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Given a group of people who might want to talk to each other, how would you pair them up? We tried this by having initial 'speed dates', where people talk to about five random people for about two minutes each, and then put those five people in order of who they would most like to talk to for longer. We then paired them up, with several rounds of pairing, based on those preference lists using Irving's algorithm for the stable roommates problem:

This is implemented here in Perl in a program known as 'StableRoommmates'. Each person lists all the other people present that they would like to talk to, in order of preference. The algorithm then attempts a 'stable matching': to pair people up such that there is no pair where both members prefer another partner to the one they have been paired with. Such a pairing is not always possible.

Caveats / Expectation management

  • not everyone will get to speak to their preferred people
  • people can be paired with people not on their preference lists
  • I haven't made much attempt yet to make StableRoommates friendly or easy for other people to use

Adaptations to Irving's algorithm implemented in StableRoommmates

(I've not attempted a mathematical/computatioanl proof of any of these, unlike the proof of the original algorithm in the original paper.)

Incomplete preference lists

Irving's algorithm assumes that everyone has listed everyone else: if you have X people, then everyone should have a prefence list X-1 long. When running an initial speed-dating session in a big unseminar, it's unlikely that there'll be time for everyone to speak to everyone else, so I adapted the algorithm to allow for partial preference lists: all people not listed by a particular person are added on to the end of that person's given preference list.

Multiple rounds of pairing

Multiple rounds of pairing are possible, with pairings from previous rounds removed from preference lists.

Random pairings when no stable pairing is found

If no stable pairing is found in a particular round, people will be paired randomly.


perl Makefile.PL
make test
make install


See bin/

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