onelab2.gms : One element dynamic extracted from TSP


Small Model of Type : GAMS

Category : GAMS Test library

Main file : onelab2.gms

$title 'One element dynamic extracted from TSP' (ONELAB2,SEQ=171)

$eolcom //

set i nodes / i1*i6 /, t tours / t1*t6 /; alias (i,j,k);

table xl(i,j) decision variables - leg of trip

             i1          i2          i3          i4          i5          i6

i1                                                                    1.000
i2                                1.000
i3                    1.000
i4                                                        1.000
i5                                            1.000
i6        1.000

parameter tour(i,j,t)  subtours;
     sets from(i)      contains always one element: the from city
          next(j)      contains always one element: the to city
          visited(i)   flag whether a city is already visited
          tt(t)        contains always one element: the current subtour;
   scalar goon         go on flag used to control loop;

* initialize
from(i)$(ord(i)=1) = yes;    // turn first element on
tt(t)$(ord(t)=1)   = yes;    // turn first element on

   next(j) = no;                       // find city visited after city 'from'
      next(j) = yes);                  // check x.l(from,j)=1 would be dangerous
   tour(from,next,tt) = yes;           // store in table
   visited(from) = yes;                // mark city 'from' as visited
   from(j) = next(j);
   if(sum(visited(next),1)>0,          // if already visited...
      tt(t) = tt(t-1);
      loop(k$(not visited(k)), // find starting point of new subtour
         from(j) = no;         // make sure we only have one element turned on
         from(k) = yes;

table goodtour(i,j,t)  subtours

               t1          t2          t3

i1.i6       1.000
i2.i3                               1.000
i3.i2                               1.000
i4.i5                   1.000
i5.i4                   1.000
i6.i1       1.000

parameter difftour(i,j,t) diff between tour and gooudtour;

difftour(i,j,t) = goodtour(i,j,t) xor tour(i,j,t);

abort$card(difftour) 'tour is wrong', tour, goodtour, difftour;