/// <summary>
/// Remove v from the tableau -- remove the column cross indices for v
/// and remove v from every expression in rows in which v occurs
/// </summary>
protected void RemoveColumn(ClAbstractVariable var)
{
// remove the rows with the variables in varset
HashSet <ClAbstractVariable> rows;
if (_columns.TryGetValue(var, out rows))
{
_columns.Remove(var);
foreach (var expr in rows.Select(clv => _rows[clv]))
{
expr.Terms.Remove(var);
}
}
if (var.IsExternal)
{
ExternalRows.Remove((ClVariable)var);
ExternalParametricVars.Remove((ClVariable)var);
}
}
/// <summary>
/// Replace all occurrences of oldVar with expr, and update column cross indices
/// oldVar should now be a basic variable.
/// </summary>
protected void SubstituteOut(ClAbstractVariable oldVar, ClLinearExpression expr)
{
var varset = _columns[oldVar];
foreach (var v in varset)
{
var row = _rows[v];
row.SubstituteOut(oldVar, expr, v, this);
if (v.IsRestricted && row.Constant < 0.0)
{
InfeasibleRows.Add(v);
}
}
if (oldVar.IsExternal)
{
ExternalRows.Add((ClVariable)oldVar);
ExternalParametricVars.Remove((ClVariable)oldVar);
}
_columns.Remove(oldVar);
}
// Add v=expr to the tableau, update column cross indices
// v becomes a basic variable
// expr is now owned by ClTableau class,
// and ClTableau is responsible for deleting it
// (also, expr better be allocated on the heap!).
protected void AddRow(ClAbstractVariable var, ClLinearExpression expr)
{
// for each variable in expr, add var to the set of rows which
// have that variable in their expression
_rows.Add(var, expr);
// FIXME: check correctness!
foreach (var clv in expr.Terms.Keys)
{
InsertColVar(clv, var);
if (clv.IsExternal)
{
ExternalParametricVars.Add((ClVariable)clv);
}
}
if (var.IsExternal)
{
ExternalRows.Add((ClVariable)var);
}
}
