ye olde 3NT lead problem

[rhm]

I think difference is small enough to consider that a coincidence.

 

I am however, astonished by the difference in total tricks between a spade and a diamond.

Just to clarify:

The numbers are not total tricks, but how often out of 1000 deals this lead will give the defense the maximum number of tricks on a double dummy basis.

For example the ♠8 will allow the defense double dummy the maximum number of defensive tricks in 669 deals of 1000, or roughly in two thirds of the deals, while the ♦4 or 3 will give you the maximum number of defensive tricks only on 498 deals of 1000 or roughly on one half of all the deals.

 

Rainer Herrmann

[beatrix45]

The fourth best ♦ is going to be led at the other table(s) most likely. You beat 3NT off the top if partner has the ♦ ace and RHO has Qxx. The other leads are not terrible, but unless you are up against better players and really need a board, they are considerably inferior, imo.

 

Simulations are very difficult and extremely labour intensive to do correctly. I am utterly unconvinced by anecdotal so-called 'evidence' from such 'research'.

[BillPatch]

. . . .

At IMPs it is close.

While a low diamond lead beats the contract more often than any other lead, the difference compared to a major suit lead is not earth shattering, 12.4% versus 14.8%, a 2.4% difference.

However, you often will lose a trick when a diamond will not beat the contract.

The 2.4% of times you beat the contract more often, and win 11 IMPs has to be balanced against the 16.5% of times where you will lose one or more IMPs in tricks.

While I agree that the finish between low spade and low heart is inconclusive, it is customary to compare the diamond lead to the better major suit. It is debatable whether to lead second best from T8x or low(Bird/Anthias recommend low from this combination because they believe that following the conventional lead may aid partner more than the statistical gain from starting unblocking on the first round with the lead of the 8. The low spade beats contract 12.5% and produces the optimal defensive trick count 66.9%. Plugging the low spade numbers into the last sentence by Rainer: "The 2.3% you beat the contract more often has to be balanced against the 19.4% you . . . lose one or more IMPs in overtricks." 17.1 low spade better in tricks -(-2.3) low diamond better at set = 19.4% extra overtricks allowed by diamond lead.

[BillPatch]

The fourth best ♦ is going to be led at the other table(s) most likely. You beat 3NT off the top if partner has the ♦ ace and RHO has Qxx. The other leads are not terrible, but unless you are up against better players and really need a board, they are considerably inferior, imo.

 

Simulations are very difficult and extremely labour intensive to do correctly. I am utterly unconvinced by anecdotal so-called 'evidence' from such 'research'.

According to Richard Pavlicek's[spelling corrected]website, the expected value from playing tens of thousands of bridge hands at three notrump by experts on vue graph championships after the opening lead is equal to the double dummy analysis value. Bird/Anthias further tens of thousands of hands from club play and several thousand hands simulated single dummy on WBridge5 with similar results.

 

Therefore we may conclude that given adequate statistical power from our sample we may draw the inference that the expected percentage that a low spade will outscore a low diamond is 17.1%. The extra overtricks saved outweigh the reduced rate of setting the contract by eight to one. Since the preponderance of the evidence indicates that equal strength contestants will win .171 board on average by leading over a field lead of the low diamond. The diamond lead is a pure bridge error.

[beatrix45]

According to Richard Pavlichek's website, the expected value from playing tens of thousands of bridge hands at three notrump by experts on vue graph championships after the opening lead is equal to the double dummy analysis value. Bird/Anthias further tens of thousands of hands from club play and several thousand hands simulated single dummy on WBridge5 with similar results.

 

Therefore we may conclude that given adequate statistical power from our sample we may draw the inference that the expected percentage that a low spade will outscore a low diamond is 17.1%. The extra overtricks saved outweigh the reduced rate of setting the contract by eight to one. Since the preponderance of the evidence indicates that equal strength contestants will win .171 board on average by leading over a field lead of the low diamond. The diamond lead is a pure bridge error.

 

Your post might be more convincing if you were able to spell Richard Pavlicek's name correctly. Have you ever actually used his hand generator? To do so correctly you have to cast a wide net that includes all possible hands consistent with the bidding. Then you get to winnow out by hand those that are not, in fact, consistent. In this case with this auction it is very labour intensive. For example, responder with 4-3-3-3 shape, decent spots, and looking at a combined 28-31 HCP won't Stayman. That done, then you have to analyze the remaining hands to see what might happen. Sometimes, declarer will have a choice of lines of play. I can see that you love your computer. Now, you need to learn some statistics and the game of Bridge.

[whereagles]

Pavlicek's hand generator had some statistical bias problems. Better check if the issue has been solved before using it.

[Mbodell]

According to Richard Pavlichek's website, the expected value from playing tens of thousands of bridge hands at three notrump by experts on vue graph championships after the opening lead is equal to the double dummy analysis value. Bird/Anthias further tens of thousands of hands from club play and several thousand hands simulated single dummy on WBridge5 with similar results.

 

Therefore we may conclude that given adequate statistical power from our sample we may draw the inference that the expected percentage that a low spade will outscore a low diamond is 17.1%. The extra overtricks saved outweigh the reduced rate of setting the contract by eight to one. Since the preponderance of the evidence indicates that equal strength contestants will win .171 board on average by leading over a field lead of the low diamond. The diamond lead is a pure bridge error.

 

Even if over the full population double dummy on average matches single dummy post opening lead, that doesn't mean it will work for any particular hand. It could be there are offsetting biases and that it does poorly with long suits headed by-KJ underestimating the cost of leading from them, but has some other thing that counteracts that over the whole population of hands.

[Mbodell]

While I agree that the finish between low spade and low heart is inconclusive, it is customary to compare the diamond lead to the better major suit. It is debatable whether to lead second best from T8x or low(Bird/Anthias recommend low from this combination because they believe that following the conventional lead may aid partner more than the statistical gain from starting unblocking on the first round with the lead of the 8. The low spade beats contract 12.5% and produces the optimal defensive trick count 66.9%. Plugging the low spade numbers into the last sentence by Rainer: "The 2.3% you beat the contract more often has to be balanced against the 19.4% you . . . lose one or more IMPs in overtricks." 17.1 low spade better in tricks -(-2.3) low diamond better at set = 19.4% extra overtricks allowed by diamond lead.

 

You have to be a little careful with the IMPs cost of an overtrick or undertrick. It is tempting to just compare to other people in the same contract who make one of the two choices (diamond lead against 3nt or spade lead against 3nt), but it could be the overtricks and undertricks are worth nothing if the other table is in slam down or in a partscore. Just one reason why playing to make/set is important.

[rhm]

The fourth best ♦ is going to be led at the other table(s) most likely. You beat 3NT off the top if partner has the ♦ ace and RHO has Qxx. The other leads are not terrible, but unless you are up against better players and really need a board, they are considerably inferior, imo.

 

Simulations are very difficult and extremely labour intensive to do correctly. I am utterly unconvinced by anecdotal so-called 'evidence' from such 'research'.

I have done lots of simulations and I beg to differ.

When I publish my simulation results I always specify my specifications, but I also know from experience there will always be some, who will critique my specifications or double dummy simulation results on general principles.

As a rule I keep my specifications simple and do not worry about the odd hand.

What I have learned from experience and experimentation is that worrying about rare exceptions are not worth it, because the final result is not affected in a significant way.

As a rule dealing out more hands does more to the precision of the result.

When you do lots of simulations you get a feeling what might affect and and what will not affect the outcome.

Once you have this experience you can do simulations properly without them being labour intensive. Good Bridge judgement, a basic understanding about statistics and logic suffice.

Of course there are bidding scenarios, which can not be simulated easily, usually because people differ too much about the requirements for a bid.

The above is not one of them.

 

I am also pretty sure that advances in bidding at the top level in the last years is in no small part due to research done based on double dummy simulations.

Those, who are over critical to simulations only handicap themself.

 

Rainer Herrmann

[whereagles]

Well, I regularly simulate stuff when I design my bidding systems.

 

So far so good w.r.t. results :)

[PhantomSac]

I choose a ♠ at IMPs and a ♥ at MP in a good field, ♦ at MP in a poor field.

 

At IMPs I'm trying to beat the contract and am assuming they barely have game values so partner has more of our values. I also assume that we are likely to be longer in the majors thanks to the auction (not a guarentee, but more likely than not, especially if they are around 25 or 26 hcp as opposed to 28 or 29 that would be even more likely to suppress the 4M in 4333). So therefore I lead the ♠.

 

In a weak field at MP I don't want to lose the board on the opening lead and "everyone" will be leading 4th best diamond.

 

In a strong field I'm not in love with leading from KJxxx in a minor, so I have to choose between the heart and the spade. It is no longer the case that I'm playing just to set. Holding them to 9 when many make 10 or 10 when many make 11 might be good enough. The risk in leading the heart is less than the diamond IMO. Maybe I should lead the spade too as there is risk from leading the heart, but we may need the tempo to get a heart trick before they run clubs and top spades, so I'll try that. Of the three situations this is the one I'm least confident is right.

 

A spade at imps? Do you guys actually lead like this? What kind of convoluted thinking makes you believe that a SPADE is the most likely lead to set 3NT? It's just absolutely absurd I'm sorry.

[PhantomSac]

As usual with these double dummy simulations, do any of you discount the hands that partner will double 3N with? Definitely some of the hands that a spade binks partner will X 3N or possibly have doubled 3N. Likewise, Rainer has the 3N bidder as "not necessarily balanced." That's great but I do not remember the last time a good player bid 1N 3N with a small singleton in a major, let alone with a void. Maybe in the old days, but nowadays most people play something at least like transferring to a minor and bidding 3M as short, or 1N 3M short, etc. Those hands should be excluded. Finally, in the real world partner will often fail to find a killing diamond shift if he gets in. I realize double dummy analysis cannot do anything about this but there is something to be said for leading your good 5 card suit making the defense easier.

 

But really not excluding partner having a double of 3N, and not excluding 1N 3N bids that have a stiff major are pretty inexcusable when doing analysis like this, and even failing to do that shows that the diamond lead will more likely beat it.

 

Forget about real world considerations like sometimes accidents happen if you lead the spade 8 and can run diamonds later (eg partner having A A in the pointed, not likely but just to illustrate, good luck getting the D shift 100 % of the time on your spade lead), or sometimes you will set up diamonds and they will need to guess the hearts which they always will double dummy, or they will need to pick up your partners club holding with a deep finesse, etc (hint: setting up a long suit is a big threat that is less big in double dummy analysis), or the fact that a spade lead will sometimes blow the suit in real life but seems passive to a double dummy analysis, a diamond is STILL more likely to beat it according to this analysis!

[PhantomSac]

 

 

At IMPs it is close.

While a low diamond lead beats the contract more often than any other lead, the difference compared to a major suit lead is not earth shattering, 12.4% versus 14.8%, a 2.4% difference.

However, you often will lose a trick when a diamond will not beat the contract.

The 2.4% of times you beat the contract more often, and win 11 IMPs has to be balanced against the 16.5% of times where you will lose one or more IMPs in tricks.

 

Rainer Herrmann

 

If your lead blows a trick 16.5% of the time double dummy that does not mean you lose an overtrick imp 16.5 % of the time. A funny thing happens at imps when you lead your long/good suit, once it is set up people often start cashing out. This is one flaw in double dummy analysis. But even with your very flawed simulation that is completely biased towards the passive lead (much like Bird), gaining 11 imps 2.4 % of the time is worth .264 imps, compared to gaining 1 imp 16.5 % of the time which is worth .165 imps, so you gain .1 imps a board by leading a diamond vs a spade. This is completely convincing to me that a diamond is much better given your simulation parameters.

[beatrix45]

I have given some thought as to how long a proper analysis of this problem might take assuming I were already set up to do this particular problem. It looks like 8-10 hours minimum, if I were very lucky.

 

1. (1hr) Generating 200-500 hands using the Pavlicek generator. Example: RHO has 15-17 HCP, no singleton and no 6+ card major suit. LHO has 10-15 HCP, no 5 card major and no singleton or void. Partner gets what is left.

 

2. (2hr) Remove any hands not fitting the actual bidding. A few of these will be removed because RHO would not have opened 1NT, but most will be hands where LHO might have used Stayman or at least not have passed. In a few cases partner might have a double. This should only take a few seconds per hand in most cases, but we have a lot of hands to examine.

 

3. (4hr) Analyze the remaining hands for their play. I would expect to have 50 to 100 hands left to analyze. Most will take only a minute or so, but a few will be difficult. This is particularly true when declarer or partner or your hand has a choice to make in the play. You cannot assume double dummy play. In the end, for a few hands you may decide to assign probabilities to the various possible outcomes. You probably should go back and use a computer playing program to vet your results.

 

4. (2hr) Translate your results into IMP or MP scores and summarize.

 

Simulations can be a wonderful tool, but if you don't do them correctly, they are worse than useless. IF YOU INTRODUCE SAMPLE BIAS OR FAIL TO ANALYZE CORRECTLY, YOU GET THE WRONG ANSWER, FOOL.

[StevenG]

4. (2hr) Translate your results into IMP or MP scores and summarize.

How do you translate your result into an MP score? Isn't your score almost entirely dependent on what happens at other tables?

[rhm]

As a rule I keep my specifications simple and do not worry about the odd hand.

What I have learned from experience and experimentation is that worrying about rare exceptions are not worth it, because the final result is not affected in a significant way.

As a rule dealing out more hands does more to the precision of the result.

As usual with these double dummy simulations, do any of you discount the hands that partner will double 3N with? Definitely some of the hands that a spade binks partner will X 3N or possibly have doubled 3N. Likewise, Rainer has the 3N bidder as "not necessarily balanced." That's great but I do not remember the last time a good player bid 1N 3N with a small singleton in a major, let alone with a void. Maybe in the old days, but nowadays most people play something at least like transferring to a minor and bidding 3M as short, or 1N 3M short, etc. Those hands should be excluded. Finally, in the real world partner will often fail to find a killing diamond shift if he gets in. I realize double dummy analysis cannot do anything about this but there is something to be said for leading your good 5 card suit making the defense easier.

 

But really not excluding partner having a double of 3N, and not excluding 1N 3N bids that have a stiff major are pretty inexcusable when doing analysis like this, and even failing to do that shows that the diamond lead will more likely beat it.

May I ask:

 

How often do you hear the bidding go

 

1NT Pass 3NT AP

 

When did you last hear the bidding go

 

1NT Pass 3NT DBL

 

The first sequence I usually hear several times per session

I can not remember when I last had the second sequence. Definitely not in the last ten tournaments I played in. I am not claiming that it does never occur though.

I also can not remember when I last transferred into a minor and then showed a singleton in a major over 1NT, even though I play that way over 1NT.

You are severely overestimating the statistical impact those hands will have on the overall result whether you exclude them or not.

 

Rainer Herrmann

[whereagles]

I haven't seen

 

1NT pass 3NT dbl

 

in like 20 years (no kidding). I have however doubled 3NT for the lead frequently in occasions like this:

 

1x pass 1NT pass

2y pass 3NT pass

pass dbl

[PhantomSac]

May I ask:

 

How often do you hear the bidding go

 

1NT Pass 3NT AP

 

When did you last hear the bidding go

 

1NT Pass 3NT DBL

 

The first sequence I usually hear several times per session

I can not remember when I last had the second sequence. Definitely not in the last ten tournaments I played in. I am not claiming that it does never occur though.

You are severely overestimating the statistical impact those hands will have on the overall result whether you exclude them or not.

 

Rainer Herrmann

 

I was definitely wrong about this since we have the ten of spades, it makes it almost impossible partner will have a double, and also since we have 6 HCP. That said I have actually seen this auction twice in my last ten tournaments, once by my partner and once by my opp, both world class players. I will admit it has almost no relevance when we have this particular hand and I was wrong, sorry. That said, I think your analysis of "it rarely goes 1N p 3N X and it often goes 1N P 3N AP" is faulty, it is also rare we are beating them on a spade lead (or any lead) on 1N P 3N, we must consider the hands where a spade lead will beat it, and how many of those partner would have doubled. If partner is doubling .5 % of the time overall, but on all of those he wants a spade lead and a spade lead beats it, that would elminate 5 of the 125 hands where a spade lead is right according to your simulation which is something. That said given that we have the ST and 6 HCP it is unlikely that is the case so I withdraw that argument.

 

I also can not remember when I last transferred into a minor and then showed a singleton in a major over 1NT, even though I play that way over 1NT.

 

This however I am just going to say shows that you are consistently not bidding well, or at least bidding abnormally, assuming you are implying you don't use that bid rather than that it never comes up. I do not know the last time I saw a good player bid 1N 3N with a singleton in a major at imps. Why play methods where you can show every hand that has a singleton in a major if you are going to not show it? It strikes me as completely gambling for little gain to not show it, any hand with a stiff in a major could obviously belong in 5m or 4M and people who claim they don't want to "give away the lead" are just masterminding in my opinion, if the opponents have a long and strong major between them they are very likely to lead it on 1N 3N anyways, and if they don't have length/strength there you're going to get to 3N anyways since partner will bid it.

 

Even if you do not show your singletons ever I do not think that is a majority action and I think it is likely to be statistically relevant that you chose to include those hands. As far as I can tell you allowed 5-5 in the minors, 6/7 card minors and short majors, and (13)(54) hand types. Those hand types combined do come up every single tournament that I play, they are not some irrelevant thing. And of course including them will favor leading spades over diamonds.

[rhm]

You misunderstood.

If I have a game force over partner's 1NT holding consisting of a long minor and a singleton in a major and no 4 cards in the other majors, I will of course describe my hand if opponents let me do so and keep quiet.

Unfortunately I can not remember when I last could transfer into a minor and show a singleton in a major and this again was the point I was making.

Holding this hand-type is rare over 1NT, though useful when it comes up.

Whether you exclude this from your simulation will not materially affect the result.

 

Rainer Herrmann

[PhilKing]

How do you translate your result into an MP score? Isn't your score almost entirely dependent on what happens at other tables?

 

If I were using this method, I would get Jack to play the hands. This would be somewhat time consuming, but would produce decent non-DD comparisons.

[lesh]

When I started playing bridge I was taught always to lead your strongest and longest suit in such action. There are a few exceptions when I havent go an entry but as a principle I stick to it.

 

Based on that I am leading both ♦ in IMPS and MPs. :)

 

I know that's a very basic understanding but at least I am doing the same over and over again and dont have to waste time and energy pinpointing the right lead. :)

[PhantomSac]

When I started playing bridge I was taught always to lead your strongest and longest suit in such action. There are a few exceptions when I havent go an entry but as a principle I stick to it.

 

Based on that I am leading both ♦ in IMPS and MPs. :)

 

I know that's a very basic understanding but at least I am doing the same over and over again and dont have to waste time and energy pinpointing the right lead. :)

 

As strongly as I feel about a diamond being right at imps, I feel equally so about a diamond being wrong at MP. If you don't want to use your time and energy thinking about the right action then why play bridge? I admit I would lead a heart not a spade at MP and maybe that's wrong but a diamond clearly frequently blows a trick that you are not going to recover (as you have little hope for an entry). That's death at MP.

[whereagles]

Come on, it's not "death" :) It's an "all-or-nothing" type of lead.

[Finch]

I have given some thought as to how long a proper analysis of this problem might take assuming I were already set up to do this particular problem. It looks like 8-10 hours minimum, if I were very lucky.

 

1. (1hr) Generating 200-500 hands using the Pavlicek generator. Example: RHO has 15-17 HCP, no singleton and no 6+ card major suit. LHO has 10-15 HCP, no 5 card major and no singleton or void. Partner gets what is left.

 

2. (2hr) Remove any hands not fitting the actual bidding. A few of these will be removed because RHO would not have opened 1NT, but most will be hands where LHO might have used Stayman or at least not have passed. In a few cases partner might have a double. This should only take a few seconds per hand in most cases, but we have a lot of hands to examine.

 

3. (4hr) Analyze the remaining hands for their play. I would expect to have 50 to 100 hands left to analyze. Most will take only a minute or so, but a few will be difficult. This is particularly true when declarer or partner or your hand has a choice to make in the play. You cannot assume double dummy play. In the end, for a few hands you may decide to assign probabilities to the various possible outcomes. You probably should go back and use a computer playing program to vet your results.

 

4. (2hr) Translate your results into IMP or MP scores and summarize.

 

Simulations can be a wonderful tool, but if you don't do them correctly, they are worse than useless. IF YOU INTRODUCE SAMPLE BIAS OR FAIL TO ANALYZE CORRECTLY, YOU GET THE WRONG ANSWER, FOOL.

 

I agree completely with PhantomSac's comments about simulations.

However, your analysis of the analysis of the problem is way out.

 

1 hour to generate 200-500 hands? Really? Your example constraints are obviously wrong (e.g. they include all 2227s which would not be considered mainstream, most people raise to game with any decent 9-count at imps, they exclude LHO having, say, a 4234 which would stayman) but assuming you write some vaguely sensible constraints it takes about 15 minutes, at most, to set this up generate the hands using any sensible program. Or I guess you are including this process in step 2.

 

I do this type of analysis fairly frequently - I don't like large DD sims but I do like to look at 50-100 possible hands and see what would happen. It takes me about an hour to generate and assess 100 hands. You don't have to come up with a result that says 'this lead is 0.1 imp better than that lead', you just have to say 'a major is better / a diamond is better / it's impossible to tell'. There's no shame in having many hands which are impossible to tell. The last simulation I did (on a choice in the bidding) came to conclusion that 'you can't tell what is right'.

[Winstonm]

I don't view this question as one of diamonds/hearts but one of passive/aggressive. At imps, the object is to defeat the contract if possible, and the best chance is to find the diamonds situated in our interest.

 

The question at mps gets much more complicated, as other defenders' leads and other contracts at other tables all factor in. However, at mps I think the best stance to take is that one is defending the standard contract unless it is obvious one is not doing so. With that as the default position, it then becomes a question of passive versus aggressive leading. In a strong auction, it seems less right to give up a soft trick (diamond lead) than to go really passive (spade lead) in hopes of not blowing any tricks. If declarer has to find his 9, 10, or 11 tricks by himself, it is fairly well assured that one will score no worse than average (provided the contract is normal) and will likely score above average when declarer plays less than double-dummy.

 

When it seems likely that the opponents are in a power auction that leads to what rates to be a decent and normal contract, the best defenders can do most of the time is not help declarer, meaning a passive lead. The times an attacking lead are called for are usually spelled out clearly, more likely to occur in suit contracts than against NT contracts.