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Shin Jin-seo 9-dan plays against the Go artificial intelligence KataGo in the second match of the SSEN Math-Hankyoung Gisinjeon held at the Korea Economic TV studio in Seoul on the 19th. / Courtesy of the Korea Baduk Association

Shin Jin-seo 9-dan has triumphed in a match against the world's highest-performing Go artificial intelligence (AI).

In the second match of the SSEN Math-Hankyoung Gisinjeon held in Seoul on the 19th, Shin Jin-seo secured a victory over the Go AI KataGo by four and a half집 (points). Defeating KataGo after a grueling 290-move battle lasting around 4 hours and 50 minutes, Shin became the first professional player to defeat KataGo in an official match.

Although this match was a handicap game where KataGo carried a two-stone disadvantage, Shin's victory is evaluated as comparable to that of Lee Sedol 9-dan, who claimed a single win (and four losses) against AlphaGo a decade ago. Developed by David Wu, KataGo is known to be an AI significantly improved from the "AlphaGo Lee" that Lee Sedol faced in the past. While a direct comparison is difficult since AlphaGo no longer plays matches, KataGo is estimated to be at a higher level than even AlphaGo Master or AlphaGo Zero, which were developed after AlphaGo Lee. Alongside China's Fine Art (Jueyi) and Golaxy, it is classified among the reigning strongest AIs, but because KataGo is open-source, it serves as the most universal standard in Go AI research. Until now, professional players had been defeated by KataGo even with a three-stone handicap, and some players even lost with a four-stone advantage.

On this day, overcoming the shock of the first match where he suffered from an unexpected early move, Shin guided the game into a large-scale joseki in the lower right corner. The 99 percent winning probability obtained from the start through the handicap was maintained until the game passed 150 moves. At the 160th move, a variable occurred where the territory difference widened from six to eight집, yet the winning probability dropped to 98 percent. Later, he also faced a crisis where the winning probability fell to 89 percent. However, Shin blocked KataGo's counterattack and proceeded with precise sequences, ultimately securing his victory. Shin analyzed that "the move executing the cut was the winning move."

Having brought the score back to a tie, Shin will challenge for a second consecutive win against the AI in the final third match to be held on the 21st. Shin receives a total of KRW 150 million for the three-match series, along with an additional allowance of KRW 50 million for each victory. If he achieves two or more wins, he will also receive a Genesis G90. This match is conducted in a format where Shin is given 5 hours and a single 30-second byo-yomi (countdown). Configured by the internet Go platform Tygem on a dedicated system coupling four RTX 3090 graphics cards in parallel, KataGo decides its moves within 20 seconds without a time limit, and Lee Dan-bi 1-dan, a professional player belonging to the Korea Baduk Association, places the stones on its behalf.

                                                                                                           Lee Jang-won