No, not really. Computers still fail due to the horizon effect. It's just that with improvements in hardware, search tree pruning, and extension calculation the horizon is a lot further away than it used to be. I don't think that any algorithm which is based on forward searching will ever be immune from the horizon effect, it's just a question of where that horizon is. I have egotistically coined what I call "Ayler Kupp's corollary to Murphy's Law" which you can find in my forum's header.

I call that effect "engine dithering", when an engine doesn't know what to do and moves its pieces back and forth without any apparent purpose. This typically happens in closed positions when the horizon effect strikes again and the engine can't search deep enough to reach a position where it finds an advantage for itself. And I can only guess that Komodo could not search deep enough to determine that the pawn grab was suicidal.

Another example of a suicidal engine is this game: Aylerkupp / Rybka vs Kutztown46 / Stockfish, 2011. It's initially interesting because Stockfish makes a positional pawn sacrifice with 11...c5 in order to get some counterplay (yes, engines can do that sometimes). After much engine dithering, Rybka retains the pawn advantage for almost 80 moves. But then it comes up against the 50-move rule. Since Rybka evaluated the position to its advantage ( [+0.65] ) after 90...Rc8, it finds a draw result unacceptable and plays 91.b4, sacrificing a pawn. Since after the pawn sacrifice it still evaluates the position as favorable ( [+0.16] ), it's satisfied with the result.

I'm thinking "the suicide effect" could be a bit more common than one might expect from the perceived all-knowing computer.

Though I'm sure it's rare on a total game % basis, I'm wondering what it would be on a lost games %.

Which leads me to the questions.

Assuming not doing the pawn grab draws, what would be the protocol for a computer vs computer draw? Do they have to wait for the 50-move rule or 3-times rep or can a computer offer a draw before hand?

Assuming both computers know White's better around move 109...Bg7 due to the open a5 square and weak b7, better but maybe not that much better. Is it possible for Komodo to play weaker evaluation moves that likely still draw or is its mandate to play the move that may be stronger for a win but more risky?

As far as attempting to answer your questions:

1. I have no idea what the % of suicide moves influence the % of lost games, other than to remark that in a human game a suicide move would referred to as a "blunder" and is understandable in many circumstances like time trouble or simple "humanness". So I wouldn't know how to characterize a computer's move as a "suicide move" or simply a "blunder" and calculate the %.

2. The protocol for a computer vs. computer draw or a computer resignation is typically not implemented in the engine but in the GUI. For example, when using the Arena GUI in engine vs. engine matches, the GUI can declare a loss for one side if the evaluation falls below a user-specified value for a specified number of consecutive moves (typically 3). The GUI can also adjudicate a draw using tablebases, when a specified number of moves are played with the evaluation at [0.00], or simply when the game reaches a specified number of moves. And other GUIs will likely have different criteria.

3. I think that all engines will play the move that they evaluate as best in any given position; they won't play a move that they consider inferior in an attempt to swindle an opponent. <Sally Simpson> and I have had several discussions along these lines and whether it would be worthwhile to have a "swindle mode" where, in a lost position, an engine might play a move evaluated to be inferior in an attempt to induce its opponent to make an inferior and possibly losing move in return. My opinion is that it is probably not worthwhile to implement and use such a "swindle mode" against a computer opponent unless the move results in an advantage that could not be perceived without a very deep search, and that the engine is able to search deeper than its opponent.

4. I don't know what version of Komodo was used in the 2015 WCCC but the latest version (9.1) evaluates the position after 109...Bg7 at [+0.48], d=35, so it assessed that White was somewhat better. Putting the Black king on c8 and the Black LSB on e8 results in an evaluation of [+0.49], d=36, essentially the same.

Thanks for the terrific information. I don't have a chess computer program so I'm probably extremely uninformed.

I had no clue about this "anti-drawing" parameter. It may explain some of those rare occurrences when a computer forgoes a likely draw for more sharp play. It seems that parameter is very human. I'd guess when set to an extreme it might forsake a lot for the "pride" of not drawing a weaker opponent.

This comes into effect when the engine is trying to decide which move to make. Normally it will choose the move that results in the highest evaluation of the position. So if the engine evaluates its position to be at a slight disadvantage, it will select a move sequence that results in a draw by repetition if there is one. But if the anti-draw parameter is other than zero, the engine will think that a move that results in a draw by repetition has a lower evaluation than a move that results in an evaluation that is only slightly inferior (negative) and so reject the drawing move.