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5 card spades and 5m332 invitational responder Advantage (or not) of opening 1NT with a 5-card major

#1 User is online   pescetom 

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Posted 2020-November-06, 08:06

I cleaned up the script some more and added the capability for 1NT opener to accept/refuse an invite in either spades or NT.
So now I can see whether invite/accept thresholds are in the ballpark and whether it is vantageous in terms of score for responder with an invitational strength 5m332 to go through some kind of Stayman (capable of locating a 3-5 major fit) or just bid in NT (using a Range Ask).
The script assumes that opener is vulnerable, that we can find the 3-5 major fit if we wish and that the opponents keep quiet.

First I did a sanity check on invite/accept thresholds, by setting the invite range 8-9 then varying ntmin from 15-17 and looking at the effect on frequency of tricks in NT and spades. At first sight it looks like accepting with any 16-17 is about right, just a little heavy for 3NT (making 45%) and light for 4S (making 64%).

Then I analysed the frequency of a better score in spades or NT by setting the invite range 8-9 and the opening range 15-17 and accepting with 16-17 (I gave this one a 400 hand run because 100 hand runs are not very consistent).
At first sight it looks like the spades score better than NT 60% of the time and worse only 26%, thus seeking a 3-5 fit is clearly advantageous.

#
# NT vs Spades comparison
#
ntmin= 15
ntmax= 17
op_ntrange= hcp(north)>=ntmin and hcp(north)<=ntmax
op_accept= hcp(north)>=16
rs_weak= hcp(south)>=4 and hcp(south)<=7
rs_invite= hcp(south)>=8 and hcp(south)<=9
rs_thingame= hcp(south)>=10 and hcp(south)<=10
rs_safegame= hcp(south)>=11 and hcp(south)<=12
rs_5m3S32= shape(south, any 5332) and hearts(south)<=3 and spades(south)==3
rs_xfer= spades(south)>=5 or hearts(south)>=5 or clubs(south)>=6 or diamonds(south)>=5
op_s5 = spades(north)==5 and shape(north, any 5332)
produce 100
##### unquote ONE condition below at a time
condition op_ntrange and op_s5 and rs_invite and rs_5m3S32
#condition op_ntrange and op_s5 and rs_safegame and rs_5m3S32
#condition op_ntrange and op_s5 and rs_safegame and rs_5m3S32
xN_tricks= tricks(north,notrumps)
xS_tricks= tricks(north,spades)
x2N_score= score(vul,x2N,xN_tricks)
x3S_score= score(vul,x3S,xS_tricks)
x3N_score= score(vul,x3N,xN_tricks)
x4S_score= score(vul,x4S,xS_tricks)
xN_score= op_accept ? x3N_score : x2N_score
xS_score= op_accept ? x4S_score : x3S_score
outcome= xN_score == xS_score ? 0 : (xN_score > xS_score ? 1 : -1)
##### unquote ONE action below at a time
#action frequency(xN_tricks,6,13)
#action frequency(xS_tricks,6,13)
#action frequency(outcome,-1,1)


TRICK FREQUENCY WHEN OPENER IS 15-17 =======================================================

Frequency of tricks in NT
Frequency :
Low	       2
    6	       5
    7	      17
    8	      30
    9	      28
   10	      12
   11	       5
   12	       1
   13	       0
Generated 2084813 hands
Produced 100 hands
Initial random seed 1604670051
Time needed   39.919 sec


Frequency of tricks in S
Frequency :
    6	       2
    7	       1
    8	      10
    9	      37
   10	      32
   11	      17
   12	       1
   13	       0
Generated 1903395 hands
Produced 100 hands
Initial random seed 1604670209
Time needed   34.395 sec


TRICK FREQUENCY WHEN OPENER IS 16-17 =======================================================

Frequency of tricks in NT
Frequency :
Low	       2
    6	       6
    7	      14
    8	      33
    9	      24
   10	      13
   11	       6
   12	       2
   13	       0
Generated 4551999 hands
Produced 100 hands
Initial random seed 1604670567
Time needed   58.682 sec


Frequency of tricks in S
Frequency :
    6	       0
    7	       0
    8	       8
    9	      28
   10	      41
   11	      17
   12	       6
   13	       0
Generated 3549704 hands
Produced 100 hands
Initial random seed 1604670293
Time needed   50.480 sec


TRICK FREQUENCY WHEN OPENER IS 17 ==========================================================

Frequency of tricks in NT
Frequency :
    6	       4
    7	      10
    8	      26
    9	      26
   10	      16
   11	      15
   12	       3
   13	       0
Generated 8974413 hands
Produced 100 hands
Initial random seed 1604670716
Time needed   89.142 sec


Frequency of tricks in S
Frequency :
    6	       0
    7	       1
    8	       2
    9	      26
   10	      47
   11	      21
   12	       3
   13	       0
Generated 8789330 hands
Produced 100 hands
Initial random seed 1604670866
Time needed   90.899 sec


BETTER SCORE FREQUENCY WHEN OPENER IS 15-17 =======================================================


Score is better in S / same in both / better in NT
Frequency :
   -1	     239
    0	      56
    1	     105
Generated 8427254 hands
Produced 400 hands
Initial random seed 1604671501
Time needed  230.419 sec

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#2 User is online   pescetom 

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Posted 2020-November-07, 10:10

I take it silence is assent :)

Yes it is not surprising that spades score better, although I did not expect it to be quite so clear.
It's a confirm that these hands have to look for a 3-5 fit, although that is a nuisance in our Stayman as they end up leaking gratuitous information about opener's hand (whether or not he has 4-card spades). But loading them into the 2 Range Ask instead does not look feasible.
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#3 User is offline   Zelandakh 

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Posted 2020-November-22, 19:51

View Postpescetom, on 2020-November-07, 10:10, said:

I take it silence is assent :)

Yes it is not surprising that spades score better, although I did not expect it to be quite so clear.
It's a confirm that these hands have to look for a 3-5 fit, although that is a nuisance in our Stayman as they end up leaking gratuitous information about opener's hand (whether or not he has 4-card spades). But loading them into the 2 Range Ask instead does not look feasible.

You could of course use 2 as Puppet Stayman, meaning that if you only care about a 5 card major, the possession (or otherwise) of a 4 card major suit is not disclosed.
(-: Zel :-)
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