/// <summary>
/// Add an edit constraint for a variable with a given strength.
/// <param name="v">Variable to add an edit constraint to.</param>
/// <param name="strength">Strength of the edit constraint.</param>
/// </summary>
public ClSimplexSolver AddEditVar(ClVariable v, ClStrength strength)
/* throws ExClInternalError */
{
try
{
ClEditConstraint cnEdit = new ClEditConstraint(v, strength);
return AddConstraint(cnEdit);
}
catch (ExClRequiredFailure)
{
// should not get this
throw new ExClInternalError("Required failure when adding an edit variable");
}
}
/// <summary>
/// Remove a constraint from the tableau.
/// Also remove any error variable associated with it.
/// </summary>
public ClSimplexSolver RemoveConstraint(ClConstraint cn)
/* throws ExClRequiredFailure, ExClInternalError */
{
_cNeedsSolving = true;
ResetStayConstants();
ClLinearExpression zRow = RowExpression(_objective);
HashSet <ClAbstractVariable> eVars;
if (_errorVars.TryGetValue(cn, out eVars))
{
foreach (ClAbstractVariable clv in eVars)
{
ClLinearExpression expr = RowExpression(clv);
if (expr == null)
{
zRow.AddVariable(clv, -cn.Weight *
cn.Strength.SymbolicWeight.AsDouble(),
_objective, this);
}
else // the error variable was in the basis
{
zRow.AddExpression(expr, -cn.Weight *
cn.Strength.SymbolicWeight.AsDouble(),
_objective, this);
}
}
}
ClAbstractVariable marker;
if (!_markerVars.TryGetValue(cn, out marker))
{
throw new CassowaryConstraintNotFoundException();
}
_markerVars.Remove(cn);
if (RowExpression(marker) == null)
{
// not in the basis, so need to do some more work
var col = Columns[marker];
ClAbstractVariable exitVar = null;
double minRatio = 0.0;
foreach (ClAbstractVariable v in col)
{
if (v.IsRestricted)
{
ClLinearExpression expr = RowExpression(v);
double coeff = expr.CoefficientFor(marker);
if (coeff < 0.0)
{
double r = -expr.Constant / coeff;
if (exitVar == null || r < minRatio)
{
minRatio = r;
exitVar = v;
}
}
}
}
if (exitVar == null)
{
foreach (ClAbstractVariable v in col)
{
if (v.IsRestricted)
{
ClLinearExpression expr = RowExpression(v);
double coeff = expr.CoefficientFor(marker);
double r = expr.Constant / coeff;
if (exitVar == null || r < minRatio)
{
minRatio = r;
exitVar = v;
}
}
}
}
if (exitVar == null)
{
// exitVar is still null
if (col.Count == 0)
{
RemoveColumn(marker);
}
else
{
// put first element in exitVar
var colEnum = col.GetEnumerator();
colEnum.MoveNext();
exitVar = colEnum.Current;
}
}
if (exitVar != null)
{
Pivot(marker, exitVar);
}
}
if (RowExpression(marker) != null)
{
RemoveRow(marker);
}
if (eVars != null)
{
foreach (ClAbstractVariable v in eVars.Where(a => a != marker))
{
RemoveColumn(v);
}
}
if (cn.IsStayConstraint)
{
if (eVars != null)
{
for (int i = 0; i < _stayPlusErrorVars.Count; i++)
{
eVars.Remove(_stayPlusErrorVars[i]);
eVars.Remove(_stayMinusErrorVars[i]);
}
}
}
else if (cn.IsEditConstraint)
{
Assert(eVars != null, "eVars != null");
ClEditConstraint cnEdit = (ClEditConstraint)cn;
ClVariable clv = cnEdit.Variable;
ClEditInfo cei = _editVarMap[clv];
ClSlackVariable clvEditMinus = cei.ClvEditMinus;
RemoveColumn(clvEditMinus);
_editVarMap.Remove(clv);
}
// FIXME: do the remove at top
if (eVars != null)
{
//_errorVars.Remove(eVars);
_errorVars.Remove(cn);
}
if (_cOptimizeAutomatically)
{
Optimize(_objective);
SetExternalVariables();
}
return(this);
}