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Showing posts from April, 2011

Constrained MDPs and the reward hypothesis

It's been a looong ago that I posted on this blog. But this should not mean the blog is dead. Slow and steady wins the race, right? Anyhow, I am back and today I want to write about constrained Markovian Decision Process (CMDPs). The post is prompted by a recent visit of Eugene Feinberg, a pioneer of CMDPs, of our department, and also by a growing interest in CMPDs in the RL community (see this, this, or this paper).
For impatient readers, a CMDP is like an MDP except that there are multiple reward functions, one of which is used to set the optimization objective, while the others are used to restrict what policies can do. Now, it seems to me that more often than not the problems we want to solve are easiest to specify using multiple objectives (in fact, this is a borderline tautology!). An example, which given our current sad situation is hard to escape, is deciding what interventions a government should apply to limit the spread of a virus while maintaining economic prod…

Useful latex/svn tools (merge, clean, svn, diff)

This blog is about some tools that I have developed (and yet another one that I have downloaded) which help me to streamline my latex work cycle. I make the tools available, hoping that other people will find them useful. However, they are admittedly limited (more about this) and as usual for free stuff they come with zero guarantee. Use them at your own risk.

The first little tool is for creating a cleaned up file before submitting it to a publisher who asks for source files. I call it ltxclean.pl, it is developed in Perl. It can be downloaded from here.
The functionality is
(1) to remove latex comments
(2) to remove \todo{} commands
(3) to merge files included from a main file into the main file
(4) to merge the bbl file into the same main file

If you make the tool executable (chmod a+x ltxclean.pl), you can use it like this:

$ ltxclean.pl main.tex > cleaned.tex

How does this work?

The tool reads in the source tex file, processes it line by line and produces some output to the standard ou…

I can run Matlab on my Mac again!

After much struggling today I managed to make Matlab run again my Mac.
The major problem was that Matlab complained about that I have the wrong version of X11 installed on my system and it won't start. As I have finished teaching today for the semester, I thought that I am going to celebrate this by resolving this issue which I was struggling with for a year or so by now. On the internet you will see a lot of advice on what to do, and as they say, the truth is indeed out there, however, it is not so easy to find. In a nutshell what seems to happen is this:

Why Matlab does not start when other applications do start (say, Gimp, Gnuplot using X11, etc.).
Matlab seems to make the assumption that the X11 libraries are located at /usr/X11/lib and it sticks to this assumption no matter how your system is configured. I use XQuartz and macports' X11 and they put stuff elsewhere. I had some legacy code sitting in /usr/X11/, which I did not use. It was a remainder of some version of X11 th…