Have you ever needed to get the top n items for a key in Pig? For instance the most popular three items in each country for an online store? You could always solve this the hard way by calculating a threshold per country and then filter on that threshold. This is neither to write or execute. What you […]
This is a summary of a talk I held Monday May 14 2012 at an XP Meetup in Trondheim. It is meant as a teaser for listeners to play with Erlang themselves. First, some basic concepts. Erlang has a form of constant called atom that is defined on first use. They are typically used as […]
Note that the pitfall is limited to MRI (standard Ruby) version 1.9.2. MRI 1.9.3, JRuby and Rubinius does not have this behavior. I have been using Rubinius 2.0 to run machine learning experiments with libsvm lately. When running in Ruby 1.9.2, I noticed that my classifier always classified all samples as negative. I though this […]
This is my presentation from JavaZone 2010 Note that during my presentation, I showed the view section and basic replication directly in Futon instead of showing the fallback in the slides. What I did show was mostly the same, but naturally I showed some variations on the mappers as well.
Read the Getting Started part of Till Klampäckel’s CouchDB on Ubuntu on AWS blog post for some general information. I see no reason to repeat those things here. Till stresses the need for a security group opening port 80, but you should also enable ssh at port 22, otherwise it will be impossible to isntall […]
Have you ever been in a situation where you needed to create a reverse lookup index of some documents you had lying around? A reverse lookup index is the kind of index used by the search engines (or Googles if you like) of this world. Creating a reverse lookup index isn’t hard, but you would […]
When developing a new system, getting end-to-end functionality and being able to demonstrate it as soon as possible is important. While doing so, it’s also an added benefit if you do not spend a lot of time writing throwaway code. I have a set of scripts that let me test and use the system that […]