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216 lines (192 loc) · 7.48 KB
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//
// Created by Jannick Borowitz on 24.04.22.
//
#ifdef USEILP
#include <algorithm>
#include <iostream>
#include <memory>
#include "DeltaOrientationsConfig.h"
#include "dyn_graph_access.h"
#include "graph_access.h"
#include "gurobi_c++.h"
#include "ilp.h"
void solveUsingILP(graph_access &orientation, dyn_graph_access &G,
const DeltaOrientationsConfig &config) {
std::cout << "Solving using ILP" << std::endl;
try {
auto env = std::make_shared<GRBEnv>();
GRBModel model = GRBModel(*env);
// set model
model.set(GRB_StringAttr_ModelName, "Minimizing Out-Degree");
model.set(GRB_DoubleParam_TimeLimit, config.time_limit);
model.set(GRB_DoubleParam_MIPGap, 0);
// set decision variables for edges
std::vector<GRBVar> edges(2 * G.number_of_edges());
for (auto &edgeVar : edges) {
edgeVar = model.addVar(0.0, 1.0, 0, GRB_BINARY);
}
graph_access G_undirected;
G.convert_to_graph_access(G_undirected);
// add constraints
GRBVar phi = model.addVar(
0.0, 1.0, 0, GRB_INTEGER); // std::numeric_limits<NodeID>::max();
phi.set(GRB_DoubleAttr_UB, G.maxDegree());
for (NodeID node = 0; node < G.number_of_nodes(); ++node) {
GRBLinExpr outDeg = 0;
forall_out_edges(G_undirected, e, node) {
outDeg += edges[e]; // sum up potential outgoing edges
if (node < G_undirected.getEdgeTarget(e)) {
NodeID target = G_undirected.getEdgeTarget(e);
forall_out_edges(G_undirected, rev_e, target) {
if (G_undirected.getEdgeTarget(rev_e) == node) {
GRBLinExpr oneDirectedEdgeExist = edges[e] + edges[rev_e];
model.addConstr(oneDirectedEdgeExist == 1,
"either directed or reversed edge must exist");
break;
}
}
endfor
}
}
model.addConstr(outDeg <= phi, "outDeg is bounded by phi");
endfor
}
// set objective
model.setObjective(GRBLinExpr(phi), GRB_MINIMIZE);
// optimize model
model.optimize();
// set solution
if (model.get(GRB_IntAttr_Status) == GRB_OPTIMAL) {
orientation.start_construction(G_undirected.number_of_nodes(),
G_undirected.number_of_edges());
for (NodeID node = 0; node < G_undirected.number_of_nodes(); ++node) {
orientation.new_node();
forall_out_edges(G_undirected, e, node) {
if (round(edges[e].get(GRB_DoubleAttr_X)) == 1) {
orientation.new_edge(node, G_undirected.getEdgeTarget(e));
}
}
endfor
}
orientation.finish_construction();
std::cout << "solution of ILP: " << phi.get(GRB_DoubleAttr_X)
<< std::endl;
} else {
std::cout << "No solution found by ILP solver" << std::endl;
exit(EXIT_FAILURE);
}
} catch (GRBException &e) {
std::cout << "Oooops something bad happend with Gurobi: " << e.getMessage()
<< std::endl;
exit(EXIT_FAILURE);
}
}
void solveUsingRelaxedILP(graph_access &orientation, dyn_graph_access &G,
const DeltaOrientationsConfig &config) {
try {
// Todo a bit hacky but it allows us to easier map between decision
// variables and edges in AdjArray
// because we get an contiguously edge vector
std::cout << "TODO update" << std::endl;
exit(0);
graph_access GStatic;
G.convert_to_graph_access(GStatic);
auto env = std::make_shared<GRBEnv>();
GRBModel model = GRBModel(*env);
// define variables
// for each (edge,endpoint) a variable is needed for setting orientation
std::vector<GRBVar> edges(GStatic.number_of_edges());
// set model
model.set(GRB_StringAttr_ModelName, "Minimizing Out-Degree");
model.set(GRB_DoubleParam_TimeLimit, config.time_limit);
model.set(GRB_DoubleParam_MIPGap, 0);
// set decision variables
for (auto &edgeVar : edges) {
edgeVar = model.addVar(0.0, 1.0, 0, GRB_CONTINUOUS);
}
// add constraints
GRBVar maxOutDeg = model.addVar(
0.0, 1.0, 0, GRB_CONTINUOUS); // std::numeric_limits<NodeID>::max();
// ToDo if we observe a performance decrease
// we maybe need to determine a better upper bound for maxOutDeg
// e.g. determine current maxDegree
maxOutDeg.set(GRB_DoubleAttr_UB, G.maxDegree());
DELTAORI_LOG("nodes: " << G.number_of_nodes());
for (NodeID node = 0; node < GStatic.number_of_nodes(); ++node) {
GRBLinExpr outDeg = 0;
NodeID currentOutDeg = 0;
forall_out_edges(GStatic, e, node) {
// Todo This now the hacky thing: e is also the position in edges
outDeg += edges[e]; // sum up potential outgoing edges
++currentOutDeg;
if (node < GStatic.getEdgeTarget(e)) {
// edges[e].set(GRB_Double)
auto target = GStatic.getEdgeTarget(e);
forall_out_edges(GStatic, rev_e, target) {
if (GStatic.getEdgeTarget(rev_e) == node) {
GRBLinExpr oneDirectedEdgeExist = edges[e] + edges[rev_e];
DELTAORI_DEBUG(DELTAORI_LOG("add oneDirectedEdgeExist bound"));
model.addConstr(oneDirectedEdgeExist == 1,
"either directed or reversed edge must exist");
break;
}
}
endfor
}
}
DELTAORI_DEBUG(DELTAORI_LOG("add outDeg bound"));
model.addConstr(outDeg <= maxOutDeg, "outDeg is bounded by maxOutDeg");
endfor
}
// set objective
model.setObjective(GRBLinExpr(maxOutDeg), GRB_MINIMIZE);
// optimize model
model.optimize();
// set solution
if (model.get(GRB_IntAttr_Status) == GRB_OPTIMAL ||
model.get(GRB_IntAttr_Status) == GRB_TIME_LIMIT) {
DELTAORI_LOG("found ILP solution");
orientation.start_construction(GStatic.number_of_nodes(),
GStatic.number_of_edges() / 2);
DELTAORI_DEBUG(NodeID maxFoundOutDeg = 0;);
// Todo set oriented edges
for (NodeID node = 0; node < GStatic.number_of_nodes(); ++node) {
orientation.new_node();
DELTAORI_DEBUG(NodeID outDeg = 0;);
forall_out_edges(GStatic, e, node) {
// create the oriented edge if model decided this way
// DELTAORI_LOG(edges[e].get(GRB_DoubleAttr_X));
if (round(edges[e].get(GRB_DoubleAttr_X)) == 1) {
orientation.new_edge(node, GStatic.getEdgeTarget(e));
DELTAORI_DEBUG(++outDeg;);
#ifndef DELTAORI_NDEBUG
forall_out_edges(GStatic, rev_e, GStatic.getEdgeTarget(e)) {
if (GStatic.getEdgeTarget(rev_e) == node) {
DELTAORI_ASSERT(edges[rev_e].get(GRB_DoubleAttr_X) == 0.5 ||
round(edges[rev_e].get(GRB_DoubleAttr_X)) == 0);
break;
}
}
endfor
#endif
}
}
endfor DELTAORI_DEBUG(
if (outDeg > maxFoundOutDeg) { maxFoundOutDeg = outDeg; });
}
// DELTAORI_LOG("max found out deg: " << maxFoundOutDeg);
DELTAORI_ASSERT(maxOutDeg.get(GRB_DoubleAttr_X) == maxFoundOutDeg);
orientation.finish_construction();
// DELTAORI_LOG("MINIMUM maxOutDegree (ILP): " <<
// maxOutDeg.get(GRB_DoubleAttr_X));
std::cout << "maxOutDegree (ILP Relaxed): "
<< maxOutDeg.get(GRB_DoubleAttr_X) << std::endl;
} else {
std::cout << "No solution found by ILP solver" << std::endl;
exit(EXIT_FAILURE);
}
} catch (GRBException &e) {
exit(EXIT_FAILURE);
}
}
#endif