Have computers changed chess openings?

[Babelardus]

Could Magnus Carlsen defeat a computer with a handicap? Say the computer was down a pawn. A knight?

The most recent handicap games against a top-level player were against Hikaru Nakamura (currently world #6) earlier this year.

The handicaps were pawn-and-move (Komodo played Black and without one pawn), pawn (Komodo played White and without one pawn), exchange (Komodo played White without a rook, Nakamura played Black without a knight), and 4-move (Nakamura played White and played 4 moves in a row before Komodo started to play).

The first three games were drawn and Komodo won the fourth. All games are at the link I provided earlier and are fun to play through if you are interested in top-level handicap chess.

Wow... a 1-2 pawn handicap weakens Komodo by about 500 ELO. It's possible to draw, and maybe, win a game. However, it doesn't give a zilch about a 4 move disadvantage. It just keeps the position closed until all it's pieces are developed, and then starts to play a normal game... crushing you by an advantage that creeps up by 1/100th of a pawn for 30 moves. I wonder how many handicap moves a player like Nakamura would need to actually win such a game. In the last game, Nakamura actually is a paw UP, and still he's 6 pawns DOWN. That's a 7 pawn (more than a rook...) positional advantage for Komodo.

Clearly, there is a lot of improvement that can be made by humans when playing chess, but I wonder if anyone ever will have the capability to obtain an improvement that large.

[Revilo]

Wow, that odds match between Komodo and Nakamura had gone completely unnoticed by me up until reading this thread. I've just browsed through the games. It's pretty much business as usual-as soon as the position opens up, the engine tears the human apart. It seems that a least knight odds are required, and even then I wouldn't put top money on the human.

As for the original question about openings having been put out of use by engine use. The question does not have a straightforward answer. No well established system has been refuted, for starters.

But there are a lot of subvariations that cannot be played anymore against an opponent who knows that he is likely to face it and thus is willing to prepare. This mostly applies to several cut-throat variations in the open Sicilian.

Apart from that, I have the impression that even the main line Najdorf Sicilian (https://en.m.wikipedia.org/wiki/Sicilia ... _Variation) isn't being used much at the top level nowadays. Economical reasons are most likely an explanation - the work required to stay ahead of opponents is huge, not to speak of the risk of mixing up something and falling apart right away.

[gowan]

Since computer programs are significantly stronger than human players, the question as to whether an opening line has been "refuted" is a moot question. For humans playing against the top programs in chess, and soon in go, the human players will lose no matter what opening line they choose. Historically, refutation of opening lines was the same thing as saying that the opponent is guaranteed an advantage from that line. It might be correct to say that, for humans, chess has been refuted.

[dfan]

Chess players don't consider it moot. For an opening line to be "refuted" means that the opponent can achieve a clear advantage when both players are competent and of equal skill. This might be human against human or computer against computer. A line is not refuted just because a grandmaster could eventually win from that position against an amateur, or a computer against a grandmaster. It is still very relevant to human-human play when a computer finds a clear refutation to a line, since (good) players learn the refutation and the followup play, and it becomes very dangerous to play it in tournaments.