In my last two posts Building a Parallella Mini-Cluster  and Bringing Up a Parallella Mini-Cluster – Trials and Tribulations  I described constructing a small cluster of 4 Parallella boards  into a case with power and cooling and initial steps at getting the cluster up and running. I finished at the point where I knew of the following problems:
My previous post Building a Parallella Mini-Cluster  dealt with physically building the cluster and ended at the point it could be switched on and off. The next stage is bringing the cluster up to a stable and usable state, and I am sorry to report that it has not been a trouble free ride and tracking down the problems is ongoing as of mid-July 2014.
One thing I should mention is that before turning on the power for the first time I installed the provided heat sinks on the Zynq FPGA chips.
I started experimenting with Raspberry Pi GPIO using Python [1,2]. Then the original Gertboard kit was released so I ordered and built one which enabled me to play with BCM2835 peripheral IO beyond basic GPIO. At the time the Gertboard had test and example C code available  that, as with the Python case, I felt could be expressed more cleanly. I thought it would be interesting to see what advantages C++, hopefully C++11, features and idioms might provide.
In this article I am going to discuss an alternative approach to using GPIO on a Raspberry Pi in Python to that taken by an early version the RPi.GPIO package. The approach occurred to me in 2012 while making a start at hardware interfacing and programming using a Raspberry Pi with some LEDs, switches and the like that had been collecting dust for 20 to 30 years. To read and write data to the GPIO lines I thought I would start with Python and the RPi.GPIO package.