Entries from Stephan Paukner

While being employed 40 hours/week I started to repeat basics in functional analysis in January 2006. In April I started to do some general reading on the subject of time-frequency analysis. I wanted to have the topic of my Master’s thesis set until May, but it took me until August to file it with the working title “Gabor Analysis for Image Processing”. The finish of my thesis had originally been targeted for Christmas 2006, but it soon was clear that it would also take the whole spring of 2007.

With May 2006 I reduced my working times to 26 hours/week, and I quit my occupation in January 2007 as I was granted a 6-month scholarship. Now I had time to do numerical experiments and to actually write my thesis. The scholarship ended by July 2007, and I hoped to have my thesis finished by September. The final work, entitled Foundations of Gabor Analysis for Image Processing, was printed in the mid of November and graded an A. I had my master exam on December 18th and finished my studies with distinction.

Some statistics: It took me 8 months to read up on time-frequency analysis (while being employed). I was in the official status of a graduand for 16 months. I authored my thesis within 9 months.

Today I had my Master exam. We were starting shortly after 11h, and at 11:56h I already had a talk with HGFei in his room. Although I had a few confusions during the “two” exams (functional analysis and measure theory), I ended up with two A’s, so it obviously wasn’t too critical. A funny thing was that K. Sigmund didn’t know what to ask me initially, because the last time he lectured measure theory was about six years ago. Nevertheless, I finished my studies with distinction and earned the academic degree Magister rerum naturae, and thus:

PROJECT ACCOMPLISHED.

In short: Debian lenny’s current libc6 version 2.7 doesn’t work on kernel 2.6.9 with SMP enabled. Downgrade to libc6 2.6 if you can’t change the kernel. You might have to do this on a non-2.6.9 (or >2.6.9) system.

Here’s the story: I use to maintain a duplicate system (on real hardware) with the same package structure as my virtual private server to be able to run through the upgrade procedures in advance. Yesterday, the regular upgrade included a new libc6 package going from 2.6.1 to 2.7. As everything worked well on the duplicate system, I started the apt-get upgrade on the virtual machine. But then dpkg crashed with an “Unknown error 530”. I could still navigate through the file system, but directory listings returned e.g.

and the system slowly began to “fade”. I tried a reboot, but the system didn’t come up again, showing a problem with the quota in the log (“Running vzquota off failed... vzquota: (error) Quota off syscall for id 12345: Device or resource busy”).

I opened a ticket at my provider, and the guy was telling me that the system were completely broken and had to be reinstalled! I was shocked and didn’t believe him. The virtualization engine provides a repair mode, but as I chroot’ed into the mounted root directory of my system, those errors came up again.

I asked the support guy to have a look at that article, but he didn’t seem to find it useful. As it became late afternoon and their support went off duty, I synced the mounted repair directory to my duplicate system overnight (about 5.6GB; I had to install rsync into the temporary system). This should enable me to chroot there and make experiments.

As I finally chroot’ed into that directory this morning, the system was working perfectly! So it couldn’t be completely broken. Another inquiry on Google unveiled this new posting. So the problems are really due to the new libc6 version! It worked on the duplicate system as it runs on kernel 2.6.22, and the virtual server depends on a custom 2.6.9! And that’s also why I couldn’t repair it with their repair system, as it uses the same kernel! On the duplicate system I looked into /var/log/dpkg.log what the previous version of libc6 was, and downloaded the libc6_2.6.1-1+b1_i386.deb from a Debian mirror. I did the downgrade and synced the directory back to the virtual server’s repair directory. I went out of repair mode and—lo and behold!—the system came up again! I also had to downgrade the locale package to match with the old libc6 version.

The support guy was glad that I provided them with a solution for a problem that could emerge for other customers as well. I’ll better stick to Debian ‘stable’ as soon as it is out.

Addendum 12/08: The correct way to fetch previous package versions is via the Debian snapshot archive, as they’re removed from the official mirrors within a short time.

I know a person who studied nutrition science. As he/she didn’t find a job afterwards due to the “uselessness”(?) of that area, he/she appended some time for a dissertation. Having earned the PhD, he/she is now even more qualified as a jobless person (or rather, as a waiter/waitress). I tended to judge this case in a disparaging manner. I mean, c’mon, studying something useless, thus not finding a job, becoming even more professional in that useless area and thus being even less able to find a job. What’s the use?

Now, as I’m finishing my own studies, I really want to justify the use of mathematics by finding a good job. Through all the years non-scientists (e.g. medics(!)) were asking me what one can do with a degree in mathematics. I want to show off that I can choose between several offers all across Europe. This is indeed already starting today with probable possibilities in both Vienna and Munich. But both of them are postgraduate positions. What should I think of that? Am I in danger that someone walks up to me, saying, “Ha ha, so you really can’t make use of mathematics and therefore do a PhD!”?

Up to now I preferred to leer at the industry, as positions are lucrative, mathematics is applied, and mere mortals get in touch with the emerging products (like automobiles, digital entertainment, communication, medical diagnostics). But at least those two mentioned postgraduate positions go into the applied direction as well. So, I’m in no case up to doing some “weird”, abstract, theoretical stuff that no-one makes use of, even if I decide to go for a PhD.

HGFei graded my Master’s thesis with an A (“Sehr gut”, i.e. excellent). (Rumor has it that this doesn’t happen too often.) I thus officially make my Foundations of Gabor Analysis for Image Processing available in the web. The PDF contains hyperlinks, what resulted in a few imperfect pagebreaks, unfortunately. Due to a small supplement before the print the pure content raised to 95 pages, 107 pages including abstract and appendix, and 123 pages all in all.

By the way, a professionally printed and bound version of one’s thesis looks so good and so much different from one’s own test prints! The cover of mine is held in claret leather with a golden imprint of my name. The work took Janetschek more than one week, but the result was worth it. I got six pieces for €32 each.

I’m finished! “Foundations of Gabor Analysis for Image Processing” became the final title, 94 pages of pure content, 105 pages including abstract and appendix, and 121 pages all in all. Currently I’m waiting for the print shop to deliver a bid. Maybe I can hand it in for appraisal during the next week. I won’t publish it in the web before it is appraised.

I can now start preparing for the Master exam. Don’t expect to hear much from me during the next weeks.

Today we wanted to visit a different beach by car. We finally decided to go to the Playa de la Arena at the west coast, as it consisted of black lava sand. The bay was only about 200 meters long, but very neat. We had nice waves, and the water was warm and clear. An advantage of the black sand is that the grains are larger and thus not that clingy, but a drawback is its stronger heat that is hard to bear without slippers. We had ice cream and coffee at a beach bar. In the evening we returned our vehicle.

The next day was our last full day in Tenerife, and we spent it at our beach. One last time we enjoyed the sun and the sea—that’s what I call a November weather! In the evening we said goodbye at a paella with seafood.

Saturday finally was our day of departure. We had to leave our room, but were allowed to stay at the hotel pool. We had a final walk at the beach and shopped some souvenirs. A van brought us to the airport, and the flight started punctually; we were seated in row 13. Unfortunately, it was already dark when we came over the Sahara Desert. We arrived in Vienna at 2.10 in the morning. It wasn’t as cold as expected, and at 3.30 we fell into our bed exhausted.

All in all, it was a fabulous holiday that I really had needed after the weeks and months writing at my Master’s thesis. I had found time to proof-read it, and I was looking forward to finish it. Regarding the Canary Islands, we agreed on getting to know the other islands as well. The next one will probably be Lanzarote in fall 2008.