Ko in Pro Games always confuses me. If a Ko comes up in my game I try to see if it is big enough. If it is I play it until it is resolved and if it is not I'll just ignore it.
But pros always start a ko then do it for a bit, and then seem to forget (I'm certain they don't and there a valid reasons for it) about it, only to come back to it after 50 moves. Can anyone help to enlighten me?

Example game I just went over right now: http://www.go4go.net/go/games/sgfview/61241 There is a ko in the lower left corner that starts in the opening and drags out until midgame

Thanks!

If you want us to give a chance on possibly commenting, you need to post the game here (if legal) so that we can see it if we do not have access to the other webpage.

There is a simple answer which may not be very satisfactory. Each move, including taking the ko and winning the ko, has its own value. The pros are just playing the biggest move on the board. When there are moves elsewhere that has more value they will play there first, and returning to the ko fight when they believe that is the biggest point.

Now it is an entirely different question as how to judge the value of each move during a ko fight. It is very complicated. That particular ko in your example has a total value close to 40 points, and total number of moves by both sides required to complete the ko fight is 5, so I would say each move is worth about 8 points when the ko started, but that is a very rough estimate.

Good question. This is something that's much less common in SDK games.

To add to what wolfking said, you might look at http://senseis.xmp.net/?LongThreat. The general phenomenon is that as the ko fight goes on, the value of the ko can in reads of decrease and the value of external moves can increase or decrease. So when the ko is not enormous, the players will only sometimes prefer fighting the ko to playing elsewhere.

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Thank you wolfking and hyperpape. I get the idea, but their reading is super strong right? So shouldn't they know. I'm gonna play a threat now, but eventually this situation created by playing the threat will be bigger than answering the ko? And if so why even bother starting the ko, if you already know you'll ignore it...

It can happen in kyu games as well. It does take some judgment and some careful thought, so it's rarer at my level. However, while I might be stubborn in a game, I can see that the ko in the lower left is not that big, while the sequence starting at 34 in the lower right is urgent.

The reason to start is it that it's worth fighting when you start it, even if it won't always be worth fighting on every following move. During the game, the biggest move or threat changes value. A first move in the corner is generally considered ~15 points. But in close combat, the value of a move can be 30 or 60 points (think of potentially losing a 30 stone group). When matters are settled, the value of each move decreases. But it can rise again.

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Occupy Babel!