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Jack leadback
#1
I'm not sure whether this comes under "Offense", "Defense" or "Pinochle Discussion". I just wanted to announce that I've added a strategy page on the Jack lead back at World of Card Games. I also created a little video tutorial that I posted to youtube.

I made the page because I couldn't find a really clear description of how this leadback works. It may seem obvious if you've been playing pinochle forever, but as a relative neophyte, I thought it was confusing. I was trying to use the strategy myself, and also program it into the bots, and it wasn't as straightforward as I thought it would be at first.

If anyone reads the above page or watches the video and has commentary, feel free to politely or not-so politely criticize it, either here or in the comments section on the page/video. I'm trying to improve the bots, and my own skills, and I hope I've done it correctly.
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#2
It looks fundamentally correct.  What I would suggest is an example or two of why the jack signal matters.  For the sake of argument, for all these examples, South is declarer after 50-pass-pass-pass, and spades are trumps.

1.  South cashes 2 club aces.  North's club suit:   AC AC KC KC JC .  North should play  KC then  JC if he chooses to signal.  If he plays an ace on South's second ace, he likely costs his side a trick.

2.  South cashes a club ace, among others.  West wins South's exit.  His ace-cashing includes 2 club aces.  East started with  AC TC TC KC JC JC .  On West's second ace, East can't afford to play his ace...same thing.  It may cost a trick.  So East's jack is the signal.

3.  You can generally use ace on ace, when it's not going to cost a trick.  South cashes 2 club aces;  North started with  AC AC TC KC QC JC .  North played  KC on the first, and can choose  AC or  JC for the second.  He'll have  TC for the 4th round of the suit, after cashing elsewhere, if he chooses the  AC .  So what's the difference?   JC would be setting up to run clubs later.   AC would be asking to get in *ASAP* ... like, North has aces he needs to get cashed before the defense gets in.  For the sake of definiteness, say South cashes 2 club aces, and 1 diamond ace.  As North, I'd play ace on ace with any of these:

TS XS XS XS XS XS AH XH XH XH XH XH AC AC TC KC QC JC UD UD

North wants to get in, to exit with the *diamond*.  To set up ruffs when South started with, say, 5 diamonds.  North's heart ace is a side bonus, but the compelling reason to make the strong signal is the diamond suit.

XS XS XS XS XH XH XH AC AC TC KC QC JC AD AD XD XD XD XD XD 

The 4th diamond will often get ruffed, so North signals to get in and cash his before the defense can take theirs.

XS XS XS XS AH XH XH AC AC TC KC QC JC AD XD XD XD XD XD XD

Both red aces are at risk.
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#3
Thanks very much! I will take a stab at adding at least one of your examples to the page, and also link back here.
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#4
I just watched the video.

One wrinkle: if both opponents have cashed, signaling often goes away. Why? Because information and strategies change completely. North declares and cashes; South gets in first and cashes. Well, East-West can expect that they have all the missing side aces. So...why signal? Smile The strategies also shift for each side.

And if each defender is in, before dummy, there's a fairly strong presumption that they *have* cashed their non-trump aces. Dummy wants to tell declarer whether to:

a) run trump out, because he has a side suit to run, or
b) attack the aces dummy thinks the defense has
c) play for an extended cross ruff...dummy forces declarer to ruff because he has long trumps as well.

Another aspect, tho: once one side has cashed all its aces, presumably, the other side should not, by and large, be touching *their* aces. Thus, the basic situation for a jack signal, should not arise very often.
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#5
(08-06-2017, 01:57 PM)ToreadorElder Wrote:  Another aspect, tho:  once one side has cashed all its aces, presumably, the other side should not, by and large, be touching *their* aces.  Thus, the basic situation for a jack signal, should not arise very often.

Thank you for this excellent comment, ToreadorElder! I've added a comment to my video which links back to this thread.

I want to make sure I understand your comment above: "once one side has cashed all its aces, presumably, the other side should not, by and large, be touching *their* aces". Is this because it is assumed that any aces played at this late stage will get trumped? The idea is to hold onto aces in the hopes of picking up any remaining tricks that do not get trumped?

If you are not playing your aces, then what should you be playing instead?
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#6
Say declarer and dummy have both cashed.  Then, why should the defense play aces?  What is to be gained?  ALWAYS be asking, why should I do this?  How does making this play advance my overall goals?  (Of course, that presumes you have overall goals.)  

Plus, consider this suit:

South  ATTxxx
West   AAKxx
North  ATxx
East    TTxxx

This is a side suit, and South is declarer.  South and North have cashed.  If West cashes, what happens?  SOUTH now has 2 tricks established once he gets trumps pulled.  East might be able to save a 10, if he's got a king as well, but he'll have to get in, at the right time...after North's trumps are gone.  And still, South will get one more trick.

It also simplifies declarer's job, to win the last trick. 

The defense generally wants declarer to be forced to ruff, so he'll lose control of the trump suit.  Alternately, the defense may just lead trump themselves.  They may need to probe...did declarer sandbag a suit?  Or, does dummy have an established suit?  If so, attack THAT...so declarer can't use it as a secondary trump suit.  

Cashing aces can be fine...but go back to the point of, what are you trying to accomplish?  And what is *declarer* trying to accomplish...and what can you do about it?  It's hard to formalize anything general because it's a matter of interpreting, not just what you have, but what's happened to this point.
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#7
Oh...just thought of another refinement.

Don't give a jack signal when you have no reason to signal.  Simplest case:  you have no side aces outside the suit you would be signaling in.  Say, with spades trumps, and declarer cashes 2 diamond aces.  Dummy has

AS XS XS XS XS AD AD XD XD XD XD XC XC XC XC XC XC XH XH XH XH

Dummy doesn't care what declarer does;  it will make no difference to him.  

It would be reasonable to not signal with

AS XS XS XS XS AD AD XD XD XD XD XC XC XC XC XC XC AH XH XH XH

Yes, you've got 1 side ace, so it's OK to signal.  

What's the issue?  When you signal, declarer is likely to switch from a plan that's sensible looking at his hand, to reach you...because you may well *need* to get in.  With either hand, you really don't.  Even with the 2nd holding, there's no strong rush to cash the heart ace.  Give declarer:

a)   AS AS TS TS KS QS JS JS AD AD XD XD XD XD XC XC XH XH XH XH
b)   AS AS TS TS KS QS JS JS AD AD XD XC XC XC XC XC XH XH XH XH

A diamond exit isn't a good idea with either.  If he has 

c)   AS AS TS TS KS QS JS AD AD XD XD XC XC XC XC XC XC XH XH XH

it's probably better in the long run for him to exit with a club, not a heart.  LOTS of clubs to be lost, no matter what, and your heart ace will still be a trick much of the time.
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