# Ratings calculation with handicap should account for board size

I noticed my rank drop unexpectedly far after losing a 6-stone 13x13 game as white. Looking at rank_utils, it appears that the ratings calculator does not take board size into account when adjusting ratings after a handicap game.

Using the rating calculator, I confirmed that my rank adjustment in this case (0.3k) would be expected for a 6-stone handicap on a 19x19 board.

However, clearly, stones in small board are worth a lot more than in a 19x19.

Is this a known issue?

What should the adjustment be? I think a reasonable starting point would be:

• For 13x13, the handicap should be multiplied by two (1 stone is treated as-if 2 stones).
• For 9x9, the handicap should be multiplied by four (1 stone is treated as-if 4 stones).

Those multipliers are based on a 19x19 being ~2x bigger than a 13x13 and ~4x bigger than a 9x9.

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Interestingly, I just realized Iâ€™ve been (unintentionally, but, effectively) sandbagging, since I play ranked handicap games on small boards with friends. We adjust the handicap every time one of us wins twice in a row. Then I take my artificially depressed rank and play against others. Now I understand why I seem to be winning a little more than my fair share of those games.

(Until the ratings calculation is updated, Iâ€™ll just play these small board handicap games unranked â€“ itâ€™s fine â€“ but generally Iâ€™d prefer to participate in the ratings systemâ€¦)

Iâ€™d like for this to happen as well. Iâ€™ve lost some motivation to play 19x19 because my 9x9 games have pushed my rank up to the point where I get slaughtered in the former.

But this has been discussed before on the forums. Apparently the overall rank appears to better reflect someoneâ€™s skill than the board rank, so that is whatâ€™s used to match people.

To be clear, Iâ€™m not discussing the multiple versions of ratingsâ€”which I think is what youâ€™re referring toâ€”just the computation of how much the rating should shift after a game result.

E.g., itâ€™s treated as â€śsurprisingâ€ť that white would lose a 6-stone game against someone 9k weaker on a 13x13, resulting in a big rating shift for both. But, it should be treated as â€śunsurprisingâ€ť, with a small rating shift, because 6-stones on a 13x13 should be even-ish for a 12k weaker opponent.

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I agree, 6 stones on 13x13 should not factor into rank the same way 6 stones on 19x19 does.

AFAIK, the autohandicap does factor in size to the handicap assignment, so Iâ€™d imagine the same mapping can be applied. Although that system has room for improvement as well, some related discussion in this thread about komi on small boards.

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I thought I remembered thatâ€¦ in which case, fully agree. It should be the same mapping for both. Even if thereâ€™s room for improvement, they should match each other and change together.

Here what itâ€™s probably supposed to be:

So it should have been 4 or 5 stones, maybe thatâ€™s just not so different from 6?

(I donâ€™t know how the server uses this in reverse to convert 13x13 stones and komi into a 19x19 equivalent for rank adjustments.)

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