[akwoo]

jillybean, on 2026-May-22, 06:07, said:

Thanks, this is the general approach, some are interested in more detail
What are your rules for #2
#3 hopefully partner did make some other bid as we are playing a f1nt

Rules for #2:

3N and 4M are to play, both based on length rather than strength.

2N and 3M are strongly invitational; 3M with a 6 card suit and 2N without.

3lower is game forcing (as is 1H-1N-2S), supposedly a real suit. You may have to lie about 'real suit' if you want to game force on strength but don't have a second suit. (I prefer to put all my lying in 3C, but that requires further artificial sequences.)

2M promises 6. 2lower supposedly promises 4. If you have 6-4 or better, rebid 2M with an absolute minimum and 2lower with a little more.

This leaves all the not-highly-invitational hands that have 5 in the major and no lower 4 card suit. You should lie at the 2 level in your longest minor, clubs if equal. (It's possible to put all the lying into 2C, but that requires further artificial sequences.)

[jillybean]

pescetom, on 2026-May-22, 15:44, said:

You can also be playing 2/1 game forcing but 1NT semi-forcing, like most of Europe and a good number of top level pairs.
In which case 1NT will rarely or never have 3=card support.
There are also other ways of revealing a weak 3=card support, such as going through 1M-2♦ in a 2/1 context.

So 2♦ is not GF?

[thepossum]

Apologies. I am sure nobody is interested inthe following numbers but I do not have the enerrgy to summarise

I was using Beling's bdeal with 10,000 hands and tried to cover South opening 1M in 1st or 2nd seat and West not overcalling, prepempting or doubling and North having a "forcing" 1NT hand

Spoiler

c= clubs, d = diamonds, h= hearts
and all the shape counts are most of the most likely shapes
shape7plusis anything wiht 7 or more in either minor
there is around 1 percent left over - mostly involving voids I guess
the reason for heart counts are first that I needed to find a bug but it is an interesting aspect of the 1NT bid
.. and I am playing SJS

c0: 35 / 10000 = 0.0035 Ań 0.00115764 (95% conf.) min: 0 max: 1 sdev: 0.0590572
c1: 283 / 10000 = 0.0283 Ań 0.00325057 (95% conf.) min: 0 max: 1 sdev: 0.165829
c2: 1157 / 10000 = 0.1157 Ań 0.00626999 (95% conf.) min: 0 max: 1 sdev: 0.319865
c3: 2371 / 10000 = 0.2371 Ań 0.00833682 (95% conf.) min: 0 max: 1 sdev: 0.425304
c4: 2824 / 10000 = 0.2824 Ań 0.00882418 (95% conf.) min: 0 max: 1 sdev: 0.450167
c5: 2024 / 10000 = 0.2024 Ań 0.00787587 (95% conf.) min: 0 max: 1 sdev: 0.401789
c6: 985 / 10000 = 0.0985 Ań 0.00584119 (95% conf.) min: 0 max: 1 sdev: 0.29799
c7+: 321 / 10000 = 0.0321 Ań 0.00345516 (95% conf.) min: 0 max: 1 sdev: 0.176266
d0: 39 / 10000 = 0.0039 Ań 0.00122176 (95% conf.) min: 0 max: 1 sdev: 0.0623281
d1: 321 / 10000 = 0.0321 Ań 0.00345516 (95% conf.) min: 0 max: 1 sdev: 0.176266
d2: 1133 / 10000 = 0.1133 Ań 0.00621304 (95% conf.) min: 0 max: 1 sdev: 0.316959
d3: 2278 / 10000 = 0.2278 Ań 0.00822134 (95% conf.) min: 0 max: 1 sdev: 0.419413
d4: 2813 / 10000 = 0.2813 Ań 0.00881372 (95% conf.) min: 0 max: 1 sdev: 0.449634
d5: 2123 / 10000 = 0.2123 Ań 0.00801597 (95% conf.) min: 0 max: 1 sdev: 0.408936
d6: 971 / 10000 = 0.0971 Ań 0.00580404 (95% conf.) min: 0 max: 1 sdev: 0.296094
d7+: 322 / 10000 = 0.0322 Ań 0.00346036 (95% conf.) min: 0 max: 1 sdev: 0.176531
h0: 116 / 10000 = 0.0116 Ań 0.00209892 (95% conf.) min: 0 max: 1 sdev: 0.107077
h1: 855 / 10000 = 0.0855 Ań 0.0054812 (95% conf.) min: 0 max: 1 sdev: 0.279624
h2: 2352 / 10000 = 0.2352 Ań 0.00831368 (95% conf.) min: 0 max: 1 sdev: 0.424124
h3: 1995 / 10000 = 0.1995 Ań 0.00783344 (95% conf.) min: 0 max: 1 sdev: 0.399625
h4: 2287 / 10000 = 0.2287 Ań 0.00823276 (95% conf.) min: 0 max: 1 sdev: 0.419996
h5+: 2395 / 10000 = 0.2395 Ań 0.00836571 (95% conf.) min: 0 max: 1 sdev: 0.426778
shape7plus=: 643 / 10000 = 0.0643 Ań 0.00480811 (95% conf.) min: 0 max: 1 sdev: 0.245287
shapem15=: 163 / 10000 = 0.0163 Ań 0.00248214 (95% conf.) min: 0 max: 1 sdev: 0.126627
shapem16=: 128 / 10000 = 0.0128 Ań 0.00220348 (95% conf.) min: 0 max: 1 sdev: 0.112411
shapem24=: 550 / 10000 = 0.055 Ań 0.00446887 (95% conf.) min: 0 max: 1 sdev: 0.22798
shapem25=: 616 / 10000 = 0.0616 Ań 0.00471287 (95% conf.) min: 0 max: 1 sdev: 0.240428
shapem26=: 548 / 10000 = 0.0548 Ań 0.00446121 (95% conf.) min: 0 max: 1 sdev: 0.227589
shapem32=: 260 / 10000 = 0.026 Ań 0.00311937 (95% conf.) min: 0 max: 1 sdev: 0.159135
shapem33=: 384 / 10000 = 0.0384 Ań 0.00376672 (95% conf.) min: 0 max: 1 sdev: 0.19216
shapem34=: 1228 / 10000 = 0.1228 Ań 0.00643353 (95% conf.) min: 0 max: 1 sdev: 0.328207
shapem35=: 1417 / 10000 = 0.1417 Ań 0.00683605 (95% conf.) min: 0 max: 1 sdev: 0.348742
shapem36=: 726 / 10000 = 0.0726 Ań 0.00508631 (95% conf.) min: 0 max: 1 sdev: 0.259479
shapem44=: 974 / 10000 = 0.0974 Ań 0.00581203 (95% conf.) min: 0 max: 1 sdev: 0.296502
shapem45=: 1290 / 10000 = 0.129 Ań 0.00657059 (95% conf.) min: 0 max: 1 sdev: 0.3352
shapem46=: 413 / 10000 = 0.0413 Ań 0.00390047 (95% conf.) min: 0 max: 1 sdev: 0.198983
shapem55=: 265 / 10000 = 0.0265 Ań 0.00314841 (95% conf.) min: 0 max: 1 sdev: 0.160617
shapem56=: 102 / 10000 = 0.0102 Ań 0.00196958 (95% conf.) min: 0 max: 1 sdev: 0.100479
shapem66=: 8 / 10000 = 0.0008 Ań 0.000554207 (95% conf.) min: 0 max: 1 sdev: 0.028273
Number of hands dealt: 360163. CPU time usage [sec]: 0.31 (x8 threads).

If anyone wonders what "Ań" means apart from a character set problem I think they aere standard errors or 1.96 of them. Not sure

EDIT small addendum. Apparently it makes 1NT 68 percent of the time plus or minus small error. No idea how bad the times it does not make are
If you have a werid 1NT hand do you risk passing and missing slam

Is David Kok on holidays

[pescetom]

 jillybean, on 2026-May-22, 17:27, said:

So 2♦ is not GF?

It is when it is not weak

It asks Opener to rebid the major, which Responder will pass if weak.

[jillybean]

pescetom, on 2026-May-23, 01:29, said:

It is when it is not weak

It asks Opener to rebid the major, which Responder will pass if weak.

Ok, so you are not agreeing a diamond fit until the 4 level to allow for the semi forcing 1nt.
I haven’t played sf, and don’t understand the benefits.

[DavidKok]

It depends on your assumptions and system. I've taken the liberty of using my own system, in which a 1NT response is semiforcing and denies a spade fit. Conditioning on a 1♠ opening by partner, a pass by RHO (so no double or overcall) and no game force, no fit and no intermediate jump shift by responder I get the following distribution of club length, simulating 100,000 occurences of this auction:

Spoiler

• 0: 0.2%
  
• 1: 2.6%
  
• 2: 11.4%
  
• 3: 25.8%
  
• 4: 31.5%
  
• 5: 22.4%
  
• 6: 4.6%
  
• 7: 1.2%
  
• 8+: 0.2%

The distribution of diamonds is identical (except for variance due to the Monte Carlo nature of the simulation). The number of hearts is slightly higher, because I overcall 2♥ more easily than 2m over a 1♠ opening so the negative inference of the pass places more hearts with responder on average.

mikeh, on 2026-May-21, 09:36, said:

The most likely, by far, is 3 clubs. Second probably 4 clubs, third 2 and fourth 5.

In particular, while this is close it is not quite in agreement with my simulations.

If I include weak spade raises, say in the 5-8 hcp range, the frequencies shift. Here's the clubs distribution again with that assumption:

Spoiler

• 0: 0.6%
  
• 1: 4.5%
  
• 2: 15.3%
  
• 3: 27.2%
  
• 4: 29.0%
  
• 5: 18.4%
  
• 6: 4.0%
  
• 7: 1.0%
  
• 8+: 0.1%

Including the invitational range instead (so that the direct raise is 6-9, and 10-11 goes through 1NT) shifts it less from my baseline, for the people not playing Maas:

Spoiler

• 0: 0.4%
  
• 1: 3.5%
  
• 2: 14.0%
  
• 3: 27.3%
  
• 4: 30.0%
  
• 5: 20.1%
  
• 6: 3.6%
  
• 7: 0.9%
  
• 8+: 0.1%

thepossum, on 2026-May-21, 20:45, said:

We are talking a serious sim here. I am sure there must be one somewhere

The above simulations take between 5.7 seconds (fastest run) and 8.6 seconds (slowest run) each.

pescetom, on 2026-May-22, 15:44, said:

You can also be playing 2/1 game forcing but 1NT semi-forcing, like most of Europe and a good number of top level pairs.
In which case 1NT will rarely or never have 3=card support.

I have seen people define 'semiforcing' in multiple different ways, and some people tie it to the presence of 3-card raises in the 1NT (and prefer to call it 'not forcing', regardless of range, if the response systemically denies 3-card support). Personally I was taught that we need to refer to a not forcing 1NT response in 2/1 as 'semiforcing' regardless of the potential presence of raises, to inform the opponents of the approximate 6-11 hcp range rather than the 'standard' 6-9 range.

jillybean, on 2026-May-23, 06:19, said:

I haven’t played sf, and don’t understand the benefits.

I do not play a two-way 2♦ gadget. Still I prefer the semiforcing 1NT. A major benefit is that opener's 2m rebids promise four cards in the suit, enabling better hand evaluation by responder their second round and improving the ability to find the right contract at the 2- or 3-level. Additionally, when opener passes 1NT with 12-14 (in my case 12-13) balanced, 1NT is often a good contract. However, sometimes it is not, and the main criticism of the semiforcing 1NT is that it harms the ability of responder to bid 1NT on a very wide range of shapely hands, assured of a rebid (which they would get in a F1NT style).

[mikeh]

I think David and I were answering different questions. I may have misunderstood but I thought that jb wanted to know the likelihood of various club lengths in auctions that began 1S 1N 2C or 1H 1N 2C, when 1N was forcng.

Thus any calculation that caters to 0-1 club is irrelevant….opener won’t rebid 2C.

Moreover, it’s not as simple as calculating the relative frequencies of 2-6 clubs, since the 2C bid also denies various other holdings.

1S 1N 2C denies 6+ spades (technically not quite but very close), 4+ hearts and 4+ diamonds. Many hands with only 7 black cards will hold a 4+ red suit so we need to elmnate those…the only time 2C shows 2 is when opener is precisely 5=3=4=2.

And it’s a small point but David’s calculations slightly overstate the odds of having 4 clubs, since on a small number of hands opener will be 5404 or 5044, and will show the red suit.

Things are slightly trickier for 1H 1N since opener will rebid 2C with most 4=5=2=2 hands.

[DavidKok]

The question at the start of the thread asked for the number of clubs held by responder, not opener.
I do not play most of opener's rebids the way you do, e.g. 1♠-1NT; 2♣ denying six spades.

[mikeh]

DavidKok, on 2026-May-24, 10:19, said:

The question at the start of the thread asked for the number of clubs held by responder, not opener.
I do not play most of opener's rebids the way you do, e.g. 1♠-1NT; 2♣ denying six spades.

I assumed JB was asking in the context of ‘standard’ 2/1, forcing 1N, in her area, which is (I think) western Canada at the moment. I have played that 2C doesn’t deny 6S, but that is very far from standard around these parts.

[thepossum]

DavidKok, on 2026-May-24, 10:19, said:

Said a lot, after I gave him the respect of mentioning him earlier
But sadly insulted me about my knowledge of sims and processing time

And his numbers are almost identical to mine - yet nobody had the decency to acknowledge them and the work and considerations I put into mine
I could post my basic script which took much longer than 8 seconds to think about and write and test - mine is just basic
When I say serious sim it would take a very long time to write all the bidding and systemic considerations

Please all of you move on from insults and disrespect - may acknowledge the effort of responding to the OP's question in detail too

My basic code is in the spoiler below to save space - some credit goes to chat GPT lol but mostly me
When I said a serious sim I was trying to be respectful to advanced players and professional sim writers
And there could easily be a logic error in seat configurations but I do not care - not sure there would be much difference in the stats - I did just run two separate runs to fix any alleged logic problem and the numbers are essentially identical in seat 1 or 2 My runs took 45 seconds - probably could be optimised
I am slightly embarassed at a logic error and biased stats but not really. And logic in two major hands and reverse considerations etc etc But I am sure the stats would not vary much. At least that was not a bias. It was opening one or the other
I imagine there is not much need for complex filters and sims to get a half decent estimate anyway but we need to please all the experts
Maybe people do not understand the anxiety associated with posting a sim on a forum like this

Spoiler

conf = {
num=10000 -- finish after accepting 1000 deals
}



-- accept only the deals in which :
function filter()

local Wovercaalls1H = (((W:hcp() >= 8 and W:spades() >= 5)

-- 1NT overcall
or (W:hcp() >= 15)

-- natural 2-level overcalls
or (W:hcp() >= 10 and W:clubs() >= 5)
or (W:hcp() >= 10 and W:diamonds() >= 5)
or (W:hcp() >= 10 and W:hearts() >= 5)

-- weak/preemptive action
or (W:hcp() <= 9 and W:clubs() >= 6)
or (W:hcp() <= 9 and W:diamonds() >= 6)
or (W:hcp() <= 9 and W:hearts() >= 6)
or (W:hcp() <= 9 and W:spades() >= 6)))


local Wovercalls1S = (((W:hcp() >= 15)

-- natural 2-level overcalls
or (W:hcp() >= 10 and W:clubs() >= 5)
or (W:hcp() >= 10 and W:diamonds() >= 5)
or (W:hcp() >= 10 and W:hearts() >= 5)
or (W:hcp() >= 10 and W:spades() >= 5)

-- weak/preemptive action
or (W:hcp() <= 9 and W:clubs() >= 6)
or (W:hcp() <= 9 and W:diamonds() >= 6)
or (W:hcp() <= 9 and W:hearts() >= 6)
or (W:hcp() <= 9 and W:spades() >= 6)))

local Wdoubles1S = ((W:hcp() >= 12
and W:spades() <= 2
and (
W:hearts() >= 3
or W:clubs() >= 3
or W:diamonds() >= 3
)))

local Wdoubles1H = ((W:hcp() >= 12
and W:hearts() <= 2
and (
W:spades() >= 3
or W:clubs() >= 3
or W:diamonds() >= 3
)))



local Sopens1H = (S:hearts() >= 5 and S:hcp() >= 11 and S:hcp() <= 21)
local Sopens1S = (S:spades() >= 5 and S:hcp() >= 11 and S:hcp() <= 21)

local NforcingNTover1H = (N:hcp() >= 6 and N:hcp() <= 12 and N:hearts() <= 2 and N:spades() <= 3)
local NForcingNTover1S = (N:hcp() >= 6 and N:hcp() <= 12 and N:spades() <= 2 )

local Eopens = E:hcp() >= 12

local Epreempts = ((E:hcp() <= 10 and E:clubs() >= 6)
or (E:hcp() <= 10 and E:diamonds() >= 6)
or (E:hcp() <= 10 and E:hearts() >= 6)
or (E:hcp() <= 10 and E:spades() >= 6))

local Epasses = (not Eopens) and (not Epreempts)

local seat1 = ((N:spades() + E:hearts() + S:diamonds() + W:clubs()) % 2 == 0)


if seat 1 then
return
(
(
Sopens1H and (not Wovercaalls1H) and (not Wdoubles1H) and NforcingNTover1H
)
or
(
Sopens1S and (not Wovercaalls1S) and (not Wdoubles1S) and NForcingNTover1S
)
)
end


--or

if not seat1 then

(Epasses and
((
Sopens1H and not Wovercaalls1H and not Wdoubles1H and NforcingNTover1H
)
or
(
Sopens1S and not Wovercaalls1S and not Wdoubles1S and NForcingNTover1S
)))
end


end

-- for each accepted deal, calculate number of tricks in NT by S:
function stats()

--local shapeN5332 = N:pattern(function(a, b, c, d) return a == 5 and b == 3 and c==3; end)
--local shapeN4432 = N:pattern(function(a, b, c, d) return a == 4 and b == 4 and c==3; end)
--local shapeN4333 = N:pattern(function(a, b, c, d) return a == 4 and b == 3 and c==3; end)

local shapem32 = N:shape(function(s, h, d, c) return d == 3 and c==2; end)
local shapem23 = N:shape(function(s, h, d, c) return d == 2 and c==3; end)
local shapem34 = N:shape(function(s, h, d, c) return d == 3 and c==4; end)
local shapem43 = N:shape(function(s, h, d, c) return d == 4 and c==3; end)
local shapem24 = N:shape(function(s, h, d, c) return d == 2 and c==4; end)
local shapem42 = N:shape(function(s, h, d, c) return d == 4 and c==2; end)
local shapem53 = N:shape(function(s, h, d, c) return d == 5 and c==3; end)
local shapem35 = N:shape(function(s, h, d, c) return d == 3 and c==5; end)
local shapem52 = N:shape(function(s, h, d, c) return d == 5 and c==2; end)
local shapem25 = N:shape(function(s, h, d, c) return d == 2 and c==5; end)
local shapem54 = N:shape(function(s, h, d, c) return d == 5 and c==4; end)
local shapem45 = N:shape(function(s, h, d, c) return d == 4 and c==5; end)
local shapem51 = N:shape(function(s, h, d, c) return d == 5 and c==1; end)
local shapem15 = N:shape(function(s, h, d, c) return d == 1 and c==5; end)


local shapem33 = N:shape(function(s, h, d, c) return d == 3 and c==3; end)
local shapem44 = N:shape(function(s, h, d, c) return d == 4 and c==4; end)
local shapem55 = N:shape(function(s, h, d, c) return d == 5 and c==5; end)
local shapem66 = N:shape(function(s, h, d, c) return d == 6 and c==6; end)

local shapem56 = N:shape(function(s, h, d, c) return d == 5 and c==6; end)
local shapem65 = N:shape(function(s, h, d, c) return d == 6 and c==5; end)

local shapem46 = N:shape(function(s, h, d, c) return d == 4 and c==6; end)
local shapem64 = N:shape(function(s, h, d, c) return d == 6 and c==4; end)

local shapem36 = N:shape(function(s, h, d, c) return d == 3 and c==6; end)
local shapem63 = N:shape(function(s, h, d, c) return d == 6 and c==3; end)

local shapem26 = N:shape(function(s, h, d, c) return d == 2 and c==6; end)
local shapem62 = N:shape(function(s, h, d, c) return d == 6 and c==2; end)

local shapem16 = N:shape(function(s, h, d, c) return d == 1 and c==6; end)
local shapem61 = N:shape(function(s, h, d, c) return d == 6 and c==1; end)

local shapem46 = N:shape(function(s, h, d, c) return d == 4 and c==6; end)
local shapem64 = N:shape(function(s, h, d, c) return d == 6 and c==4; end)




local shape7plus = N:shape(function(s, h, d, c) return d > 6 or c > 6; end)






local c = N:clubs()
local d = N:diamonds()
local h = N:hearts()

count( "c0", c==0)
count ("c1", c==1)
count ("c2", c==2)
count ("c3", c==3)
count ("c4", c==4)
count ("c5", c==5)
count ("c6", c==6)
count ("c7+", c>6)

count( "d0", d==0)
count ("d1", d==1)
count ("d2", d==2)
count ("d3", d==3)
count ("d4", d==4)
count ("d5", d==5)
count ("d6", d==6)
count ("d7+", d>6)



count( "h0", h==0)
count ("h1", h==1)
count ("h2", h==2)
count ("h3", h==3)
count ("h4", h==4)
count("h5+", h>4)


count("shapem32=",shapem32 or shapem23)
--count("shapem23=",shapem23)
count("shapem34=",shapem34 or shapem43)
--count("shapem43=",shapem43)
count("shapem24=",shapem24 or shapem42)
--count("shapem42=",shapem42)
count("shapem35=",shapem35 or shapem53)
--count("shapem53=",shapem53)
count("shapem45=",shapem45 or shapem54)
--count("shapem54=",shapem54)
count("shapem15=",shapem15 or shapem51)
--count("shapem51=",shapem51)
count("shapem25=",shapem25 or shapem52)
--count("shapem52=",shapem52)

count("shapem33=",shapem33)
count("shapem44=",shapem44)
count("shapem55=",shapem55)
count("shapem66=",shapem66)

count("shapem56=",shapem56 or shapem65)
--count("shapem65=",shapem65)

count("shapem36=",shapem36 or shapem63)
--count("shapem63=",shapem63)

count("shapem26=",shapem26 or shapem62)
--count("shapem62=",shapem62)

count("shapem16=",shapem16 or shapem61)
--count("shapem61=",shapem61)

count("shapem46=",shapem46 or shapem64)
--count("shapem64=",shapem64)

count("shape7plus=", shape7plus)

local nt = tricks(N, "NT")
count("nt =7", nt>6)

end

[jillybean]

Thanks all, apologies for the poorly written OP, ensuing confusion and heated discussions.
I now have my answer and another rabbit hole to explore. My regular partner does play semi forcing nt in other partnerships, showing the 12-13 balanced

[pescetom]

jillybean, on 2026-May-23, 06:19, said:

Ok, so you are not agreeing a diamond fit until the 4 level to allow for the semi forcing 1nt.
I haven’t played sf, and don’t understand the benefits.

Belated reply

Like Davidkok, I do not play the 2♦ gadget and do not link it specifically to semiforcing.
But FWIW I don't see it creating problems when Opener has a diamonds fit: Responder could rebid below 3♦ showing 5 diamonds, in any case 4♦ by Opener is clear.
I would be more concerned about losing inferences from Opener's 2M rebid, such as 6 cards or a 14 HCP limit.