E. Kowalski's blog

         Comments on mathematics, mostly.

Archive for Computers


P. vs. NP and all that

Filed under: Computers,ETH,Mathematics @ 17:46

The coming Monday, Tuesday and Thursday, A. Wigderson will be in Zürich to give the yearly Pauli Lectures, with a general title of “The computational lens”. It seems to be the best possible time to share the following insight

from one of my family’s Minecraft sessions…



Filed under: Computers,Language,Literature @ 19:06

One of the nicest things about Linux (and Open Source software in general) is that new versions often offer clear measurable improvements on the previous ones. And another is that this does not usually require abandoning whatever might have been worth keeping from other computer-ages. In particular, if one has very old software, there’s a good chance that one can still keep them working, even if they are written for a completely different operating system, through the wonders of emulation. In my case, this applies to Windows 3.1-era dictionary cdroms, and to Motorola 68000-era Mac software.
Recently, I had somewhat lapsed in performing the necessary tweaks to make these old programs work on my laptop (a decidedly modern 4-core Lenovo), but on upgrading Fedora, I decided to try again. It’s quite amazing that, through the wonders of Wine, I can enjoy again the Grand Robert de la Langue Française


(originally available for MS-DOS and Windows 3.1) as well as the American Heritage Dictionary

(though I use the O.E.D instead when I’m connected to the ETH network). The Grand Robert is the best anti-pedant tool I know against so-called défenseurs de la langue française; it usually reveals that their favorite anglicisms are perfectly French (e.g., opportunité, in the sense of “occasion, circumstance”, which goes back to 1355 in French, and is at least as French as Baudelaire…)

I’m even more impressed to be able to boot the equivalent of my old Mac SE30,

and thereby play with, or recover, the old files I used to work with during my PhD thesis and before. (In fact, the emulator boots in something like 1.5 seconds on my laptop, which is about a hundred times faster than it ever did in real life…) Afficionados will note the realistic 512 x 384 resolution of the screen.



Filed under: Computers,Mathematics @ 19:47

I have a weakness for programming languages. Given the time and opportunity, I would gladly learn a new one every few months, and apart from TeX (in its programming language guise) and Perl, which I both abhor because of their atrocious syntax, I usually find something to like in all languages. I have even composed what may be the only illustrated children story ever written in pure Postscript (“The story of the triangle that grew”.) But my favorite language remains Lisp, especially in its Common Lisp variant, which is the one I know best (with Emacs Lisp a close second). I was therefore saddened to learn today of that the creator of Lisp, John McCarthy, recently passed away.

(Interestingly, according to Wikipedia, McCarthy had a PhD in math under Lefschetz…)


Inkscape and LaTeX

Filed under: Computers,Mathematics @ 16:10

I’m a great fan of the open-source vector-drawing software Inkscape. Although I don’t have that many figures in my papers (or notes), I’ve found it quite accessible and easy to use to produce high-quality results. And just yesterday, as I wanted to add a picture to my notes on expander graphs, I learnt of a very nice new feature: from version 0.48 onward, one can select a special option when saving a drawing as PDF that creates an auxiliary LaTeX file, which can then be incorporated in the source file (using the standard \input command) and which contains (and processes) all the text found in the drawing. This makes it very easy to add arbitrary LaTeX (math) formulas with Inkscape.

For example, the SVG file

produces a PDF file

and a LaTeX file, and when the latter is inserted, the document reveals the beautiful picture



Filed under: Computers,Mathematics @ 19:13

On my page of notes and unpublished writings I’ve just added a very old preprint of Ph. Michel and me, after realizing yesterday that I wanted to point out something in it (that was never actually published) to a student, but that I couldn’t locate the TeX file for it anywhere. Fortunately, Philippe had a better-organized archive…

Here, “old” means that it goes back to 1997, which is a time when I used OzTeX on a Mac with 24 megabytes of memory and a 400 megabytes hard drive to typeset this file (and my PhD thesis). And old also means that the TeX file is in LateX 2.09 format… (I was actually surprised that the modern LaTeX 2e was still able to compile it with no difficulty whatsoever).

But when it comes to antiquated computer technology and old writings, my proudest exhibit is my very first publication:

This goes back to January 1986, and is the complete listing of a wonderful piece of computer software, published in the French periodical Hebdogiciel. Back in those days (when I suspect that some of my readers were not yet born), the typical storage equipment for a “personal computer” was a standard K7 tape, or a single 3 inch (non)floppy drive. Computer networks for personal use did not really exist, and there were a few dozen mutually incompatible computer brands, each of which sold with basically no software except a Basic programming language. In Hebdogiciel, every week, one listing was printed (and readers were supposed to type it if they wanted to use those programs…) for each of the most popular brands. (In my case, Amstrad; I was the proud owner of the renowned CPC 664). All these programs were sent by other readers like me.

Amusingly, if I remember right, Hebdogiciel would actually pay the authors of their programs (I think the amount paid was measured by the number of lines, hence a tendency — maybe laudable — for authors to incorporate wide expanses of beautifully delineated comments in their programs…)

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