This quick start assumes that you have virtualbox and vagrant installed on your machine. There is nothing in the tournament code that requires either virtualbox or vagrant so if you run linux and have PostgreSQL installed you can probably run it anyway, at least I did !-)

But for the virtual machine case, proceed as follows:

`$ git clone git@github.com:alcarruth/tournament-results

$ cd tournament-results/vagrant

$ vagrant up

$ vagrant ssh

At this point you should be logged into the virtual machine as user vagrant. At the new vm prompt enter the following:

$ cd /vagrant/tournament

`$ psql -f tournament.sql

This will create the tournament database its tables and views. Then you can run the following:

$ ./tournament_test.py

$ ./tournament_demo.py

This project utilizes the PostgreSQL relational database software and the python programming language to implement a Swiss Pairings style tournament database. In addition to the functions specified by the project assignment, other functionality is included to simulate a tournament and to pretty print the standings after each round. See tournament_demo.py for more.

The pairing algorithm pairs players with an equal or almost equal number of wins. In the case of an odd number of players, a player with the least number of wins is paired with a dummy player who always loses.

The pairing algorithm is guaranteed not to pair players who have previously played each other. The algorithm proceeds by producing a candidate pairing and checking that it includes no previously paired players. If it does, the list of players is randomly shuffled and another candidate pairing is generated. This is repeated until a valid pairing is found.

Note that there is no guarantee that this shuffling will arrive at a valid pairing. I believe the probability of succes is high, however. The ethernet protocol behaves in a similar way and it's inventor, Robert Metcalfe is credited as saying the protocol "works in practice, but not in theory". So far, this pairing algorithm seems to work pretty well "in practice".

All files for project P2 are contained within the vagrant/tournament directory. There is one SQL file:

• tournament.sql

This is used to initialize the tournament database by creating the database, tables and views used by the program. This can be done from the bash prompt:

`$ psql -f tournament.sql

There are three tournament python files:

• tournament.py
• tournament_test.py
• tournament_demo.py

The implementation of the tournament program is entirely in tournament.py and tournament.sql. The file tournament_test.py contains the unit test that came with the assignment and the file tournament_demo.py contains some code to run a 16 person tournament simulation.

In thinking about this swiss pairing stuff I couldn't help but think there was something familiar about the sizes of the groups when the players were grouped by their number of wins after each round. It definitely reminded me of Pascal's triangle. So I have here pascal.py in which I tried to investigate this relationship.

Nothing much came of the pascal.py exercise. It seemed to only be applicable in the case where the number of players is a power of two. That is, when there is a 'full bracket' of players. But it was fun none-the-less.