private int FindPivotRow(int pivotCol)
{
int pivotRow = -1;
for (int i = 1; i < SimplexTable.GetLength(0) - 2; i++)
{
if (SimplexTable[i, pivotCol] > 0)
{
pivotRow = i;
break;
}
}
if (pivotRow == -1)
{
return(pivotRow);
}
for (int i = pivotRow + 1; i < SimplexTable.GetLength(0) - 2; i++)
{
if ((SimplexTable[i, pivotCol] > 0) && ((SimplexTable[i, 0] / SimplexTable[i, pivotCol]) <
(SimplexTable[pivotRow, 0] / SimplexTable[pivotRow, pivotCol])))
{
pivotRow = i;
}
}
return(pivotRow);
}
private void FindInitialCosts()
{
int costMRow = SimplexTable.GetLength(0) - 1;
int costRow = costMRow - 1;
for (int j = 0; j < SimplexTable.GetLength(1); j++)
{
SimplexTable[costRow, j] = 0;
SimplexTable[costMRow, j] = 0;
for (int i = 1; i < SimplexTable.GetLength(0) - 2; i++)
{
if (SimplexTable[0, Basis[i - 1]] == -M)
{
SimplexTable[costMRow, j] += (SimplexTable[i, j] * (-1));
}
else
{
SimplexTable[costRow, j] += (SimplexTable[i, j] * SimplexTable[0, Basis[i - 1]]);
}
}
if (SimplexTable[0, j] == -M)
{
SimplexTable[costMRow, j] += 1;
}
else
{
SimplexTable[costRow, j] -= SimplexTable[0, j];
}
}
}
public Tuple <double, double[]> Calculate()
{
ConvertToStandardForm();
AddArtificialVariables();
FindInitialCosts();
int prev = -1;
while (true)
{
int pivotColumn = FindPivotColumn();
if (pivotColumn == -1 || pivotColumn == prev)
{
if (Math.Round(SimplexTable[SimplexTable.GetLength(0) - 1, 0], 10) != 0)
{
return(null);
}
else
{
double[] xOpt = new double[Prob.CountVariables];
for (int i = 0; i < Basis.Length; i++)
{
if (Basis[i] - 1 < Prob.CountVariables)
{
xOpt[Basis[i] - 1] = SimplexTable[i + 1, 0];
}
}
if (additionalVars.Count != 0)
{
foreach (KeyValuePair <int, int> pair in additionalVars)
{
xOpt[pair.Key] -= xOpt[pair.Value];
}
}
double optObjectiveValue = SimplexTable[SimplexTable.GetLength(0) - 2, 0];
if (Prob.Minimize[CriteriaInd] == true)
{
optObjectiveValue *= -1;
}
return(new Tuple <double, double[]>(optObjectiveValue, xOpt));
}
}
else
{
int pivotRow = FindPivotRow(pivotColumn);
if (pivotRow == -1)
{
return(null);
}
Basis[pivotRow - 1] = pivotColumn;
FindNewSimplexTable(pivotRow, pivotColumn);
prev = pivotColumn;
}
}
}
public void MakeConstantsPositive()
{
for (int i = 0; i < Prob.CountConstraint; i++)
{
if (Prob.Constants[i] < 0)
{
for (int j = 0; j < SimplexTable.GetLength(1); j++)
{
SimplexTable[i + 1, j] *= -1;
}
}
}
}
private int FindPivotColumn()
{
List <int> minInd = new List <int>();
double minM = SimplexTable[costMRow, 1];
for (int j = 2; j < SimplexTable.GetLength(1); j++)
{
if (SimplexTable[costMRow, j] < minM)
{
minM = SimplexTable[costMRow, j];
}
}
for (int j = 1; j < SimplexTable.GetLength(1); j++)
{
if (SimplexTable[costMRow, j] == minM)
{
minInd.Add(j);
}
}
if (minInd.Count == 1)
{
return(minInd[0]);
}
else
{
double min = SimplexTable[costRow, 1];
int pivotCol = minInd[0];
foreach (int j in minInd)
{
if (SimplexTable[costRow, j] < min)
{
min = SimplexTable[costRow, j];
pivotCol = j;
}
}
if (min >= 0 && minM >= 0)
{
return(-1);
}
else
{
return(pivotCol);
}
}
}
private void FindNewSimplexTable(int pivotRow, int pivotColumn)
{
double[,] oldTable = new double[SimplexTable.GetLength(0), SimplexTable.GetLength(1)];
Array.Copy(SimplexTable, oldTable, SimplexTable.Length);
double pivotElem = SimplexTable[pivotRow, pivotColumn];
for (int j = 0; j < SimplexTable.GetLength(1); j++)
{
SimplexTable[pivotRow, j] = oldTable[pivotRow, j] / pivotElem;
}
for (int i = 1; i < SimplexTable.GetLength(0); i++)
{
if (i == pivotRow || oldTable[i, pivotColumn] == 0)
{
continue;
}
for (int j = 0; j < SimplexTable.GetLength(1); j++)
{
SimplexTable[i, j] = oldTable[i, j] - (oldTable[i, pivotColumn] * SimplexTable[pivotRow, j]);
}
}
}