gistfile1.txt

# 
# CONFERENCE SCHEDULING
#
# Finds a solution to scheduling all the education
# sessions at the annual conference
#

/* Rooms, Days, Times */
set ROOMS;
set DAYS;
set TIMES;

/* Presenters, Topics */
set PRESENTERS;
set TOPICS;

/* Sessions: index, ID, topic, rank, presenter */
set SESSIONS, dimen 5;
set S := setof{(a,b,c,d,e) in SESSIONS} a;

/* Assignment */
var x{d in DAYS, t in TIMES, r in ROOMS, s in S}, binary;

/* Objective Function */
minimize obj:
  sum{d in DAYS, t in TIMES, r in ROOMS, s in S} x[d,t,r,s];

/* Constraint 1: each session is scheduled exactly once */
s.t. c1 {s in S} :
  sum{d in DAYS, t in TIMES, r in ROOMS} x[d,t,r,s] = 1;

/* Constraint 2: each day-time-room doesn't have more than
 * one session scheduled
 */
s.t. c2 {d in DAYS, t in TIMES, r in ROOMS} :
  sum{s in S} x[d,t,r,s] <= 1;

/* Constraint 3: each day-time doesn't have a presenter
 * in more than one scheduled session
 */
s.t. c3 {d in DAYS, t in TIMES, p in PRESENTERS} :
  sum{r in ROOMS, s in S} x[d,t,r,s] <= 1;


/* SOLVE! */
solve;

/* Output */

printf "\n";
printf "=============================================\n";

for {d in DAYS} {
  for {t in TIMES} {
    for {r in ROOMS} {
      for {s in S} {
        for {{0}: x[d,t,r,s] == 1} {
          printf "%s\t%s\t%s\t%s\n", d, t, r, s;
        }
      }
    }
  }
}


/* DATA */
data;

set ROOMS       := A B;
set DAYS        := Thu;
set TIMES       := 900 1000;
set TOPICS      := Bio Tech Math;
set PRESENTERS  := Tom Jerry Nancy;

set SESSIONS :=
  1   20A   Bio   9   Tom
  2   3B1   Tech  8   Jerry
  3   7KC   Math  7   Tom
  4   L9U   Bio   6   Nancy;

/* EOF */

end;