Recent News

[click here to zip down to the schedule of public lectures]


2018 began for me with an absolutely incredible 80th birthday celebration called Knuth80, held in the delightful city of Piteå in northern Sweden. It's impossible for me to thank adequately all of the wonderful people who contributed their time to making this event such a stunning success, certainly one of the greatest highlights of my life.

Here, for instance, is a video made by Dagens Nyheter (“Sweden's New York Times”), featuring their science editor Maria Gunther:

Many of the happenings were also captured digitally in state-of-the-art audio and video, so that others will be able to share some of this joy. You can listen to the music here, and you can watch it here, thanks to Michael Angeletti of Stanford's Media Preservation Lab. His playlist makes it easy for you to watch any individual chapter at will, or the whole set, either in 2D or 3D. Enjoy!

(click for hi-res photo of the participants, by Sagar Savla and drone) (and here are many more photos from Sagar and the Google team)

Check out a cool video

The church in Ontario that will be sponsoring the Canadian premiere of my organ composition Fantasia Apocalyptica in November has posted an excellent “trailer”, which illustrates and explains quite beautifully what I was trying to achieve while writing this music.

A coffee-table book

I'm also pleased to announce the publication of Fantasia Apocalyptica Illustrated, which features the 128 illustrations that Duane Bibby created to accompany the music of Fantasia Apocalyptica.

Many readers have been entranced by Duane's artwork in The TeXbook, The METAFONTbook, and numerous other texts. Now you can see how he has magnificently risen to the challenge of continuing the centuries-old tradition of telling the powerful stories in the Book of Revelation visually, as carried out by great artists such as van Eyck, Dürer, El Greco, Rubens, Blake, etc.

Each image appears together with an excerpt from the Greek text of Revelation, an English translation, and a musical translation, as presented in the world première of Fantasia Apocalyptica earlier this year.

Let's celebrate everybody's full names

One of the delights of Wikipedia is that its biographies generally reveal a person's full and complete name, including the correct way to spell it in different alphabets and scripts.

When I prepared the index to Volume 1 of The Art of Computer Programming, I wanted to make it as useful as possible, so I spent six weeks compiling all of the entries. In order to relieve the tedium of index preparation, and to underscore the fact that my index was trying to be complete, I decided to include the full name of every author who was cited, whenever possible.

None of my textbooks had done this. But in Caltech's library I learned that the Catalan numbers had not only been investigated by Lamé, Catalan, Rodrigues, and Binet, they had been studied by Gabriel Lamé, Eugène Charles Catalan, Benjamin Olinde Rodrigues, and Jacques Philippe Marie Binet. I also had become personally acquainted with Nicolaas Govert de Bruijn, Edsger Wybe Dijkstra, Charles Antony Richard Hoare, etc., so I had lots of good data. My index presented Russian names like Andreĭ Nikolaevich Kolmogorov in a westernized transcription.

Later, when I typeset the index to the second edition of Volume 2, using an early prototype of TeX in 1980, I had the ability to include Chinese and Japanese names in their native form. And by the time the third editions came out in the 1990s, I was also able use Greek, Hebrew, and Cyrillic alphabets, and to present Arabic and Indian names in appropriate native scripts. At last I did not have to rely entirely on transliteration when listing the name of the father of algorithms, Abu Ja‘far Mohammed ibn Mūsā al-Khowārizmī. I even hand-crafted an ancient Sumerian name by using METAFONT to draw the necessary characters of a cuneiform alphabet.

Over the years, many people have told me how they've greatly appreciated this feature of my books. It has turned out to be a beautiful way to relish the fact that computer science is the result of thousands of individual contributions from people with a huge variety of cultural backgrounds.

And at last, thanks to Unicode, the world's alphabets and scripts are present on almost everybody's computers and cellphones. So it's easy now for people who use different writing systems to share their names with each other.

The American Mathematical Society has just launched a great initiative by which all authors can now fully identify themselves, without becoming egocentric and immodest. It's an extension to the Author Profile feature that was introduced some years ago: You can now characterize your name, not only in the customary western alphabets used in traditional AMS publications, but also in any native script.

It's really easy to update your profile: Ed Dunne has given nice step-by-step instructions together with several well-chosen examples. (See the related story by Allyn Jackson in Notices of the American Mathematical Society, January 2018, pages 59–60.)

I strongly encourage everybody to document their full names at the AMS site, as soon as possible. Just go to and identify yourself. That database already contains more than 860,000 authors, so you'll be in good company. Even if you weren't born in a country with exotic characters, I urge you to complete your author profile by including any middle name(s) that you have. Those names shouldn't appear only in a few legal papers and on your dissertation, even if you never actually use them in publications. They are an important part of life. The rest of us shouldn't have to wait to learn your full name until Wikipedia has a page for you.

Of course, if you have only two names, that's fine too.

The middle third of Volume 4B

One of the most important sections of The Art of Computer Programming has been published in preliminary paperback form as Volume 4, Fascicle 6: “Satisfiability”. Here are excerpts from the hype on its back cover:

This fascicle, brimming with lively examples, introduces and surveys “Satisfiability,” one of the most fundamental problems in all of computer science: Given a Boolean function, can its variables be set to at least one pattern of 0s and 1 that will make the function true?

Satisfiability is far from an abstract exercise in understanding formal systems. Revolutionary methods for solving such problems emerged at the beginning of the twenty-first century, and they've led to game-changing applications in industry. These so-called “SAT solvers” can now routinely find solutions to practical problems that involve millions of variables and were thought until very recently to be hopelessly difficult.

Fascicle 6 presents full details of seven different SAT solvers, ranging from simple algorithms suitable for small problems to state-of-the-art algorithms of industrial strength. Many other significant topics also arise in the course of the discussion, such as bounded model checking, the theory of traces, Las Vegas algorithms, phase changes in random processes, the efficient encoding of problems into conjunctive normal form, and the exploitation of global and local symmetries. More than 500 exercises are provided, arranged carefully for self-instruction, together with detailed answers.

I worked particularly hard while preparing some of those exercises, attempting to improve on expositions that I found in the literature; and in several noteworthy cases, nobody has yet pointed out any errors. It would be nice to believe that I actually got the details right in my first attempt. But that seems unlikely, because I had hundreds of chances to make mistakes. So I fear that the most probable hypothesis is that nobody has been sufficiently motivated to check these things out carefully as yet.

I still cling to a belief that these details are extremely instructive, and I'm uncomfortable with the prospect of printing a hardcopy edition with so many exercises unvetted. Thus I would like to enter here a plea for some readers to tell me explicitly, ``Dear Don, I have read exercise N and its answer very carefully, and I believe that it is 100% correct,'' where N is one of the following exercises in Volume 4 Fascicle 6:

Please don't be alarmed by the highly technical nature of these examples; more than 100 of the other exercises are completely non-scary, indeed quite elementary. But of course I do want to go into high-level details also, for the benefit of advanced readers; and those darker corners of my books are naturally the most difficult to get right. Hence this plea for help.

Remember that you don't have to work the exercise first. You're allowed to peek at the answer; in fact, you're even encouraged to do so. Please send success reports to the usual address for bug reports (, if you have time to provide this extra help. Thanks in advance!

The first third of Volume 4B

Volume 4B will begin with a special section called ‘Mathematical Preliminaries Redux’, which extends the ‘Mathematical Preliminaries’ of Section 1.2 in Volume 1 to things that I didn't know about in the 1960s. Most of this new material deals with probabilities and expectations of random events; there's also an introduction to the theory of martingales.

You can have a sneak preview by looking at the current draft of pre-fascicle 5a (55 pages), last updated 03 May 2017. As usual, rewards will be given to whoever is first to find and report errors or to make valuable suggestions. I'm particularly interested in receiving feedback about the exercises (of which there are 131) and their answers (of which there are 131).

There's stuff in here that isn't in Wikipedia yet!

Adventurous people might also dare to take a peek at the current draft of pre-fascicle 5b (“Introduction to Backtracking”), and the current draft of pre-fascicle 5c (“Dancing Links”). I hope to have Volume 4 Fascicle 5 complete and available in paperbook later this year or early next year.

Public lectures in 2018

Although I must stay home most of the time and work on yet more books that I've promised to complete, I do occasionally get into speaking mode. Here is a current schedule of events that have been planned for this year so far:

Friday January 12, room A117, LKAB-salen, at Luleå University of Technology, 1030--1130
Public lecture, “All Questions Answered” (watch video)
Tuesday January 16, room Q1 at the Royal Institute of Technology in Stockholm, 1700--1900
An informal lecture directed to 3rd-year students of computer science, “All Questions Answered”
Wednesday January 17, in the Siegbahn lecture hall, Ångström laboratory, Uppsala University, 1515--1645
An informal lecture directed to undergraduate students of information technology, “All Questions Answered”
Tuesday April 17, 7pm, Rudder Theatre, Texas A&M University
The 2017-2018 Trotter Prize Lecture, “Translating the Bible into music” (view slides)
Wednesday April 18, 1pm, Stephen W. Hawking Auditorium (MIST), Texas A&M University
An informal improvised lecture, “All Questions Answered” (preceded by a public lecture on theoretical physics by Michael Duff at 12:15)
Wednesday October 31, 3:30pm in the Arts Lecture Hall room 116 University of Waterloo
An informal improvised lecture, “All Questions Answered” [watch video]
Thursday November 1, 7:30 pm, in Hagey Hall Theatre at the University of Waterloo
The 2018-2019 Pascal Lecture, Part 1, “Computer Science, the Bible, and Music” [watch video]
Friday November 2, 7:30 pm, in room M3-1006 at the University of Waterloo
Informal discussion of my organ-and-video composition Fantasia Apocalyptica: “Constraints as a source of inspiration” [watch video]
Sunday November 4, 3pm, at First United Church Waterloo
The American premiere of Fantasia Apocalyptica performed by Jan Overduin. (I will be helping to run one of the video tracks that accompany this composition.) [watch video]
Tuesday December 4, 6:30pm, in the NVIDIA Auditorium, Huang Engineering Center
A "Computer Musing" --- Dancing Links [the twenty-fourth annual Christmas Lecture] [watch video]

Click here for the “recent news” that was current at the end of 2017, if you're interested in old news as well as new news.

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