30 November 2009

Fun at the Tollemache Qualifier 2009

The Tollemache Qualifier is an intense, gruelling event for players and TDs. I had three appeals, relating to Law 46 B (different intention is incontrovertible), Law 21 B (misinformation / "fielded misexplanation") and Law 40 B (illegal agreement).

One hand was free from ruling but was a curious lead problem; in particular the defence have to finesse the ten in dummy's A10xxx to defeat 6NT. (As I discovered on the train home, trying to make sense of the double dummy analysis on the hand records.)

Board 22K 8 7 5 3
(Rotated)8 7
4
A 10 5 4 2
J 3Q 6 2
Q 6 5 3 210 9 4
7 3 210 6 5
K 8 7Q J 9 3
A 10 9
A K J
A K Q J 9 8
6

Some played in 6D or 6S and some tried a grand slam. You always lead a trump against grand slams? A trump is the only lead to defeat 7D but a trump is the only lead to let through 7S.

According to the double dummy analysis, South can't make 6NT but North can. The defence must lead clubs otherwise declarer can duck a spade to establish his twelth trick. North ducks the club and the defence must continue clubs, otherwise declarer can reach this position.

K 8 7
-
-
A 10
J 3Q 6 2
Q-
--
K 8J 9
A 10 9
J
8
-

The D8 executes a double guard squeeze, North discarding another spade.

If East leads a club it must be an honour and whether he leads the other honour or a small club at trick two, the club guard is isolated; whichever of East or West retains a club honour is caught in a simple squeeze. South throws HJ on a small club return and throws a spade on a second club honour from East.

But if South is declarer, West must lead a small club, finessing C10. East takes the finesse and can lead CQ at trick two: both defenders are able to retain a high club. This destroys the timing for the double sequeeze, as South is prematurely sequeezed out of one of his major menaces.

Easy game!

21 November 2009

Application of Law 12

There is still some strange wording in Law 12 covering what was previously described as the distinction between "consequent" and "subsequent" damage; "subsequent" damage could have been due to wild or gambling action by the non-offending side, by their serious error, or just "failure to play bridge". However, I think the effects are clear: for the offending side (OS) we adust if they obtain a table result better than they would have without the infraction; but the non-offending side (NOS) do not get an adjustment for damage which is self-inflicted, defined as due to a serious error or wild or gambling action (WoGA).

In practice there are four cases: all damage is self-inflicted, some is self-inflicted, no self-inflicted damage, or no damage at all. There are scores we have to consider

  1. the score for the Actual table result (including any serious error or WoGA)
  2. the score for the result Before infraction (assigned by Law 12C1c or Law 12C1e)
  3. (≥ A) the score for the result that Could have been scored, with the infraction but without serious error (could be weighted?)

The overall damage can be divided as

  • Real damage: DR = B − C
  • Self-inflicted damage: DS = C − A

Starting from C ≥ A there are four cases

  • C ≥ A > B: no advantage, no damage, no adjustment;
  • C ≥ B ≥ A: all damage self-inflicted, no real damage DR ≤ 0 (virtual damage), NOS get A, OS get B;
  • B > C = A: no self-inflicted damage, DS = 0, NOS get B, OS get B;
  • B > C > A: real damage and some self-inflicted.

In the final case, the OS get B and the NOS get A + B − C. The adjustment for the non-offending side can be seen as either

  • actual score + real damage: A + DR = A + (B − C); or
  • adjusted score − self-inflicted damage: B − DS = B − (C − A) = A + B − C.

Examples

NS bid to 4H and EW "use UI" to compete to 4S, which is doubled. In defending 4SX, NS might revoke (a serious error) and lose a trick they would otherwise score. The result in the other room is 4H=, NS +420. This is the normal result in 4H, so B (the result before the infraction) is 0 IMP. The type of adjustment depends on the table result.

4SX-1 NS +100. Revoke

A = IMP(100-420) = −8 IMP. Without the revoke: 4SX-2 NS +300. C = IMP(300-420) = −3 IMP.

Real damage DR = 3 IMP, self-inflicted damage DS = 5 IMP.

Offending side (team of EW) get 0 IMP, non-offending side (team of NS) get 0 + (−8) − (−3) = −5 IMP.

4SX-2 NS +300. Revoke

A = −3 IMP. Without the revoke: 4SX-3 NS +500. C = IMP(500-420) = +2 IMP. No real damage (DR < 0).

Offending side get 0 IMP, non-offending side get −3 IMP (table result).

4SX-2 NS +300. No revoke

A = C = −3 IMP. No self-inflicted damage (DS = 0). Both sides get 0 IMP.

4SX-3 NS +500.

A = +2 IMP. No damage. Table result for both sides.