Opening selection TCEC 19 superfinal

 Here are Jeroen Noomen's comments on the opening selection for the TCEC 19 superfinal:

"Here are the most important details regarding my selection of the openings for the TCEC 19 superfinal:

• After the TCEC 18 superfinal two bonus events were played with short, balanced openings. The result was predictable: more than 90% draws and a lot of games where evaluations stayed close to 0.00 with not much happening. Thus the conclusion is clear: to keep computer chess (and TCEC!) interesting, unbalanced openings with higher book exits are absolutely necessary.
• The TCEC 19 superfinal book was mostly completed in April 2020. After seeing the TCEC 18 superfinal in which there were a couple of busted lines, I decided to do a thorough quick check with Stockfish and Leela on the TCEC 19 superfinal book. This led to the removal of a couple of busted lines on July 3rd, which were replaced by more proper lines. Normally I don't change books anymore when they are finished, but because of the TCEC 18 superfinal experience I decided to act and make reparations. 
• As usual, all important openings will be played; just like in the TCEC 18 superfinal there will be a lot more risky opening lines compared to TCEC 16 and before. However, the TCEC 19 superfinal book will be less extreme than the TCEC 18 superfinal book, which was a bit too much in my opinion.
• The chosen lines typically have a length between 1 move and 13 moves; there are four lines which are only 1 move (i.e. the first white and black move), there is one line with 14 moves of book. Of the 1 move lines one is rather topical, the other three are unbalanced.
• A few hints: in this superfinal we will see the return of the Grünfeld Indian, an opening that always causes me headaches, as most lines are too drawish for TCEC superfinal purposes. Of course the King's gambit is present as well. 
• Average move length is 6.44 (which is 0.6 lower compared to the TCEC 18 superfinal)
• There are sharp lines in the set, as well as positional lines, more complex lines, lines with opposite castling ("SALC", i.e. short and long castling), dubious lines, lines with an imbalance in material and gambits; my personal favourite lines are #12, #17, #20, #28, #36 and #48 through #50.
• As TCEC is also followed by strong grandmasters and we also see TCEC games mentioned at theoretical websites as https://www.chesspublishing.com/content/, I now also prefer to include some theoretically important lines, to see if the engines can produce interesting novelties. 
• The complexity of a position and the book exit evaluation are the most important selection criterions. Book exits have been checked with classical Stockfish (development version, contempt = 0) on a 16 core Ryzen system and Leela Chess Zero v0.26.0, with the net that played in the TCEC 18 superfinal. As mentioned above, book exits are significantly higher compared to season 16 and before, to keep the games interesting and avoid boring draws. Nevertheless, there are also some lines with a lower book exit, especially in the theoretically interesting lines.
• As I mentioned in my article about the TCEC 18 superfinal book, I now prefer 1-0 1-0 results over two straight forward draws. In effect the result is the same: 1-1. But two wins give more excitement. 
• I have avoided positions that could lead to many exchanges and/or have a high draw rate in correspondence chess (I prefer draw rates of 50% or less), as well as positions with symmetrical pawn structures and positions that could lead to easy wins for the side with an advantage. The last aspect is becoming more and more difficult, with strong hardware, a long time control and engines being so strong. Of course risky lines means that the chance of 1-0 1-0 is increasing.
• What do I expect? Frankly speaking I don't know, now that Stockfish also 'went NN'. So I am a bit cautious: 20 wins is the minimum I'd like to see. In any case: enjoy the superfinal!

ECO code distribution

ECO A: 11 lines

ECO B: 14 lines

ECO C: 11 lines

ECO D: 4 lines

ECO E: 10 lines

Move length distribution

1 move: 4 lines

2 moves: 1 line

3 moves: 2 lines

4 moves: 10 lines

5 moves: 6 lines

6 moves: 5 lines

7 moves: 4 lines

8 moves: 6 lines

9 moves: 3 lines

10 moves: 3 lines

>10 moves: 6 lines