Shredder 9 on top of the world

3/1/2005 – It is one of the most successful chess programs of all time, winning countless computer chess tournaments and topping the computer rating lists. Now a brand-new version of Shredder is out, even more powerful than its predecessor. It has a beautiful 3D glass chess set and an interesting retroanalytical feature.

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A short introduction to Shredder 9

By Peter Schreiner

The chess engine Shredder, the work of German programmer Stefan Meyer-Kahlen, has for a long time now been one of the best in the world. No other program has won as many computer chess world championship titles, and in this highly competitive field Shredder has been leading the world rankings (the “SSDF list”) for some time now. All of this is a testimonial to the quality of Meyer-Kahlen’s work.

The top programs on the current SSDF computer ratings list. The following is a list of the top twenty programs. Naturally the brand-new Shredder 9 has yet to be tested, as is the case with the latest update of Fritz 8.0 (which is automatically installed when you log into the Playchess server).

1 Shredder 8.0 CB
2 Shredder 7.04 UCI
3 Junior 9.0
4 Deep Fritz 8.0
5 Junior 8.0
6 Shredder 7.0
7 Deep Fritz 7.0
8 Fritz 8.0
9 Deep Junior 8.0
10 Gandalf 6.0
11 Fritz 7.0
12 Hiarcs 9.0
13 Shredder 6.0 Pad UCI
14 Chess Tiger 2004
14 Shredder 6.0
16 Chess Tiger 14.0 CB
17 Chess Tiger 15.0
18 Deep Fritz
19 Chessmaster 9000
20 Gambit Tiger 2.0

Now Shredder is available in the version 9. If you look back at the remarkable level the previous version achieved you may be forgiven for asking just how much Shredder 9 could have been improved. Well, for one thing it is even stronger than its predecessor. The actual improvements in playing strength were achieved mainly in the area of the king safety. Shredder now evaluates its defensive resources more accurately and, as an additional bonus, recognises more quickly weaknesses in the position of the enemy king. This leads to an improved and more dynamic attacking style.

The graphical interface of Shredder, with rendered 3D pieces

Another clear improvement is the behaviour of the engine in closed positions – always the nemesis of chess programs. Shredder 9 knows better how to play in untactical and blocked positions than its predecessors (and most of its colleagues). In addition even its legendary endgame technique has been further improved and is more precise, due to a better understanding of endgames in which the drawing chances are very high. We would like to mention that the search function, a trademark power point of the program, has also been improved and optimised.

The beautiful virtual reality glass pieces you get with Shredder 9

As we all know the power of contemporary chess programs is so high that hardly any user has a chance of actually beating them. The main use of a newer and stronger program is therefore in their ability to analyse positions and prepare their human owners for competitive chess. And it is in this area that Shredder 9 has improved considerably.


Shredder 9 has a new and improved retroanalytical function, one that is automatically activated when you switch the engine into analysis mode. The retroanalysis functions as follows: when you are studying a position you should try out certain critical lines, i.e. execute them on the board. Then return to the original position and try different alternatives. While you are doing this you will notice that Shredder understands the position better and better, and will of its own accord suggest improved variations. This is because it has evaluated the critical variations very deeply, and actually remembers its evaluation of the positions it has encountered in these analytical forays.

Experts will interject that this is not a new technique, and in fact Shredder itself has used retroanalysis for many years now. The improvement in Shredder 9 is that the program stores the results of previous analysis and integrates these results into the current search much more efficiently. You can test any number of lines to any depth, and you will see how well the program uses the results in its evaluation of the base position. This is especially true in very complex positions.

The best way to explain the retroanalytical function is with a practical example. We do this with a famous game and a very deep move.

Mukhin,Evgeny B - Tal,Mihail [E46]
URS-chT Moscow, 1972

In the above position the move 1...e5 wins for Black. But Shredder, like most other programs, cannot see this immediately. In fact it considers the positions slightly better for White. But if we suspect that 1…e5 may be the winner we can easily verify it with the program. Simply execute the move on the board and then play through the lines that Shredder is suggesting. This is what it looks like:

12/12 0:00 +1.03 1...e5 2.Bxe5 Rxd3 3.Kxd3 Bb5+ 4.Kd4 Na4 5.e4 Rd8+ 6.Ke3 Rd3+ 7.Ke2 Rd5+ 8.Ke3 Rxe5 9.Rac1 Bc6 10.Kf4 (215.605) 219

13/13 0:02 +1.03 1...e5 2.Bxe5 Rxd3 3.Kxd3 Bb5+ 4.Kd4 Na4 5.e4 Rd8+ 6.Ke3 Rd3+ 7.Ke2 Rd5+ 8.Ke3 Rxe5 9.Rac1 Bc6 10.Kf4 (547.538) 221

14/14 0:03 +1.03 1...e5 2.Bxe5 Rxd3 3.Kxd3 Bb5+ 4.Kd4 Na4 5.e4 Rd8+ 6.Ke3 Rd3+ 7.Ke2 Rd5+ 8.Ke3 Rxe5 9.Rac1 Bc6 10.Kf4 (860.237) 231

15/15 0:06 +1.03 1...e5 2.Bxe5 Rxd3 3.Kxd3 Bb5+ 4.Kd4 Na4 5.e4 Rd8+ 6.Ke3 Rd3+ 7.Ke2 Rd5+ 8.Ke3 Rxe5 9.Rac1 Bc6 10.Kf4 (1.464.837) 238

While playing through the above lines Shredder 9 is learning more and more about the position, and when you get back to the starting position you are able to analyse the position properly, with Shredder enthusiastically favouring the black chances:

1…e5 2.Bc5 [2.Bxe5 Rxd3 3.Kxd3 Bb5+ 4.Kd4 Na4 5.Kd5 (5.e4 Rd8+ 6. Ke3 Rd3+ 7. Ke2 Rd5+ 8. Ke3 Rxe5) 5...Kf7 6. Bd4 Bf6 7. Bxf6 gxf6]

2... Rxd3 3. Kxd3 Bb5+ 4. Kc2 Na4 5. Kb3 [5. Kd1 Nxc5 (5... Bf6 6. Bxa7 (6. e4 b6)) 6. bxc5 Bxc5 (6... Rxc5 7. a4 Bc6 (7... Rd3 8. Rc1 b5 (8... Rd5 9. Rc8+ Kf7 10. Rc7 Kf6 (10... e4 11. Rxb7 Ra5) (10... Ke6 11. Rxb7) 11. Rxb7) 9. axb5 Rxb5) 8. Ke2 b5 9. axb5 Bxb5+ 10. Kd1) 7. a4 Be8 (7... Bd7 8. Ke2) 8. Ke2 Bb4 9. Rhc1 Rxc1 10. Rxc1 Bxa4] Tal ended the game with 5...b6 6.Nc4 bxc5 7.Nxe5 cxb4 8.Rac1 Nc5+ 9.Kxb4 a6 0-1.

To work the retroanalysis properly it is important to execute a line and then take back the moves slowly, allowing the program to finish the current play in its search, and not to jump over any of the moves. Give Shredder time to understand and digest. This technique will provide you with a very powerful analytical tool.

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