TOKYO -- The recent losing streak that the world's top go player has endured against an artificial intelligence program marks a shift in perceptions of the game that has rocked the sport.

The three consecutive victories Google's AlphaGo achieved over Chinese professional Ke Jie, widely regarded as the world's best player, in late May have confirmed the software's overwhelming superiority.

On May 27, the last day of the three-part match, the sound of Ke's sobbing filled the room where he was competing with the AI program in Wuzhen, near Shanghai.

About three hours into the game, Ke saw the writing on the wall and left his seat for 10 minutes to cry.

With an all-but-infinite set of possibilities, go is said to be one of the most complex board games ever to have existed.

Ke said he blamed himself and became distraught as the gap between his ability and AlphaGo's became clear amid huge global attention.

The program played "too perfectly," he said. "I was immensely frustrated by constantly losing."

He also said he struggled to figure out the intention behind many of the program's moves.

AlphaGo's strategy goes beyond currently accepted go theory. One internationally recognized professional player was seen trembling while watching games in which the software played against itself, as seemingly randomly placed stones set up winning positions.

One-time world champ Shi Yue also said, with a resigned expression, that he has never seen moves like these and is unlikely to in the future.

Self improvement

Every move a human player makes has a meaning and is in accordance with their strategy.

Even when they find themselves in a losing position, they seek to make the most balanced overall moves to give themselves the best chance of recovery.

AlphaGo, however, appears to throw the strategy textbook out of the window.

In some cases, it suddenly eases up on an opponent just when certain moves would be expected. In others, it ignores a "sweet spot" and places stones all over the board.

"I assume that it is the result of it pursuing moves with the best chance of victory," said Wang Ming-wan, a master player and expert on go-playing AI at the Japanese go organization Nihon Ki-in.

But has AlphaGo surpassed human intelligence?

Demis Hassabis, CEO of DeepMind, the British Google subsidiary behind AlphaGo, said the program has honed its skills mainly by playing against itself and rarely by learning human records. Due to the difficulty of making positional judgements and possible scenarios numbering 10 to the power of 360, it was thought at least 10 years would be required for AI to outperform human players.

But the development of AlphaGo is only three years old.

The developer combined two methods to train the program. Deep learning, which involves studying vast amounts of previous human records, and playing repeatedly against itself.

Phenomenal speed

Even with a three stone handicap, the current version of AlphaGo will not allow a year-old version of itself win -- a development likened to going from strong amateur player to top professional.

AlphaGo will "retire" from competing against human players, but its success has triggered a race to study and develop go-playing AI across the world.

China's information technology giant Tencent Holdings' Fine Art has reached a level at least on a par with the world's top player within a year of development.

Japan's DeepZenGo claimed a victory against Yuta Iyama, the country's top player and holder of six titles, in March.

There is also a plan to hold a global competition for computers this year in China.

We have entered an era where records of go games between AI with increasing ability are being produced in large quantities.The world of Shogi, or Japanese chess, is also facing the same trend.

Professional shogi player Yoshiharu Habu said there would be no existential value of professional shogi or go players if games between AI programs become more interesting.

"What is called into question is whether we can create the value in human-versus-human games being more interesting and fascinating," he said.

(Nikkei)