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Ethereum: Synchronising with the Blockchain

You synchronise with the Ethereum blockchain by starting a local node. It’ll take a while to catch up with the most recently created blocks, but once you’ve downloaded the full history, further updates will be relatively quick. You’ll also need a good chunk of storage space available (around 15 Gb should be sufficient right now, but this will grow with time).

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Ethereum: DIY Tools for Smart Contracts

What tools do you need to start working with Ethereum smart contracts?

The Solidity Online Compiler provides a quick way to experiment with smart contracts without installing any software on your machine. Another promising online alternative is Cosmo.

However at some stage you’ll probably want to put together a local Ethereum development environment. Here are some suggestions for how to do that on an Ubuntu machine.

Since I’m just feeling my way into this new domain, I’m not sure to what degree all of these are necessary. I do know for sure, that Truffle and testrpc are crucial.

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NTP: Synchronise Your Watches

Just like an old fashioned grandfather clock, time time on your computer’s clock can slowly drift. You can quickly verify the accuracy of your clock by comparing it to It’s not unusual for it to be anything from a few seconds to a couple of minutes out. For most purposes this is not a major issue, but there are some applications which are very time sensitive.

NTP (Network Time Protocol) is a tool which will synchronise your computer’s clock with a network of accurate time servers, ensuring that it’s always accurate.

There’s a lot to be said about NTP, but this is a quick guide to getting it up and running on an Ubuntu machine.

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An Ethereum Package for R

Bitcoin has become synonymous with “cryptocurrency”. Ethereum is another cryptocurrency which, although not as hyped at Bitcoin, presents some attractive characteristics. The foremost of these is the ability to create sophisticated smart contracts.

This post introduces the new ether package for interacting with the Ethereum network from R.

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Moving a Running Process to screen

I am not sure how many times this has happened to me, but it’s not infrequent. I’m working on a remote session and I start a long running job. Then some time later I want to disconnect from the session but realise that if I do then the job will be killed.

I should have started job in screen or tmux!

So, is it possible to transfer the running process to screen? (Or, equally, to tmux?) Well it turns out that it is using the reptyr utility. I discovered this thanks to a LinkedIn post by Bruce Werdschinski. A slightly refinement of his process is documented below.

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Creating an Amazon Machine Image

Creating an Amazon Machine Image (AMI) makes it quick and simple to rebuild a specific EC2 setup. This post illustrates the process by creating an AMI with ethminer and NVIDIA GPU drivers. Of course you’d never use this for mining Ether because the hardware costs are still too high!

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Using Large Maps with OSRM

How to deal with large data sets in OSRM? Some quick notes on processing monster PBF files and getting them ready to serve with OSRM.

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EC2 Missing Disk Space

This morning I created a r3.xlarge spot instance on EC2. The job I’m planning on running requires a good wad of data to be uploaded, which is why I chose the r3.xlarge instance: it’s cost effective and, according to AWS, has 80 Gb of SSD storage.

So I was a little surprised when I connected to the running instance and found that the root partition was only around 8 Gb. This is what I did to claim that missing disk space.

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Variable Names: Camel Case to Underscore Delimited

A project I’m working on has a bunch of different data sources. Some of them have column names in Camel Case. Others are underscore delimited. My OCD rebels at this disarray and demands either one or the other.

If it were just a few columns and I was only going to have to do this once, then I’d probably just quickly do it by hand. But there are many columns and it’s very likely that there’ll be more data in the future and the process will need to be repeated.

Seems like something that should be easy to automate.

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Analysis of Feedback from satRday [Cape Town] 2017

We recently announced the second satRday (Cape Town) conference scheduled to take place on 17 March 2018. Obviously we want this to be bigger and better than this year’s event, so we are paying careful attention to the feedback that we received from the first event.

This is a quick analysis of the feedback. We sold 192 tickets and gave out 11 complimentaries to the event. There were 107 responses to the feedback survey, which means that we heard back from more than half of the people who attended, which is hopefully a representative sample.

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Durban Twitter Analysis

I was invited to give a talk at Digifest (Durban University of Technology) on 10 November 2017. Looking at the other speakers and talks on the programme I realised that my normal range of topics would not be suitable. I needed to do something more in line with their mission to “celebrate the creative spirit through multimedia projects from disciplines such as visual and performing arts” and to promote “collaboration across art, science and technology”. Definitely outside my current domain, but consistent with many of the things that I have been aspiring to.

To be honest, I was pleased to be invited, but when I sat down to consider what I would talk about, I found myself at a loss. I’m not currently engaged in anything that ticks many of those boxes.

But I am loathe to turn down an opportunity to speak. So I made a plan. In retrospect it was not a terribly good plan. But it was workable. I decided to speak about gauging sentiment relating to the city of Durban using data from Twitter. You can find my talk outline here. This post touches on some of my results.

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Hello Durban, tell me how you're doing!

Hello Durban, tell me how you're doing!
Everybody speaks their mind on Social Media. So, what are people saying about Durban? I'll harvest the Twitter stream to answer this question, making use of some simple analytics, sentiment analysis and machine learning.

This talk was presented at Digifest (Durban University of Technology) on 10 November 2017.

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Conference Bucket List

A list of conferences and meetups I’d like to speak at in the next few years.

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Installing NVIDIA Graphics Driver on Ubuntu

Recipe for installing the NVIDIA binary drivers on Ubuntu.

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Running OSRM with Docker

I’ve now been through the process of setting up OSRM a few times. While it’s not exactly taxing, it seemed like a prime candidate for automation.

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Exporting HTML Presentations to PDF

Building a presentation with reveal.js is such a pleasure. And the results looks so good. Seriously doubt that I will ever use anything like PowerPoint again. Although it’s possible to export a presentation directly to PDF using a style sheet, this doesn’t always work perfectly (IMHO).

Fortunately there’s another way: decktape. It works with reveal.js and a bunch of other HTML5 presentation frameworks.

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Quick Wordpress Install with Docker

I’ve just put together a Wordpress site for my older daughter. It’s hosted on DigitalOcean and all of the infrastructure is handled with Docker. This post describes the steps in the (easy) install process.

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Diagnosing Killed Jobs on EC2

I’ve got a long running optimisation problem on a EC2 instance. Yesterday it was mysteriously killed. I shrugged it off as an anomaly and restarted the job. However, this morning it was killed again. Definitely not a coincidence! So I investigated. This is what I found and how I am resolving the problem.

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Removing Redundant Hostnames with NGINX

While poring over my Google Analytics data I noticed the notification below.

Obviously this is not a train smash, but it is compromising the quality of my data. And it also offends my OCD. This is what I did to fix the problem.

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Hosting a Plumber API on AWS

I’ve been putting together a small proof-of-concept API using R and plumber. It works flawlessly on my local machine and I was planning on deploying it on an EC2 instance to demo it for a client. However, I ran into a snag: despite opening the required port in my Security Group I was not able to access the API. This is what I needed to do to get it working.

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