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posts for 2009. (page 1.)

a bit more than one year after gary gygax died, another of the inventors of dungeons & dragons died: dave arneson. rest in peace.

while updating some old posts with photos (just designwise, no content changed), i once again experienced a complete lockdown: the server became incredible slow and was floaded with apache processes, and i had to shut down and kill -9 all apache processes several times to be able to continue to do anything except waiting. this isn’t the first time this happend, but this time i had apache’s logging enabled (waiting for something like this) to see what was causing all the accesses. well, out of the 13.000 logfile entries (ranging over a week, i think), around 3.300 were by wordpress – and 99.9% of these happend in the last few hours, while i was updating the old posts. it seems that every time i updated a post, wordpress accesses all links and images in the post, also the local ones, and downloads them. yes, downloads them – also the big versions of panoramas. and if i’m updating posts with often 10–30 photos, some of them large, this clearly explains why the web server was dying. to put it that way, wordpress dosed itself. (the funny thing is that it did not first use a head first, to see what kind of link this is, but starts with a get to first download the whole thing. after downloading all links and images, it uses head on them.)
anyway. i don’t know at the moment what to do against that.
but another annoying thing is that the blog is loading rather slow. i also decided to see what is causing this. well, it turns out that the old main page was doing 298 sql queries. after disabling role scoper, this jumped down to 34, with loading times more or less the same. but then, i disabled the tag cloud. this just saved one query, but reduced the page generation time from around 10 to 2 seconds. wow. enabling role scoper again (i really need that one), i now have a bit less than 50 queries with maybe 4-5 seconds of page creation time.
well, still far from optimal, but already faster.

posted in: daily life thoughts www
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i was thinking on using latex in maybe some blog entries, maybe here or maybe somewhere else. so i decided to see what existing plugins there are. after a bit of searching, i stumbled over wp-latex, which is apparently also used by wordpress.com. unfortunately, it has a kind of clumsy syntax (“$latex formula$” instead of simply “$formula$”). and it has no support for display style formulae, i.e. something centered in its own line, as opposed to inline formulae which try to fit neatly into the text.

so i tried to fix that. and it worked out, and i can still use a “normal” $ by appending a blackslash in front of it. well, euler's identity is e^{i \pi} + 1 = 0, as simple as that. if you want to see something more complicated:

let K be a number field or an algebraic function field. then, we have the following commutative diagram with exact rows and columns:

\xymatrix{ & 0 \ar[d] & 0 \ar[d] & 0 \ar[d] & \\ 0 \ar[r] & \calO^* / k^* \ar[r] \ar[d] & \Div^0_\infty(K) \ar[r] \ar[d] & T \ar[r] \ar[d] & 0 \\ 0 \ar[r] & K^* / k^* \ar[r] \ar[d] & \Div^0(K) \ar[r] \ar[d] & \Pic^0(K) \ar[r] \ar[d] & 0 \\ 0 \ar[r] & K^* / \calO^* \ar[r] \ar[d] & \Id(\calO) \ar[r] \ar[d] & \Pic(\calO) \ar[r] \ar[d] & 0 \\ & 0 & H \ar@{=}[r] \ar[d] & H \ar[d] & \\ & & 0 & 0 & }

here, T simply denotes the cokernel of the map \calO^* \to \Div^0_\infty(K) which assigns to every unit \varepsilon \in \calO^* its principal divisor (\varepsilon); in particular, T \cong \Div^0_\infty(K) / (\Princ(K) \cap \Div^0_\infty(K)). finally, H denotes the cokernel of the degree map \Div(K) \to \G, where in the number field case, \G = \R, and in the function field case, \G = \Z.

this is written as follows:

 1 let \$K\$ be a number field or an algebraic function field. then,
 2 we have the following commutative diagram with exact rows and 
 3 columns: 
 4 \$\$\xymatrix{ & 0 \ar[d] & 0 \ar[d] & 0 \ar[d] & \\ 0 \ar[r] & 
 5 \calO^*  / k^* \ar[r] \ar[d] & \Div^0_\infty(K) \ar[r] \ar[d] & 
 6 T \ar[r] \ar[d] & 0 \\ 0 \ar[r] & K^* / k^* \ar[r] \ar[d] & 
 7 \Div^0(K) \ar[r] \ar[d] & \Pic^0(K) \ar[r] \ar[d] & 0 \\ 0 \ar[r]
 8 & K^* / \calO^* \ar[r] \ar[d] & \Id(\calO) \ar[r] \ar[d] & 
 9 \Pic(\calO) \ar[r] \ar[d] & 0 \\ & 0 & H \ar@{=}[r] \ar[d] & H 
10 \ar[d] & \\ & & 0 & 0 & }\$\$
11 here, \$T\$ simply denotes the cokernel of the map \$\calO^* \to
12 \Div^0_\infty(K)\$ which assigns to every unit \$\varepsilon \in 
13 \calO^*\$ its principal divisor \$(\varepsilon)\$; in particular, 
14 \$T \cong \Div^0_\infty(K) / (\Princ(K) \cap \Div^0_\infty(K))\$. 
15 finally, \$H\$ denotes the cokernel of the degree map \$\Div(K) \to 
16 \G\$, where in the number field case, \$\G = \R\$, and in the 
17 function field case, \$\G = \Z\$.

note that this example also shows a problem: namely, the vertical alignment of the inline formulae sucks bigtime. let's see how to fix this...

posted in: math www
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i just read on blabbermouth that miika tenkula, once lead guitarist of sentenced when they still existed, died on february 19th, 2009, at the age of 35. that’s definitely too young.
thanks for your music. and rest in peace, miika.

there was a new version of wordpress out, so i (finally) upgraded. the layout of the admin area completely changed; i already heard about that before. i don’t know if it’s better or worse than the old one, but i stumbled over one thing which is really annoying: in case you write private articles (like me) to ensure that in case the role scoper plugin stops working (or is simply disabled due to upgrades), nobody can see the private stuff (instead of everyone), you will find out that the new version of wordpress automatically publishes articles as soon as the visibility is set to private! this is pretty annoying, as i usually do that as one of the first things before writing (most of) the post itself.
another thing which got worse is the size of the tags field (for the simple tags plugin), which now resides in the right (narrow) column. before, it was prominently seated directly below the area where the post content itself is written (which is rather wide). as i often use a long list of tags, this makes things more confusing than they have to be.

posted in: www
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today i was rather surprised when i got a facebook message around 14 o’clock, from a friend i haven’t seen for years, and who moved back to calgary a month before i came here, asking whether i’d like to join her for a hockey game of calgary’s flames, which apparently are known all around the world. they played against the buffalo sabres, which resulted in a very exciting game. first, the flames ruled the playground with 2:0. then, the sabres caught up, resulting in 2:2 which lasted until the end of the second period. then, in the third and last period, the flames scored another 3 goals, making them the winners. well. it’s fascinating how much commercials you can put in such the game.
a thing which was a bit strange was the motto, “salute to the military / we are commitment”. before the game started, the national anthem was played, with a group of soldiers standing on the playground together with the players. apparently, the canadian military also set up a merchandize / information place somewhere in the arena, and during some of the intermedite fun games with visitors, soldiers took part. all this surprised me pretty much, i’ve never seen something similar before.
oh, and harvey was there, too.*

today, i went on a second walk, this time north from my place. here are some impressions.

a beautiful view downwards onto a half-frozen river:

i don’t know how to describe this in words, but it’s simply beautiful. even though i don’t think this picture captures the full beauty the “ice flowers”, here it is:

i think today i experienced the coldest temperatures i had outside in my whole life: -23 degrees celsius. well, and i found a reason why wearing glasses suck: if you try to protect your mouth and nose by putting a scarf in front of it, your breath will cloud your glasses and finally, the water on the glasses will freeze so your view is perfectly blocked. didn’t feel as funny as it sounds, but i survived :)

posted in: daily life
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today, i saw dracula (imdb). the one from 1931. well, you might now think, “so what?” well, i did not just saw the movie on a big screen, but the more important reason – the one which made me pay CAD 52 for this show – was the score. the original movie did only had music played during the intro and the outro. until 1998, when minimalist philipp glass was given the task to write a score. he composed a string / piano piece, performed by him and the kronos quartet, under the direction of michael reisman. well, a philipp glass score together with the movie is still no reason to spend that much money – but a live performance of the score by philipp glass and the kronos quartett themselves, together with the movie, definitely is. the whole thing happend in the context of the high performance rodeo 2009 in calgary; an advertisement can be found here.
this was actually the first time i saw the movie. and probably the first time i saw béla lugosi in a movie not made by ed wood. well, it was quite funny, even though some of the dialogs were hard to follow because of the score.
anyway. this event was definitely worth its money.

since january 4th, i’m living in calgary now. here a few impressions from inside the place where i’m living this time:

and here a few impressions from a walk i took today. also compare them to these photos i took last may, as i ended in the same park i began with in last may. note that the current temperature got up to +14 degrees celsius right now (3 p.m.), this morning it was a bit less but still positive.

some ducks swimming in parts of the river which are not covered by ice:

finally, the place where i’m staying. very easy to recognize due to euler’s identity scratched into the concrete: