The Chess Mind

A tablebase is a database for endings with very few pieces, typically running in conjunction with a chess engine like Fritz, that offers perfect play from the starting position through mate (or to maintain the draw, when applicable). Five-piece tablebases (i.e. both sides' kings + three other units) have been available for something like six or seven years (maybe longer), and some 6-piece tablebases have been available for a while as well.

They can be purchased online at an affordable price (around $50), but for those who wish to sacrifice convenience (and perhaps not only convenience - see below), one can utilize the tablebases for free on this website. (Hat tip: Alex Herrera)

It's much, much better than nothing, but you are losing out on one thing by using the online freebie approach (in addition to convenience): the link between tablebase and pre-tablebase positions. Sometimes the link will be obvious: you can clearly see that such-and-such a 5- or 6-piece ending can be forced, but on other occasions it won't be anywhere near as obvious. That could prove significant for those of you engaged in postal chess (in events where using engines is legal); otherwise, probably not - unless you're a serious endgame aficianado.

A few posts ago, I offered this position for your solving pleasure:



It's Black to move, and the readers' task (if they choose to accept it, of course) is to figure out not only what Black should do (not just on this next move, but to provide a variation) but what the proper result should be. When you've got it all worked out, or just want to see the solution, click here.

As mentioned a few posts ago, Aronian defeated Bacrot by a 1.5-.5 score, thereby qualifying for the finals of the ongoing World Chess Cup. That's how things go in a knockout event: some win, some lose, but the tragedy of the match was that Bacrot resigned in what looks like an objectively drawn opposite-colored bishop ending. The drawing tendencies of such endings are well known, and even if they don't guarantee a draw, they do give the weaker side a healthy push towards the safe haven.

But it doesn't work if you resign first! Have a look here, mourn for Bacrot, and learn some lessons - about opposite-colored bishops, of course, but also that you shouldn't resign until you're sure your opponent knows how to win in the final position.

Black to move: what should he do (a variation, not just a single move) and what ought to happen? The answer will be given in a couple of days. (A note for the new and a reminder for the regulars: for your benefit, don't use a computer as an analytic aid; for the benefit of others, don't post your answer in the comments.)