# b_ r t k n_ r

## thoughts & experiences.

### Does modulus of sum of a uniform distribution also produce a uniform distribution?

I have been working on an Ethereum lottery Dapp with folks attending a meetup hosted by Strange Labs (Gloucester Road, Bristol) and we faced a problem where we realised that Solidity does not have a built in random number generator and therefore picking a winner turned out to be more difficult that anyone imagined.

### Permission issues with xpra 0.15.x on Ubuntu 16.04 Xenial when tunnelling through SSH

I often log into a remote SSH terminal to use an ipython shell. In doing so, it is necessary for me look at figures invoked by matplotlib as I am exploring and analysing data. For this, I have comfortably been using a combination of screen and xpra. However, I recently hesitantly upgraded my Ubuntu distribution from 14.04 Trusty Tahr to 16.04 Xenial Xerus. And with all upgrades, I expected minor breakages. Little did I realise that it would break xpra and interrupt my workflow sending me down a rabbit hole internet trawling for solutions. Turns out it is a known issue on on launchpad but the discussion has not been active for a while and the provided solutions were incomprehensible to a lay user. It appears that simply updating xpra to the latest version resolves the issue.

### Enabling MathJax on a Jekyll server when offline

I like MathJax. It does a great job displaying equations on web pages written using $\rm\LaTeX$. However, I recently wrote a Jekyll blog post which uses MathJax and tried to view it on a locally deployed server while commuting on a train journey with no Internet connection. Then, I realised that it did not render the equations at all because it relied on sending AJAX requests to a remote server. Something had to be done and this is how I went about fixing it.

### How to fix TeXcount !!! File/text was not valid utf8 encoded. !!! warning

In the process of writing my thesis which I have now handed in, I had to quite often check that I was not exceeding the word limit by running the following command:

### Getting Aimsun 8.1.3 to work on Ubuntu 16.04

After installing TSS’s Aimsun 8.1.3 on Ubuntu 16.04 (x64 build) on my machine, I tried to launch the program. However, the icon would appear briefly and close without any indication of what the problem was. The problem became obvious when starting up Aimsun through terminal using the following command:

### Mundane, Surreal

Sometimes, the mundane assumes a surreal form and takes one by surprise. I had the pleasure of this encounter this morning and I felt the need to share it.

### What me eat by Macka B

I love this song. Vegan solidarity!

### Use crontab to log CPU temperature on OSX!

I have just set up a way to automatically log temperature using OSX terminal because my computer was frequently overheating and I wanted to investigate why. Here is breakdown of how I did it.

### Find and delete files and folders in OSX terminal

Finding and deleting files and folders in OSX is simple. Open your terminal. In order to just find your files/folders (non destructive):

### Converting lots of raster files from one reference system to another

I had to convert lots of OSGB EPSG:27700 raster files to LonLat EPSG:4326 format and here is how I did it on my OSX terminal. I also wanted to change the format from *.asc to *.tif. Supposing you already have gdal libraries installed, just run the following code: