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 Post subject: katago's aggression strategy
Post #1 Posted: Tue Nov 23, 2021 1:51 pm 
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I have been studying some opening principles for katago's aggression strategy (from very conservative to very aggressive).

To me, the biggest change in strategy is how it deals with weak points and cutting points. And when splitting a side, the very conservative player will ensure life, playing away from living groups. When very conservative, they prioritise invading the opponent's moyos (approaching 3-4) and splitting their sides. When very aggressive, they slowly ensure they can prevent the opponent living easily in their area (including playing the bizzare looking 3-3 4-4 shimari), adding a move in the middle of their side and pincering any stone that approaches. This may sound contradictory but it really works.

This principle also seems to apply to cross-cut fights. The conservative player will try to rescue all the stones, saying "let's all live, you can live with more points, I'll bribe you". In fact they tend to cut to sacrifice more often. Whereas the aggressive player will choose a thin line of cutting stones to either make a wall (with lots of cutting points) by double hanes (forcefully responding to all the opponent's key point moves) or anticipate severely attacking (or even capturing) one side or the other on a large scale. The aggressive player is very sensitive to how thick they are on the rest of the board even if it is over 5 stones away. The conservative player seems to focus on local profit.

The aggressive player seems to view any side of the opponent that the opponent has played 3 moves on as small and says "I can still lean on that to build by own moyo" and after their own corners are defended, will be eager to play a very far extended moyo as long as they have many stones in that area (say six to zero) even if there are wide holes on the sides. This includes playing the 4-4, 7-3 shimari sometimes.

In a fight where the stones are one on one, (or one on zero as mentioned above - preemptive defences), this is where the differences in strategy are most apparent. Balanced play tends to defend your own group first at the boundary of access to territory/eyespace/centre influence. Conservative will do so in a more defensive way - moving towards open space rather than obsessing over the corner mutual eyespace points. Aggressive will prefer to pincer and is less likely to tenuki unless it sets up a splitting attack - the attitude seems to be "this area is already mine if I add a move to attack, so I can't let you add another move to settle."

If there is a fight where you have the advantage of 2 stones to 1 and you have to add another move to defend, then very aggressive tends to defend with the same move as the even player. 3 stones to 1 similarly - after all, you can't get around the fact you need the same 4 stones to capture a ponnuki, however much stronger you are than your opponent. However, I find that the conservative player often won't add another move to defend (because in order to be efficient and attack on a larger scale you tend to need to pincer and create another group that isn't connected to your original 2 stones) and will tenuki instead to live on the other side of the board.

If there is a fight where you have the disadvantage of 1 stone to 3 or more, this is where it gets interesting. Conservative will play to reduce the area gradually from the outside by taking big points. Conservative seems more willing to attach to the opponent's stones in order to make shape now and probe. Aggressive will leave it for now but pre-emptively get solid in the area that the opponent will profit from an attack. Then it will mess around playing all sorts of loose shape points (3rd line splits under high stones) and eventually rescue a group deep in the opponent's moyo often making a large centre wall themselves, quickly living locally, or just creating aji in sente and playing tenuki. Aggressive knows there is only one area they need in order to profit and must keep aiming to seal off that area regardless of if there are cutting points or the opponent has space to live inside.

However games between the balanced player seem to go on for a long time with a lot of tense probes and middling shapes - trying to defend slightly more efficiently but still leaving a cutting point. The timing of when the opponent exploits this and the direction they attack from is very complicated because the stones are somewhat tangled up and the opponent's stones can be vulnerable too.

My feeling is that it is easier to learn strategies from the conservative or aggressive player since the balanced AI is just too complicated (pincer - counter-pincer and on and on).

 Post subject: Re: katago's aggression strategy
Post #2 Posted: Sat Nov 27, 2021 12:34 am 
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Very interesting! I assume you are doing this with "playoutDoublingAdvantage". What levels are you classifying as "very conservative" and "very aggressive"?

Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

 Post subject: Re: katago's aggression strategy
Post #3 Posted: Sat Nov 27, 2021 10:21 am 

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Daniel tried this out in the British Championship title match! My commentary (audio, so just the variations):

 Post subject: Re: katago's aggression strategy
Post #4 Posted: Sat Nov 27, 2021 6:52 pm 
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It would be nice if these ideas were illustrated with diagrams. It is already a bit clearer what was meant now that I have briefly browsed the SGF, It is interesting I'll try look at it closer later.

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