Hi all I have what I hope is a simple problem with a simple solution that I am missing. This is from level up v7 / best endgame moves for black. The book is saying to choose the more conservative A here, but it is not clear to me why B doesn't work since, white moving back at A after black B isn't viable. I am clearly missing something obvious here I hope? Any help would be appreciated..

-avi

Capturing at "b" gives White a sente for 3 points in the corner. And "a" dominates "b", as Black always does at least as well by playing it.

Edited typo.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Hi Thanks again.. I think I understand... the extra point one gets is not worth losing sente?

Losing sente is not worth it. And you don't really get an extra point, anyway.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Regardless of whether you play A or B now, you must eventually play A. A general rule worth remembering is that if you have a choice and one of the choices must eventually be played anyway then you might as well go ahead and play it first. The except is when your second choice has an immediate threat which is not there otherwise. Clearly this is not the case here.

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Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).

In Go, often the exceptions are the rule. Another situation (not necessarily just for endgame) is
if you must play a move to live (or connect, or cut, etc.), sometimes you want to play other local (or even global)
good sente moves first, before finally coming back to play the one necessary move.

Interesting point. I've heard this as the proverb "force before living" or "forcing moves first". I don't think the rule of thumb that Dr. Straws cites is in tension with "forcing moves first". Forcing moves doesn't refer to all sente moves, or even to all good sente moves, but specifically to ones that lose their meaning after some point of contention has been disposed of.

In cases where there are forcing moves to exploit, the whole point is that capturing the b4 stone (for example) isn't necessary, and that there are plenty of other, more profitable ways that black could live (while letting white save b4), if white were to refuse to submit to the forcing moves.

(Not to say that there aren't exceptions to Dr. Straw's principle, though - this is Go, after all!)

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Thanks all this has been tremendously helpful. There were a few more problems that are like this that I was missing the intuition behind the appropriate move. Part of where I was going awry is everyone's insight that clearly I would have to go there anyway in this problem, so there is no gain of points (which was the obvious (in hindsight) aspect here that I was missing), as well as thinking clearly about sente. Looking back that is the same theme that underlies the rest of these problems where I was making the incorrect move.

The question of sente vs. gote is very important, and rests upon the fact that there are (normally) other plays on the board. For this problem, if you just look at the local region, whether you play "a" or "b" does not matter. But when you think about the rest of the board and sente vs. gote, it becomes plain that "a" is correct.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

Another surprising example is the following shape, where white is unable to block at "a" due to black's tesuji response at "b", but where the marked stone is present.

Click Here To Show Diagram Code

[go]$$c How to respond?
$$ ---------------------
$$ | . . . . a 1 . . . .
$$ | . . . . b O X X . .
$$ | . . W . . O O X . .
$$ | . . . O O X X . X .
$$ | . . . O X . . . . .
$$ | . . O X X . . . . .[/go]

Typically when you can't block directly, you learn to draw back a space at , giving the following result where black reduces white in sente:

Click Here To Show Diagram Code

[go]$$c First try
$$ ---------------------
$$ | . . . 4 3 X 5 . . .
$$ | . . . 6 2 O X X . .
$$ | . . W . . O O X . .
$$ | . . . O O X X . X .
$$ | . . . O X . . . . .
$$ | . . O X X . . . . .[/go]

But in this case, White can play the following surprising move for . At first glance, it looks like this gives up a point compared to above because now black can poke as far as "a".

Click Here To Show Diagram Code

[go]$$c Surprising response
$$ ---------------------
$$ | . . . a . 1 . . . .
$$ | . . . 2 . O X X . .
$$ | . . W . . O O X . .
$$ | . . . O O X X . X .
$$ | . . . O X . . . . .
$$ | . . O X X . . . . .[/go]

But black poking in is gote thanks to the marked white stone:

Click Here To Show Diagram Code

[go]$$c Gote for black
$$ ---------------------
$$ | . . 4 3 5 X 7 . . .
$$ | . . . O 6 O X X . .
$$ | . . W . . O O X . .
$$ | . . . O O X X . X .
$$ | . . . O X . . . . .
$$ | . . O X X . . . . .[/go]

So white can get later, giving a result that's 2 points better than the "First try" diagram above, or else get equivalent compensation by gaining sente to play elsewhere if black actually does spend his whole turn here.

Click Here To Show Diagram Code

[go]$$Wc White's followup
$$ ---------------------
$$ | . . . . 1 X . . . .
$$ | . . . O . O X X . .
$$ | . . W . . O O X . .
$$ | . . . O O X X . X .
$$ | . . . O X . . . . .
$$ | . . O X X . . . . .[/go]