The Filipino chesser, now playing for the United States, needed 41 moves of a Queen’s Gambit Declined to halve the point with Radjabov and remain half-a-point behind the leaders with 4.5 points.

GM Vasily Ivanchuk of Ukraine and world champion Magnus Carlsen of Norway are tied for the lead with 5 points.

Ivanchuk was held to a draw by Dutch GM Anish Giri after a marathon 102 moves of Queen’s Gambit Accepted while Carlsen bested world women’s defending champion GM Hou Yifan of China in a 54-move Sicilian Defense duel.

Tying with So were French GM Maxime Vachier-Lagrave and Chinese GM Ding Liren, who both posted victories over their respective foes.

Vachier-Lagrave defeated Croatian GM Ivan Saric in 32 moves of Sicilian Defense, even as Ding dominated Dutch GM Loek Van Wely after 29 moves also of a Sicilian Defense game.

Other results saw GM Baadur Jobava of Georgia downing GM Wojtaszek of Poland in 37 moves of a Bogo-Indian Defense, and GM Levon Aronian of Armenia splitting the point with GM Fabiano Caruana of Italy after 47 moves of a Nimzo-Indian duel.

So next faces the dangerous Ivanchuk in the next round.