Monthly Archives: December 2020

Long live opalstack!

I finished migrating my webserver from webfaction to opalstack. For those wondering if this is a good idea, I would recommend it. It was fairly painless.

Having said that, I did lose a little data: exactly the one post that warned that I was moving! I don’t know how this happened, but after checking this is the only thing lost in the transfer.

But in total, migrating and setting up the various websites (static, php, wordpress, flask) was straightforward, although nontrivial. Migrating email and ensuring that I had no email downtime was more important to me, and more annoying.

In total, the accounts I manage had on the order of 10k email messages, which is not very many in the big picture. Creating new matching mailboxes and mailusers was very easy, but somehow the transferring of the messages was a surprisingly time-consuming endeavor.

I also learned that complete DNS propagation for my email took about 41 hours. Well actually, google/gmail took 41 hours, and every other email service detected the change within 23 hours. I suppose this has something to do with the vast multitude of caching that google/gmail must do. But it was very easy (though slightly annoying) to manually sync email for the whole time. (Actually, I’d expected it to take up to 72 hours, so this wasn’t so bad).

Long live the opalstack.

(As the one post where I warn about migration disappeared, I’ll note that I moved because godaddy bought webfaction and have been changing the service/running it into the ground. I liked webfaction before they were bought, and I’ve used them for almost 10 years. Hopefully opalstack will stay stable for many years to come.)

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Talk on computing Maass forms

In a remarkable coincidence, I’m giving two talks on Maass forms today (after not giving any talks for 3 months). One of these was a chalk talk (or rather camera on pen on paper talk). My other talk can be found at https://davidlowryduda.com/static/Talks/ComputingMaass20/.

In this talk, I briefly describe how one goes about computing Maass forms for congruence subgroups of $\mathrm{SL}(2)$. This is a short and pointed exposition of ideas mostly found in papers of Hejhal and Fredrik Strömberg’s PhD thesis. More precise references are included at the end of the talk.

This amounts to a description of the idea of Hejhal’s algorithm on a congruence subgroup.

Side notes on revealjs

I decided to experiment a bit with this talk. This is not a TeX-Beamer talk (as is most common for math) — instead it’s a revealjs talk. I haven’t written a revealjs talk before, but it was surprisingly easy.

It took me more time than writing a beamer talk, most likely because I don’t have a good workflow with reveal and there were several times when I wanted to use nontrivial javascript capabilities. In particular, I wanted to have a few elements transition from one slide to the next (using the automatic transition capabilities).

At first, I had thought I would write in an intermediate markup format and then translate this into revealjs, but I quickly decided against that plan. The composition stage was a bit more annoying.

But I think the result is more appealing than a beamer talk, and it’s sufficiently interesting that I’ll revisit it later.

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