The complete program follows. You can also view the entire program online in the file YourSolverHome/examples/src/freq.cpp.

#include <ilsolver/ilosolverint.h>
 
ILOSTLBEGIN
 
const int nbCell               = 25;
const int nbAvailFreq          = 256;
const int nbChannel[nbCell] =
  { 8,6,6,1,4,4,8,8,8,8,4,9,8,4,4,10,8,9,8,4,5,4,8,1,1 };
const int dist[nbCell][nbCell] = {
  { 16,1,1,0,0,0,0,0,1,1,1,1,1,2,2,1,1,0,0,0,2,2,1,1,1 },
  { 1,16,2,0,0,0,0,0,2,2,1,1,1,2,2,1,1,0,0,0,0,0,0,0,0 },
  { 1,2,16,0,0,0,0,0,2,2,1,1,1,2,2,1,1,0,0,0,0,0,0,0,0 },
  { 0,0,0,16,2,2,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,1,1 },
  { 0,0,0,2,16,2,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,1,1 },
  { 0,0,0,2,2,16,0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,0,0,1,1 },
  { 0,0,0,0,0,0,16,2,0,0,1,1,1,0,0,1,1,1,1,2,0,0,0,1,1 },
  { 0,0,0,0,0,0,2,16,0,0,1,1,1,0,0,1,1,1,1,2,0,0,0,1,1 },
  { 1,2,2,0,0,0,0,0,16,2,2,2,2,2,2,1,1,1,1,1,1,1,0,1,1 },
  { 1,2,2,0,0,0,0,0,2,16,2,2,2,2,2,1,1,1,1,1,1,1,0,1,1 },
  { 1,1,1,0,0,0,1,1,2,2,16,2,2,2,2,2,2,1,1,2,1,1,0,1,1 },
  { 1,1,1,0,0,0,1,1,2,2,2,16,2,2,2,2,2,1,1,2,1,1,0,1,1 },
  { 1,1,1,0,0,0,1,1,2,2,2,2,16,2,2,2,2,1,1,2,1,1,0,1,1 },
  { 2,2,2,0,0,0,0,0,2,2,2,2,2,16,2,1,1,1,1,1,1,1,1,1,1 },
  { 2,2,2,0,0,0,0,0,2,2,2,2,2,2,16,1,1,1,1,1,1,1,1,1,1 },
  { 1,1,1,0,0,0,1,1,1,1,2,2,2,1,1,16,2,2,2,1,2,2,1,2,2 },
  { 1,1,1,0,0,0,1,1,1,1,2,2,2,1,1,2,16,2,2,1,2,2,1,2,2 },
  { 0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,2,2,16,2,2,1,1,0,2,2 },
  { 0,0,0,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,16,2,1,1,0,2,2 },
  { 0,0,0,1,1,1,2,2,1,1,2,2,2,1,1,1,1,2,2,16,1,1,0,1,1 },
  { 2,0,0,0,0,0,0,0,1,1,1,1,1,1,1,2,2,1,1,1,16,2,1,2,2 },
  { 2,0,0,0,0,0,0,0,1,1,1,1,1,1,1,2,2,1,1,1,2,16,1,2,2 },
  { 1,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,0,0,0,1,1,16,1,1 },
  { 1,0,0,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,1,2,2,1,16,2 },
  { 1,0,0,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,1,2,2,1,2,16 }
};
 
IlcRevInt** freqUsage;
 
 
class IlcFreqConstraintI : public IlcConstraintI {
protected:
  IlcIntVarArray _x;
 public:
  IlcFreqConstraintI(IloSolver s, IlcIntVarArray x)
    : IlcConstraintI(s), _x(x) {}
  ~IlcFreqConstraintI() {}
  virtual void post();
  virtual void propagate() {}
  void varDemon(IlcIntVar var);
};
 
ILCCTDEMON1(FreqDemon, IlcFreqConstraintI, varDemon, IlcIntVar, var);
 
void IlcFreqConstraintI::post () {
  IlcInt i;
  for (i = 0; i < _x.getSize(); i++)
    _x[i].whenValue(FreqDemon(getSolver(), this, _x[i]));
}
 
void IlcFreqConstraintI::varDemon (IlcIntVar var) {
  IlcRevInt& freq = *freqUsage[var.getValue()];
  freq.setValue(getSolver(), freq.getValue() + 1);
}
 
IlcConstraint IlcFreqConstraint(IloSolver s, IlcIntVarArray x) {
  return new (s.getHeap()) IlcFreqConstraintI(s, x);
}
 
 
 
ILOCPCONSTRAINTWRAPPER1(IloFreqConstraint, solver, IloIntVarArray, _vars) {
  use(solver, _vars);
  return IlcFreqConstraint(solver, solver.getIntVarArray(_vars));
}
 
 
IlcInt bestFreq(IlcIntVar var) {
  IlcInt max = -1;
  IlcInt maxIndex = 0;
  IlcInt i;
  for(IlcIntExpIterator iter(var);iter.ok();++iter){
    i=*iter;
    if (*freqUsage[i] > max){
      max = *freqUsage[i];
      maxIndex = i;
    }
  }
  return maxIndex;
}
 
ILCGOAL1(Instantiate, IlcIntVar, var) {
  if (var.isBound()) return 0;
  IlcInt val = bestFreq(var);
  return IlcOr(var == val,
               IlcAnd(var != val,
                      this));
}
 
void SetCluster(IlcIntVar var, IlcInt clusterSize) {
  var.setObject((IlcAny) clusterSize);
}
 
IlcInt GetCluster(IlcIntVar var) {
  return (IlcInt) (var.getObject());
}
 
static IlcChooseIndex2(IlcChooseClusterFreq,
                       var.getSize(),
                       GetCluster(var),
                       IlcIntVar)
 
ILCGOAL1(MyGenerate, IlcIntVarArray, vars) {
  IloSolver solver = getSolver();
  IlcInt chosen = IlcChooseClusterFreq(vars);
  if(chosen == -1)
    return 0;
  return IlcAnd(Instantiate(solver, vars[chosen]),this);
}
 
ILOCPGOALWRAPPER1(MyIloGenerate, solver, IloIntVarArray, vars) {
  return MyGenerate(solver, solver.getIntVarArray(vars));
}
 
IlcInt partialsum[nbCell];
inline IlcInt acc(IlcInt i, IlcInt j) {
  return partialsum[i]+j;
}
 
int main(){
  IloEnv env;
  try {
    IloModel model(env);
    IloSolver solver(env);
 
    IlcInt i, ii, j, jj;
    IlcInt usedFreq = 0;
    IlcInt nbXmiter = 0;
 
    for (i = 0; i < nbCell; i++) {
      partialsum[i] = nbXmiter;
      nbXmiter += nbChannel[i];
    }
 
    IloIntVarArray X(env, nbXmiter, 0, nbAvailFreq - 1);
 
    for (i = 0; i < nbCell; i++)
      for (j = i; j < nbCell; j++)
        for (ii = 0; ii < nbChannel[i]; ii++)
          for (jj = 0; jj < nbChannel[j]; jj++)
            if (dist[i][j] != 0 && (i != j || ii != jj))
              model.add(IloAbs(X[acc(i,ii)] - X[acc(j,jj)]) >= dist[i][j]);
 
    model.add(IloFreqConstraint(env, X));
 
    solver.extract(model);
 
    for (i = 0; i < nbCell; i++)
      for (ii = 0; ii < nbChannel[i]; ii++)
        SetCluster(solver.getIntVar(X[acc(i,ii)]), nbChannel[i]);
 
    freqUsage = new (env) IlcRevInt* [nbAvailFreq];
    for (i = 0; i < nbAvailFreq; i++)
      freqUsage[i] = new (env) IlcRevInt(solver);
 
    solver.solve(MyIloGenerate(env, X));
 
    for (i = 0; i < nbCell; i++) {
      for (j = 0; j < nbChannel[i]; j++)
        solver.out() << solver.getValue(X[acc(i,j)]) << "  " ;
      solver.out() << endl;
    }
    solver.out() << "Total # of sites       " << nbXmiter << endl;
    for (i = 0; i < nbAvailFreq; i++)
      if (freqUsage[i]->getValue() != 0)
        usedFreq++;
    solver.out() << "Total # of frequencies " << usedFreq << endl;
  }
  catch (IloException& ex) {
    cout << "Error: " << ex << endl;
  }
  env.end();
  return 0;
}
 
 

Output

The strategy used here allows the program to find good solutions. Indeed, on this data, it leads directly to the optimal solution. Here is the output:

25  41  57  73  89  105  121  137
1  21  37  53  71  87
6  23  39  55  75  103
0
2  18  34  50
4  20  36  52
75  10  27  43  59  96  112  128
13  30  46  62  80  99  115  131
13  35  51  67  83  99  115  131
19  64  80  96  112  128  144  160
0  16  32  48
8  26  42  58  74  90  106  122  138
2  24  40  56  72  88  104  120
4  28  44  60
11  30  46  62
20  36  52  68  84  100  116  132  148  164
18  34  50  66  82  98  114  130
9  25  41  57  73  89  105  121  137
7  23  39  55  71  87  103  119
5  21  37  53
10  27  43  59  75
6  22  38  54
0  21  37  53  71  87  103  128
1
3
Total # of sites       148
Total # of frequencies 95