Carsten's blogspot

Progress in the predator prey simulation

2009-07-03T19:12:09Z

Since yesterday a lot things improved.

In this example I killed all but one rabbit after 1200 rounds and all but one wolve after 7700 (of 10000) rounds:

Quickpost this image to Myspace, Digg, Facebook, and others!

Help Yourself: Predator Prey Simulations with PyQt4

2009-07-02T14:28:01Z

As you may know I am a biology teacher. Next term I will teach Ecology. One part of that is the relationship between predators and prey (wolves and rabbits, for example). There are quite some mathematical model for these relationships, in school we mostly teach a simplified version of the Lotka-Volterra system.

This kind of stuff really needs a simple application to test the influence of certain factors. For example,

what happens if after two years we kill all but 5 predators?

what happens if after two years we kill all but 5 prey?

what happens if after 1 year, for whatever reasons, the rabbits become more fertile?

There are tools schools can buy, but a) they suck and b) they are very expensive.

Introducing: "Predator and Prey" by Carsten Niehaus (tm)

As you can see the basic stuff all works. When happens when I start with just on predator but 20 prey but let the predators be more efficient hunters? Look here:

The application is written in PyQt4 using matplotlib. I would really like to express one thing: Python + Qt4 rocks. Seriously, the whole application has only 306 lines including comments!

Are you interested in the code or even in helping me writing a cool PP-Simulation? Do you think this should go into KDE EDU? I am hosting everything in GitHub: PP in GitHub.

[LazyWeb] DualHead: Hardware suggestion

2009-06-28T09:36:35Z

Hey,

I just got a second LCD for free. Of course I'd like to use it ;-) Currently, my computer has an old ATI card which doesn't support a second LCD-Panel (it is an ATI RV350 AR Radeon 9600).

I just noticed that I have 0% knowledge about graphics adapters... And I don't care about them, to be honest. All I want is KDE on two LCDs and be able to move windows between the two panels ;-)

I never ever play games on that machine and only do EMail, Firefox and OpenOffice on it. That means 3D performance is completely unimportant, I am sure the slowest chip is more than fast enough. As I am using the machine a lot passive cooling would be really nice. 3D effects in KDE would be nice, of course.

Question: Which graphics card would you buy if you were me?
Criteria:

Works on Linux (I am using Chakra (Arch Linux))

Dualhead is easy to configure (that means documented and I don't need to compile my own X.org or kernel and such)

Inexpensive

Silent

Thanks you for your suggestions.

Our firstborn

2009-06-10T19:58:08Z

Python class variables and code dupclication

2009-04-16T13:38:37Z

Hello

I am having a Python problem. I have two classes, both inheriting the class 'Animal'. I want a counter, that means Animal.count_of() should return the number of objects.

Please have a look at this code:

class Animal(object):
    number = 0

    def __init__(self):
        Animal.number += 1

    def __del__(self):
        Animal.number -= 1

    def count_of(self):
        print Animal.number

class Laus(Animal):
    def __init__(self):
        Animal.__init__(self)

class Bug(Animal):
    def __init__(self):
        Animal.__init__(self)


l1 = Laus()
l1.count_of()
l2 = Laus()
l1.count_of()
l3 = Laus()
l1.count_of()
l4 = Laus()
l1.count_of()

b1 = Bug()
b1.count_of()

This is not working because both classes are using the same class variable (number) which means the number in the last line is 5, not 1. I could obviously have one class variable for Bug and one for Laus, but that would mean I'd have to have two .count_of()-methods as well (and more would have to be duplicated, I only pasted a stripped down code).

Is there a trick to have one base-class Animal with a counter or do I really have to do everything twice?

OpenStreetMap and routable maps

2009-03-22T13:07:54Z

W00p.

I just prepared a geocachingtour. I am using a Garmin GPS device and the OpenStreetMap maps. Even though my city is really complete (over 99% of the streets, pretty much ever pub is in ;-) I update the map every month or so. Spelling mistakes, the rural areas get better and better each day and so on.

Today I discovered that the map for Garmin devices is now routable! That means I have a navigation system for my bike. How cool is that?!

OSM starts to seriously rock. A year ago and today: What a difference.

Casting an int to a float in Python 2.6

2009-03-15T10:17:50Z

Moin

Does

%d / %d is %f" % (num1, num2, float(num1)/num2)

have any (dis)advantages over

%d / %d is %f" % (num1, num2, float(num1)/float(num2))

? Both work. If one number is a float both are treated as a float, as far as I know.

Does the first line have any (technical) disadvantages over the second?

Wifi-Map of my school

2008-11-09T18:57:52Z

In my school we are currently rearranging many things including our Wifi-network. We have many (30 or so) Accesspoints all over the school. We want to know two things about our network:

So far the accesspoints are were we _think_ they should be. But for obvious reasons (like we don't know how think some walls are, if certain fire resistant doors absorb wifi-signals or not...) we have no clue if our distribution is good or not. So we want a "signal strength map" of our school.

Second, we want a map on which we can see if a certain accesspoint is in reach of another accesspoint. This is of course a sub-project of the first point.

As we are a school we don't want (or can) spend money here. The best tool so far seems WireShark, NetStumbler is Windows-only, but seems even better. Kismet is also such a tool but its GUI looks like I need a year to learn how to use it.

Do you have other suggestions?

New Python app: Python really rocks :) (I still don't know where to hosts those apps)

2008-10-29T21:26:48Z

Just like earlier I needed an application. This time I needed something that simulates the relations between predator and prey (see here). My students will use a simple simulation with dices so see those relations. The problem is that it takes ages to roll 400 times (that is what you need to get good statistics). So they only roll the dices for about 50-70 times, discuss the trends they see.

The next step will be my simulation based on the same rules. 77 python lines later that app is done :-) "All" I need is a nice PyQt4 interface for it, right now it is a pure shell application. But it already exports to CSV (just three lines :). In OOCalc this loooks like this:

Quite nice and the code is really simple. Python rocks.

PS: No clue where to host this, I don't want such a tiny tool on sourceforge.net. Perhaps I should bundle all my biology simulation tools in one application (KSmallBiologyTools like (and no, I will not use that name)) and host _that_ application somewhere.

PyQt4 rocks... Is there a (public) need for this kind of application?

2008-10-01T19:31:08Z

Moin

As a biology teacher I am sometimes teaching about how our brain (memory) works. One way to test it is to read out loud the words while my students listen (between 10 and 40 words). When all words have been read they have 2 minutes to write them down.

Depending on the number of words and on the words themselves the results differ a lot. For example, if the words are interconnected ("hammer", "nail") those pairs are remembered quite well.

If you do this with 10 groups you have a problem: There is no way to read the list 10 times in the same way. Two solutions:

(1) Tape you reading and simply play the MP3-file.

(2) Display the words.

As a programmer (2) is much easier and more fun ;-) As I love PythonQt4 I simply wrote an application doing this:

As you can see I added a couple of words lists: One syllable, two syllables, more than two syllables and five lists of similar sounding words (man, ham, spam, damn, ...). You can configure the display time and see all words of a list. I am using a projector to display the words in the classroom.

This application is doing exactly one thing and is doing it well (ok, it won't win a design award...). As far as I know there is no such tool for schools around. So I wonder if there is a place for this kind off application. It is to specialized for kdeedu or Plasma, I think.

By the way: The application has only 129 lines of code including 11 lines of licence, 10 lines for the data, comments and white space. Python + Qt4 rocks :-)

Geocaching

2008-09-19T17:16:26Z

In the last 2 weeks I geocaching. So far I found (cacher-lingo: logged) 10 caches. Yesterday I did my first Nightcache. Those caches can only be found at night, in this case because light reflecting discs are used that cannot be seen at day (or almost: they are white on white background 10 meters away from a road. At night it was pretty easy to see them by using a torch).

Geocaching is fun! :)

Marble 0.6.1 now also in my school

2008-09-19T17:12:53Z

From today on 32 laptops in my school have Marble 0.6.1 on Windows XP installed. Runs nicely. Lets see how our geography teachers like it!

Next week I will install it on another 16 machines.

Eigen 2.0 beta 1 released

2008-09-15T19:00:05Z

Benoît Jacob asked me to publish this great news for him as his blog disappeared from this planet...:

We just released the beta version of Eigen 2.0. It has matured a lot over recent weeks as quite a number of apps have been ported to it: Avogadro, KOffice (mainly Krita and a little KSpread), KGLLib, SolidKreator, KGLEngine. We plan to release 2.0 later this fall.

There is now a quite decent Tutorial which is a good starting point if you are interested in Eigen.

Besides polishing for the upcoming 2.0 release, we are already making big plans for the future. Version 2.1 will have a complete Sparse module, which will be very useful for Krita and Step. Gael had been doing the ground work for this module, and recently Daniel Gomez joined us and contributed several improvements.

We still are very few developers -- Daniel is basically the 3rd one, with Gael and me, although a few guys have been helping occasionnally in the past. We definitely can use more help (hint, hint). For that reason we try to polish the documentation a lot, and we can mentor any prospective contributor. Here is a TODO with many available jobs, all you need is C++ and some math background.

[Lazyweb] Using TrueCrypt for Linux and Windows?

2008-08-26T17:38:36Z

Moin

This is my situation:

I have data on my Linux machine at home (several thousand files, about 10 gigabyte). I am using that PC several hours a day. The filesystem is Ext3.
Quite regularly I need some of my data at work which is a Windows-only land... I am thinking about buying a 2.5" HDD (USB). For various reasons I have to encrypt my data.

Currently the best solutions seems to be TrueCrypt as it is OpenSource and works on Linux and Windows. I used it on Windows, but never on Linux.

One problem is that I need to be able to read the data on our Windows XP and 2000 machines and that means that I'd need to make the hard disk use FAT which will probably cause problems (I have tons of files with umlauts and I cannot even count the occasions where an umlaut made huge problems when I converted FAT <--> EXT*).

So my question to you, dear Lazyweb, is if a 2.5" USB HDD with TrueCrypt is the best way to go. I'd use rsync to sync between my computer and the USB HDD.
I also thought about an U3 stick but that doesn't work on Linux...

Thanks.

Icons for elements in Kalzium: Contextinformation

2008-08-07T10:21:09Z

Moin

I just added a feature (local git tree for now) to Kalzium: When you are in the iconic mode (that means where instead of chemical information you see SVG-icons like in the next screenshot) you see information about the icon.

For example to some of us it might not be clear why Lithium is represented by a battery or Sulfur by a match. This information is now in the extended legend-widget:

For one, this is just a demo-text. The information is there but needs to be written in good and easy-to-understand english. Anyone?
Also, I am not sure how to present the information... Perhaps someone with taste and a sense for good GUI design could help me here a bit?

Converting any window into plasmoid

2008-06-30T12:47:49Z

Moin

Somehow Vladimirs blog disappeared from the planet, that is what he asked me to tell you about his work on Plasma. Please read the cool details (with screenshots) here:

http://ksvladimir.blogspot.com/2008/06/converting-any-window-into-plasmoid.html

Anybody to compile a Qt app on Windows for me?

2008-06-12T15:23:30Z

Hi

I need a really small Qt4 application on Windows XP Professional. That catch is that it has to be self-contained as on the target PCs there is no Qt4 installed. The whole application is 10 lines of code plus one .ui file.

I tried to compile Qt4 statically but gave up after two hours. Vista seems to hate me and I hate Vista, that is for sure.

Anyone? I'd send you the files per email. If you are willing to help me out just send a mail to cniehaus at kde,org.

[Update]: Thanks for all your replies! Patrick Spendrin was the first and already provided me a working .exe file.

OpenStreetMap party in Oldenburg (North Germany)

2008-06-03T19:32:09Z

Hallo, ich werde am 5. / 6. July 2008 eine OSM-Party in Oldenburg veranstalten. Wer Lust hat, daran teilzunehmen, möge sich hier eintragen und/oder sich bei mir melden.

http://wiki.openstreetmap.org/index.php/Oldenburg_mapping_party

10 GPS-Geräte werden von der Geo-Factory bereitgestellt.

__________________________________________

Hello, on the 5 and/or 6 of July 2008 an OSM-Party will be held in Oldenburg, Germany. If you would like to attend please add yourself to the Wikipage and contact me directly.

http://wiki.openstreetmap.org/index.php/Oldenburg_mapping_party

10 GPS-devices will be provided by the Geo-Factory.

Folding at Home, KDE-Team

2008-05-25T18:03:29Z

A couple of years ago I joined Folding At Home. There is a KDE-team for which I folded in 2002. We are getting old, right? :-)

Now that I have a fast computer again I restared using F@H in the background. It is only using one of my two cores, so I can run it all the time.

Well, perhaps you are also interested in helping this biochemical and non-profit project? The teamnumber is 461.

PyQt4: 500 lines of code later

2008-05-01T17:28:05Z

Yesterday I blogged that I decided to use PyQt4 in my class. A few hundred lines of code later I start to like Python. It is quite a nice language so far. The indendation thing still drives me mad from time to time (there seems to be no sane editor for python that autoindents my code... Usually I am using VIM, but it is not correctly indenting my files for some reasons. Need to google a bit more for Python-specific vim scripts/settings, I guess.

But I have one issue I cannot resolve (in a nice way). I am loading data from a CSV file. One data set is just True/False, in the file represented by "1" and "0". The only way to make this work is this code:

liquid = bool(int(row[6]))

Without the casting from string to int the casting to bool is not working. In other words, I cannot directly cast from string to bool. I guess there is a more pythonic way, if you know it please tell me :-)

PyQt4 success, a coding class in my school

2008-04-29T17:30:54Z

In the next term I will (for the first time) be teaching a coding class at my school. I had a few must-have criteria for the language and toolkit of choice:

Language

Has to be a scripted language as then no compiler is needed. Is easier to understand and less error-prone

Has to be free as in beer and freedom

Has to run on Windows 2000, XP, Vista and Linux

Has to have a german reference (for my students)

Has to have a good textbook (for me), if possible written in german

Has to have a good Editor

Perl, Python, Ruby are left

Perl, Python, Ruby are still left

Perl, Python, Ruby are still left

Perl, Python, Ruby are still left

Perl, Python, Ruby are still left

Perl, Python, Ruby are still left (Notepad++ works great for all three languages)

Ok, so I looked at good toolkits for all three languages. My clear favorite is Ruby, for several reasons. I love the language, I know the language, Richard does a great job maintaining the Qt- and KDE-bindings, the PickAxe is a perfect book to learn Ruby from and so on. But I did not choose Ruby. For a very simple reason. Lets see:

Has to be free as in beer and freedom

Has to have a good documentation for me (as I need to be a few steps ahead of my students)

Has to have a german documentation for my students

Has to run on Windows 2000, XP, Vista and Linux

Has to have a german examples/tutorials which run out of the box (for my students)

Qt, GTK and wx variants of Perl, Python and Ruby are left

Qt variants of Python and Ruby are left. Sorry for wx and GTK, but there are no good documents I could use. This alone rules you out. Beside this, I'd always prefere Qt as I know that toolkit. But I would have taken wx and GTK to the next level if they had better docs. wxPython has "ok" docs, but compared to what I found for PyQt4 it is still quite thin.

PyQt4 and QtRuby4 are still left. Now wxPython and PyGTK would have died anyway.

PyQt4 is left. Works like a charm on Windows and Linux. I often used QtRuby on Linux and so far never on Windows. It seems it once existed but is no longer maintained. A shame, really, as Ruby is such a great language.

So it will be PyQt4.

Python has a great free (beer and freedom, written in german) book which I will probably buy as a dead-tree version (I hate reading a book at the screen).

There are many, many, many good tutorials, workshops and so on.

Very good class documentation.

Even a book for PyQt4 itself (which is a huge plus).

I guess wxPython is on the second place. It also has a good book and compared to the other options a good documentation in general. Well, PyQt4 is nice, I already wrote a few hundred lines of code with it. I hope my students will also like my choice :-)

MP3 Player vs. Windows vs. Carsten

2008-04-26T18:42:27Z

Today I bought 4 GB MP3-Player. First thing I did was to copy a nice playlist from Amarok to the device (on the product box Trekstor even claims the device to be Linux compatible, nice :-), of course it just worked. After a while I had sound problems when listening to Big Pimpin'/Papercut by Linkin Park/Jay Z.

I thought, ok, let's update the firmware. Of course, the software for that is Windows only (and english-only, btw, nice for those 4 billion of us not speaking english), so I switched the OS. I installed the Software and started it. It requires root-privileges. Huh?

Well, I entered the admin-password and 20 minutes later I gave up. First, Windows recoqnized the device without any problem. From one minute to the other it is an unknown device. I tried hard with all my windows-fu and failed. The is no way to connect to the device it seems...

The funny thing is that Windows Media Player is able to play songs directly from the device... Cool, right?

/me reboots to Linux where things just work (for me, at least)

PS: The sounds issues I had are fixed now, it was a headset problem.

Basic Git-foo

2008-04-18T16:29:22Z

As I just helped Vladimir to understand the basics of Git I though I can as well blog about this and make others understand Git as well. I guess this might be a start for a tutorial on techbase.kde.org? What do you think?

Update: I did just that. Lets improve the tutorial there and make it more KDE centric.

Setting up Git

First, I started a new Git repository and added one file to it.

carsten@moinmoin:~/git> git init
Initialized empty Git repository in .git/
carsten@moinmoin:~/git> echo "Test content" > testfile

Now I will check what the status is. I will list one untracked file, that means the file has not yet been added to the repository.

carsten@moinmoin:~/git> git status
# On branch master
#
# Initial commit
#
# Untracked files:
# (use "git add ..." to include in what will be committed)
#
# testfile
nothing added to commit but untracked files present (use "git add" to track)

In the next three commands I will add the file, commit the file and then check for the status again.

carsten@moinmoin:~/git> git add testfile
carsten@moinmoin:~/git> git commit
Created initial commit 246d7aa: This is the first commit
1 files changed, 1 insertions(+), 0 deletions(-)
create mode 100644 testfile
carsten@moinmoin:~/git> git status
# On branch master
nothing to commit (working directory clean)

Ok, as you can see the file has been commited. Now I will demonstrate what happens when I am changine the contents of the file:

carsten@moinmoin:~/git> echo "new content" > testfile
carsten@moinmoin:~/git> git status
# On branch master
# Changed but not updated:
# (use "git add ..." to update what will be committed)
#
# modified: testfile
#
no changes added to commit (use "git add" and/or "git commit -a")
carsten@moinmoin:~/git> git commit -a
Created commit 14a9802: Second commit
1 files changed, 1 insertions(+), 1 deletions(-)

You see that Git noticed the changes in the file. "git-commit -a" commits all changes in the repository.

Branches are cheap in Git

git-branch shows you the branches of the repository, the one with the '*' is the active one. So lets create a new branch called "bugfix-branch" and assume we want to fix a branch there. After this fix (in this case the new file) I will merge back all the hard work into the master branch.

carsten@moinmoin:~/git> git-branch
* master
carsten@moinmoin:~/git> git branch bugfix-branch
carsten@moinmoin:~/git> git checkout bugfix-branch
Switched to branch "bugfix-branch"
carsten@moinmoin:~/git> git branch
* bugfix-branch
master
carsten@moinmoin:~/git> echo "a second file" > newfile
carsten@moinmoin:~/git> git commit -a
# On branch bugfix-branch
# Untracked files:
# (use "git add ..." to include in what will be committed)
#
# newfile
nothing added to commit but untracked files present (use "git add" to track)
carsten@moinmoin:~/git> git add newfile
carsten@moinmoin:~/git> git commit -a
Created commit 3264357: This file is here for a demonstration of Gits branch- and merge feature
1 files changed, 1 insertions(+), 0 deletions(-)
create mode 100644 newfile

Ok, the bug is fixed now. Next step: Checkout the master branch and merge the two branches:

carsten@moinmoin:~/git> git checkout master
Switched to branch "master"
carsten@moinmoin:~/git> ls
testfile
carsten@moinmoin:~/git> git merge bugfix-branch
Updating 14a9802..3264357
Fast forward
newfile | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
create mode 100644 newfile
carsten@moinmoin:~/git> ls
newfile testfile

Lets now have a look at the log of the testfile

carsten@moinmoin:~/git> git log
commit 14a9802e249413003d1fa40002baa025aa54c75f
Author: Carsten Niehaus <carsten@moinmoin.site>
Date: Fri Apr 18 18:07:18 2008 +0200

Second commit

commit 246d7aad05139314e7ff62a5becb6c930f72fb8f
Author: Carsten Niehaus <carsten@moinmoin.site>
Date: Fri Apr 18 18:06:33 2008 +0200

This is the first commit

Step moved to kdeedu

2008-04-05T15:38:11Z

Today, Vladimir moved Step from kdereview to kdeedu. This means that KDE 4.1 will ship it! This week I demonstrated Step to several of my students (7th and 10th grade) and got a little feedback.

This feedback already resulted in several changes including the ability to easily modify the speed of the simulation:

Other recent changes include the tutorial. Vladimirs woman added five tutorial. The following video shows one of them (the second) and also demonstrates how easy it is to "play" with Step: I added a rectangular to the simulation to see what happens when the ball bounces against it...

We hope to get more bugreports and ideas for Step, now that it is inside an official KDE repository. What we currnently would like to get from users is more tutorials and more example. Interested in helping us?

[Step] Help needed for the documentation

2008-04-03T19:32:34Z

The Step team has a small job to offer, everybody is well suited for this one so don't miss a chance to enter the Free Software World! You do not need to be able to code.

In Step, everything should have a small help-text. We are doing this by creating simple HTML-file like this for example. As you can see, the file is quite simple.

All you would need to do is to choose an item without a helpfile (that is pretty much everything, you can really cherry pick!), write the text and send the file to me, Vladimir or the kdeedu-list.

Interested?