Jan Varho

New Site

After my old WordPress setup broke one time too many I finally decided to convert the site to something nicer to work with. I ended up going with Pelican, which is a static site generator using Python.

It seems quite basic at first, though I'm sure there are features waiting to be discovered. The main advantage is that I no longer need to worry about software updates when not actually changing the site. Another is that practically any hosting setup works painlessly.

I tried to fix up all intra site links, but others are hopelessly broken, so you may have been directed to this page instead of what you were looking for. Sorry!

Why Windows is a Pain

AKA: .NET Sucks

I just had to reinstall a Windows XP virtual machine. To make all my programs run I had to manually hunt down and install four versions of the .NET runtime (1.1, 2.0, 3.0 and 3.5. Soon it will be five with 4.0) and the Visual C++ redistributable. Then Windows Update found several updates/SPs to all of them. In all this took at least eight reboots (lost count), though I might have been able to skip some if I felt daring.

Had I only had a plain old original WinXP CD instead of the SP3 one, I'd also had to install each Service Pack one at a time and reboot a lot more.

Cf. Ubuntu, where the installer downloads updates while you are installing (if you are connected) and even afterwards a single run of the update manager or a couple of apt-get invocations are all that's needed. At most a single reboot is required and only if there's a kernel update.

Efficient Implementation of Community Detection Using Extremal Optimization

Just uploading this short note/paper here in case anyone ever finds it useful and so I won't lose it again. I wrote this last year, during the summer as I worked on networks.

I implemented a fast - O(lg^3(n)n), almost linear - modularity optimization (community detection) algorithm based on the extremal optimization algorithm of Duch and Arenas (in turn based on Boettcher and Percus on other problems). The pdf details the algorithm and also has notes on the dataset I downloaded from arXiv to run the algorithm on.

I've glossed over a lot of details, but on the off chance it's useful, feel free to contact me for more information.

Download: Efficient Implementation of Community Detection Using Extremal Optimization (pdf, 112KB)

Solving Vista Networking

My first impressions after using Windows Vista extensively are somewhat positive. The only major problem that remains is that I'm completely unable to have Windows Network work between the Vista machine and another desktop with XP. However, there were other problems, one of which had to do with "limited network connectivity".

The way to solve that came up after some major Googling (major because the help in question wouldn't come up without the term 'DHCP'): Vista uses a broadcast DHCP flag that wasn't used by XP and some routers cannot handle that properly. So I appliedthe suggested registry tweaks and it started working.

In my case the default setting was DhcpConnForceBroadcastFlag set to 1

• which I removed from the registry. After that I added <span class="userInput">DhcpConnEnableBcastFlagToggle with a value 1 and the network connectivity warnings disappeared. Oh, a reboot was necessary, of course.</span>

Weird how everything in Windows needs a reboot: I also had a printer problem which magically disappeared after a system reboot. One really hopes they'll come up with another way to sort problems in some future version of Windows...