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To model computer networks a traffic model is needed. One can have a traffic model used for generation of traffic, and one for analysis of traffic. This post is about the latter. Such traffic model captures properties of traffic in such a way that analysis is possible, and these results can then be used to dimension a network. E.g. some people are interested in loss, others in delay, and others need to analyze the multiplexing gain so they can calculate the necessary bandwidth.


2014-07-16 [E] [D]
programming Comments 0

PieCrust, this site's backend, is getting slower as more posts and pictures are added. I guess this is mainly due it being written in php, a scripted language.

So I've been checking out alternatives.

I wanted something that worked fast, offered all or most of PieCrust's features that I used and was fun to tinker with so I could implement the missing features.

Since most dynamic languages are slower than the compiled ones, I preferred something compiled, which reduced the number of options significantly. Furthermore, even though I love Haskell, it can be quite difficult to get it to compile on shared hosting.

This more or less left a couple of options in go. And my companion was found in gostatic, a very fast static site generator written in go, using golang templates with a small code base that was quite understandable.

As it is written in go with only three dependencies, it's quite easy to compile and get working. It didn't offer all features that I wanted (such as pagination, including files and assets), but the source code was small enough so I could implement all features and a compatibility layer with PieCrust (so I did not to have to rewrite all pages and posts).

And, as I was updating the site, I also added lazy image loading for posts, quite useful for my travel posts with lots of images :)

As for now, it seems to do pretty well for my setup, generating the complete site in 10-20s on dreamhost (the large variance is due to it being on a shared host), and less than 5s on my main computer, compared to PieCrust's +60s.

2014-07-13 [E] [D]
music,jazz,live Comments 0

Gent Jazz is an old familiar to me, where I've seen B.B. King perform, and two years ago Paco de Lucía (RIP, sniff sniff).

This time Joshua Redman, Hiromi Uehara and Chick Corea were the same day at a festival. How could one say no to that?

It was a rainy day, but the music made it all worthwile; Joshua played some great tunes, Hiromi was amazing, and Chick Corea & Stanley Clarke were just perfect. And of course, the duet Hiromi - Corea with Spain at the end of the day was just a pure pleasure to watch and listen.

This page is intended for footage, pictures and reviews of that day.


A while ago I submitted a paper to a PhD workshop AIMS, and it got accepted. As it was to be held in Brno, a place I've visited before as part of my explorations in Czech Republic, I decided to go afterwards to Slovakia, as it's a relatively small country, right next door.

And so, I left a couple of days before AIMS to go see my old friends Prague and Olomouc and their inhabitants, then attend the conference in Brno, followed by some exploring and hiking in Slovakia.


It all starts at an early Saturday morning, at 5:25, when my alarm went off. It was the first time I used my tablet as my alarm. I couldn't figure out how to disable it, so I just shut it down (that'll teach him!) and went to take a shower. After I exited the shower, I suddenly heard the alarm sounding, as if nothing had happened. This time I was able to turn it off, but until this day I don't know how.


2014-05-31 [E] [D]
hardware,linux Comments 0

Got myself yesterday a Lenovo Yoga Tablet 10, a 10.1" Android 4.2 tablet.

I finally decided to get a tablet, as it might be useful when playing some piano and not having to look at my laptop. Now I can just comfortably put it on my sheet music stand, and display anything I need.

I chose to get this one, as it was immediately available, not too small nor too large, with good battery life (18 hours, they report) and reasonably priced.

So far, it feels sturdy, the stand mode is quite enjoyable. The camera lacks in quality (but well, it's not as if I'm going to use it as my main camera), browsing is sometimes a bit slow (I think, as I can't really compare with other tablets) and the minimum volume is way too loud (but is a problem in general with Android, it seems).

If I find any valuable apps, I'll update this post :)


2014-05-06 [E] [D]
linux,code Comments 0

Recently I bought a Raspberry Pi which I intended to use for some little projects. One of those projects is to use it as a relay to my wireless headphone, which isn't as portable as I would've liked: the basestation needs to be connected to the audio-out jack of my laptop, making my laptop rather immobile.

So I had to the idea of plugging the wireless headphone basestation into the Raspberry Pi, and send my laptop's audio data over wifi to the RPi.

There are a couple of solutions, involving jack and pulseaudio, but I wanted something very simple (both jack and pulseaudio took longer than I wanted to get it working, even though the time I put in might be more than the time I would've, researching more PA or jack :)).

My initial idea was to capture ALSA's output, redirect it to a fifo that get's piped to Raspberry, where a player like aplay just plays it onto the jack-out.

In what follows, I refer to the raspberry as speakers and server as the one producing the sound, like a laptop.

TLDR: Update ~/.asoundrc, download and execute ./ --both speakers-ip


2014-04-24 [E] [D]
osx Comments 0

OSX has a pretty nice dictionary, but is a lacking in available dictionaries. provides a lot of translation dictionaries.

I also recently discovered that three-finger tapping on a word will open the entry for that word :)

Just having finished a batch of work, and easter holidays. What more reason does one need to go out and see a little bit of the world?

As I didn't want too much hassle of moving to my destination, the plane was already left out, and the feasible options were reduced more or less to the train. Checking the trains from Belgium to somewhere else, I thought about going to Lille. Good connection, and a cheap ride. That's the way I like it :)

Lille is next to Belgium, and although it is the capital of the Nord-Pas de Calais region and the prefecture of the Nord department. In 2008 Lille got a lot of attention due to the film Bienvenue chez les Ch'tis which broke La Grande Vadrouille's record of 17 million admissions, which spawned interest in tourism since. It is not too big of a place, so I could explore it all, at an easy pace.

My train of 9.55 a.m. was right on time. At the site and when buying my ticket (one-way, as I had no idea yet when I'd return) it was said that the train only went to Mouscron. From there on, there was a bus that'd take us to the Lille-Flandres station. However, on the train they said it was a direct connection to Lille-Flandres (they even called for it in the morning to confirm), however, before arrival they corrected themselves. Excellent communication :/ A whole slew of people were already waiting for the 11.40 a.m. bus, but it let us wait for about half an hour.

Mouscron station

Lille-Flandres station, 300m away from Gare de Lille Europe


2014-04-11 [E] [D]
/tag/ Comments 0

gimp allows you to open and edit pdfs. However, multipage pdf support is primitive: it allows you to read each page in a separate layer, but one can not save back to a multipaged pdf.

A simple solution [1] is to export the layers in reverse order (Layers -> Stack -> Reverse layer order) as a .mng file (Multiple-image Network Graphics), and use ImageMagick's convert to rewrite it to a pdf: convert file.mng -compress Zip file.pdf

[1] source

2014-04-04 [E] [D]
programming,code Comments 0

I just added a new project to my projects page: ImgCmp.

It allows one to compare visually and easily many images in a large set of files. For more information, a better screenshot and downloads with more info, go to its project page

Quick download links:

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