/// <summary>
/// Gets variable, which indicates creative row
/// </summary>
public string GetCreativeVariable(SimplexTable table, ProblemForGomory problem)
{
var maxVariables = new List<string>();
var maxFractionalPart = new Fraction();
foreach (var basisVariable in table.GetBasis())
{
if (!problem.WholeConstraints.Contains(basisVariable.Key))
continue;
var fractionalPart = GetFractionalPart(basisVariable.Value);
if (fractionalPart > maxFractionalPart)
{
maxVariables.Clear();
maxFractionalPart = fractionalPart;
}
if (fractionalPart == maxFractionalPart)
maxVariables.Add(basisVariable.Key);
}
if (maxVariables.Count == 1) return maxVariables[0];
maxFractionalPart = new Fraction();
var maxVariable = string.Empty;
foreach (var variable in maxVariables)
{
var sumOfFractionalParts = new Fraction();
foreach (var rowVariable in table.GetRow(variable).Key)
sumOfFractionalParts += GetFractionalPart(rowVariable);
var ratio = sumOfFractionalParts != 0
? GetFractionalPart(table.GetRow(variable).Value) / sumOfFractionalParts
: new Fraction();
if (ratio <= maxFractionalPart) continue;
maxFractionalPart = ratio;
maxVariable = variable;
}
return maxVariable;
}
/// <summary>
/// Makes cutoff
/// </summary>
public new KeyValuePair<Fraction[], Fraction> MakeCutoff(SimplexTable table,
string creativeVar, ProblemForGomory problem)
{
var j = 0;
var creativeRow = table.GetRow(creativeVar);
var row = new Fraction[creativeRow.Key.Length + 1];
foreach (var variable in table.Variables)
row[j++] = GetCoefficientForCutoff(variable, table, creativeVar, problem.WholeConstraints) * -1;
row[j] = new Fraction(1, 1);
return new KeyValuePair<Fraction[], Fraction>(row, GetFractionalPart(creativeRow.Value) * -1);
}
private Fraction GetCoefficientForCutoff(string variable, SimplexTable table, string creativeVar,
ICollection<string> wholeConstraints)
{
var varIndex = table.IndexOf(variable);
var creativeRow = table.GetRow(creativeVar);
var varCoefFractionalPart = GetFractionalPart(creativeRow.Key[varIndex]);
var freeCoefFractionalPart = GetFractionalPart(creativeRow.Value);
if (wholeConstraints.Contains(variable))
return (varCoefFractionalPart <= freeCoefFractionalPart)
? varCoefFractionalPart
: freeCoefFractionalPart / (1 - freeCoefFractionalPart) * (1 - varCoefFractionalPart);
return (creativeRow.Key[varIndex] >= 0)
? creativeRow.Key[varIndex]
: freeCoefFractionalPart / (1 - freeCoefFractionalPart) * (-1 * varCoefFractionalPart);
}
/// <summary>
/// Makes cutoff
/// </summary>
public KeyValuePair<Fraction[], Fraction> MakeCutoff(SimplexTable table,
string creativeVar, ProblemForGomory problem)
{
var j = 0;
var creativeRow = table.GetRow(creativeVar);
var row = new Fraction[creativeRow.Key.Length + 1];
foreach (var coefficient in creativeRow.Key)
row[j++] = GetFractionalPart(coefficient) * -1;
row[j] = new Fraction(1, 1);
return new KeyValuePair<Fraction[], Fraction>(row, GetFractionalPart(creativeRow.Value) * -1);
}
private bool HaveNegativeRowsWithoutNegativeElements(SimplexTable table)
{
foreach (var basisVar in table.GetBasis())
{
if (basisVar.Value >= 0) continue;
var haveNegative = false;
foreach (var tableElement in table.GetRow(basisVar.Key).Key)
{
if (tableElement >= 0) continue;
haveNegative = true;
break;
}
if (!haveNegative) return true;
}
return false;
}
