There are lots of things an instructor can do during a lesson to help a student, such as reviewing games, answering questions, or having the student do "indicative" puzzles. But I also include three types of exercises which I periodically rotate for a student who has ongoing lessons:
- a de Groot - where the student "thinks out loud" in an interesting position, trying to find a move just as he would do in a long time control game,
- I play an entire game against an intermediate computer "out loud". The student gets to see in "real time" the thinking process I use on each move in order to play a strong game, and
- A DATSCAN - "Dan-Assisted Thinking"
My student and I discussed the many ways to address White's threat of 19.Rxb7. Placing a rook on b8 seemed out because of 19.Bf4, removing the guard (I trust you saw that - if you did not even attempt to refute 18...R(either)b8, that amounts to "Hope Chess"). Nor did we find any reasonable counter-attack.
So that left defensive moves like 18...Ra7, 18...Re7, 18...b6, and 18...b5. My student felt that 18...Ra7 looked odd, but I pointed out that this gets ready to double rooks on the a-file, where White has an isolated pawn. This rook is also flexible in that it can swing over to the center, say Rae7, after a late move of the b-pawn. My student also thought that 18...b5 looked awkward due to the c-pawn, but my experience told me that grandmasters often make moves like this, making the a-pawn backward and letting the pawns guard themselves. However, some lines of analysis after 19.Nb4 had me questioning whether I wanted to put the pawn on b5 after all. My student liked the flexible 18...Re7 and, after a while, I liked that perhaps best too, although I thought that 18...Re7, 18...Ra7, and 18...b5 were all close, with 18...b6 trailing by a bit (but it had some ideas to recommend it, too). We finally both picked 18...Re7, me by just a tiny bit.
It turned out Houdini 3 thought all four moves were reasonable - the spread was only about 0.15 pawns, which means choosing one over the other should not take a lot of time, and is not critical. A fifth move, the strange 18...Nd7, allowing 19.Rxb7 Ne5 was also a computer line). The computer's #1 choice at 26 ply was Anand's 18...Ra7 with 18...b6 a surprising but close second. The computer gave Anand a slight advantage at that point (so did we in our evaluation!), but Harikrishna went on and held the draw.
Over the years, many students have developed a preference for one exercise over the others. Interestingly, it seems spread about even: some prefer a de Groot, others like the games against the computer, and a third group the DATSCAN!