Welcome

This is my home in the virtual world, where I write about things that I want to share. The freely available software that I've written as well as some of the photographs I've taken over the years can also be found here. Please use the navigation links on the right if you are looking for something.

Recent articles

1. Convert RCS history to git

   Before the rise of git, I used rcs as my version control system. Because I want to standardize on git, I am slowly converting old repositories.

   In this article I’ll be converting my old perl scripts in ~/src/perl.

2. Doing calculations with Python

   As an engineer I do a lot of calculations. These can be done with pen and paper and a calculator, in an IPython notebook or in a throwaway spreadsheet. All of these methods have shortcomings, though.

   Pen and paper is hard to share and (in my case) hard for others to read. In IPython you can assign the results of calculations to a variable, but you have to perform a separate action to display them. And spreadsheets in general show you the results but not the calculations.

   So I wrote a simple function in Python to help me with that. Using this function I can print both simple assignments and relatively complex calculations. And it shows both the calculation and the result.

3. Improving my Python coding

   With leading white space governing the indentation level and so the grouping of statements, Python code already looks relatively clean.

   Yet there are additional tools that will help you improve your code.

4. Structures in Python

   Sometimes I miss the C’s plain old struct in Python.

   Of course Python has dictionaries, but I prefer to write a.b over a['b'].

   Here are several ways of doing something akin to a struct in Python.

5. Fixing dependencies after mesa ports consolidation

   After the 2017-05-12 mesa port consolidation, there were packages left with missing dependencies. This is how to fix them

6. Evaluating Zstandard compression

   Recently I became aware of the zstd compression program. I wanted to see how it stacks up against gzip, bzip2 and xz.

   TL;DR

   Compression with zstd is blisteringly fast.

   But xz still yields the smallest files.

7. Removing big files from git history

   By accident I checked 60-odd full-size photographs into the git history of my website. I shrunk them in a next commit, but the history was still there leading to a bloated .git directory. This took a lot of time when making backups. This documents how I cleaned up this mess.

8. Using gnuplot from Python

   According to my revision control systems (rcs in those days), I’ve been using gnuplot to make graphs since at least 2002. And I’ve got it set up via a custom gnuplotrc to match the style of the TeX documents I often use the graphs in.

   At work we have an Instron 3369 machine for material testing. Recently, I wanted to visualize some tensile test data in ways that I couldn’t get into the test report.

9. Comparing stock ffmpeg with optimized ffmpeg

   Recently FreeBSD changed the multimedia/ffmpeg port to drop the -ffast-math and -fno-finite-math-only from the CFLAGS when building an optimized binary. The following experiment was conducted to see how much of a difference this makes.

10. PDF tricks

    This article contains several useful tricks for manipulating PDF files.

    The focus of this article is on Open Source and Free software, that are available for UNIX-like operating systems. These tools are made for use on the command-line of a shell.