CODEWITHSUNDEEP
ampl
user55531
user55531

Reputation: 145

writing large number of constraints in AMPL

I am trying to solve small instances of TSP in AMPL. But the subtour elimination constraints are too many even for a small instance. What would be a efficient way to write these constraints in AMPL. thanks

Upvotes: 1

Views: 520

Answers (1)

vitaut
vitaut

Reputation: 55524

Here's the usual formulation of a set of subtour elimination constraints in AMPL

subj to SubtourElim {k in SS diff {0,2**n-1}}:
   sum {i in POW[k], j in S diff POW[k]: (i,j) in LINKS} X[i,j] +
   sum {i in POW[k], j in S diff POW[k]: (j,i) in LINKS} X[j,i] >= 2;

taken from http://ampl.com/FAQ/tsp.mod.

Since the number of constraints grows exponentially with n, instead of adding all of them in advance you can add them dynamically in an AMPL script as described here.

Upvotes: 1

Related Questions