[ewanmcteagle]

This is not correct. In the professional ranks 1p is often no weaker than 9p because often the young players start out at 1p and are very strong because selection pressure is much greater. The 9p rank in Japan also came partly out of just playing a lot for a lot of years so that accomplishment was not as great as it seems. In any case, active professional players for the most part are not dramatically stronger than one another. The range for the most part is about 2 stones, maybe 3.

Even though Fan Hui is not an active professional in the traditional sense this is an absolutely huge accomplishment and leap in playing ability by computers. BTW, Michael Redmond is not particularly strong by professional standards.

(Edit: The correlation between strength and rank now as noted below is due to promotions more often coming from acheivements: If you win at X you get promoted to 7p immediately, if you win at Y you get promoted to 9p. You cannot win a big tournament and keep your low rank. Here is an example of someone who went from 3p to 9p in one match: https://en.wikipedia.org/wiki/Fan_Tingyu. But professionals cannot give each other 6 stone handicaps when one is 9p and the other is 3p)

[cobaltblue]

This is not quite correct either. 1p is of course generally much stronger than an arbitrary amateur dan (even some (many? most?) 9d amateurs) and you can advance up the pro ranks quickly by winning certain games, but you can see the histograms yourself that while there's a clump of 9ps everywhere but China there's still a distribution. http://senseis.xmp.net/?ProfessionalRankHistograms Another problem is you don't lose your 9p rank once you earn it. It would be nice if there was an international Elo system tracking all the 9ps of various countries to rank them properly... Maybe someone's tried to calculate rankings independently? Still, I think it's pretty uncontroversial that someone who's been a lower-rank pro for longer than a few years is going to be significantly weaker than their higher-rank peers.

[hyperpape]

There are two major attempts at international ratings today. Dr. Bae Taeil does ratings for Korea, and Remi Coulom produces ratings independently, based on the database at go4go.net (http://goratings.org is the site).

Taeil's method seems unusual, though it may well be justified . I think he's using a relatively complete database of games, but I don't know for sure. Coulom has a very well regarded mathematical model, but we know that there are some gaps in the database, which a) may skew international comparisons, and b) may result in inaccurate ratings for players with few games in the database (but those players are usually not top players in the world).

See my comment below: there are very few 1p players near the top, unsurprisingly.

[hyperpape]

I feel like this is mostly misleading. Look at a list of top players (goratings.org). The top fifty is mostly players 5p and up. There are a few 3p or 4p Chinese players running around, and apparently even 1 1p (Li Qincheng) but by and large, there is a relation.

[hokkos]

The beaten player is ranked 633 (Fan Hui).

[hyperpape]

Yes. He's a case where you'd make exactly the right assumption if just told his rank.

Though I should warn: as a low level pro who moved to Europe, this database has very little data on him. His European results indicate that he's stronger than Pavol Lisy, Alexander Dinerstein, and Mateusz Surma, who all rate higher than him here.