by Steve Lopez

The Mega package of ChessBase 7 includes the 4-CD set of Ken Thompson's five piece endgame CDs. These CDs are also available as a separate set. This week we'll take a look at them and how they're used.

Ken Thompson of Bell Labs created these CDs a number of years ago for a variety of reasons: to help chessplaying computers (which are notoriously bad in the endgame), to settle some sticky questions about FIDE's 50-move rule (it had long been suspected that it was impossible to settle some minor piece endgames in less than the required 50 moves), and basically to see if it could be done. These CDs are not playing programs; they're databases that contain every possible position with a set number of pieces on the board. By using these databases, it's possible to set up a five-piece endgame position and get near-instantaneous information on whether an endgame is a win or draw and how many moves it will take to achieve that result.

Let's take a look at how they're used. First you'll need an endgame position. When we refer to "five piece endgames", we're referring to how much wood is on the board. This means that Kings and pawns are each counted as "pieces" and that there can be no more than one pawn on the board total, e.g. one pawn for one player, not one pawn for each player.

There have been a number of documentation revisions to these CDs down through the years. My set of CDs dates back to 1993 and I had literally no documentation with mine. The upshot is that I don't know what the current documentation looks like, so please forgive me for not giving you references to your current documentation.

I do know that the current documentation refers to installing the contents of these CDs to your hard drive. Please forget that part. These 4 CDs will take up a hideous amount of drive space. You're better off just using the CDs.

Somewhere in your documentation is a list of which endgames are covered on which CDs. My list is inside the jewel case for CD #4. Our first step is to get a five-piece endgame position up on the board in ChessBase 7. You will occasionally run across a master or gransmaster game in which one of these endgames appears. This tends to be relatively rare, so instead of searching for one I'm going to just set up a position on the chessboard.

Looking at my list of endgames, I spot Queen vs. two Rooks. This one looks interesting, as I've often heard players debate whether it's better to have the Queen or the Rook pair.

Going to the Game menu in ChessBase 7, I select "Setup position", which allows me to set up any board position I choose. I'll now need to set up the exact endgame as it appears in my documentation, that is, a Queen vs. two Rooks. When the required pair of Kings is included, we now have a five piece endgame -- there are exactly five units on the chessboard:

I chose what I thought was a pretty interesting position. It's White's turn to move. His King is in its castled position. The Queen is centralized, giving it a lot of mobility. Black's King is in the opposite castled position and his Rooks are separated and don't directly support each other. Note, however, that White can't check Black on the back rank without being captured.

Next I go to the red button that lets me start or stop an analysis engine. Clicking it, I choose "Start CD-Rom 1-4". A new window appears on my screen:

This CD selector window has a number of important functions. First it lets you select the letter of your CD drive. This is crucial for users who have more than one CD drive. For most of us, this will default to the correct drive letter.

Second it will tell you on what CD(s) the endgame in question appears. This information is given in the check boxes to the right of the CD numbers. In this case, the endgame Queen vs. two Rooks is on CDs 1 through 3.

Third, it allows you to tell ChessBase which CD you have in the drive by clicking the appropriate radio button to the left of the CD number.

Once this box comes up, I see that I can insert CD 1, 2, or 3 into the drive to get the analysis of this endgame position. I put CD 1 into my D drive and click the radio button to the left of 1 in the list. Then I click "OK". After a few seconds (during which the CD is accessed), we see the following table appear in the analysis window:

This window contains every legal move in that position as well as the result if that move is played (assuming, of course, perfect play by both players). We see here that 1.Qc4+ is followed by "M3". What this means is that the material balance will change in favor of White in three moves if White plays 1.Qc4+. Translated, this means that White will capture a Rook in three moves, gain a material edge, and transpose into a different endgame (Queen vs. Rook).

There's a long list of moves that end in "M0". This means that the material balance won't change and that the game should eventually be drawn.

The last group of moves contain the mate symbol: "#". Notice that each of these moves is preceded by a minus sign. This means that White will be mated in that number of moves should one of these candidate moves be played.

So I can see that in this position, White's only option is to check with Qc4. I'll make that move and see what happens:

Once the move is made on the board, the CD is again accessed and a new menu of candidate moves is presented. Black's only hope is 1...Kb7 -- anything else leads to mate.

After playing 1...Kb7 on the board, the menu changes again and shows 2.Qe4+ as the only non-losing and non-drawing move, followed by "M2". After this move is made, I see a choice of six moves for Black, all of which lead to mate. 2...Kb6 leads to the longest mate (32 moves), so I make that move on the board. Now I see that 3.Qxh7 leads to a mate in 32 moves, and so on. I can easily step through the remaining moves and see the quickest possible win for White.

This extreme accuracy of analysis is possible because there isn't a chess program generating moves. All that's occurring here is a database of positions being accessed and threaded together in a orderly fashion with the results being reported back to me, the user.

Let's find an ending in which a pawn is involved. How about Rook and pawn vs. Rook?

Like the last endgame, this endgame is also on CD 1. After clicking "OK", I see this:

Dang! Look at this! Despite the extra pawn, it's only a draw no matter what White plays. Interesting...

Frequently in the five piece endgames containing a pawn, you'll see the letter "P" followed by a number. This means that the pawn will promote in that number of moves (again transposing into a different endgame).

Many users ask why six piece endgames aren't on CD. The reason is because of the storage space required. It's not possible to store all the positions for a six piece endgame on a CD. This is also the reason why multi-pawn endgames aren't on CD -- even disallowing underpromotions, each pawn could conceivably promote to a Queen or Knight; each of those choices transposes into a completely different endgame.

These endgame databases have already changed some perceptions about the chess endings. Dr. John Nunn has written a series of advanced endgame books while making extensive use of these CDs. Correspondence players who find themselves in pure piece endings are allowed to consult these CDs by nearly all correspondence chess organizations. Chessplaying computer programs are now taking advantage of these endgame databases as well (Deep Blue had access to them during the second match against Kasparov. Despite what you may have heard, none of these positions came up during any of the games so the information on the CDs was never referenced). Chess writers can find these CDs a valuable aid (I used them myself in a game I annotated in Battle Royale a few weeks ago). Tournament directors can use them as an adjudication aid.

These CDs can be valuable to the average over-the-board player as well. Take a look at the Rook and pawn position I gave earlier. Most average players would play that endgame out. I now know to offer a draw in a similar position and won't lose any sleep over the half-point.

When using these CDs, keep the following abbreviations in mind:

Until next week, happy endgame studying! Have fun!

You can e-mail me with your comments, suggestions, and analysis for Electronic T-Notes. If you love gambits, stop by the Chess Kamikaze Home Page and the Yahoo Chess Kamikazes Club.