Capturing race

Capturing races confuse the heck out of me. Here’s an example:

How do you even begin to evaluate these positions? I’m White and I’m not sure if I should eat away Black’s liberties right away, play defensive move for my group to gain liberties or just play away. Plus I can sacrifice part of my group but should I try to keep everything alive.

Counting Black’s liberties look pretty straightforward but what to do in positions where the groups are split up or can be split up? This is just one example so both general advice and advice for this one example are welcome.

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I posted a few things in your linked review… but take it with a grain of salt. My liberty counting is not the best either :slight_smile: The theory is pretty well explained in this senseis article: .

What I do… is basically count every move I need to make to take away an outer liberty as 1, then skip every move which requires a response from my opponent. That way I know how many approaching moves it takes for one side to take away the outer libs (i don’t count these moves because obviously, my opponent cannot take away my group’s outer liberty if he has to reply elsewhere). Then I calculate the difference, adjust for sente and see if the result differs from 2.


But the number of inside liberties has to be accounted for too? If there’re a lot of inside liberties then the difference in outside liberties needs to be higher for one side to win.

I left some move comments in this review, starting at move 193.

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In essence it is quite simple:

  1. Eyes balance (incl. big eyes vs. small eyes)
    These are first thing you look at. Imbalance on the eye aspect effectively prevents seki as an option. You do want to be ahead in this race, as the loser needs to take the common libs to win.
  2. Simple algebra exercise (Op - opponent external, C - common, Pl - players external):
    win Pl > Op + C: if you are ahead and want to kill it doesn’t matter where to start, but usually it’s a good habit to start from outside, unless you are looking for some liberty reducing throw ins to take early on
    seki not a) and Pl + C > Op: if you are not ahead just make sure you can achieve seki (the easiest way to do it is to not fill common libs)
    loss otherwise: if you are behind … well, try to not die in gote

If you have sente, count equality in your favour.

In the example above:

  1. You cannot get ahead in eye race, so seki becomes likely option.
  2. You need 5 moves to fill blacks outside libs
    win you don’t have enough libs to fill both outside an common libs
    seki because there are 3 common libs, you just need 3 more to be safe. This is the only thing you want to know. Just have that answer in your head (do I have 3 external libs?) while making decisions about responding to opponent moves
    loss not this time :wink:

To make it even simpler. You need to start from above calculation, but as long as your counting is not more by 1 off, it’s as simple as taking outside libs. Look for moves that fill extra libs in sente (like throw-ins) for you or your opponent.

Of course things can get complicated when there is Ko involved, but not by much.