ICFP Contest 2015
Cult of the Bound Variable


Please see constitution.txt for participants.


This is Standard ML code to compile with mlton. The makefile should do that.
./driver.exe runs our "best" solution, managing everything but memory limit; use play_icfp2015 for that.

We are very tired! We found 15 power words (phrases.sml) using a
variety of techniques, mostly guessing, and algebra.


<3

Cult of the Bound Variable

<<<<< MERGE CONFLICT

Overview
--------

Our solvers generally work in two phases: first, play Hextris well; then,
attempt to insert phrases of power into the solution.  Playing Hextris
well involves a variety of game tree searches over "lock steps" that are
reachable from a unit's initial position.  Once a sequence of lock steps
are chosen, power phrase insertion (PowerThirst) attempts to find ways of
inserting phrases of power into the sequence of moves making up a lock step
while maintaining its target position as reachable.  We attempt to insert
each power phrase at least once.


Phrases of Power
----------------

To find phrases of power, we built a tool, PowerBall, to construct maximal
sequences target words that are legal, sometimes perturbing the beginning
of the sequence with some commands to move away from the top (hog, b, p).
We seeded a database of target words with everything we could think of or
find reference to relating to the Cthulhu mythos, H. P. Lovecraft, Stross's
Laundry Files series, Buckaroo Banzai, and a few other topics that we felt
were thematically appropriate, e.g., Church of the Subgenius, Discordianism,
Robert Anton Wilson, and various other bits of nerd culture.

For a full list of target words and phrases, see powerball.txt.

We manually ran the "experiments" produced by PowerBall and added any
negative results to PowerBall's "exclusion" list -- PowerBall carefully
ignores any phrase that's already known to be a phrase of power or any
phrase that is known *not* to be a phrase of power because it's a substring
of a solution known to contain no phrases of power.

We also built a tool, PowerWalk, to digest the situation where we accidentally
stumbled upon a phrase of power in a submitted solution -- if the contest
server's score differs from our own, we can use some math and some computation
to determine candidate substrings that could account for the discrepancy by
being considered phrases of power.  Unfortunately, it only really discovered
one power word this way, which was "bap", which actually wasn't a power word
at all but merely a bug in the contest server's score computation.  ("bap" is
isomorphic to "ei!", a bona fide power phrase.)  PowerWalk was nonetheless
useful for providing a list of candidates to visually scan for plausibility
when PowerBall discovered that a phrase of power was embedded in a large string
with many potential target words -- usually, the only actual complete phrase of
the appropriate target length would be obvious in a list of candidates.