Running rails with postgres

On my brother's advice, I spent a few hours configuring rails to run with postgresql instead of just SQLite. It took a couple hours, but I figure it will be worth it, since postgres is a production-quality database, not just a bunch of text files.

See Ruby on rails in EC2 in 20 minutes for the first part of the setup -- I use the same bitnami AMI to get started.

For the most part, I followed the steps here, but I had to do a little extra work to get the pg gem to install properly.

Here's the exact sequence of command line configuration steps:

    1  sudo apt-get install postgresql
    2  sudo apt-get update
    3  rails new icouncil -d postgresql
    4  sudo apt-get install libpq-dev
    5  bundle install
    6  ls
    7  cd icouncil/
    8  ls
    9  bundle install
   10  sudo su postgres
   11  psql
   12  sudo apt-get install postgresql
   13  sudo su postgres
   14  apt-get install gedit
   15  sudo apt-get install gedit
   16  sudo vi /etc/postgresql/8.4/main/pg_hba.conf
   17  sudo /etc/init.d/postgresql-8.4 restart
   18  psql postgres -U icouncil
   19  cd config
   20  vi database.yml
   21  cd ..
   22  rake db:create:all
   23  which psql
   24  sudo gem install pg -- --with-pg-dir=/usr/bin
   25  sudo gem install pg -- --with-pg-dir=/usr
   26  rake db:create:all
   27  rake db:create
   28  vi Gemfile
   29  bundle install
   30  rake db:create
   31  rails server
   32  history

If you want to do it even cleaner than me, I suspect this sequence would work--haven't tried it yet, though.

sudo apt-get update
sudo apt-get install gedit
sudo apt-get install libpq-dev
sudo apt-get install postgresql

sudo su postgres

sudo vi /etc/postgresql/8.4/main/pg_hba.conf
sudo /etc/init.d/postgresql-8.4 restart
psql postgres -U icouncil

rails new icouncil -d postgresql
cd icouncil/
vi Gemfile
cd config
vi database.yml
sudo gem install pg -- --with-pg-dir=/usr

bundle install
rake db:create
rails server

snowCrawl bug fixes and easier downloading

I've made a few small fixes to the snowCrawl python library. (See the updates page for details.)

The most important change is that I've created zipped and tar-gzipped versions of the repository for download. Now you can get snowcrawl even if you don't speak subversion. See the downloads page for one-click downloads.

Why philosophers should care about computational complexity

Read this paper a month or two back.  It's a truly fascinating discussion of the mathematics of computational complexity ("How hard is it to find an answer to a problem in class X using algorithm Y?") and its implications for some puzzles in philosophy.

Turns out that understanding complexity classes can add a lot to the way we think about our own minds. Examples include:

• Do I "know" what 1,847,234 times 345 is?
• Is it possible to cheat on the Turing test?
• Can waterfalls think?
• When can you prove you know something without revealing *how* you know it?
• If my grandkids learn to time travel, do I have to worry they might kill me?

There's math, but Aaronson has gone to a lot of effort to keep it manageable and well-explained. Highly recommend it.

(BTW, the paper has been out there for a few months. I'm posting now because it's related--a little--to the review of computational social science I've been working on.)