Difference: ANetworkDesignProblem (5 vs. 6)

• Problem Description
• Problem Formulation
• Computational Model
• Results
• Conclusions

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STUDENT TASKS


1. Comment the AMPL files san_design_neos.mod, san_design.dat and san_design_neos.run from san_design.zip. Run these files to find the optimal SAN design to support the flow requirements. Write a management summary for your solution.

What to hand in   ??? Mike to look at??? You commented AMPL files. Your management summary.


Extra for Experts' Tasks


1. One problem that often arises in network design (and other mixed-integer programming) is that of symmetry. If components in the network have the same properties, then mixed-integer programming will consider all the combinations of these components even though many combinations represent the same network. The following constraints:

subject to LinkAntisymmetry {l in LINKS} :
  card({k in LINKS : (from[k] = from[l]) and (to[k] = to[l]) and
                     (ord(k) > ord(l))}) * UseLink[l] >=
  sum {k in LINKS : (from[k] = from[l]) and (to[k] = to[l]) and
                    (ord(k) > ord(l))} UseLink[k];
  
subject to HubAntisymmetry {h in HUBS} :
  card({g in HUBS : ord(g) > ord(h)}) * UseHub[h] >=
  sum {g in HUBS : ord(g) > ord(h)} UseHub[g];

subject to SwitchAntisymmetry {s in SWITCHES : s <> last(SWITCHES)} :
  card({t in SWITCHES : ord(t) > ord(s)}) * UseSwitch[s] >=
  sum {t in SWITCHES : ord(t) > ord(s)} UseSwitch[t];


can be used to remove symmetry from the SAN design problem if all the hubs, switches and links have the same properties (i.e., bandwidth capacity, number of port slots, etc).

Add these constraints to san_design_neos.run and solve the SAN design problem again. Describe how these constraints remove symmetry. Comment on their effect on the solver's progress.

What to hand in  A brief (1 page or less) summary comprised of your description of how the antisymmetry constraints work and their effect on the solver's progress.
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