Dit verslag is overgenomen van het Engelstalige liveblog van Peter Boel.
16:11 Percentages
At the start of the 5th round (the 4th round for the matches) Loek van Wely made the percentages public of the moves that were identical with the computer's first choice in the match games.
Match game 2:
Ivanchuk 58%
Wei Yi 68%
Adhiban: 67%
Van Foreest 54%
Match game 3:
Ivanchuk 60%
Wei Yi 28%
Adhiban 33%
Van Foreest 75%
For Round 2 of the Open, Casper Schoppen had the highest percentage with 82%.
For round 3 Tania Sachdev had the best score with 88% (actually it was Harmen Jonkman with 100% but that was because he stayed in bed). For round 4 Stefan Kuipers had the best 'computer score' with 82%.
From round 3 of the Open, Sipke Ernst got the prize for the most attractive win. For round 4 there was no best game prize, but there was a consolation prize for Bardhyl Uksini who had resigned against Xu Xiangyi in a winning position.
In the matches 1.e4 was again played in both games: Ivanchuk went for a Sicilian with 2...e6 again, and Van Foreest and Adhiban repeted their Italian game.
15:22 Short draw on board 1
A very short draw on the top board of the Open. The most interesting thing that can be told about the game between Gritsak and Saduakassova was that it was a quadruple fianchetto!
Orest Gritsak
15:26 Adhiban too ambitious...?
It looks as if Adhiban's 15...g4 was too ambitious. There is no good follow-up to be seen on Black's action on the king's wing while his centre is completely demolished.
The struggle on the other board (Wei Yi-Ivanchuk) is interesting but still looking balanced.
16:00 A coffeehouse variation
Today's Van Foreest-Adhiban game is certainly setting the cogs in motion.
Instead of 18...gxh2+, which was played after more than half an hour's thought, Commentator Ivan Sokolov, who played Van Foreest last year, came up with a 'coffehouse variation':
18...Nh5 19.exd6 Nf4 20.d7+ Bxd7 21.Bxf7+ Ke7 22.h3 Bxh3 23.gxh3 Nxh3+ (Van Wely suggested first 23... Qc8, e.g. 24.Ba2 Nxh3+ 25.Kf1 Ng5!? 24.Kf1 Qc8 (24...Nf2 to promote the h-pawn also doesn't work: 25.Rxd8 Nxd1 26.Rdxd1! (defending h1) 26...h3 27.Bc4! followed by Kg1 and bringing the knight over - the dangerous-looking pawns are effectively blocked!) 25.Bg6 Nf2 26.Qb3 Now White is threatening something... 26...Qh3+ 27.Ke2 and White wins.
16:09 Van Foreest consolidates
Van Foreest, who was down a pawn in each of his previous games with Adhiban here, has now quite cleverly consolidated. 20.f4! was quite practical, putting an end to all Black's attacking aspirations, and after 23.Rf1 Black was forced to enter an ending with a minus pawn and several weak pawns as well.
16:23 Wei Yi gets upper hand?
Ivanchuk has taken a risk by leaving his bishop on f8 and now his position looks suspect. Will Wei Yi be able to bounce back?
Wei Yi signing a Yearbook, with himself on the cover, before today's game.
16:29 Siem van Dael takes the afternoon off
Siem van Dael forced a quick perpetual with white against Stefan Kuipers in a Two Knights' game - taking a rest day in a tournament which is going very well for him so far.
An under-20 draw as an under-20 player? We didn't do that in the old days.
16:54 Beerdsen misses big chance
Thomas Beerdsen won today, but he regretted giving mate in 1!
Here Beerdsen played 24...Rh8#, missing the chance to play 24...Rf7+ 25.Kg8 and then give mate by castling queenside.
17:01 Both Wei Yi and Van Foreest two pawns up, but only Van Foreest is better
As expected, Jorden van Foreest has won a second pawn on d6 and Adhiban is now struggling to find counterplay.
Wei Yi has conquered the c5-pawn after Ivanchuk finally decided to play 21...Be7, but now the strength of his 20...h3 move becomes clear: Black's pieces are so active that a draw is starting to seem likely.
Vasily Ivanchuk
17:21 Kuljasevic... and Machteld win!
The duel between the Elo favourites in the Open, between Davorin Kuljasevic and Xu Xiangyu, ended in a win for the Croatian GM. More on that later!
10-year-old Machteld van Foreest did it again, she just overplayed Carsten Stanetzek with black. Where will this end...?
17:51 Comments on the Wei Yi-Ivanchuk finish
Here's a short analysis of the finish of the game Wei Yi-Ivanchuk:
Of course Ivanchuk had looked deeper than us all. The final point of his h-pawn sally, 20...h3!, was sufficient to keep his disadvantage within bounds:
21.Rd1
'Maybe I should have played 21.gxh3', Wei Yi said afterwards. But Black gets good counterplay.' There can follow: 21...Rh5!? (but 21... Be7 22.Bxe7 Qxe7 23.Rxc4 O-O as in the game also looks playable, of course) 22.f4 Be7 23.Rxc4 Rd8 24.Qf3
Rxg5+ 25.fxg5 Qxe5 26.g6 Rd2!? with crazy complications.
21...Be7 22.Bxe7 Qxe7 23.gxh3 O-O 24.Rxc4 Rfd8!
Not worrying about pawns, activity is what these endings are all about!
25.Rxd8+ Rxd8 26.Rxc5 Qg5+ 27.Qg3 Qd2 28.Qh4 Rb8 29.Qc4
There's nothing to be gained for White here.
29...Qg5+ 30.Qg4 Qd2 31.Qc4 Qg5+ 32.Qg4 Qd2 33.Qc4 1/2-1/2
18:18 Post-mortem of Van Foreest-Adhiban
Adhiban said, 'I probably mixed up something in my preparation, I'm not sure now if 15...g4 is the move.' Jorden van Foreest had also prepared this line: 9...Ng6 is the top move of the computer, but it has hardly ever been played. Anand-Giri in last year's Candidates went 9...c6. The engine gave 0.00 in this line all the time, but still I decided to try it.'
The black attack 'looked like a strange King's Indian', Van Foreest said. There are people who say the entire King's Indian is incorrect - in any case, it looks as if this line of today is.
We called White's 20.f4 a practical move. Van Foreest had of course considered 20.exd6, 'but I wasn't sure there. 20...Qg5 looks dangerous'.
Here are some sample lines.
The players mentioned 21.dxc7 and now 21...Ke7! 22.Rd8 Qg3+ 23.Kg1 h3 24.Qd2 h2+ 25.Kh1 Qe5 26.Qe1 Ng3+ 27.Qxg3 Qxg3 28.Rxh8 is still good for White, but it's very understandable that Jorden wanted to avoid such lines.
21.d7+ looks safer but is not so clear either: 21...Bxd7 22.Rxd7 Qg3+ 23.Kg1 h3 24.Bxf7+ Kf8 25.Qd2 Nf6! (now 25...h2+ 26.Kh1 Qe5 is ridiculous due to 27.Bxh5) 26.Rd5! (if 26.Rd4 Kxf7 followed by ...hxg2 and ...Rag8 gives Black a lot of play) 26...Nxd5
27.Bxd5 Rd8 28.Nc2 (the white queen can't move) 28...c6 29.Nd4 cxd5 30.Ne6+ or 29...Ke8 30.Nf5 Qxg2+ 31.Qxg2 hxg2 32.Bxc6+ bxc6 33. Kxg2, both with just a small edge for White.
Of course the endgame with the extra pawn was better. Adhiban managed to drum up counterplay, but it wasn't enough to save the game.
18:47 Comments by Davorin Kuljasevic
Davorin Kuljasevic had a good day because he beat one of his major rivals, Xu Xiangyu, who is not yet a GM but has exactly the same rating (2549). Here's what happened.
'Probably around here Black went wrong', Kuljasevic said. 'He tried to complicate the position.'
18...Na4?!
Better looks 18...Nbd7 19.Bxc5 Nxc5 with fine counterplay - Black wins his pawn back.
19.Bd4 Rxe2?!
Also not the best according to the Croatian GM. 'Now I get to trap his knight.'
20.b3 Nb2 21.Rfc1
With the nasty threat of 22.Bf1.
21...Nc6 22.Bxg7 Nd3 23.Rc3 Nxf2
24.Nd4 Rexa2 25.Rxa2 Rxa2 26.Nxc6 Kxg7 27.Nb4 Rd2 28.Bxd5
And with a piece down, Xu resigned.
Kuljasevic (31) has not been seen a lot at Dutch tournaments: 'In fact the last time I was here was 15 years ago when I played the international youth tournament in Hengelo, with Erwin l'Ami and Jan Smeets. It's great to be here now', Kuljasevic, 'especially since my wife (Iva Videnova, PB) is also playing.'
18:54 Pruijssers wins
Casper Schoppen resigned his game against Roeland Pruijssers. His knight sac on move 22 looked very interesting, but accurate defence brought the GM from Apeldoorn the point after a few more hours' work.
Earlier, Sipke Ernst beat Tania Sachdev, and Lucas van Foreest got the better of Ivo Maris with a piece sac that did work - like a dream.