reversible play - loss and gain

    Keywords: EndGame

Discussion moved here from last section of One-Two-Three.

Black hasn't gained  

Charles In this example the point is that Black has gained nothing yet, if we're just talking endgame. Simply playing B1 and W2 isn't typically kikashi - effective forcing play - because White a is now better than it was before B1 was played.

In fact that claim is in a state of tension with the sente gains nothing idea (which could be called a OneTwo concept).

Bill: Which claim? B1 - W2 not only gains nothing for Black, it loses something.

Charles Then next we may have Black a - White b, a sente exchange. Out of the three statements

  1. the B1/W2 exchange loses Black something
  2. the Black a- White b exchange gains nothing
  3. the B1 to White b exchange of four plays gains nothing

at least one must be untrue, no? In the diagram it could be that this is a double sente (for all we know), but assuming it is really Black's (one-sided) sente to play here (we can add context to make that apparent) I'd say, of these statements, 1 and 3 are true, and 2 is false (that is not a sente-gains-nothing case). Bill, please give us your interpretation.

Bill: Black a is not sente. A gote played with sente does gain something. And for free! The proverb does not apply to that situation. :-)

So 2) and 3) are false. Black a - White b gains more than B1 - W2 loses.

As for a case where Black a is sente, B1 - W2 may not be sente.

Here is a case that is plainly Black's sente.

1-2 principle  

B3, W6 tenuki. B7 at 1.

We make the usual assumptions that the corner is Black territory and to the right is White territory.

The sequence, B1 - W2, B4 - W8 is the normal 3-point sente for Black. And after B1 - W2, the local count remains the same.

Is the position worse for Black than the original? Yes, it is, but it is not a loss in terms of the saying, Sente gains nothing, which refers to the local count. It is worse for Black because White's reverse sente is larger than before.

Before, if W4, then B5 - W1, to gain 3 points. Now, after B1 - W2, if W4, B5 is gote. White is 1 1/3 points better off now, on average. B1 - W2 raises the local temperature but leaves the count the same.

See Double Sente is Relative, example 1, for another related position.

reversible play - loss and gain last edited by CharlesMatthews on May 19, 2003 - 09:09
RecentChanges · StartingPoints · About
Edit page ·Search · Related · Page info · Latest diff
[Welcome to Sensei's Library!]
Search position
Page history
Latest page diff
Partner sites:
Go Teaching Ladder
Login / Prefs
Sensei's Library