Tomorrow/today (Wednesday) is a rest day at Wijk aan Zee, and after four rounds Anand and Nakamura lead with 3/4, with Aronian, Giri and Vachier-Lagrave half a point behind.
The day's games were very exciting and a lot of fun to analyze (and I was quite pleased to see that most of my pre-computer analysis held up!), but also extremely time-consuming. (Don't worry, I haven't spent the past 12 hours working on the games, but it was a fair chunk of time.) Here's a quick recap:
Anand-Wang Hao: Anand repeated the same 4.f3 line used by Kramnik in round 3 against Wang Hao, but did it better. 16.Nd4 was a nice novelty and led to a surprisingly quick win. I say "surprisingly", because this motif is well-known (as you'll see) and I would have expected Wang Hao to be better prepared for it. Easier said than done, I suppose, especially against Anand!
Aronian-Nepomniachtchi was simply an opening disaster for Black. Nepo's 8...cxd4 was apparently an OTB "inspiration" that just about loses for a simple tactical reason.
Shirov-Vachier-Lagrave was the third decisive game of the day, and it was a short game as well. Shirov played the same bloodthirsty line against the Gruenfeld Topalov used with such success against Anand in game 1 of their match, but a lot of work has gone into the line on Black's behalf since then. White was never able to make his attack work, and burning bridges only led to a speedy loss.
Giri-Nakamura: Nakamura started the day alone in first, and had to work very hard to finish it with a share of the lead. By transposition they reached the "Flexible" or "Kasparov" variation of the Nimzo (4.Nf3), quickly reaching a position where White enjoyed serious pressure in return for a damaged pawn structure. Nakamura gave up a pawn to break the pressure, and the rest of the way sought to show that the pawn would not be enough. It wasn't, thanks to Nakamura's excellent defense.
Ponomariov-Carlsen was an excellently played game. Ponomariov played very aggressively against Carlsen's Hedgehog, and the latter had to defend very precisely to stay alive.
Grischuk-Kramnik was also a (half-) triumph for good defense, this time in a "Semi-Slav" English.
L'Ami-Smeets: The last intra-Dutch battle of the tournament was drawn as well, but here it wasn't a finely balanced struggle between attack and defense. L'Ami was simply better, and only a few inaccuracies allowed Smeets to escape with a fairly quick draw.
Standings After Round 4:
1-2. Anand, Nakamura 3
3-5. Aronian, Giri, Vachier-Lagrave 2.5
6-10. L'Ami, Kramnik, Ponomariov, Nepomniachtchi, Smeets 2
11-12. Grischuk, Carlsen 1.5
13. Wang Hao 1
14. Shirov .5
For followers of the live ratings, Anand leads with a hefty 2815.2, ahead of Aronian's 2807.1 and the world's strongest fashion model's 2804.9. Nakamura has moved into 9th, while Shirov is in danger of falling off the page. Still, with nine rounds to go, practically anything can happen.
In group B, Luke McShane's 100% score finally stopped, but he still leads with 3.5 points, a full point ahead of Sargissian, Fressinet, Navara and Efimenko.
In group C, Italian GM Daniele Vocatura also has 3.5 points, putting him half a point ahead of Mark Bluvshtein and Ilya Nyzhnyk.
The group A games are here, with my comments.