Mechanical Symapthy

I came across this article written by Martin Fowler

http://martinfowler.com/articles/lmax.html

Original I was looking for more info about the LMAX Disruptor after Nathan Marz talked about replacing the traditional queues with the LMAX Disruptor in his Storm 0.8 to increase the overall performance in a meetup.

In second part of the Martin Fowler's article, it was the first time I read the term "Mechanical Sympathy". According to the article, quote "The term comes from race car driving and it reflects the driver having an innate feel for the car, so they are able to feel how to get the best out of it." unquote.  Basically, you need to understand how the modern hardware work in order to squeeze the last drop of the performance. In these days, it is no longer just the disk is a very slow operation, even memory is a very slow operation as well. You want to make sure that your code and data are in the cache to get the performance.


This reminds me the old day when I worked on the embedded system, you needed to consider both the software and hardware could provide in order to come up the best solution.

How to install R on Cloudera CDH3

I wanted to play with the RHadoop package to see how R worked with Hadoop. Since the demo CDH3 image I was using from Cloudera did not bundle R, the first thing I had to do was to install R. Easy, I thought, I just needed to install the 3 R rpms from CRAN and it would be done.

Turned out the R rpms had a lot of dependencies (about 20-30 of extra rpms required) and the easiest way to install them was to install the EPEL (extra package for enterprise linux) repo first. Unfortunately the repo location returned from the google search (http://download.fedora.redhat.com) didn't seem to be working any more. Finally, I found the right repo and everything was done in just 2 commands:

$ sudo rpm -Uvh http://dl.fedoraproject.org/pub/epel/5/x86_64/epel-release-5-4.noarch.rpm $ sudo yum install R *replace the x86_64 with i386 if you are installing on a 32-bit system.