Have to disagree, I cannot see a slow choke here.

The lad sacs a pawn to climb all over Magnus's f7 pawn and conduct an oppo-Bishop attack.

Magnus defends with guile and hold the attack off.

But here:

click for larger view

If White had played 32.Qf7 (looks OK to me) instead of the 32.Rf7 (the idea of Rf7 being intending to play Rxg7 and Qf7+ this was too slow.) then Magnus would have to leave a heavy piece on the back rank to stop a Queen check.

Then maybe we may have been treated to a slow choke with an inclining of what was to come. But I'm seeing a draw.

32.Qf7 Qd3+ 33.Ke1! Qd8 34.Kf1. Maggie would have to do shuffling about to squeeze a point out of that one. Who knows maybe the lad saw 32.Qf7 and knocked it back because he did not want a draw.

Instead Magnus won it with a short sharp counter attack mating the lad 6 moves after 32.Rf7. He was/is good at that kind of manuever.

Of course there was <17.Bc4?! Nxh3+ 18.gxh3 Qxf3 > when White had to play 17.h4, 17.a4 or put a rook on b1 to maintain an equal position.

Then there was <20...Rf8 21.Rd1! => instead of 20...Re7 (Stockfish 7 - 64 bits POPCNT). Now Black cannot challenge the possession of the 'd' file, at least for a while.

<21...Qg5+ 22.Rg3 Qf6?! 23.Rdd3! > Obvious. 21...Kh8! 22.Rd7! (of course not 22.Bxf7?? Rxf7 23.Qxf7 Qxd1+ 24.Kg2 Rf8! 25.Qc4 Qb1 Stockfish 7 - 64 bits POPCNT) f5! 23.Be2 Qg5+ 24.Rg3 Qf6 = Stockfish 7 - 64 bits POPCNT.

click for larger view

Instead of <22...Qf6?!>, Carlsen should have played 22...Qf4! 23.Rxg6 (or 23.Rd7 Rad8! (if 23...Kh8 24.Qd1 Qxe4 25.Bxf7 Qf4 26.Qf3 = Stockfish 7 - 64 bits POPCNT) 24.Bxf7+ Kh8! 25.Rxd8 (only move) Rxd8 26.Bxg6 Qc1+ 27.Kg2 (or 27.Kh2) Rd1 = Stockfish 7 - 64 bits POPCNT) Rad8 = Stockfish 7 - 64 bits POPCNT.

<23...g5?! 24.Rgf3! > Carlsen is slowly getting on the brink of defeat... 23...Kh8 24.Rdf3! Qh4 25.Bxf7 Qxe4 26.Bxg6 Qe1+ 27.Kg2! e4 28.Rf5 Rae8! Stockfish 7 - 64 bits POPCNT.

<26.Bxf7?! Rad8 > Stronger is 26.Rxf7! Rxf7 (only move) 27.Bxf7 Stockfish 7 - 64 bits POPCNT. Now Carlsen is breathing more easily.

<28.Kf1?!> A strange move. 28.Qc2 followed with Qe2 Stockfish 7 - 64 bits POPCNT.

click for larger view

<30...Rc6?! 31.Rf3 >

<32.Rf5> Hagberg is repeating the position of the 30th move, maybe to gain some time on the clock. There was 32.Rf7! Rd7 33.Qe6! Rxf7 (or 33...Rd6 34.Qf5 Stockfish 7 - 64 bits POPCNT) 34.Bxf7 Stockfish 7 - 64 bits POPCNT.

<32...Rd2?!> Carlsen could also have repeated the position with 32...Rc6, but there was the already mentioned 32...Qd7! 33.Kg2 Qe6 Stockfish 7 - 64 bits POPCNT.

<33.Rf7? Qd3+! => 33.Kg2 or 33.Bg4 Stockfish 7 - 64 bits POPCNT.

<36.Bxb7? g4 (only move)> While trying to survive the time control, Hagberg is collapsing! He removes the bishop so the rook would support the f2/pawn. But there was a better way of doing it: 36.Bg4! h5 (only move) 37.Qe6! hxg4 (only move) 38.Qe8+ (only move) Kh7 39.Rxg7+ (only move) Kxg7 40.Qe7+ = the only move with a perpetual check and a drawn game.

<37.Qe6??> After this, Black mates in 2 moves. White was still holding after 37.c4 (only move) e4! (threat: Bg7-d4) 38.Qg3! gxh3+! 39.Kh2 Qxg3+ 40.Kxg3 Rd3+! 41.f3! e3! 42.Kxh3 Stockfish 7 - 64 bits POPCNT. The bishops are not on the same color and material is equal.