Losing the third round to Mikhailo Oleksienko of Ukraine, Harikrishna bounced back in style and outwitted Socko out of a King's Indian defense game where the Indian played white.
Socko went for the thematic central breakthrough in the centre but soon realised that white had too much counter play on the queen side.
Harikrishna was at his technical best in the middle game after the queens got traded and exerted pressure in copy-book fashion to win a pawn.
On what turned out to be a tough day for him, Abhijeet Gupta had to sweat before he could get a draw with Matthieu Cornette. The English opening gave Cornette a slightly better endgame and following an error Gupta found himself pushed to the wall.
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However, a timely exchange salvaged the day as Gupta converted to a level Bishop and pawns endgame. The draw was agreed to in 53 moves.
Harikrishna and Gupta are among those who have three points each sharing the seventh spot in the strongest open of the world and these two are currently the best performing Indians in the fray. There are five rounds still remaining.
The best result by an Indian in the fourth round, however, came on a much lower board. International Master Shardul Gagare almost ended the comeback hopes of highly rated and ninth seed Arkadij Naiditsch of Germany.