//// END PUBLIC INTERFACE ////
/// <summary>
/// Add the constraint expr=0 to the inequality tableau using an
/// artificial variable.
/// </summary>
/// <remarks>
/// To do this, create an artificial variable av and add av=expr
/// to the inequality tableau, then make av be 0 (raise an exception
/// if we can't attain av=0).
/// </remarks>
private void AddWithArtificialVariable(ClLinearExpression expr)
/* throws ExClRequiredFailure, ExClInternalError */
{
ClSlackVariable av = new ClSlackVariable(++_artificialCounter, "a");
ClObjectiveVariable az = new ClObjectiveVariable("az");
ClLinearExpression azRow = expr.Clone();
AddRow(az, azRow);
AddRow(av, expr);
Optimize(az);
ClLinearExpression azTableauRow = RowExpression(az);
if (!Approx(azTableauRow.Constant, 0.0))
{
RemoveRow(az);
RemoveColumn(av);
throw new CassowaryRequiredFailureException();
}
// see if av is a basic variable
ClLinearExpression e = RowExpression(av);
if (e != null)
{
// find another variable in this row and pivot,
// so that av becomes parametric
if (e.IsConstant)
{
// if there isn't another variable in the row
// then the tableau contains the equation av=0 --
// just delete av's row
RemoveRow(av);
RemoveRow(az);
return;
}
ClAbstractVariable entryVar = e.AnyPivotableVariable();
Pivot(entryVar, av);
}
Assert(RowExpression(av) == null, "RowExpression(av) == null)");
RemoveColumn(av);
RemoveRow(az);
}
