/// <summary>
/// Fix the constants in the equations representing the edit constraints.
/// </summary>
/// <remarks>
/// Each of the non-required edits will be represented by an equation
/// of the form:
/// v = c + eplus - eminus
/// where v is the variable with the edit, c is the previous edit value,
/// and eplus and eminus are slack variables that hold the error in
/// satisfying the edit constraint. We are about to change something,
/// and we want to fix the constants in the equations representing
/// the edit constraints. If one of eplus and eminus is basic, the other
/// must occur only in the expression for that basic error variable.
/// (They can't both be basic.) Fix the constant in this expression.
/// Otherwise they are both non-basic. Find all of the expressions
/// in which they occur, and fix the constants in those. See the
/// UIST paper for details.
/// (This comment was for ResetEditConstants(), but that is now
/// gone since it was part of the screwey vector-based interface
/// to resolveing. --02/16/99 gjb)
/// </remarks>
protected void DeltaEditConstant(double delta,
ClAbstractVariable plusErrorVar,
ClAbstractVariable minusErrorVar)
{
ClLinearExpression exprPlus = RowExpression(plusErrorVar);
if (exprPlus != null)
{
exprPlus.IncrementConstant(delta);
if (exprPlus.Constant < 0.0)
{
InfeasibleRows.Add(plusErrorVar);
}
return;
}
ClLinearExpression exprMinus = RowExpression(minusErrorVar);
if (exprMinus != null)
{
exprMinus.IncrementConstant(-delta);
if (exprMinus.Constant < 0.0)
{
InfeasibleRows.Add(minusErrorVar);
}
return;
}
var columnVars = Columns[minusErrorVar];
foreach (ClAbstractVariable basicVar in columnVars)
{
ClLinearExpression expr = RowExpression(basicVar);
//Assert(expr != null, "expr != null");
double c = expr.CoefficientFor(minusErrorVar);
expr.IncrementConstant(c * delta);
if (basicVar.IsRestricted && expr.Constant < 0.0)
{
InfeasibleRows.Add(basicVar);
}
}
}
/// <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);
}