Stephan Meyer-Kahlen

Translated to english by Alexander Schmidt, the original version in german language can be found on playwithatena.com.

When will Shredder finally match the human world champion? The computerchess fans are waiting, and waiting...

Shredder by Stefan Meyer-Kahlen is the undisputed number one of all chess programs (engines). Who can doubt this facts after so many successes Stefan was able to achieve? Six world champion titles (1996 WC micro, 1999 WC of all classes, 2000 WC micro, 2001 WC micro, 2002 WC blitz, 2003 WC blitz and all classes) and many other titles e.g. IPCCC tournaments in Paderborn, 2000, 2001, 2002 or the fourth international CSVN tournament in Leiden 2004. The versions Shredder 7.04 and 8.0 are leading in nearly all important ratinglists. Nevertheless the successful German programmer didn’t take a creative break and continued the developement with Shredder 9.0.

January 28, 2005
On February 7th, Shredder 9 UCI and Deep Shredder 9 UCI will be available here on http://www.shredderchess.com for 49.95 resp. 99.95 EUR / USD. Additionally Shredder Classic 1.2 will be out for 29.95 USD / EUR. All versions will be delivered with an improved version of the Shredder user interface. Shredder Classic 1.2 is a FREE UPDATE for all Shredder Classic 1.x customers, an upgrade from Shredder Classic 1.x to Shredder 9 UCI costs 24.95, to Deep Shredder 9 UCI 74.95 EUR / USD. An upgrade from Shredder 9 UCI to Deep Shredder 9 UCI costs 54.95 EUR / USD.

If you have further question or want to be informed directly on the release please contact: (email address can be found on Stefans webpage)

Troy with Brad Pitt as the warrior “Achilles” was one of the most successful movies of the year 2004. Achilles and Shredder have some things in common!?

After a combat scene (chapter 3, two war portions with thousands of warriors, the best fighters of the two parties face each other). Achilles defeats the fear exciting combat machine of the disliked side.

Achilles stands after this great combat scene in front of thousands warriors of the defeated army and says:

Army leader: "Who are you, soldier?"
Achilles: "Achilles, son of the Peleus"
Army leader: "I will note this name"

Actually "we", the friends of computer chess, can project this scene on your achievement and/or your chess program Shredder. We noted the name Shredder and since Shredder 7.04 also the saying of Achilles "Is that really all?" is, regarding your opposition, applicable. Do you presently think to give your destroying machine a even more meaningful name such as e.g. "Achilles"?

SSDF Ratinglist (In the most other ratinglists the difference of Shredder 8 to the opponents is bigger)

Stefan Meyer-Kahlen, always friendly and willing to give
information, also if he misses a title.
(here at the 12^th Computerchess championship 2004 in Ramat-Gan, Israel).
Stefans program was undefeated and finished 2^nd in this tournament!

Picture source: ChessBase, http://www.chessbase.com
Shredder 9.0 will be also available as "native" ChessBase engine.

No, I think the name Shredder fits very well. As I often told before, the actual reason why Shredder is named Shredder is not because he shall destroy or shredder his opponents. At the time during the naming I was windsurfing in every free minute, and as a student you have very much of free minutes :-) By surfing on the waves one shredders the wave with the finn, this is the true reason, why Shredder is named like that. In the course of the time additionally the second meaning, i.e. that it is shreddering the opponents applied more and more.

Finally Troy was conquered by the trojan horse cunning. Partially your cunning exists surely also in the co-operation with your book author Sandro Necchi (Italy). Do you check book variants yourself or do you leave this part exclusively for Sandro? How often do you exchange opinions and results?

Correctly, I am very satisfied with co-operation with Sandro. Usually Sandro works very independently on the book. However, we often discuss variants and consider, what we can play with Shredder. Meanwhile Sandro knows Shredder so well, he is able to estimate better than myself which variant is good for Shredder and which is not so good. I also make repeatedly suggestions for it, e.g. Sandro, shouldn`t we try variant X or Y. Sometimes it works then, sometimes unfortunately not. Meanwhile the book developed very well and particularly in the tournament book we have a very good system of courses and variants, where we can adjust ourselves flexibly to the opponents and the tournament situation.

During tournaments under the Arena Chess GUI I mainly use the opening book of Harry Schnapp. With the analysis of Shredders lost games, using the "Mainbook" of Harry, I noticed that Shredder does not have a disadvantage out of the book, but later in very opened midgame positions it is tactically susceptible (I cannot find other weaknesses). Comparing the books, I think Sandro tries to avoid such openings. In many other phases of the game Shredder 8.0 appears clearly improved to me compared to Shredder 7.04. I have the impression that the probable increase of the playing strength is nearly compensated due to the determined weakness. As a total result there is an increase of the playing strength with longer times controls and long-term analyses.

Did you weaken Shredder 8.0 tactically to strengthen the positional part? Could you give us in principle a few information about the ideas to increase the playing strength between the Shredder versions mentioned above?

Stefan Meyer-Kahlen:
No, Shredder 8 is not weakened tactically, at least not consciously. Since Shredder 8 there was a completely new search in Shredder, which is extremely selective. As a result Shredder 8 always calculates a few halfmoves deeper than its predecessor. Of course the difference in the search depths of both versions are not simply comparable with each other, however I believe that the new search is much better and there is also clearly more room for further improvements.

For example I continued to refine the search in the new Shredder 9, and there is still no end for the improvements in sight. Of course with a very selective search it may happen that something important is overseen, on the other hand things can be found which you would never find with a classical search or only with multiples of time. However, I do not think that tactics is a weak point of Shredder. The difference between Shredder 8 and Shredder 7.04 is by my judgement also more largely than in Sweden. However, Shredder 9 is coming and I believe that I did a further step ahead.

Regarding the last question it would be interesting to know whether you have more fun with tactical, strategic or positional games. Do you like to watch endgames or do you rather see them as a necessary evil? Or maybe differently: You are sitting in front of your TV, watching a game between two admitted grandmasters. Do you wish an open, tactical or rather a quiet positional game with an open end in the endgame?

Stefan Meyer-Kahlen:
I prefer positional play, thus relatively quiet games without large tactical complications. My idols Capablanca and Karpow played like that, and at the time I was active myself, I played my own games in that way. Of course this transmitted on Shredder though this has changed with the last versions. Shredder is not any more the pure positional player like in past , he can sometimes attack strongly. However I try to let Shredder not become a Kamikaze aggressor. Its attacks should always stand on a relative solid basis. That works very well and I am very satisfied with the current style of Shredder.

With amateur programs it can be observed often that the playing strength drops with the transition from the midgame to the endgame. Not only within this area your chess program satisfies the highest requirements. Was this phase of the game retrospectively the most complex development area in Shredder?

Stefan Meyer-Kahlen:
That is hard to say, all areas where and are very complex. In the endgame there is the fact that to each rule there are always very many exceptions, that’s why this thing is very complicated. Because of Shredders high search depths during the midgame it reaches very frequently with the evaluation the endgame, so a good endgame evaluation is very important also for the midgame. However, I always tried to program Shredder as balanced as possible, thus to cover all ranges of the game evenly. I think that this is also one of the strengths of Shredder, that it is good in each discipline and does not have clear weaknesses.

Your way to the number 1 "was accompanied" by different personalities of the scene. I tell you three names and ask you to give a short comment in one sentence to each name:

Ingo reached a lot with his 3-Hirn and enriches the computer chess scene again and again with new ideas. Ossi is better than its call, he was always very fair to me. Matthias developed a very good company with very good products.

You are not only the author of the strongest chess program, but you also created a very popular GUI. Since some time you also offer your programs on your own website. How many time do you spend on the improvement of your programs and the sales and how can you manage this with your job and your family?

Stefan Meyer-Kahlen:
Shredder is my job, so I spend my whole work time on it. It is true, the sales and the work on http://www.shredderchess.com is very time consuming but it is also much fun. The work on the GUI is a nice alteration to the work on the engine because here you can see the progress very well. When I work on the GUI I want to do some determined things in a day or a week, after that this things are finished. With the engine it is different. Here I work days or weeks intensively and at the end there is no result because the great idea don’t work. Unfortunately sometimes you can see this only after you tried it out. Of course the experience grows with such misses, nevertheless sometimes I need something different to engine programming, that alone would not satisfying to me in the long term. In the meantime I have two little daughters and I want to spend as much time as possible with them. I am lucky to have the office at my home, every time I want I can have an even more beautiful alteration to my work, spending some time with my family.

Before Shredder became the No 1 of the chess programs the strength of the programs was quite even to each other. In the last year the question witch is the strongest program is undisputed under the users. How do you manage to be always a step ahead your competitors and what does Shredder better compared to Fritz and the others?

The work on Shredder is very time consuming, because, like stated above, not everything works as introduced. In the past I had always luck to have additional good ideas. The most effective work on the Shredder engine is not done at the keyboard, it is done in the head. What I mean is that I cannot just sit in front of the monitor saying, so, and now I will improve Shredder. First you need an idea. I don’t have the best ideas at the computer, they appear if I am thinking intensively about it or if I do something totally different and suddenly there is an idea. Maybe this sounds strange but in principle it’s like that. Also important is a good team of testers, they systematically try to investigate the improvements or degradations of a version then. I prefer to work intensively with a few people compared with big teams where the accomplishment of the communication among themselves raises many new problems. It is extraordinarily difficult to find good and reliable testers.

The User community looked forward to Shredder 9, now it is finally available. Where are the differences compared to Shredder 8 and what are the changes in the Shredder Classic GUI?

Shredder 9 UCI , please click on the picture to get an enlargement (173 kB)
Further information under: http://www.shredderchess.com

The new engine has a better evaluation of defending resources and recognizes forthcoming king attacks earlier. This applies to the own and the opponent king. Shredder 9 should also play with a little bit more pressure than it’s predecessor. Hard to win positions in the endgame are now evaluated more drawish than by Shredder 8. Out of that there are many small improvements. New in the GUI are the graphics which looks much more modern now. We also opened a server where at the moment more than 750 GB of endgame tablebases are placed, that means all currently available 5- and 6-men tablebases. The new GUI can access this server directly, so its not necessary to install the tablebases on the local computer to have them available. Shredder is able to evaluate the correct value for every move, also the wildcard analysis works online. The access is such fast, you could think it’s all on your local computer.

Again and again there are chessplayers spending much time with computer chess and specializing on the game against computers. Sometimes such an expert is able to draw with a careful and closed game or even to win with a long term sacrifice against the 800 ELO points stronger opponents. Is hunting ELO points in computer chess rating lists your primary goal of the development of Shredder or are there other aspects like the games against humans?

Stefan Meyer-Kahlen:
The most important thing for me is that Shredder plays good chess. That means I don’t try to optimize Shredder against humans or machines, but simply to teach him good chess. My attitude is that one successfully plays against humans and machines, if one plays good chess.

In the meantime there are some amateur programs with public source code available. Do you look on such sources and can a repeated world champion get new ideas from them? Which program do you consider to be particular interesting?

I didn’t look intensively on a source code. I took a quick look on the source code of Fruit and I directly noticed that everything looks very clean. I also looked inside Crafty, but I didn’t get any new ideas too. I didn’t see more programs but it’s good to have strong programs with source code, as a beginner you don’t have to start from zero and you can look what the others are doing.

In the computer chess forums the prices of Shredder 9 were partly criticized. In the past the multiprocessor version and the Shredder Classic Interface were added as a free bonus to the Chessbase product. With Shredder 9 you changed to usual market prices, the update for Shredder Classic customers is even available for 24,95 Euro. Will you continue this fair update strategy and can you understand the criticism on the prices?

Yes, of course I can understand the criticism if Shredder is suddenly getting more expensive. But in fact the development, maintenance and improvements of a parallel search is very time and work consuming. This wasn’t payable with the past prices. Others found that out earlier than myself. Nevertheless I think that (Deep) Shredder 9 has a good cost-performance ratio. The update from Shredder Classic to Shredder 9 UCI is close the border. But I think this is a special case because some customers purchased Shredder Classic in the faith to get a Shredder with full power. I cannot simply tell them: “Many thanks, and now pay the full price if you want Shredder”. I didn`t think about the prices and updates for the next generation of Shredder yet. I will in any case try to make a good offer to my regular customers.

At that time the Greek warriors went with thousands of ships to Troy. The ship with the black sail (Achilles and his attendants) stated the other ships. Fictitiously we could imagine also the fact that you and not Achilles are standing at the nose of the ship, looking concentrated forward on the open sea. Which logo decorates your black sail?

You may select only one logo, consider the ships of the other engine programmers behind you.

After your boat arrived in Troy and you where able to strike back the first attacks, riders with Chess960 flags appear on the right flank. The army leader comes to you and passes provocatively a scepter. "The ruler of Mainz lent this scepter to me! Would you like to implement Chess960 in your UCI protocol?" Thousands of persons follow the scene in the internet... what’s your answer?

Stefan Meyer-Kahlen:
So far I didn’t implement it :-)
However, in the summer a Chess960 tournament for computers will take place in Mainz. I am not averse to participate there. If I will do so, of course the engine, the GUI and the protocol will be extended. However it has still not a very high priority for me.

For me a free protocol means "compatibility". Compatibility provides animation! Martin Blume (arena programmer) likes the 6 UCI II extensions a lot. Very interesting is among other things the possibility of weakening Engines by ELO. Unfortunately this option is not realized by an engine programmer yet. Did you implement it in Shredder 9.0 and/or did you give Shredder Classic 1.2 full UCI II support?

Yes, sure, starting from Shredder Classic 1.0, GUI and engine support all extensions. By the way, the extensions were developed in endless discussions with other programmers and were actually many more time consuming than I had planned. I would not call the extensions UCI II, they are conscious (nearly) completely up- and downward compatible.

Stefan, it does not really make sense to develop a third engine protocol for Chess960. UCI offers itself for Chess960 and many persons from the Chess960 group are united in this question. It would be possible to create an own Chess960 engine protocol but must that really be? Each further protocol would lead only to a further uncertainty by the users. It would be nice to have a UCI III with Chess960 extensions!

Would it be acceptable for you, if another programmer develops UCI III with Chess960 extensions and/or embed the specification of Chess960 in the UCI III protocol?

Stefan Meyer-Kahlen:
I think that already much people thought about an extension of UCI for Chess960. If I will do an extension, I will discuss these for sure with people, which already thought a lot about this topic.

Would you presently again do the daring decision to create an engine protocol? Please consider your whole temporal expenditure, which you already took on this matter. I would not like to know at all, how many emails you answered about UCI!

Right, like I described above I did spend very much time in UCI, much more, than I had originally thought. However, I think that the work was worthwhile. I need a good protocol for the connection of my GUI with my engine, UCI is very suitable for this. But I am glad that there is now such a protocol and I do not have to sketch a new one.

You cannot sleep, you drag yourself in the middle of the night to your PC because a new idea does not disappear from your thoughts. You turn on the computer and a elf welcomes you on your screen?! She speaks to you:

"Stefan, you please thousands of people with your activities in computer chess. I will now fulfil one of your desires for you"

While deleting your recycler because of security reasons the computer crashes with the following message:

With the enormous playing strength of Shredder, surely many promising ideas will land fast in the recycler. It is no longer comprehensible for the majority of the users that you can still improve Shredder at all. I could admire now your recycler for the first time with this message and the little trick by our elf. Does the reality look really like that? How big is the proportional portion of the ideas, which dissolve in air? Of course you can also tell us what you would have wished by the elf :-)

It is not such dramatically, but, as already mentioned above, many ideas are for the recycler. However, it is never completely senseless because with the time I got a good feeling what is working and what is not. That is of course not completely correct all the time but I can sift out many ideas without large danger before, and I can concentrate on success promising ideas. The trick when wishing is not to tell what the wish was, right? If I had really a desire, it would be surely nothing from the computer chess area, because there are clearly more important things in the life and in the world.

Frank spoke about the advantages of the UCI protocol, keyword „compatibility“. Many users wish the unrestricted use of the favourite engine under the favourite GUI. Doesn’t the use of the original opening book belong to this? Is there a little hope for us that the Shredder engine can access the fantastic opening book by Sandro Necchi also under other GUI’s in the future?

I got lately many inquiries regarding this which I cannot ignore. However, when converting a book problems arise again and again, since all book formats do not support the same things. But I am already thinking about it.

The fascination in computer chess is based among other things in the constant fight of best humans against the best machines. But in the known events in the past mostly Fritz was fighting on the side of the machines. Why wasn’t there a match between Garry Kasparov and Shredder in the past, and how are the chances for such a comparison?

Stefan Meyer-Kahlen:
It is not my decision whether Shredder gets such a match or not. I cannot do anything more than to create an as good as possible engine. If Kasparov want to play against another program, he is to do that. Some time ago it was a large desire of me to get such a match, meanwhile I am thinking differently. It would be nice if Shredder gets such a match but I don’t care if Shredder doesn’t.

Against humans Garry Kasparov is dominating, against machines he had because of his offensive style many problems in the past. Couldn’t a grandmaster easily dominate the machines with a consequent Anti-Computer-Strategy or can a good opening book or other techniques prevent this? How is Shredder prepared for the fight against humans?

Stefan Meyer-Kahlen:
A Human cannot dominate the machines anymore, that’s for sure. A very good human player can play for a draw with much discipline, but if he want to win the risk to lose is extremely high. Shredder plays good chess, that’s the best preparation against humans and other machines.

The chess programs get, because of improved hardware and new programming ideas, stronger and stronger. At the risk you have to answer this question frequently: Will the best programs be beatable for humans in the foreseeable future or will there be a new generation of Grandmasters, growing up with the machines and playing more successful against them?

Stefan Meyer-Kahlen:
Both will happen. The machines will become stronger and stronger and they will defeat the humans sometimes in the future. The younger Grandmasters will understand the computer play better but at the end it will not help them very much.

Many thanks that you made yourself available for this interview and thanks for the interesting views of your thoughts and the development of Shredder. Before you are now going to buy the Troy DVD: Is there anything more you want to tell your fans?

Stefan Meyer-Kahlen:
I didn’t see Troy yet, unfortunately visiting the cinema isn’t on my list with two little children.

Further publication of this interview is allowed and wished as long as full a indication of the sourse is made:

Furthermore one condition is the complete casting. (e.g. in printed media)
Frank Quisinsky and Alexander Schmidt, Schweich, den 03. Februar 2005.