Advogato blog for vicious

Diffy Qs notes at 20000 downloads

Mon, 6 Feb 2012 01:29:38 GMT

So the differential equations textbook just reached 20000 downloads from unique adresses. The real analysis textbook is close behind (despite being a year younger) at around 19200. The rate is growing, it started out at around 200 per week for both in the fall and is now pushing 400 a week. As an overwhelming percentage of the hits come from google I think google might have ranked the pages higher. So if you want to help out with the project of free textbooks: link to the books on your blog, page, whatever. And press those social buttons on the page, I guess that also does it.

It’s also interesting to see how ipv6 is doing. So far, 82 ipv6 adresses looked at the real analysis book and 43 for the diffyqs. As ipv6 was active for about half a year on the server, it’s still a very tiny percentage. There were about 6-7 thousand ipv4 addresses looking at the diffyqs book during that time frame and about 8-9 thousand for the real analysis book. But at least someone is using ipv6 (if I could get an internet provider that offered ipv6, I’d use them, but I didn’t find such in Madison).

When will the beheading start

Sat, 21 Jan 2012 23:29:18 GMT

It is always good to know when will other people want to cut off your head. Let us look at when were most heads cut off: that was probably the French revolution. OK, what made people want to cut off other people’s heads? Extreme inequality. OK, what was the Gini coefficient? Well, one estimate is 59 [1]. OK, so if we look at the US Gini coefficient it seems to be rising approximately linearly since 1980. In particular, US Census Bureau (via Wikipedia [2]) has the following data:

1980	40.3
1990	42.8
2000	46.2
2009	46.8

Let us do linear regression to obtain:

2020	50.0
2030	52.4
2040	54.8
2050	57.1
2058	59.0
2060	59.5
2070	61.9
2080	64.3

So, I guess people will start trying to cut other people’s heads off around 2058. We’re all safe till then.

[1] Christian Morrison, Wayne Snyder The income inequality of France in historical perspective, European Review of Economic History, 4, 59-83.

[2] Wikipedia.org, Gini Coefficient.

Biking

Fri, 20 Jan 2012 22:29:37 GMT

So, it was -15 celsius (barely positive farenheit) and snowing this morning, actually it’s still -15 and still snowing. Surely only a complete moron would bike to work today. Actually the ride was pretty good. Yesterday it was -18 and I think I can tell the difference (though it was not snowing). The downside of biking in this weather is that the gears are refusing to shift. The levers just sort of stick and nothing happens. Fortunately, I’m in a reasonable gear right now.

Another downside is that I have these cool hybrid tires on the mountain bike. Sort of like road tires with spikes only on the sides, which is reasonable in terrain and much smoother than regular mountain bike tire on the road. They were really good at the UCSD campus (San Diego) where I’d go off road often and it never snowed. Because they kind of suck on snow.

Newspapers will be half the size on wednesday

Tue, 17 Jan 2012 23:26:37 GMT

With the Wikipedia blackout, what will journalists do? There will be a lot less in the wenesdays edition, though on the plus side it will have a better chance to be correct or at least original. Also, all school essays that were due wenesday will be turned in a day late.

New chapter in real analysis notes

Sat, 19 Nov 2011 00:04:13 GMT

I finally posted a new version of the real analysis book with the new metric space chapter, it weighs in at 192 pages now (with 12pt font though). It also fixes a now record number of errata; though my standard for what is an erratum rather than just a simple obvious typo has dropped slightly. One thing that makes me feel better about errata is that it seems Rudin’s 3rd edition of principles still has some errata that is essentially the same as what I did (independently, not that I really worry about taking credit for errata:).

The differential equations book nowadays seems to be hitting fewer and fewer problems: 6 errata in the past year, 2 of which have been in new stuff added before the summer. This is despite several people using the books and one ongoing partial translation. So I guess they are rather “correct” by now.

My goal right now is to get them to be correct rather than perfect. So I haven’t really been reordering things or rewriting things that could be improved. I’ve been at most doing small improvements in exposition. The main thing is that I want to spend time doing other things too of course:)

Wisconsin

Sat, 27 Aug 2011 03:04:38 GMT

On the way to Madison we were trying to see what the Wisconsin ski resorts look like. Seems like the toughest runs are rated double-black-bunny.

No more overheating

Tue, 12 Jul 2011 20:06:21 GMT

Pissed off about the CPU overheating, I wrote a simple daemon. It monitors the core temperatures and sets the cpufreq governor to powersave when temperature in either core is above 90 deg celsius, and sets it back to ondemand when it gets below 75 in both cores (those numbers I pulled out of my ass, they might need tuning). It simply polls the temperature every 2 seconds. There is no configuration or anything, simply change code and recompile. It’s all the neurons I’m willing to commit to this problem.

Yes I know performance might suffer since the CPU can go even further, but I don’t care about performance, I care about the machine not turning off randomly. I guess ondemand is actually better poewr (and heat) wise when everything is normal, but when then heat is high, powersave does come to the rescue.

Here is the code for those that want to do something similar. You might need to modify it heavily. I called it noverheatd.c, I simply compile the thing with something like gcc -O2 -Wall noverheatd.c -o noverheatd, placed the resulting binary in /root and then in /etc/rc.local I added /root/noverheatd &. The parts that need modification is set_policy where you need to set the number of cpus your kernel thinks it has, and then in the main loop you need to set the right coretemp paths for all the coretemps you have. I had to run “sensors-detect” as root from the lm_sensors package to obtain those guys.

Books

Mon, 27 Jun 2011 23:05:01 GMT

About a week ago I finally added those new extra exercises I’ve been promising on the webpage (almost 150 new exercises) to my differential equations book. These are now with solutions. I did not want to add solutions to existing exercises. I still feel that it’s better to not have solutions. But I guess having some exercises with solutions does make the students feel better. Plus it seems this was an argument against using my book in at least department (not enough exercises and no exercises with solutions). So there. Some of the new exercises are interesting, many are just simple plug and play exercises to get students going. I’ve added all of them as exercises numbered 101 and above so that I would not change existing numbers. I suppose the “even/odd” thing is the common theme, but this has the added advantage that I can have fewer exercises without solutions.

As for the real analysis book. After having taught with Rosenlicht at UCSD (because my book doesn’t have metric spaces), I decided I will use my book at Madison this coming fall. This requires that I write up some metric space stuff. So I will be adding a Chapter 7 to the book. It will probably not be completely polished by the fall, so I might keep it separate even for the fall and only add it once all the bugs are caught after teaching with it. The plan is to do first everything on the real line and then do metric spaces. I found that metric space stuff was a bit too abstract for the students if I jumped right in. It might be better to do first sequences and continuity with real numbers only. I will skip some other material such as series though, and cover other material more lightly, due to time constraints. As for other news on the book: It is now (in slightly modified form) the standard book at University of Pittsburg.

We have to kill you to save you

Mon, 27 Jun 2011 22:04:29 GMT

This is funny in a very dark sort of way. Let’s do some numbers: Suppose that after some time about 100 people a year die from extra radiation exposure due to all these scanners. That’s a fairly low number, it would be impossible to
even notice this number from the cancer statistics. Given the millions of people that get scanned every year and that spend sufficient time near those scanners, that’s a tiny percentage. Now let’s see, let’s suppose we take the last 50 years of plane travel before 2001 and we notice that number of people killed in terrorist attacks including 2001 is a little more than 3000. That’s about 60 a year. Let’s suppose that no terrorist attack ever happens again (yeah right). Still we’d be killing almost twice as many by our security measures.

I wish my granddad were alive, this is what he did (nuclear hygiene). It would be nice to ask if 100 is a reasonable estimate.

Army of math

Mon, 27 Jun 2011 18:05:23 GMT

Doing math is like being in the military it seems, at least if you want to be in the academia. You don’t really get much of a choice where you go work, you sort of get an assignment. Especially in this job market. The idea is the following: you send about 100 applications (if looking for research jobs), then about 50 of those you won’t consider anyway, though you don’t know that when applying. Then out of the next 50 you might get some interviews, and some of those you decide you don’t want to go to. Then you get an offer from a place you didn’t interview at, for a postdoc, for which you didn’t really apply (actually I got two such offers this year). The whole process takes about half a year, though then you get 2 weeks to decide once you get an offer.

My first job application 4 years ago when I went to Illinois was a bit simpler. I applied to 100 places. 50 of those were tenure-track positions where I had no chance straight out of the PhD. The 50 were postdocs, out of which probably 5 I was a reasonable candidate for since no place will hire a postdoc unless they have a group in your area. Out of that I got two offers around the same time, and one sort of informal offer. Then you pick, and go live in the midwest for 3 years.

So we spent 3 years in Illinois, 1 year in San Diego, next up to 3 years in Wisconsin, then …? Wisconsin will be the 3rd state that Maia will be living in and she’s only going to be 5. So when someone asks her “Where’d you grow up?” Then instead of saying: “We moved around, my dad was in the military” she’ll sat “We moved around, my dad was a mathematician.”

Well at least it will make for a more interesting story. I wish the job market gets better so that I can find a permanent job I like. I know it sounds like whining, since I have a guaranteed job for next 3 years (though it’s also guaranteed I will not have that job in 3 years time).

Academia is one of those careers where you’re well in your thirties before you really can possibly settle down. And before your salary starts reflecting the level of eduction you got. Professors at top schools do get paid well, but it takes a long time. As a programmer, I could be making the amount of money I hope to be making 10 years from now as a mathematician, 10 years ago.

Then you hear someone say “Oh this or that person couldn’t get a job in the industry so he went to academia” … yeah right … that’s the easy way out.