[Knurdler]

I found the following summary:
http://web2.acbl.org...opiropidepo.pdf

They point out that if the interference suit is higher than our trump suit, DIPO has a problem showing 2 keycards. So they recommend DEPO (X = 0 or 2, P = 1 or 3).

They recommend DIPO if the interference suit is lower than our trump suit (X = 1, P = 0, next up = 2 without queen of trump).
Questions: have I got their intention right? How do we show 3 keycards? How do we show 2 with the queen of trump? Why not keep it simple and always use DEPO?

[smerriman]

The normal responses (assuming 1430) to 4NT are:

cheapest bid: 1/4
second cheapest bid: 0/3
third cheapest bid: 2 without queen
fourth cheapest bid: 2 with queen

DOPI/DIPO doesn't change this at all. You still get exactly the same information; they simply consider double and pass to be the two cheapest bids; the next bid is 2 without queen, and the bid after that is 2 with the queen.

DEPO is used when you don't have enough room to make these responses without being too high. You don't get anywhere near the same amount of information - e.g. you can't distinguish between 0, 2, or 4 keycards, or find out about the trump queen - the opponents have forced you to make a guess, and you're trying to make use of what space you have as much as possible.

[mycroft]

D0P1 - and if you read it that way, rather than with the letters, it makes more sense - works well with "low level" interference. If you're confused, and play Keycard, you can write it as DFS/RFS/PSS which, as well as having an enjoyably puerile reading of the acronym, makes it even clearer ((Re)Double is the First Step, Pass is the Second Step). (I would check the article again. If they're recommending D1P0, that's just as playable, but "nobody" does it. So I bet they're recommending D0P1/DEPO. Go ahead with your partnership, but expect to be surprised playing with anyone else!)

The thing about "above 5 of the trump suit" isn't that you have "not enough space", it's that you can't afford with *any* response, especially playing keycard where "responses" show 2 keycards, to bid, because it forces slam(*). There *always* has to be the opportunity for partner to say "Our best result now is defending", whether it's the common "we're off two KCs, we can't make slam, take the points" or "oh they made a mistake, let's try for 1100".

Therefore, with interference past 5 of your trump suit, You Can't Bid. You only have two safe calls; pass and double. Therefore, DEPO (Double Even, Pass Odd).

Yes, there's an issue where they bid 5 of the suit below your trump suit, and you're too high with "2-and-the-queen". But that's so rare that using "5 trump" as the boundary line is just easier to remember, the one time a year it comes up.

(*) This is the "problem" your article points out about showing 2, with or without the queen. Not that "there isn't enough space to explore" the best slam; if two isn't enough, you're now going down in slam when you could have defended for a plus.

[pescetom]

Knurdler, on 2024-January-16, 14:08, said:

They recommend DIPO if the interference suit is lower than our trump suit (X = 1, P = 0, next up = 2 without queen of trump).

As smerriman said, essentially people play that X is the first reply, P is the second and so on.
The confusion with DOPI and DIPO is not so much because of using letters to replace numbers but because:
a) most people number things starting from 1, but C programmers and whoever invented these acronyms start from 0
b) some people play 0314 where the first reply shows 0 keycard, others play 1403 where the first reply shows 1 keycard
c) some people want to "hard wire" the number of the reply to the number of keycards that it shows (hence DIPO, I imagine).

Thinking about it, D1P2 might be the best acronym.
In any case, Double is the first reply (so playing RKCB 1403 it shows 1 or 4 keycards).

Knurdler, on 2024-January-16, 14:08, said:

Why not keep it simple and always use DEPO?

You can do that if you like, so long as your partner is on the same page.
You lose a bit of definition when they interfere low, but it's probably a wise decision at Novice/Beginner level.

[DavidKok]

I've always played DOPI as "Double shows the reply showing 0 (or 3), Pass shows the reply showing 1 (or 4)". Hence the acronym. The whole 'steps' interpretation doesn't come into it. DEPO (Double = Even, Pass = Odd), DIPO (Double = 1/4, Pass = 0/3) and other forms are similar.
At any rate all that matters is that you play double and pass on these rare sequences the same way as partner.

[smerriman]

pescetom, on 2024-January-19, 12:23, said:

a) most people number things starting from 1, but C programmers and whoever invented these acronyms start from 0

The acronym DOPI came from the fact that Double shows 0 aces, Pass shows 1 ace, not from 0-indexing. It was just kept when RKCB took over.

DavidKok, on 2024-January-19, 12:28, said:

The whole 'steps' interpretation doesn't come into it.

It comes into it when you have 2 keycards, which was the bit the OP was confused by. But doesn't come into the acronym, agreed.

[pescetom]

smerriman, on 2024-January-19, 12:29, said:

The acronym DOPI came from the fact that Double shows 0 aces, Pass shows 1 ace, not from 0-indexing. It was just kept when RKCB took over.

Agreed, but it is also useful when handling interference in other relays, not just Blackwood/RKCB.
With the additional complication that there might be a reason (valid or not) to play Pass rather than X as the first reply.
My choice is to KISS and always play X as the first reply (I also always play 1403, but I consider that an independent choice).

[Knurdler]

Love this forum. No one at my club wants to discuss minutia. It was only after I studied replies to my question, that I realised how little I know.

So far, we never had anyone interfere with our slam bidding. Maybe as lowly club players, we should forget the whole schemozzle and play D = penalty, P = weak, 5/6/7 of our suit = natural.

I present my revised interpretations and questions arising.

Interference suit ranks below ours
The most popular scheme is D0P1: X = 0 or 3, P = 1 or 4. In other words X replaces 5♦ and P replaces 5♣.
If their bid is 5♦, then we retain the original meanings of 5♥ = 2 without queen of trump and 5♠ = 2 with the queen of trump.
If their bid is 5♣ and ours suit is ♠ and we have 2 keycards: is our next step ♦ or ♥?
If their bid is 5♥ and ours suit is ♠ and we have 2 keycards: is 5♠ = 2 without queen of trump and we just have to do without a bid for 2 with the queen of trump?

Interference suit ranks above ours
If we want to reply below 6 level, we have to use DEPO.
X = 0, 2 or 4, P = 1 or 3.
We just have to do without any more detail.

[pescetom]

Knurdler, on 2024-January-20, 01:57, said:

The most popular scheme is D0P1: X = 0 or 3, P = 1 or 4. In other words X replaces 5♦ and P replaces 5♣.

As previously said, I suggest you play X as cheaper than P, so X replaces 5♣ and P replaces 5♦.
Call it whatever you want

Knurdler, on 2024-January-20, 01:57, said:

If their bid is 5♣ and ours suit is ♠ and we have 2 keycards: is our next step ♦ or ♥?

I think it is better to always use the cheapest bid available as the third step and so on: so here ♦ = 2, ♥ = 2+Q.

Knurdler, on 2024-January-20, 01:57, said:

If their bid is 5♥ and ours suit is ♠ and we have 2 keycards: is 5♠ = 2 without queen of trump and we just have to do without a bid for 2 with the queen of trump?

I suggest 5♠ = 2 with no indication of Q.

You also have to decide what you do over an X of 4NT (the simplest choice is to ignore).


But I was serious when I said it was perfectly ok for Beginners and Intermediates to ignore all this and just use DEPO/REPO over any interference.
Interference happens maybe once a year.