// Update the walkabout strengths and stay flags of all variables
// downstream of the given constraint. Answer a collection of
// unsatisfied constraints sorted in order of decreasing strength.
//
public ArrayList removePropagateFrom(Variable outvar)
{
outvar.determinedBy = null;
outvar.walkStrength = Strength.weakest;
outvar.stay = true;
ArrayList unsatisfied = new ArrayList();
ArrayList todo = new ArrayList();
todo.Add(outvar);
while (!(todo.Count == 0))
{
#if USE_STACK
Variable v = (Variable)todo[todo.Count - 1];
todo.RemoveAt(todo.Count - 1);
#else
Variable v = (Variable)todo[0];
todo.RemoveAt(0);
#endif
for (int i = 0; i < v.constraints.Count; ++i)
{
Constraint c = (Constraint)v.constraints[i];
if (!c.isSatisfied())
{
unsatisfied.Add(c);
}
}
Constraint determiningC = v.determinedBy;
for (int i = 0; i < v.constraints.Count; ++i)
{
Constraint nextC = (Constraint)v.constraints[i];
if (nextC != determiningC && nextC.isSatisfied())
{
nextC.recalculate();
todo.Add(nextC.output());
}
}
}
return(unsatisfied);
}
// Recompute the walkabout strengths and stay flags of all variables
// downstream of the given constraint and recompute the actual
// values of all variables whose stay flag is true. If a cycle is
// detected, remove the given constraint and answer
// false. Otherwise, answer true.
// Details: Cycles are detected when a marked variable is
// encountered downstream of the given constraint. The sender is
// assumed to have marked the inputs of the given constraint with
// the given mark. Thus, encountering a marked node downstream of
// the output constraint means that there is a path from the
// constraint's output to one of its inputs.
//
public Boolean addPropagate(Constraint c, int mark)
{
ArrayList todo = new ArrayList();
todo.Add(c);
while (!(todo.Count == 0))
{
#if USE_STACK
Constraint d = (Constraint)todo[todo.Count - 1];
todo.RemoveAt(todo.Count - 1);
#else
Constraint d = (Constraint)todo[0];
todo.RemoveAt(0);
#endif
if (d.output().mark == mark)
{
incrementalRemove(c);
return(false);
}
d.recalculate();
addConstraintsConsumingTo(d.output(), todo);
}
return(true);
}
