Blog & White

Jyväskylä se situe à 62.22°N, 25.73°E. Le graphique ci-contre représente la durée du jour en 2008 en fonction de la date (du 1er janvier au 31 décembre). Le défaut aux alentours de l'équinoxe est probablement dû à une problème d'arrondi et au fait que les calculs prennent l'équinoxe pour point de départ. Je ne m'attendais pas à ce que la courble soit aussi linéaire à distance des solstices, ni qu'elle soit aussi « pointue » aux solstices.

Ici, les heures de lever et de coucher du soleil. Le décalage fin mars et fin octobre sont dûs au passage à l'heure d'été et au retour à l'heure d'hiver.

Beaucoup plus étrange ici, le midi solaire (mi-chemin entre le lever et coucher du soleil) n'est pas à un intervalle de temps constant du midi civil comme on pourrait s'y attendre. Encore plus étrange, cette courbe a deux maxima et deux minima qui ne sont pas au même niveau et qui ne correspondent pas à des dates clés. Les points d'inflexion, en revanche, semblent situés aux solstices et aux équinoxes.

Ici la même courbe sans le passage à l'heure d'été pour davantage de lisibilité. La forme en « escalier » de la courbe est dûe à la précision des valeurs calculées, qui est limitée à la minute. On remarque en particulier que le décalage entre les midis solaire et civil varie entre 0 et 32 minutes, avec un décalage moyen d'environ 18 minutes lus sur le graphe (17 minutes par calcul si on considère le décalage en longitude entre Jyväskylä et le centre du fuseau horaire à 30.00°E).

Thé vert, grandes feuilles torsadées. Les feuilles sèches on un parfum fruité (abricot sec) et peut-être un peu grillé. L'infusion est plus verte, assez douce et peut-être un peu fruitée (abricot sec encore une fois).

I just tested Synergy. This little tool allows to share one keyboard and mouse between several computers sitting next to each other (that is, each computer needs to have its own display) over the network. When the mouse cursor reaches the edge of the screen, it moves to the screen of the computer next to that edge (and the keyboard's focus too, of course). The great thing is that it works in Linux (and other Unices), in MacOS X and in Windows. So it's perfectly possible to have a mix of all these types of systems, and it woks seamlessly, without any extra hardware.

J'ai reçu aujourd'hui (enfin hier, vu l'heure qu'il est) la carte topographique au 1/20 000è de Jyväskylä que j'avais commandée mercredi soir. Service rapide !

Voici donc deux courbes de niveau pour un trajet Hinkalo — Agora, en voiture et à vélo (les chemins parcourus sont totalement différents). Le dénivelé total est de 93 m.

Le trajet en voiture est long de 4680 m. Du point de départ au rond point de Keljonkeskus situé entre les deux supermarchés, le dénivelé est de 80,5 m pour une distance parcourue de 2000 m, ce qui fait une déclivité moyenne de 4%, mais avec des pointes à 14% sur Tuulimyllyntie et 13% sur Myllyjärventie.

Le trajet en vélo est long de 3380 m. Du point de départ jusqu'au petit tunnel, la déclivité moyenne est de 5,7%, mais avec peu de variation sur ces 1100 m de trajet.

This is the follow-up to the previous episode.

Today's discussion with Ville was concluded more or less like that: he claimed that having access to the source code is of no use for him although he can code, because he has never been able to gather the necessary energy to start hacking an existing software. Well, that's his problem, isn't it? I devote some of my free time to hack software (in a very insignificant way, I'm sure) to adapt it to my needs, he devotes his to something else. And I enjoy my small software hacks. I'm proud of myself when I manage to understand MPlayer's subtitles code and add support for DVB subtitles, or when I add support for X11's screensaver protocol to perl's X11::Protocol module. And let's be honest: L^AT_EX is ridiculously complicated, but I enjoy fighting the beast and bending it to my will.

I have loads of fun doing things myself. I make my own pizzas from scratch (dough and tomato sauce, altough I don't grow the tomatoes, olives and wheat, nor do I breed pigs or milk cows), I make my own ice-cream, my own Home Theater PC, my own blog engine, my own Carcassonne meeples. Buying something ready-made feels like a waste of money if I can do it myself for a reasonnable cost in time. I'm not going to devote large amounts of time on large projects such as writing my own operating sytem, word processor or image manipulation software, mainly because the time it would cost me compared to the benefit I would get out of it compared to using the existing tools is not worth it. Hacking oversized projects don't really interest me, even if they have bugs and I'd like to fix them. But I very much appreciate that small, one-person -sized softwares are free for me to hack when I set my mind to it.

The ones who consider the freedom given by free software to be useless are the ones who are too busy/lazy to take advantage of it and have more money at hand than time.

This is the follow-up to the previous episode.

So, is free software always better than the other kind? Jonne claimed that the “freedom” aspect of free software isn't an advantage for him, because free software is hard to change, and it takes a long time to implement the new feature you would like to add to it. The alternative would be to send a bug report or feature request to the developers. But both in free project and proprietary ones you may reach grumpy developers, who will consider your request as low priority.

Now the real difference between free and proprietary is that in the case of free software, you have the right to do it yourself. It may be difficult and take an enourmous amount of time (such as integrating CMYK in GIMP, which was not designed orginally to handle anything else than RGB), but it is possible if you are willing to devote resources (time and/or money) to it. With a proprietary software, if the developers don't want to implement your feature, there is no appeal. Jonne's argument was that you can always find a software (free or not) that does what you want. I claim that this is not always true.

The first example is that when I built my leffakone five years ago, there was no software running on Linux that supported DVB subtitles and automatic TV commercial removal. Actually, there was no software that was supporting these two features at all. So I took the time to implement them myself (and yes, MPlayer's subtitle code is an horrible mess). The second example is a recent problem with Python's X11::Protocol module. It had a bug that I managed to identify thanks to the source code, and I found a way to go around it. I submitted a bug report, but to this day (over a month later) it has still not been answered. X11::Protocol was exactly what I needed, but had it been proprietary, I wouldn't have been able to find a workaround, and would have needed to settle with a sub-optimal solution, which would not have been doing exactly what I want.

Jonne also claimed that developers don't need the source code of a software, but the software should be designed so that it can be extended. Firefox is a good example: a lot of features can be added as “extensions” and the developers don't need to access Firefox's source code. But not all software is designed to be extensible, especially if it is in the (financial) interest of the publisher to prevent anyone to develop an extension without its blessing. This means that if the extension you want to develop doesn't follow the publisher's commercial strategy, you won't be allowed to do it. And again there will be no appeal. An no, you don't always find another software that does the same thing and would allow you to develop your extension.

And guess what? Most of the software available nowadays is not extensible. That is, it's not meant to be easy to extend. If you want to change its behavior or fix a bug, you have no choice but to dig into the source code. And even if the software has been designed with extensibility in mind, it doesn't mean that the data it exports through its extension API contains all the information you need for your purposes. A good example of this if my blog engine, Bloxsom. It was designed to be extensible, most of the work is done by extensions rather than by the software's core. But for implementing features such as multiple languages and multiple categories, I had to change the core, because the extension API was not enough. And I don't know any other blog engine that fits my requirements. But hey, I don't know all the blog engines in the world, so I may be wrong.

To be continued.

I started to use free software in 1996 (or was it 97?), with Slackware 3.0. The first reason why I decided to learn Linux is because Unix systems were the ones used by real coders. Windows already looked too much like a toy, had the bad reputation of a shaky house built over the sand of MS-DOS. And also because it was cool (from a geek's perspective, of course). The reason why I continued to use free software was that even though free software is free as in “free speech”, it is also free as in “free beer”. There were software filling my needs, and I adapted the topic of my free-time projects to what was available on Linux. For example, I could have continued to play aimlessly with SoundForge in Windows, but coding an IRC bot in Perl on Linux was more appealing. It was a creative process, the creation of somethat that acts (if only by reflex), on the contrary of something you contemplate with more or less awe (like music or a painting). And also, the IRC bot was working on my behalf, providing a service.

I had a long discussion with two colleagues the other morning, who claimed that Free Software is a fad. I didn't agree with them at first, thinking about the origins of the free software movement, but after reflection I have to admit that in the last five years it actually has turned into a fad. Not a passing fad like clothing fashion (although the pointy shoe fashion could have changed more quickly for my taste), but in the sense of something that a lot of people use, and who use it because everybody else is also using it. The reason for this is that free software is free (as in “free beer”) and people are more often than not choosing something free over something they have to pay for. The average software user doesn't care whether he has the right to modify software or not. He's a user, not a developer, and he doesn't know how to use this right. I guess plenty of users still use warez software or free (as in “beer”) proprietary software instead of free software, because warez doesn't cost more than free software (at lease from the point of view of money). In some cases, one free (as in “speech”) software can drive the fad. This is the case of Firefox I guess, which was in its time technically superior to Internet Explorer (it respected the standards of the Web and had popup and ad blockers). And I wouldn't be surprised that Firefox has been the main driving force behind the free software fad.

To be continued.

Suite de l'épisode précédent.

J'ai passé aujourd'hui un certain temps à discuter de mécanique auto avec Henrik et en particulier de la consommation rélle d'une voiture. On a fini par en revenir au problème de trouver la courbe de consommation spécifique des moteurs de nos voiture, mais il semble que les constructeurs tiennent à garder ces informations secrètes… En revanche, Henrik a trouvé un article en allemand de Helmut Tschöke et Hanns-Erhard Heinze publié dans le Magdeburger Wisseschaftsjournal de 2001 qui compare les consommations de divers types de moteurs (essence, essence à injection directe, diesel à injection directe pour voitures personnelles et les véhicules utilitaires).

Les auteurs indiquent entre autres qu'étant données les masses volumiques et les densités énergétiques différentes entre l'essence et le diesel, à consommations énergétiques égales, le moteur diesel a une consommation moyenne inférieure. Cependant le diesel produit davantage de CO₂ que l'essence, à consommations égales. Mais les consommations moyennes des voitures à essence et diesel ne sont justement pas égales.

Un peu plus loin, ils se demandent s'il est possible de construire une voiture qui consomme seulement 1 ou 2 L/100 km (la Volkswagen Lupo 3L a été conçue pour ne consommer que 3 L/100 km en moyenne) et concluent que ce n'est pas possible, mais qu'on pourrait descendre à 2 ou 2,3 L/100 km.

Les auteurs introduisent finalement la notion de facteur de mobilité (FM), égal au produit de la consommation par le temps nécessaire à la parcourir divisé par le nombre de personnes transportées. Sur un trajet de 300 km, le piéton a un FM de 30, le vélo 7, la voiture 7,8, le car 1,4, le train 1,6 et l'avion 5,5 (le piéton consomme l'équivalent de 0,5 L/100 km et le vélo 0,35). Ma voiture a un FM de 6,1 avec 4 passagers et 8,1 avec 3 passagers.

Thé vert, uniquement fait de petites feuilles courtes (bourgeons?). Les feuilles sèches ont une odeur qui me rappelle le chocolat noir 72% de Kalev. La première infusion est orange pâle et a un goût de riz soufflé. Après, c'est plus flou.

FOAF means Friend of a Friend. It's an RDF vocabulary that allows to describe oneself and link to people one knows. In other words, it forms a distributed social network, independant from any service provider such as Facebook, LinkedIn, Orkut and so on. It doesn't allow you to send messages to other people in your network, or any of the activities that are often associated with social networks, it only describes you and your relations to the people you know.

Here's my FOAF descriptor, that you can also view through FOAFer. There's also FOAF-a-Matic, a simple web tool that creates a basic FOAF descriptor for you (a more advanced descriptor will required to write RDF by hand, though). Finally, there is also a FOAF Generator that creates a FOAF descriptor based on your Facebook profile.

So if you feel geeky enough to get your own FOAF descriptor and if you know me, let me know about it :)

I've been thinking how to automatise the process of setting the car engine's heating time in the morning depending on the outside temperature. Since heating is not overly expensive, I've decided that a cheap timer switch should do the trick. As to how long the engine should be heated… Well, statistics may help here. The graphs on the left represents the average temperature in the morning at 6 and at 8 over the past 6 years (2002 – 2008). From the graph, it's easy to see that there are clear periods where the temperature is between this and that limit.

In a nutshell and in month-day format:

• 01-01 – 03-01: 2 hours
• 03-01 – 03-25: 1 hour
• 03-25 – 05-01: 30 minutes
• 05-01 – 10-01: no heating
• 10-01 – 12-15: 30 minutes
• 12-15 – 12-31: 1 hour

This represents 214 hours of heating in the year, amounting to 6.90 EUR (with a 400 W heater, and a rate of 0.08 EUR/kWh). With the additional inside heater (add 950 W), it costs 23.30 EUR. This is almost 40% more expensive than the optimised calculation in the previous article, but a device combining termperature sensor with a clock is hard to find and will cost 50 to 100 EUR, when a mechanical clock switch can be found for 5 EUR.

On conseille de chauffer la voiture si la température de l'air descend en dessous de 5 °C. La durée de chauffage varie en fonction de la température:

• 5 °C à -5 °C: 30 minutes
• -5 °C à -10 °C: 60 minutes
• < -10 °C: 120 minutes

En 2007, la température le matin à 8 heures était:

• < 5 °C et > -5 °C pendant 159 jours
• < -5 °C et > -10 °C pendant 23 jours
• < -10 °C pendant 33 jours

Ceci nous fait 168 heures de chauffage sur l'année (en comptant les week-ends), donc à 400W de puissance de chauffage et à 0,08 EUR le kWh, ça nous fait 5 EUR par an. Si on rajoute le chauffage de l'habitacle (950W), on arrive à 18 EUR par an.

Ingrédients

• 100g pistaches épluchées, non-salées
• 100g sucre glace
• 1 blanc d'½uf

Préparation

Mixer les pistaches avec le sucre jusqu'à obtention d'une poudre fine. Ajouter le blanc d'½uf et mélanger à la cuillère (le mélange devient trop épais pour le mixer).

<noursy> qu'est-ce que ça change pour le commun des mortels qu'on descende du singe ou d'Adam ?
<loupi> ben on saurait s'il faut manger des bananes ou des pommes :)