data.

[whereagles]

Thing is, gathering data for real-life dummy play isn't as simple as turning the crank. It requires a lot of time and research to get examples from expert play. But yeah I agree that DD objectors need it to be taken seriously.

 

Discrediting science is routine in the first times but in the long run proving its simplifying assumptions are insufficient requires evidence. Blind faith also works, but you need a continuous supply of gurus to keep people "under control".

[sfi]

So my partner and I separately each read one of these books a while ago and the results, while anecdotal, are illuminating. All play was at national competitions.

 

I read the leading vs. suit contracts and it clearly improved my leads. There were several examples where I beat contracts I would have not otherwise done so, and only one instance I can remember where my previous choice would have worked out better. My partner didn't notice any change in leading style, so it did not affect his decision-making process.

 

He read the leading vs. NT contracts a few months earlier. The very next tournament I started noticing that my inferences from the opening lead were often not valid, which meant that my defence was frequently less than optimal. I don't know whether his lead choices were an overall net gain or loss, largely because I did not realise why they had changed until the middle of the second tournament.

 

I finally started reading the leading vs. NT contracts book before the last tournament and it all made much more sense. At last I could see why he was making the choices and that made the defence more comfortable. And I even paid attention when I picked up the following hand to lead against a 1NT - all pass auction:

 

A963

AQ87

954

Q5

 

The passive diamond lead hit partner's long suit and we beat the contract 3 tricks on a hand where our teammates made an overtrick in the same contract on a different lead (it doesn't really matter which one).

 

So, what conclusions have I drawn?

1. Defence against suits is much less about cashing length tricks, so it is much less important to hit the side's best suit. This means that the types of inferences drawn from the opening lead vary greatly between the two books, and it's easier to apply the leads vs. suits without involving partner.

2. There may be a double dummy bias in the analysis, but the practical advice has achieved positive outcomes in most cases.

3. Not letting partner know about your change in leading tendencies can throw the defence off. Talk to partner about the theory, particularly if you are going to stop leading 4th best from your long suits.

 

My partner thinks the NT book gives more valuable advice, while I think the suit book does. I wonder if this is because we each prefer the one we read first or whether there is a substantive difference between them.

[PrecisionL]

Yes, the NT book confirmed the style of opening leads my partnership has been using for 3 years!

[whereagles]

Excellent post there, sfi.

 

The books results clearly hint at a change in lead style and, consequently, at lead conventions.

 

At NT, the old "low from HHxx" needs to be changed to "top card from HHxx".

At suit contracts, since leading unsupported aces is important, you might want to try Rusinow leads.