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reGrouper is a Python desktop application for putting people in 'optimal' groups - ones in which as few people as possible are in the same group more than once or are paired with the same person multiple times. It is useful for tasks like assigning students to groups that rotate each month or generating seating charts for a multi-day event.

reGrouper can be run either from the command line or from a GUI.

###Installation The reGrouper GUI requires matplotlib and numpy, both of which can be installed with pip:

pip install numpy
pip install matplotlib

To run the tests, you'll need nose:

pip install nose

Install reGrouper by cloning this repository:

git clone </your/desired/path/to/grouper>

(Note: reGrouper was written for Python 2.7.6. It has not been tested with other versions.)

###Running from the Command Line To run reGrouper from the command line, use

grouper <people file> <num days> -s <size of groups>


grouper <people file> <num days> -n <number of groups>

people file is a .csv or .txt file containing peoples' names, one per line. num days is the number of days, or rounds, you are making groups for. size of groups is the preferred size of each group. number of groups is the preferred number of groups.

reGrouper requires that you enter either size of groups or number of groups, but not both.

If you'd like to run reGrouper from anywhere, mark reGrouper's as executible and add it to your path:

cd path-to-grouper
chmod u+x
ln -s path-to-grouper/ /usr/local/bin/grouper

Now you can run, e.g.:

grouper <people file> <num days> -n <number of groups>

from any directory.

reGrouper's output is a CSV file containing the lists of individuals sitting at each table on each day. By default, it is named 'output.csv'. You can change its name by using the -f option in the command line, e.g:

grouper <people file> <num days> -n <number of groups> -f <filename>

###Running from the GUI reGrouper comes with a simple GUI*. To start the GUI from the command line, run:


###Optimization Rules reGrouper uses the following criteria:

  • Produce groups of the requested size and number
  • Minimize the number of pairs grouped together multiple times.
  • Minimize the number of trios grouped together multiple times.
  • Minimize the number of people placed in the same spot (e.g. Group 5) multiple times.

###Algorithm reGrouper utilizes two separate algorithms: a simple greedy strategy that populates the tables day-by-day, placing each person at the spot that seems most optimal for him when his name is drawn, and a simulated annealing algorithm that generates a solution and switches people around repeatedly in a search for the optimal solution. (For the curious, I've written a blog post about simulated annealing).

By modifying the greedy and anneal settings in, you can turn these two parts of the algorithm on and off independently. I've found I get the best solutions when both of them are enabled:

greedy = True # turns on greedy algorithm
anneal = True # turns on simulated annealing

If anneal is True but greedy is False, the annealing algorithm begins from a random solution. If both are set to False, reGrouper returns a random solution.

###Preferences reGrouper comes with the following configuration settings, set in

Config Parameter Possible Values Purpose
greedy (True/False) Enable/disable the greedy grouping algorithm
anneal (True/False) Enable/disable the annealing algorithm
display_progress (True/False) If True, displays the current temperature and best cost at the end of each annealing iteration.
verbose (True/False) Print debugging messages
super_verbose (True/False) Print even more debugging messages
num_tries (integer >= 1) The number of attempts to make. Default is 1.
T (float >= 0) the initial annealing temperature. Default is 1.
alpha (float between 0 and 1) The proportion by which to decrease T at the end of each annealing iteration. Default is 0.95.
T_min (float between 0 and T) The temperature at which to stop if an acceptable solution has not yet been found. Default is 0.001.
max_acceptable_cost (int >= 0) The cost at which to stop searching for a better solution and return the current one. Default is 0, which corresponds with perfectly satisfying all constraints.
iterations_per_temp (int >= 0) the number of switches to make at each temperature while annealing. Default is 500.

The last five parameters correspond with simulated annealing.

###Performance reGrouper's performance is hampered by the expense of computing its cost functions. Depending on the specific parameters, generating groupings of 100 people can take 15-30 minutes. If you just need a 'good-enough' grouping, set the anneal setting to False.

* Like the rest of reGrouper, the GUI is written in Python, using the Tkinter library. reGrouper has a desktop interface rather than a web one because it is descended from an earlier desktop application.