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Tests for a double-dummy solver designing evaluation scheme?

#61 User is offline   tysen2k 

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Posted 2005-September-12, 11:47

Blofeld, on Sep 12 2005, 09:33 AM, said:

Can I just check: your guidelines for the suitability of preempting are based on the probability that our par score is a sacrifice?

If so, I imagine that 5440 hands rank highly because it's likely that there are big fits all over the place. But your preemptive methods need to be able to locate the right fit. Unless you're checking the probability that we have a sacrifice in our longest suit?

It's interesting data, but if you have enough time, I'd really like to know precisely what it represents.  :D

You are right that the data has no indication of how easy it is to find our best fit. This is just to give an indication of which hands are the kinds that are likely to produce sacrifices. But I don't think finding a sacrifice in our longest suit is really the right way to go. After all if you specify a preemptive opening that is specifically a 5440 hand, you are much more likely to find a fit very easily. So I guess it's data that suggests how you should design your preempt structure.
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#62 User is offline   Blofeld 

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  Posted 2005-September-12, 14:21

Yes, but it would be also be interesting to know the effect of having a side suit when making a standard pre-empt.

e.g. Opening 2 with 4s on the side. Assume that we're never to going to find the heart fit. How often will this cost? How often will it gain?

I suppose that ideally I'd like to see both sets of data. Figures for the ideal case, and figures that may tell us when it's relatively safe to distort.
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#63 User is offline   tysen2k 

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Posted 2005-September-12, 14:55

Blofeld, on Sep 12 2005, 12:21 PM, said:

e.g. Opening 2 with 4s on the side. Assume that we're never to going to find the heart fit. How often will this cost? How often will it gain?

I'm not going to re-run everything again, but I can give you this quick simulation:

If we have 6 spades and 4 hearts, our best sacrifice is:

spades 69%
hearts 25%
minor 6%

If we have 4 spades and 6 hearts, then our best is:

hearts 64%
spades 29%
minor 7%

Note that for this test, if we can take the same number of tricks in both majors sacrificing against a minor, then spades is said to be the best (about 7% of the cases).

Tysen
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#64 User is offline   tysen2k 

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Posted 2005-September-29, 17:01

Okay, this is an attempt to show you specifically how important the location of your shortness is when deciding to preempt. I have used my study that I did earlier on predicting the chance of a sacrifice bid and tried to map that to a sort of “preempt index.” On this index, a 2 represents what I would consider to be the bare minimum for a "normal" weak-2 bid. Similarly a 3 is the bare minimum for a 3-level preempt and a 4 is for a 4-level preempt. [Edited definition] Obviously some people may like weaker or stronger definitions for their preempts.

For this experiment, I looked at the 24 different suit permutations of the following hand:

KQJxxxx
xxx
xx
x

So the trick-taking ability of all 24 hands are the same, the only difference is which suits are long or short. So how much difference does it make?

Pattern   Preempt Index
2=1=7=3   3.82
1=2=7=3   3.81
3=1=7=2   3.80
1=3=7=2   3.76
3=2=7=1   3.74
2=1=3=7   3.73
2=3=7=1   3.72
1=2=3=7   3.72
3=1=2=7   3.67
7=1=3=2   3.64
1=3=2=7   3.63
7=1=2=3   3.63
1=7=3=2   3.52
1=7=2=3   3.52
7=2=3=1   3.50
7=2=1=3   3.48
3=2=1=7   3.48
2=7=3=1   3.48
2=7=1=3   3.47
2=3=1=7   3.46
3=7=2=1   3.44
3=7=1=2   3.44
7=3=2=1   3.36
7=3=1=2   3.36

[Edited values. Order is preserved, only absolute values have changed]

There is almost “half a preempt level” in difference between the top and bottom of the list. Notice that the diamond preempts dominate. Now look at the club preempts. They are pretty good except when they have diamond shortness which really drops their level. Spade preempts with heart shortness are good, but when they have 3 heart cards they fall to the bottom of the list. Heart preempts depend on their spade length, but to a lesser extent.

Naturally you could repeat this for other shapes like 7330, but I'm sure you'd find the same trends.

Tysen
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#65 User is offline   tysen2k 

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Posted 2005-September-30, 11:40

Okay, here's a little contest/game. What is the best preempt you can make that has 2173 shape? This hand:

xx
x
KQJxxxx
xxx

was given for illustration and has a PI of 3.82. But you can get to 4.01 with different honors. Who can guess it?
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#66 Guest_Jlall_*

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Posted 2005-September-30, 11:45

xx x QJT9xxx xxx
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#67 User is offline   tysen2k 

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Posted 2005-September-30, 13:20

Well, Justin, you won. Sort of. Okay, I messed up. I had a typo somewhere and with that error, yes indeed

xx x QJTxxxx xxx

was at the top of the list (there isn't enough data to judge the value of a 9). However, I found the typo and after fixing it, it turns out that

xx x KQJxxxx xxx

is on top. That's my original example, so it makes this contest quite lame. :rolleyes:

These are the values my formula produces (assuming all side suits are empty):

KQJxxxx	3.82
KQJTxxx	3.80
QJTxxxx	3.77
JTxxxxx	3.74
KJTxxxx	3.71
Jxxxxxx	3.69
QJxxxxx	3.69
QTxxxxx	3.66
KJxxxxx	3.66
KQxxxxx	3.65
KQTxxxx	3.65
Qxxxxxx	3.60
KTxxxxx	3.57
Kxxxxxx	3.55
Txxxxxx	3.46
xxxxxxx	3.42
AKQJxxx	3.22
AQJTxxx	3.21
AKQJTxx	3.21
AKJTxxx	3.21
AKQxxxx	3.19
AQJxxxx	3.18
AKQTxxx	3.18
AKJxxxx	3.16
AQTxxxx	3.16
AJTxxxx	3.14
AJxxxxx	3.13
AQxxxxx	3.13
AKTxxxx	3.12
AKxxxxx	3.09
ATxxxxx	3.08
Axxxxxx	3.07


QJTxxxx is still way up there. Notice that every single preempt with an Ace is at the bottom of the list. It's just to valuable on defense and makes a sacrifice less likely. And there's a big jump between the best hand with an Ace and the worst one without it. Naturally side Aces are even worse than trump Aces. Also note that if you usually count playing tricks to determine your preempts that you will count Axxxxxx and KQxxxxx the same. Some food for thought.
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#68 User is offline   MickyB 

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Posted 2005-September-30, 13:24

Wow, that aces thing is far more pronounced than I would have predicted. I've got my excuse ready for next time I preempt on xxxxx xxx xxx xx, "At least I didn't have an ace partner!"

Think KQJTxxx would come out ahead of KQJxxxx in a larger sample - not that I'm asking for one :rolleyes:

This post has been edited by MickyB: 2005-September-30, 13:25

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#69 User is offline   awm 

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Posted 2005-September-30, 13:45

Some questions about this:

(1) How is the "preempt level" determined?

(2) Why is "our best contract is a sacrifice?" a good measure? It seems perfectly fine to open 3 when we are making 4...

It seems to me that the bad times to preempt are:

(1) Times when the preempt is already past the par contract. For example, I open 3 vulnerable and opponents can double me for 800, and they don't have a slam. Obviously sometimes even these bids work out if the opponents judge wrong, but in principle my preempt gives them the chance to obtain a number they never could've gotten if I passed.

(2) Times when the par contract is us playing in a suit other than the suit or suits described by my preempt. For example, I open 3 and our only making game is 5. It will often be difficult to get there (especially if partner doesn't have magnificent clubs of his own and/or if 4 over 3 is some kind of artificial asking bid).

(3) If my preempts are defined in such a way that an extremely wide range of shapes and/or strengths is possible, it may be hard for partner to put us at the proper level. However, this isn't an argument that "we shouldn't preempt on certain hands" so much as that we have to pick and choose which hands our system will permit preempts.

I think I'd mostly look for cases (1) and (2) to try to decide which hands not to preempt. With pronounced single-suited hands it's probably good enough to measure the par contract. With two-suited hands when only single-suited preempts are available (for example, I hold 6-1-1-5 with no two-suited weak bid available, how many spades should I open?) the second constraint becomes more critical.
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#70 User is offline   Blofeld 

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  Posted 2005-September-30, 13:59

Nice data!

Am interested:

Quote

Naturally side Aces are even worse than trump Aces.

How much worse? In particular, I can see trump aces being bad when they add to your defence by being able to take them and then give partner a ruff.
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#71 User is offline   tysen2k 

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Posted 2005-September-30, 15:07

awm, on Sep 30 2005, 11:45 AM, said:

(2) Why is "our best contract is a sacrifice?" a good measure? It seems perfectly fine to open 3 when we are making 4...

This is one of the things we are debating here. Is this really the right thing to measure? If not, what would be better?

You bring up a lot of other valid points, but I'm not sure that all of them answer the question "when is the best time to preempt?" If you open 3 and can make 4 and (I'm assuming) the opps can't make anything higher, was that really the best time to preempt? Yes we made it to the right spot but if the opps don't have anything higher that we can't bid over did we really need to jump? Every time 4 makes doesn't mean we always get there. Partner may not guess right to raise it up. We might reach 4 more often if we start with 1 than with 3.
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#72 User is offline   tysen2k 

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Posted 2005-September-30, 15:15

Blofeld, on Sep 30 2005, 11:59 AM, said:

Quote

Naturally side Aces are even worse than trump Aces.

How much worse? In particular, I can see trump aces being bad when they add to your defence by being able to take them and then give partner a ruff.

It looks like changing a club spot card to an ace lowers the rating by about 25% more than changing a diamond spot to an ace.
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#73 User is offline   MickyB 

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Posted 2005-September-30, 15:36

I reckon the best measure of a preempt is what level we can bid to without going beyond par.
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#74 User is offline   tysen2k 

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Posted 2005-September-30, 16:01

MickyB, on Sep 30 2005, 01:36 PM, said:

I reckon the best measure of a preempt is what level we can bid to without going beyond par.

That won't work because

AKxx
AKx
AKx
AKx

Is a horrible preempt but has a very high expected par level.
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#75 User is offline   MickyB 

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Posted 2005-September-30, 17:18

It is a horrible preempt because you need the room for your own investigation, which isn't really part of the scope of this thread so far, and would be very difficult to incorporate. I think putting a limit on the maximum strength of the preempting hand would make the 'par level method' work.
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#76 User is offline   awm 

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Posted 2005-September-30, 17:30

Ok, here's a fairly concrete question.

Suppose that I am going to open a hand with a spade preempt at some level. We can say this is an okay opening if the following constraints hold:

(1) The level of spades that I bid is not beyond the par spot.
(2) The par contract involves our side playing in spades.

Hands like AKxx AKx AKx AKx are bad preempts because it's not particularly likely that spades is our best strain.

Note that the above constraints indicate that any hand that's "okay" to open 4 is also "okay" to open 2. This is pretty obvious in terms of safety level, but our goal in general is to preempt to the highest "reasonably safe" level. We'll also need to determine what our preempts should look like; for example if we choose to preempt 2 with xxxxx xxx xxx xx, we probably shouldn't also open 2 with AKxxxx x Kxx x, even if both are "reasonably safe" 2 openings. However, this is perhaps a separate issue.

So the question here is, how likely are we to be "okay" if we open various hands with 2, 3, 4 and so forth?
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#77 User is offline   MickyB 

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Posted 2005-September-30, 17:40

Yes I like that. Constraint 2 probably needs rephrasing - I think your intention was, at level vul, for 4S making 8 tricks to be ok if they can make 5C? So "We can make at least as many tricks in spades as in any other strain" sounds better. Might be useful if our overbidding/reaching the wrong strain could be measured in IMPs rather than just success or lack of?
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#78 User is offline   Blofeld 

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Posted 2005-September-30, 18:05

Adam's suggestion still runs slightly afoul of Tysen's objection, I think:

AKQJxxx
AK
AK
x

Is a fairly poor preempt, even if though we can open it at the 6-level without going past par, and we're likely to want to play in spades. But possibly combining it with Mike's second constraint could work.

---

My idea (not really sure about this, but thought it worth throwing into the mêlée) is that preempts will tend to be better on hands where you expect the par contract for NS and the par contract for EW to be relatively close.
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#79 User is offline   awm 

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Posted 2005-September-30, 20:38

I don't see a particular problem with opening 6 on:

AKQJxxxx
AK
AK
x

Provided that your agreement is that a 6 opening shows 12 top tricks. This will prevent the opponents from finding a good sacrifice.

There are a lot of questions about agreements here. For example, a 1 preempt on:

AKxx
xx
xxxx
xxx

might be right for various reasons. But most of us don't have a 1 preempt available. The goal here is to figure out which preempts are "too reckless" to be reasonable, not to determine what your agreements should be. I think it's reasonable to discount partner's potential evaluation problems here; it seems clear we need some sort of agreement about what sorts of hands open 2 for example. Likely the goal is to devise this agreement such that we include as many as possible of the "reasonable" preempts without giving partner a problem he won't solve.
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#80 User is offline   Blofeld 

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Posted 2005-October-01, 06:10

I suppose that the problem is the (all too high) chance of missing a grand slam. Can partner raise with any ace?

What about:
AKQJxxxxx
AKQ
-
x
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