public static double MIP_arc_based(int SAA_m, int SAA_type, int sample_size)
{
int trial_limit = sample_size;
System.Console.WriteLine("Constructing the MIP with Gurobi...");
double solution = -1;
try
{
GRBEnv env = new GRBEnv("mip1.log");
GRBModel model = new GRBModel(env);
//model.Parameters.Presolve = 1;
GRBVar[] y_j = new GRBVar[E];
GRBVar[,] x_ir = new GRBVar[N, sample_size];
System.Console.WriteLine("Creating y_i (edges)");
for (int i = 0; i < E; i++)
{
y_j[i] = model.AddVar(0.0, 1.0, 0, GRB.BINARY, "y_" + node_index[unique_arcs[i].Key.Head] + "_" + node_index[unique_arcs[i].Key.Tail]);
}
System.Console.WriteLine("Creating x_ir");
for (int i = 0; i < N; i++)
{
for (int r = 0; r < sample_size; r++)
{
x_ir[i, r] = model.AddVar(0.0, 1.0, 1.0, GRB.CONTINUOUS, "x_" + i + "_" + r);
}
}
model.ModelSense = GRB.MINIMIZE;
//----------------------------------------------------------
//--------------- create the constraints
int counter = 0;
GRBLinExpr temp_exp2;
temp_exp2 = 0.0;
System.Console.WriteLine("Starting the constraints... Total : " + (trial_limit * N + 1) + " constraints");
// exactly k initial active users
for (int i = 0; i < E; i++)
{
temp_exp2.AddTerm(1.0, y_j[i]);
}
model.AddConstr(temp_exp2 == K, "constraint_y");
temp_exp2 = 0.0;
//--- influence constraints x_i_r <= Sum_j (y_j) j in all accessing nodes to i (total of N.R constraints)
//string[] neigh_arr;
GRBLinExpr temp_exp;
int j = 0;
temp_exp = 0.0;
int counter2 = 0;
ReadData temp_arc = new ReadData();
for (int r = 0; r < trial_limit; r++)
{
for (int i = 0; i < N; i++)
{
//if (SAA_tree_list[r][i].Count > 0)
//if (x_exist[r, i] == true)
{
//x_ir[i, r] = model.AddVar(0.0, 1.0, 1.0, GRB.CONTINUOUS, "x_" + i + "_" + r);
temp_exp.AddTerm(1.0, x_ir[i, r]);
//if (SAA_tree_list[r][i].Count <= N)
{
foreach (UInt16 node in SAA_pred_list[r][i]) //my predecessors can activate me
{
var x = unique_arcs.FindIndex(a => a.Key.Head == node_set[(int)node] && a.Key.Tail == node_set[i]);
//int arcID=unique_arcs.IndexOf()
temp_exp2.AddTerm(-1, x_ir[(int)node, r]);
temp_exp2.AddTerm(1, y_j[x]);
model.AddConstr(temp_exp + temp_exp2 >= 0, "constraint_2" + (counter + 1));
temp_exp2 = 0.0;
counter++;
}
}
} //end of if for null neighbourhood
temp_exp = 0.0;
} //end of for loop for nodes
} //end of for loop for sample size R
for (int r = 0; r < trial_limit; r++)
{
for (int i = 0; i < I; i++)
{
temp_exp.AddTerm(1.0, x_ir[(int)initial_infected[i], r]);
model.AddConstr(temp_exp >= 1, "constraint_3" + (counter + 1));
temp_exp = 0.0;
}
}
//no need for this in edge blocking
//for (int i = 0; i < I; i++)
//{
// temp_exp.AddTerm(1.0, y_j[(int)initial_infected[i]]);
// model.AddConstr(temp_exp == 0, "constraint_3" + (counter + 1));
// temp_exp = 0.0;
//}
model.Write("model.lp");
//model.Write("modelGRB2" + SAA_m + ".mps");
//model.Write("modelGRB2" + SAA_m + ".lp");
GRBModel p = model.Presolve();
p.Write("presolve.lp");
model.Optimize();
if (model.Status == GRB.Status.OPTIMAL)
{
Console.WriteLine("Obj: " + model.Get(GRB.DoubleAttr.ObjVal));
solution = model.Get(GRB.DoubleAttr.ObjVal);
List <UInt16> SAA_sample_result = new List <UInt16>(K);
int isfractional = 0;
result_set = new List <ushort>();
for (int jj = 0; jj < y_j.Count(); ++jj)
{
if (y_j[jj].X > 0.001)
{
//result_set.Add(node_set[jj]);
result_set.Add(node_set[jj]);
SAA_sample_result.Add((UInt16)jj);
System.Console.WriteLine(y_j[jj].VarName + "=" + y_j[jj].X);
if (y_j[jj].X < 0.9)
{
System.Console.WriteLine("Fractional value found");
System.Console.ReadKey();
isfractional = 1;
}
}
}
if (isfractional == 1)
{
System.Console.WriteLine("To conitnue click...");
System.Console.ReadKey();
}
SAA_list.Add(SAA_sample_result);
}
else
{
Console.WriteLine("No solution");
solution = 0;
}
// Dispose of model and env
model.Dispose();
env.Dispose();
}
catch (GRBException e)
{
Console.WriteLine("Error code: " + e.ErrorCode + ". " + e.Message);
}
return(solution);
}
public static Graph RunSolver(Graph graph)
{
GRBEnv env = new GRBEnv();
env.Set(GRB.IntParam.OutputFlag, 0);
env.Set(GRB.IntParam.LogToConsole, 0);
env.Set(GRB.IntParam.Presolve, 2);
env.Set(GRB.DoubleParam.Heuristics, 0.0);
GRBModel model = new GRBModel(env);
GRBVar[] variables = new GRBVar[graph.NumberOfEdges];
model.SetCallback(new LPSolverCallback());
Dictionary<Edge, GRBVar> edgeVars = new Dictionary<Edge, GRBVar>();
// Add variables to the LP model
for (int i = 0; i < graph.NumberOfEdges; i++)
{
variables[i] = model.AddVar(0.0, 1.0, 0.0, GRB.BINARY, "x_" + i);
edgeVars.Add(graph.Edges[i], variables[i]);
}
model.Update();
// Add constraints to the LP model
Console.Write("\rRunning LP. Creating constraints...\r");
//var nonTerminals = graph.Vertices.Except(graph.Terminals).ToList();
ulong conNr = 0;
//var terminalCombinations = new List<List<Vertex>>();
// Assume, without loss of generality, that Terminals[0] is the root, and thus is always included
int rootNr = 1;
foreach (var rootTerminal in graph.Terminals)
//var rootTerminal = graph.Terminals[0];
{
Console.Write("\rRunning LP. Creating constraints... {0}/{1}\r", rootNr, graph.Terminals.Count);
foreach (var combination in GetBFS(graph, rootTerminal))
{
var nodes = combination.ToList(); //new HashSet<Vertex>(combination);
if (nodes.Count == graph.NumberOfVertices || graph.Terminals.All(nodes.Contains))
continue;
//Debug.WriteLine("Combination: {0}", string.Join(" ", nodes));
//for (int i = 1; i <= nodes.Count; i++)
{
var edges = nodes//.Take(i)
.SelectMany(graph.GetEdgesForVertex)
.Distinct()
.Where(x => x.WhereOne(y => !nodes.Contains(y)));
GRBLinExpr expression = 0;
foreach (var edge in edges)
expression.AddTerm(1, edgeVars[edge]);
model.AddConstr(expression >= 1.0, "subset_" + conNr);
conNr++;
if (conNr % 100000 == 0)
{
//model = model.Presolve(); //Pre-solve the model every 1000 constraints.
int constrBefore = model.GetConstrs().Length, varsBefore = model.GetVars().Length;
Debug.WriteLine("Presolve called.");
var presolved = model.Presolve();
Debug.WriteLine("Model has {0} constraints, {1} variables. Presolve has {2} constraints, {3} variables",
constrBefore, varsBefore, presolved.GetConstrs().Length, presolved.GetVars().Length);
}
}
}
//Debug.WriteLine(" ");
//Debug.WriteLine(" ");
rootNr++;
}
//terminalCombinations.Add(new List<Vertex>(new[] { graph.Terminals[0] }));
//for (int j = 1; j < graph.Terminals.Count - 1; j++)
// terminalCombinations.AddRange(new Combinations<Vertex>(graph.Terminals.Skip(1), j).Select(combination => combination.Union(new[] { graph.Terminals[0] }).ToList()));
//long nonTerminalSetsDone = 0;
//long nonTerminalSets = 0;
//for (int i = 0; i <= nonTerminals.Count; i++)
// nonTerminalSets += Combinations<Vertex>.NumberOfCombinations(nonTerminals.Count, i);
//for (int i = 0; i <= nonTerminals.Count; i++)
//{
// foreach (var nonTerminalSet in new Combinations<Vertex>(nonTerminals, i))
// {
// foreach (var nodes in (from a in terminalCombinations
// select new HashSet<Vertex>(a.Union(nonTerminalSet))))
// {
// var edges = nodes.SelectMany(graph.GetEdgesForVertex)
// .Distinct()
// .Where(x => x.WhereOne(y => !nodes.Contains(y)));
// GRBLinExpr expression = 0;
// foreach (var edge in edges)
// expression.AddTerm(1, edgeVars[edge]);
// model.AddConstr(expression >= 1.0, "subset_" + conNr);
// conNr++;
// }
// nonTerminalSetsDone++;
// if (nonTerminalSetsDone % 100 == 0)
// Console.Write("\rRunning LP. Creating constraints... {0}/{1} ({2:0.000}%)\r", nonTerminalSetsDone, nonTerminalSets, nonTerminalSetsDone * 100.0 / nonTerminalSets);
// }
//}
// Solve the LP model
Console.Write("\rRunning LP. Creating objective & updating... \r");
GRBLinExpr objective = new GRBLinExpr();
for (int i = 0; i < graph.NumberOfEdges; i++)
objective.AddTerm(graph.Edges[i].Cost, variables[i]);
model.SetObjective(objective, GRB.MINIMIZE);
Console.Write("\rRunning LP. Tuning... \r");
model.Tune();
Debug.WriteLine("Presolve called.");
model.Presolve();
Console.Write("\rRunning LP. Solving... \r");
Debug.WriteLine("Optimize called.");
model.Optimize();
Graph solution = graph.Clone();
HashSet<Edge> includedEdges = new HashSet<Edge>();
for (int i = 0; i < solution.NumberOfEdges; i++)
{
var value = variables[i].Get(GRB.DoubleAttr.X);
if (value == 1)
includedEdges.Add(solution.Edges[i]);
}
foreach (var edge in solution.Edges.ToList())
if (!includedEdges.Contains(edge))
solution.RemoveEdge(edge);
Console.Write("\r \r");
return solution;
}
