Life In 19x19

jts wrote:Adding 5 to 3 - not my strong point.

I once put a stone on the second line in atari, and then tried to remove it.

Bill Spight wrote:
There is a 3 pt. reverse sente for White at Q-01, which beginners should learn.

Bill, are you saying that W should play Q1 (sorry for a very obvious question!)? It seems to me that B just plays P1, and then W must respond at R1, giving sente to B?

I get the horrible feeling that is exactly what you have said in your post, which I have just foolishly repeated, but I can't see why that would be desirable for W to play unless there was no other move available.

I'm off to look up reverse sente again. It must be the 10th time I have looked up the definition.

Okay, scratch that entire post, except why should it be played? On the Sensei's page, http://senseis.xmp.net/?ReverseSente it says these plays are rarely played before the opponent gets the chance to play them?

Hopefully this time the definition will sink in. And I see from the same page that you have added yet another thing to learn! Thanks Bill!

bleep wrote:Okay, scratch that entire post, except why should it be played? On the Sensei's page, http://senseis.xmp.net/?ReverseSente it says these plays are rarely played before the opponent gets the chance to play them?

Hopefully this time the definition will sink in. And I see from the same page that you have added yet another thing to learn! Thanks Bill!

Well, hm. Maybe the SL page needs a rewrite. Reverse sente isn't at all rare in amateur games. I don't think there's necessarily anything rare about them in pro games (other than the fact that so many games are resigned before the endgame). The point is that you should plan on your opponent getting all his sente moves, because he will usually be able to take them before you do, and if he does permit you to take one, you should expect that there will be another gote move that is just as large for him to take after you give up the initiative.

But in this game both players played a lot of small moves in the center between, say, 174 and 194. For almost any of these moves, you would have been better off playing one of the moves Bill highlights. B has waited too long to take his sente.

Bill Spight wrote:There is a 3 pt. reverse sente for White at Q-01, which beginners should learn.

Oops! I thought that the weakness of the two R-file stones in the corner was enough to make the Black hane-connect sente. I should have verified that. It does not. My bad.

bleep wrote:Bill, are you saying that W should play Q1 (sorry for a very obvious question!)? It seems to me that B just plays P1, and then W must respond at R1, giving sente to B?

I get the horrible feeling that is exactly what you have said in your post, which I have just foolishly repeated, but I can't see why that would be desirable for W to play unless there was no other move available.

{snip}

On the Sensei's page, http://senseis.xmp.net/?ReverseSente it says these plays are rarely played before the opponent gets the chance to play them?

I have added variations to the SGF file at move 166 to illustrate the three plays. It does not explain everything about them, by any means.

On the question of playing sente. Gote is symmetrical in that whichever player makes the play gains the same, on average. Sente is asymmetrical. The player with sente gains more than the player with reverse sente. However, the reply to sente gains the same, so the exchange gains nothing on average. (Note that there are different meanings of sente. It is possible to make an exchange with sente that gains something because the opponent has nothing better. There are a couple of examples in the variations of the SGF file, as it turns out. But it is true of sente in the technical sense.)

Because of this asymmetry we say that the player with sente has the privilege of playing it. The reason is that normally he can make the sente play when there are other plays on the board that gain less than that play but more than the reverse sente play. Then his opponent replies, because the reply, being the same size as the sente play, is also larger than anything else on the board. OC, it is possible to construct whole board positions that are not normal, but normally the player with sente has the privilege.

jts wrote:

bleep wrote:Okay, scratch that entire post, except why should it be played? On the Sensei's page, http://senseis.xmp.net/?ReverseSente it says these plays are rarely played before the opponent gets the chance to play them?

Hopefully this time the definition will sink in. And I see from the same page that you have added yet another thing to learn! Thanks Bill!

Well, hm. Maybe the SL page needs a rewrite. Reverse sente isn't at all rare in amateur games. I don't think there's necessarily anything rare about them in pro games (other than the fact that so many games are resigned before the endgame). The point is that you should plan on your opponent getting all his sente moves, because he will usually be able to take them before you do, and if he does permit you to take one, you should expect that there will be another gote move that is just as large for him to take after you give up the initiative.

IMO, reversion to the previous page would be a plus. It said that the reverse sente is somewhat unusual.

Thanks for clarifying that Bill.