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Shusaku Number
    Keywords: People

Mathematicians brag about their [ext] Erdös numbers[1]. Go players can brag about their Shusaku numbers. Shusaku has a Shusaku number of 0. If you have played a game with Shusaku, your Shusaku number is 1. If you have played a game with someone whose number is 1, your number is 2, and so on. If you've never played, your number is infinite.

(If you've played a few dozen games online among disparate players, your ShusakuNumber is probably finite. If your ShusakuNumber is finite, it's almost certainly less than 10.)

What's your Shusaku number?


Like a Six Degrees of Separation for Go... interesting.


If you ever had the honour of playing against Iwamoto Sensei it is at most 4. Based on games in GoGod (except the last one :))

Honinbo Shusaku (0) -- Iwasaki Kenzo (1) -- Tamura Yasuhisa (2) -- Iwamoto Kaoru (3) -- Jan van Rongen (4)

I didn't have that honour! But I still get a 5:

Shusaku (0) -- Iwasaki Kenzo (1) -- Shusai (2) -- Go Seigen (3) -- Takemiya (4) -- Alberto Rezza (5)

There are probably better bridges than "Shusai --> XX". Iwasaki Kenzo died in 1913, Shuei died in 1907, Shugen died in 1917. Although they were too young to play any official games both Shuei and Shugen were sons of Shuwa and most likely knew Shusaku. There is an excellent chance that they played him as children. People like Segoe (d. 1972), Iwamoto (d. 1999), Hayashi Yutaro (d. 1983) directly spanned the gap between the beginning of the century and modern times. -- Dave Sigaty

BobMcGuigan My number is at most 4 via an unusual path in that two of the players are female: Bob--Shiratori Sumiko--Kita Fumiko--Shuho--Shusaku.

JaredBeck: I also use the Shiratori Bridge:

Honinbo Shusaku - Shuho - Kita Fumiko - Shiratori Sumiko - Michael Redmond - Alexandre Dinerchtein - Jared Beck (6)

Anyone who has played the user "breakfast" on KGS has a Shusaku Number of 6.

BobMcGuigan It's interesting to speculate on who wouldn't have a Shusaku number. I'm sure there are such people. For example two people who "found" go in a game shop, bought a set, learned the rules from the enclosed pamphlet, and have only played each other. On the other hand, anyone who's ever played anyone who has ever played ...(iterate ad libitum) ... anyone who has ever played any pro, even in a simultaneous game, would have a Shusaku number (I'm sure the pros are all connected to Shusaku).


Shuei played Shuho providing additional "bridge" to Shusaku. Shuei, who died 1907, may provide a better bridge than Shuwa, who died in 1873. KariganeJunichi died in 1953, late enough to have played many of todays more senior professionals.

Shusaku (0) -- Shuho (1) -- Shuwa (2)
Shusaku (0) -- Shuho (1) -- Shuei (2) -- Karigane Junichi (3)

The earliest opponents recorded on [ext] http://www.GoBase.org for Hayashi Yutaro (3) are Shusai, Kitani Minoru and Go Seigen. So, Hayashi Yutaro may not be a better 'bridge' to Shusaku.

Iwamoto's (3) connection to Shusaku suffers the same problem per [ext] http://www.GoBase.org. Iwamoto (3) connects via Shusai, Kitani Minoru and Go Seigen as well.

Could someone with a copy of GoGoD or Master Go check for better links to Shusaku? -- Velobici

The games in the databases from the early 20th century come from a limited number of books (e.g. Igo Hyakunen) plus a few published game collections such as Shusai, Go, Kintani, and Hashimoto Utaro. This limits what we can demonstrate from the readily available sources, but realize that there are huge gaps in the information. --DaveSigaty

I tried the other connections too, but they all run into some problems. Of course there is the formal problem of the availability of a game record. On the other hand Iwamoto is very unlikely to have a lower Shusaku number. He did not arrive in Japan until 1911 and reached Sho-dan in 1917. Segoe moved to Tokyo when he was 20 (1908) where he was promoted to 2 dan in the end of that year. So he might have played against Iwasaki or Shugen. Which would give all his pupils Shusaku number (3), including Cho Hun-hyeon. But again -- we need the game records to be sure -- Jan van Rongen


MtnViewMark: Do we count teaching games or only games played to win?


A refinement of the idea would be your Winning Shusaku Number: which is one greater than the least Winning Shusaku Number of all the people you've ever defeated (at an even game, say).


Stefan: How do deshi feel about Shindo Hikaru as a bridge? He has played Shusaku's go engine on multiple occasion, and therefore carries a 1. The problem probably is to find a game between Shindo and somebody with us here in meatspace.

BlueWyvern: How would you define meatspace? (BTW, Maybe Umezawa Yukari has a Shusaku # of 2)

Jared: Meatspace is a term from Gibson's novel Neuromancer, and refers to real life, the opposite of cyberspace.


[1] The practice for Erdös numbers is that Paul Erdös has uniquely the Erdös number 0. Then everybody else has Erdös number defined to be one greater than the minimum of their co-authors' Erdös numbers. As in graph theory the reflexive edges are discarded: one does not consider either the papers under Erdös' single authorship or, analogously, Shusaku's solitaire games.


I've been told that Paul Erdös enjoyed playing go -- in fact, that it was his only hobby aside from visiting other mathematicians. Can anyone corroborate this? Any idea how strong a player he was? Do we have any readers with a Erdös Go number of 1 (played a game of go with Paul Erdös)?

Charles Matthews Yes, I played him twice. The first time was probably around 1975. He was around 2 kyu then. I played him a few years later, and he was perhaps a little stronger; but given his habits that might not be significant. There is even a photo I've seen of him playing, in an AMS publication - sadly he was in hane at the head of three bad shape there.

Matt Noonan: In Budapest there is an annual Erdös Pal Go tournament (as of 2001). Too bad he can't make it...

enel: Unfortunately my Erdős Go Number is 2 only (Erdős-Göndör-enel). I saw him sometimes while he playing in Budapest. He has a "famous" saying related to the go game. "May play go wrong, but must not play slow". Erdős played very quickly.

ChadMiller: I wonder what Erdős' ShusakuNumber was.


Evand: I'd be interested in knowing James Kerwin's Shusaku number. Is it low enough to provide a useful bridge? If someone with a database could look into it, I'd find it interesting. Thanks.

BobMcGuigan: Kerwin was a student of Iwamoto (see above) so he probably played at least one game with him.

Velobici: James Kerwin has a Shusaku number that is not greater than 4: Shusaku - Iwasaki Kenzo - Honinbo Shusai - Iwamoto Kaoru - James Kerwin.

FFLaguna: DrStraw has a Shuusaku number of 4 and a Go Seigen number of 2! Convo him for a game, or some such! ^.^



This is a copy of the living page "Shusaku Number" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.