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 Post subject: Re: This 'n' that
Post #541 Posted: Mon Apr 08, 2019 11:47 am 
Oza

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Bill

Just as background for your splendid efforts.

I have been trying to come to terms with what I thought was something odd about facing shimaris in pro play. Like you, I think, I was brought up in go during the Takagawa era. What I learnt then was that the main direction of play from the ikken tobi shimari was along the side that makes an L shape. The reason was that this leads to a box shape rather than a tray shape. I have been increasingly puzzled lately (even before AI times) as I have noticed more and more pros favouring the other ("open") side. I cannot recall seeing anything about this in fuseki books.

This is so extreme that (from memory) of over 200 games that I have with facing ikken tobi shimaris, in only two, I think, was the centre mid-point played.

Where one kogeima shimari faces an ikken tobi shimari, the centre mid-point play was rather more common, but still close to disappeared from pro play around 2010, or even earlier.

But - big BUT - where a kogeima shimari faces another kogeima shimari, the centre mid-point is a very common play even today.

That has long baffled me. But in the light of what the bots have shown us, one vaguely possible thought has come to me: a contact play at the third-line root of the shimari seems powerful with a kogeima shimari, but less so against the ikken tobi shimari. Is that side therefore favoured for an extension from the kogeima simply to avoid that sort of contact play. I have seen nothing in print to support that, but I do recall that Yi Ch'ang-ho led a fashion for playing a very early contact play on the second line. Could it be that he was on the same lines as the bots but just didn't realise the third line was better than the second for the contact play?

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 Post subject: Re: This 'n' that
Post #542 Posted: Mon Apr 08, 2019 12:39 pm 
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Thanks, John. Very interesting. :)

If you have any positions that seemed puzzling, if you send the references for the GoGoD sgfs we can take a look at them here. :)

As for outside third line contact plays, IIRC they were fairly common before the 20th century. I don't recall whether they were in the context of shimari vs. shimari, though.

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 Post subject: Re: This 'n' that
Post #543 Posted: Tue Apr 09, 2019 3:20 am 
Oza

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Quote:
If you have any positions that seemed puzzling


Bill: I didn't keep any record of specific games, and I mainly just looked at one side of the board using Kombilo.

However, one associated thing I noticed was that when facing shimaris occurred, often neither player seemed in a rush to grab the mid-point (to my surprise), or to be bothered by the fact the opponent got there first. What often happened (again, from memory) is that when the opponent played C10, the other player was happy to take C8. The way I rationalised this was to assume this implied two box shapes (after E10 and E8), but my analogy was to see these as pails rather than boxes. I saw the players as taking their pails to the well and carrying water back to the house.

The C10-E10 player filled his bucket to the brim and so got potentially more water, but had a big risk of spilling some and had to walk back very slowly. The C8-E8 player only filled his pail three-quarters full but didn't have to worry much about spillage and could walk back very briskly and get on first with other things.

In other words, there was some sort of quantity-quality trade-off. I'm pretty sure that applies in go, too, though I'm unsure how. But time may be an unexpected factor, though in the literal time-limit sense rather than the Go Seigen sense of getting round the board quickly. In the days of Takagawa and other big-bucket people, having up to 13 hours each to think possibly meant you could take the risk of filling a potentially leaky bucket (i.e. pre-consider all the aji and erasure possibilities). I suspect that nowadays, with shorter limits, players have become me pragmatic and are more often happy with an underfilled bucket. (Maybe the Henry and Liza bucket roles have been reversed ? :))

Here's something a bit different. It's not quite the same thing as you are discussing, but may offer a sidelight. It's from a Genjo-Chitoku game (my book is now finished and had several examples of the sort of thing that baffles me here, which is why I possibly sound "primed" on this topic).



After White 8, Black does not rush to play R10. White 10 (by Genjo) obviously has ladder implications, but still, with the subsequent moves, has an air of the sort of whole-board play and influence rather than thickness the bots are showing us, especially with 16 (which allows Black a mid-point play at 17, which, however, later commentators thought was too close to White's influence. The modesty of the tsume at 18 is instructive (because he is about to strengthen Black with 20-21. Turning away at 22 (because he cannot attack Black on the right yet) also has bottish overtones to me.

Here is another G-Ch example, though less baffling to me:



White 12 favours the "wrong" extension (less baffling because 13 and 14 can be regarded as miai). But the attempt to overconcentrate Black immediately with 16 etc is an aspect of bot play that modern Japanese players have latched on to strongly.


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 Post subject: Re: This 'n' that
Post #544 Posted: Tue Apr 09, 2019 3:45 am 
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Thanks, John! Ah, yes, Genjo vs. Chitoku. :) That 5-5 rang a bell. Cool move. :cool:

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 Post subject: Re: This 'n' that
Post #545 Posted: Wed Apr 10, 2019 7:38 am 
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Some comments and Elf variations for the second game. Some surprising error estimates. :o



Edit: Added variation for :w12:.
Edit: And another. :)

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 Post subject: Re: This 'n' that
Post #546 Posted: Thu Apr 11, 2019 6:44 am 
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In the first game, both players had a blind spot about the top left corner, such that Elf's analysis had a seesaw effect, with each player losing points on almost every play for not playing in the top left corner. Still, there are some fascinating variations. :)


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 Post subject: Re: This 'n' that
Post #547 Posted: Thu Apr 11, 2019 8:15 pm 
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re n11, I think a lot of the value comes not from its attacking element, but its defensive reverse sente aspect: denying black the pleasing haengma of running plus shape attack at n12. It's double sente.

Ignoring the peep is probably only justified because of giving komi: in a no komi game Black can probably get away with the heavier play of the game denying white easy cash (though I'd like to see how Elf uses aji of those cut stones later:the right side isn't solid cash). Komi or not though, I suspect the suggested large Knight jump on a white shape point is just better than the one point jump. Because white didn't do the close pincer Black can play thinner. (or even should to avoid inefficiency, we can anticipate shoulder hit or attachment against the 2-space pincer in which case one point jump is overconcentrated.)

The 5-4 doesn't have particularly complicated variations does it? If it was a 5-3 I could understand black not going in as "I know going in is probably the best move, but I'm scared my opponent has some secret new taisha variation to trick me so I won't go in" whilst white thinks "I don't need to close the corner because I've psyched out my opponent with my mad taisha skills". Also notable that white closed it in a bigger way than Elf recommended this game, presumably lack of komi requiring more ambitious play.

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 Post subject: Re: This 'n' that
Post #548 Posted: Thu Apr 11, 2019 11:09 pm 
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Uberdude wrote:
re n11, I think a lot of the value comes not from its attacking element, but its defensive reverse sente aspect: denying black the pleasing haengma of running plus shape attack at n12. It's double sente.


Well White N-11 takes on a defensive character after Black L-16. But without N-11 in place, I suspect that Black would approach the top left corner at G-17, as he does in at least one variation. But then if White plays a one space pincer and after Black jumps out, plays M-16, N-11 looks very nice. Perhaps that's why Elf played Black L-16. :scratch: :-|

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Ignoring the peep is probably only justified because of giving komi: in a no komi game Black can probably get away with the heavier play of the game denying white easy cash (though I'd like to see how Elf uses aji of those cut stones later:the right side isn't solid cash).


Well, certainly Black tends to play conservatively with no komi. Such a large furikawari would be quite a bold stroke. ;) But if Black believed, with Elf, that the top left corner was the hottest spot on the board, getting there first would be attractive. (OC, in that case Black would have played there earlier.)

Quote:
Komi or not though, I suspect the suggested large Knight jump on a white shape point is just better than the one point jump. Because white didn't do the close pincer Black can play thinner. (or even should to avoid inefficiency, we can anticipate shoulder hit or attachment against the 2-space pincer in which case one point jump is overconcentrated.)


Yes, I don't think that Elf says much about no komi go, particularly about White's play. But, especially in the early game, I we can learn a good bit from its analysis. Most preferred plays with 7.5 komi will remain preferred with no komi, even though the win rate estimates would be different. I think that the large knight's jump versus the one space jump is a case in point. :)

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 Post subject: Re: This 'n' that
Post #549 Posted: Wed Apr 17, 2019 9:51 am 
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Evaluation and Tic-Tac-Toe

Traditional go evaluation does not depend upon whose turn it is and assumes perfect play. Minimax evaluation depends upon whose turn it is and assumes perfect play. Winrate evaluation depends upon whose turn it is and assumes imperfect play (except when the winrate is 100% or 0%). OC, for Tic-Tac-Toe we know perfect play.

Lately I have been wondering how to introduce the idea of traditional go evaluation to those who know nothing about it, and the idea of using Tic-Tac-Toe came to mind. I learned a little something about Tic-Tac-Toe and I thought I would write it up. :)

Despite not knowing perfect play in go we can evaluate the empty board. Because of symmetry it has an average value of zero. The result with perfect play when Black plays first has to be the negative of perfect play when White plays first, and their average is zero. The same reasoning applies to Tic-Tac-Toe. Traditional go evaluation has not been very successful in making a strong go player. One reason for that is that another variable, that of temperature, is important. You can’t simply rely upon the average value of a position. Tic-Tac-Toe provides a good example of this, which I shall illustrate using go diagrams.

Click Here To Show Diagram Code
[go]$$Bc Value 0
$$ -------
$$ | . . . |
$$ | . . . |
$$ | . . . |
$$ -------[/go]


The empty board has a value of zero and the final board also has a value of 0, counting a win for Black as +1 and a win for White as -1. It’s temperature is 0.

Click Here To Show Diagram Code
[go]$$Bc Value 0
$$ -------
$$ | . . 1 |
$$ | . . . |
$$ | 2 . . |
$$ -------[/go]


After :b1: takes one corner, :w2: takes the opposite corner. By symmetry we know that this board also has an average value of 0. But it has a temperature of 1. Whoever plays first can win with perfect play.

Click Here To Show Diagram Code
[go]$$Bc Value 1
$$ -------
$$ | 5 a 1 |
$$ | . b 4 |
$$ | 2 . 3 |
$$ -------[/go]


:b3: forces :w4:, and then :b5: produces a won position. Even if White plays first Black has the miai of “a” and “b” to win; if White takes one, Black takes the other. The players could stop play now and declare a Black win.

When I was a kid I was unaware of this little trick, because I always made my first play in the center, whether as X or O.

It’s a good illustration of why simply knowing the traditional go value of a position is not enough to base play on. After :w1: White may reason that :w2: is OK because it returns the board to its original value of 0. But :w2: raises the temperature to 1 and allows Black to win. I believe that using minimax evaluation chess programs used to (and maybe still do) evaluate only quiescent positions, for a similar reason.

Suppose we did not know perfect play for Tic-Tac-Toe. What would the winrate value of the first play? We do not know, because winrate values depend upon imperfect play, and we do not know the error functions of the players. However, I think we can say something about error rates, even without that knowledge.

Click Here To Show Diagram Code
[go]$$Bc Error
$$ -------
$$ | . 1 5 |
$$ | 2 3 . |
$$ | . 4 . |
$$ -------[/go]


:w2: is a mistake. Opening on the side gives the second player 2 potential errors out of 8 plays (1 out of 5 if you eliminate symmetrical plays.)

Click Here To Show Diagram Code
[go]$$Bc Error
$$ -------
$$ | 3 . 5 |
$$ | 2 1 . |
$$ | . . 4 |
$$ -------[/go]


:w2: is a mistake. Opening in the center gives the second player 4 potential errors out of 8 plays (1 out of 2) if you eliminate symmetrical plays.)

Click Here To Show Diagram Code
[go]$$Bc Error
$$ -------
$$ | 2 . 1 |
$$ | . . . |
$$ | . . 3 |
$$ -------[/go]


:w2: is a mistake. :b3: transposes to a win we have already seen (by symmetry).

Click Here To Show Diagram Code
[go]$$Bc Error
$$ -------
$$ | . 2 1 |
$$ | . 5 4 |
$$ | . . 3 |
$$ -------[/go]


:w2: is a mistake.

Click Here To Show Diagram Code
[go]$$Bc Error
$$ -------
$$ | 3 . 1 |
$$ | 2 . . |
$$ | . . . |
$$ -------[/go]


:w2: is a mistake. :b3: transposes to the win in the previous diagram.

Opening in the corner gives the second player 7 possible errors out of 8 plays (4 out of 5 if you eliminate symmetrical plays).

My guess is that a bot trained on winrate evaluation, but not to perfect play, would be quite likely to make the first play in a corner. ;)

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 Post subject: Re: This 'n' that
Post #550 Posted: Wed Apr 17, 2019 6:30 pm 
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Bill Spight wrote:
Evaluation and Tic-Tac-Toe

Traditional go evaluation does not depend upon whose turn it is and assumes perfect play. Minimax evaluation depends upon whose turn it is and assumes perfect play. Winrate evaluation depends upon whose turn it is and assumes imperfect play (except when the winrate is 100% or 0%). OC, for Tic-Tac-Toe we know perfect play.

Lately I have been wondering how to introduce the idea of traditional go evaluation to those who know nothing about it, and the idea of using Tic-Tac-Toe came to mind.


This reminded me about a very simple computer which can be used to implement Reinforcement Learning for Tic Tac Toe, consisting of 300 matchboxes :-)
https://www.belloflostsouls.net/2019/03 ... c-toe.html

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 Post subject: Re: This 'n' that
Post #551 Posted: Wed Apr 17, 2019 8:39 pm 
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sorin wrote:
This reminded me about a very simple computer which can be used to implement Reinforcement Learning for Tic Tac Toe, consisting of 300 matchboxes :-)
https://www.belloflostsouls.net/2019/03 ... c-toe.html


Yeah, Martin Gardner wrote about that in his column in Scientific American. :)

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 Post subject: Re: This 'n' that
Post #552 Posted: Wed Apr 17, 2019 9:38 pm 
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Bill Spight wrote:
Opening in the corner gives the second player 7 possible errors out of 8 plays (4 out of 5 if you eliminate symmetrical plays).

My guess is that a bot trained on winrate evaluation, but not to perfect play, would be quite likely to make the first play in a corner. ;)


Bill, I think there is something wrong with this conclusion. The reason I say that: a bot trained from zero will eventually find out that opening in the center results in wins more often than opening somewhere else.

Also, about "bot trained on winrate evaluation, but not to perfect play": this distinction matters only for trivial games, like Tic Tac Toe, while for any interesting games, no bot can be trained "to perfect play" :-)

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 Post subject: Re: This 'n' that
Post #553 Posted: Thu Apr 18, 2019 4:31 am 
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sorin wrote:
Also, about "bot trained on winrate evaluation, but not to perfect play": this distinction matters only for trivial games, like Tic Tac Toe, while for any interesting games, no bot can be trained "to perfect play" :-)


Quite so. :)

sorin wrote:
Bill Spight wrote:
Opening in the corner gives the second player 7 possible errors out of 8 plays (4 out of 5 if you eliminate symmetrical plays).

My guess is that a bot trained on winrate evaluation, but not to perfect play, would be quite likely to make the first play in a corner. ;)


Bill, I think there is something wrong with this conclusion. The reason I say that: a bot trained from zero will eventually find out that opening in the center results in wins more often than opening somewhere else.


The defense to the center opening is to play in a corner (of which there are four). The only defense to a play in a corner is to play in the center (only one point); the second player has no leeway. :)

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 Post subject: Re: This 'n' that
Post #554 Posted: Thu Apr 18, 2019 7:20 am 
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Yeah, the corner opening is often better than the center opening against humans too.

Even if they respond in the center (the single non-losing reply), you can still sometimes steal a game from them if they're unfamiliar with the position like this:

Click Here To Show Diagram Code
[go]$$B
$$ -------
$$ | 3 . . |
$$ | . 2 . |
$$ | . . 1 |
$$ -------[/go]


Now, if they play one of the corners, you win. Back in early grade school, I won some games this way against people who were overconfident that they could never lose at tic-tac-toe, but who didn't actually think about their moves. Avoiding these pitfalls requires more than 1 move lookahead, whereas most (although not all) of the center-opening lines after initial reply only require the defender to further play moves to prevent an immediate win, without needing any lookahead. Along with unfamiliarity for many opponents, this makes the corner opening much stronger than the center.


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 Post subject: Re: This 'n' that
Post #555 Posted: Thu Apr 18, 2019 8:13 am 
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Bill Spight wrote:
sorin wrote:
Bill Spight wrote:
Opening in the corner gives the second player 7 possible errors out of 8 plays (4 out of 5 if you eliminate symmetrical plays).

My guess is that a bot trained on winrate evaluation, but not to perfect play, would be quite likely to make the first play in a corner. ;)


Bill, I think there is something wrong with this conclusion. The reason I say that: a bot trained from zero will eventually find out that opening in the center results in wins more often than opening somewhere else.


The defense to the center opening is to play in a corner (of which there are four). The only defense to a play in a corner is to play in the center (only one point); the second player has no leeway. :)


I see now what you mean, you are right! I was under the wrong assumption that first player wins by starting in the center - so Tic-Tac-Toe is harder than I thought :-)

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 Post subject: Re: This 'n' that
Post #556 Posted: Thu Apr 18, 2019 8:22 am 
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Tic-Tac-Toe is very hard for a go player, because you always try to capture opponent's stones.

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 Post subject: Re: This 'n' that
Post #557 Posted: Thu Apr 18, 2019 9:05 am 
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jlt wrote:
Tic-Tac-Toe is very hard for a go player, because you always try to capture opponent's stones.


Pente, anyone? ;)

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