diff -r d59bea55db9b -r c445c931472f examples/fctp.mod
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/fctp.mod	Mon Dec 06 13:09:21 2010 +0100
@@ -0,0 +1,93 @@
+/* FCTP, Fixed-Charge Transportation Problem */
+
+/* Written in GNU MathProg by Andrew Makhorin <mao@gnu.org> */
+
+/* The Fixed-Charge Transportation Problem (FCTP) is obtained from
+   classical transportation problem by imposing a fixed cost on each
+   transportation link if there is a positive flow on that link. */
+
+param m, integer, > 0;
+/* number of sources */
+
+param n, integer, > 0;
+/* number of customers */
+
+set I := 1..m;
+/* set of sources */
+
+set J := 1..n;
+/* set of customers */
+
+param supply{i in I}, >= 0;
+/* supply at source i */
+
+param demand{j in J}, >= 0;
+/* demand at customer j */
+
+param varcost{i in I, j in J}, >= 0;
+/* variable cost (a cost per one unit shipped from i to j) */
+
+param fixcost{i in I, j in J}, >= 0;
+/* fixed cost (a cost for shipping any amount from i to j) */
+
+var x{i in I, j in J}, >= 0;
+/* amount shipped from source i to customer j */
+
+s.t. f{i in I}: sum{j in J} x[i,j] = supply[i];
+/* observe supply at source i */
+
+s.t. g{j in J}: sum{i in I} x[i,j] = demand[j];
+/* satisfy demand at customer j */
+
+var y{i in I, j in J}, binary;
+/* y[i,j] = 1 means some amount is shipped from i to j */
+
+s.t. h{i in I, j in J}: x[i,j] <= min(supply[i], demand[j]) * y[i,j];
+/* if y[i,j] is 0, force x[i,j] to be 0 (may note that supply[i] and
+   demand[j] are implicit upper bounds for x[i,j] as follows from the
+   constraints f[i] and g[j]) */
+
+minimize cost: sum{i in I, j in J} varcost[i,j] * x[i,j] +
+               sum{i in I, j in J} fixcost[i,j] * y[i,j];
+/* total transportation costs */
+
+data;
+
+/* These data correspond to the instance bal8x12 from [Balinski]. */
+
+/* The optimal solution is 471.55 */
+
+param m := 8;
+
+param n := 12;
+
+param supply := 1 15.00,  2 20.00,  3 45.00,  4 35.00,
+                5 25.00,  6 35.00,  7 10.00,  8 25.00;
+
+param demand := 1 20.00,  2 15.00,  3 20.00,  4 15.00,
+                5  5.00,  6 20.00,  7 30.00,  8 10.00,
+                9 35.00, 10 25.00, 11 10.00, 12  5.00;
+
+param varcost
+      :   1    2    3    4    5    6    7    8    9    10   11   12  :=
+      1  0.69 0.64 0.71 0.79 1.70 2.83 2.02 5.64 5.94 5.94 5.94 7.68
+      2  1.01 0.75 0.88 0.59 1.50 2.63 2.26 5.64 5.85 5.62 5.85 4.94
+      3  1.05 1.06 1.08 0.64 1.22 2.37 1.66 5.64 5.91 5.62 5.91 4.94
+      4  1.94 1.50 1.56 1.22 1.98 1.98 1.36 6.99 6.99 6.99 6.99 3.68
+      5  1.61 1.40 1.61 1.33 1.68 2.83 1.54 4.26 4.26 4.26 4.26 2.99
+      6  5.29 5.94 6.08 5.29 5.96 6.77 5.08 0.31 0.21 0.17 0.31 1.53
+      7  5.29 5.94 6.08 5.29 5.96 6.77 5.08 0.55 0.35 0.40 0.19 1.53
+      8  5.29 6.08 6.08 5.29 5.96 6.45 5.08 2.43 2.30 2.33 1.81 2.50 ;
+
+param fixcost
+      :   1    2    3    4    5    6    7    8    9    10   11   12  :=
+      1  11.0 16.0 18.0 17.0 10.0 20.0 17.0 13.0 15.0 12.0 14.0 14.0
+      2  14.0 17.0 17.0 13.0 15.0 13.0 16.0 11.0 20.0 11.0 15.0 10.0
+      3  12.0 13.0 20.0 17.0 13.0 15.0 16.0 13.0 12.0 13.0 10.0 18.0
+      4  16.0 19.0 16.0 11.0 15.0 12.0 18.0 12.0 18.0 13.0 13.0 14.0
+      5  19.0 18.0 15.0 16.0 12.0 14.0 20.0 19.0 11.0 17.0 16.0 18.0
+      6  13.0 20.0 20.0 17.0 15.0 12.0 14.0 11.0 12.0 19.0 15.0 16.0
+      7  11.0 12.0 15.0 10.0 17.0 11.0 11.0 16.0 10.0 18.0 17.0 12.0
+      8  17.0 10.0 20.0 12.0 17.0 20.0 16.0 15.0 10.0 12.0 16.0 18.0 ;
+
+end;