plaes.org

As our campus is using Chillispot for local LAN management one sometimes has to fire up a browser to see why nothing is getting through. Because Webkit-based Epiphany has a bug that doesn't properly load the login page, I have to start up a second browser, fetch some random url to see whether my network session has been expired and finally log in if it's the case.

I got a bit tired of this so I made myself a Chillispot auto-login script :)

I also found a Murphy's law that might summarize what I feel:

Whenever you need a crucial file from the server, the network will be down.

Suppose you need to transfer some files from Linux machine to another machine that does not have any other file transfer client available than browser (ie - regular Windows machine). So instead of trying to figure out how to configure Apache and/or start copying files to Apache's htdocs dir, you can simply do this in a directory containing these files:

python -m SimpleHTTPServer

I wish I had known it few years ago...

For the past week, I have been working on my pdesolve() functionality so it would be possible to solve some first-order PDE's using the method of characteristics. Although, progress has been slow, following is already possible (if you have pulled my branch):

In [1]: from sympy import *
In [2]: from sympy.solvers.solvers import *
In [3]: from sympy import Derivative as D
In [4]: t,x,y,z = symbols('txyz')
In [5]: a = Symbol('a', Real=True)
In [6]: u = Function('u')
In [7]: eq = Eq(D(u(x, t), t) + a*D(u(x, t), x))
In [8]: eq
Out[8]: 
  d             d              
a⋅──(u(x, t)) + ──(u(x, t)) = 0
  dx            dt             
In [9]: pdesolve(eq, u(x, t))
Out[9]: [F₁(x - a⋅t)]

So, if interested, you can view the code on my github repository.

School finally ended last week (no exam results yet, though) and I took a long-long trip back home.. Week started slowly due to the deadly combination of the forgotten laptop power cord, Midsummer day, Victory Day and best weather ever. This resulted in lots of grilling, beer and also a small side-effect: my GSoC mentor is probably quite angry now for missing my weekly update again...

Back to Sympy now.

So far all my various doc-related fixes have been committed to upstream, and I have decided to bite the bullet and start implementing the variable separation for PDEs. So far some very simple testcases based on first-order equations work, but I have some trouble with equations containing higher order derivatives. You can pull from gihtub/pde-separate and please break it :)

This sometimes happens in real life :)

18:32 < plaes> hmm..
18:32 < plaes> [ 2546.243316] emerge[4717]: segfault at 7fff860ddac8 ip 00007fff867c4ebe sp 00007fff860ddad0 error 6 in libpython2.6.so.1.0[7fff866d3000+159000]
18:32 < plaes> any ideas?
18:33 <@DrEeevil> what did you do?
18:33 < plaes> emerge --sync :)
18:34 <@DrEeevil> please go away ;)
18:34 < plaes> well, `sudo emerge --sync`
18:34 <@DrEeevil> sudo go away! ;)

I went through my local sympy branches and cleaned up some smaller fixes in order to submit them upstream. I did not push the PDE stuff yet, as I feel it needs some more testing. So only four patches this time:

Added corner case for Bernoulli equation.
Small cleanups to the ODE solver and tests.
Fix typo: s/trascendental/transcendental
Fix path to aboutus.txt url.

And also a small note to myself how to publish and delete remote branch:

git push server local_branch:remote_branch
git push server :remote_branch

I have spent almost whole day playing with Zope and so far I am not very impressed. Come on - it is 2009 already, but you still have not fixed your product to make it Python-2.5 compatible. Both Zope2 and Zope3 require 2.4 in order to work... I'm really wondering whether enterprise adoptions are good for open source projects.

Yesterday I bit the bullet and managed to add a simple solver for the separable variables PDE case into Sympy.

I have also set up a git repository viewer and my two patches can be viewed on the pde-upstream branch.