001/******************************************************************************* 002 * Copyright (c) 2017 Pablo Pavon Marino and others. 003 * All rights reserved. This program and the accompanying materials 004 * are made available under the terms of the 2-clause BSD License 005 * which accompanies this distribution, and is available at 006 * https://opensource.org/licenses/BSD-2-Clause 007 * 008 * Contributors: 009 * Pablo Pavon Marino and others - initial API and implementation 010 *******************************************************************************/ 011 012 013 014 015 016 017 018 019 020 021package com.net2plan.examples.ocnbook.offline; 022 023import java.util.List; 024import java.util.Map; 025 026import com.jom.OptimizationProblem; 027import com.net2plan.interfaces.networkDesign.IAlgorithm; 028import com.net2plan.interfaces.networkDesign.Net2PlanException; 029import com.net2plan.interfaces.networkDesign.NetPlan; 030import com.net2plan.interfaces.networkDesign.NetworkLayer; 031import com.net2plan.utils.Constants.RoutingType; 032import com.net2plan.utils.DoubleUtils; 033import com.net2plan.utils.InputParameter; 034import com.net2plan.utils.Triple; 035 036import cern.colt.matrix.tdouble.DoubleFactory1D; 037import cern.colt.matrix.tdouble.DoubleMatrix1D; 038import cern.jet.math.tdouble.DoubleFunctions; 039 040/** 041 * Solves several variants of unicast routing problems, with flow-path formulations 042 * @net2plan.description 043 * @net2plan.keywords JOM, Flow-path formulation, Flow assignment (FA) 044 * @net2plan.ocnbooksections Section 4.2, Section 4.6.3 045 * @net2plan.inputParameters 046 * @author Pablo Pavon-Marino 047 */ 048public class Offline_fa_xpFormulations implements IAlgorithm 049{ 050 private InputParameter k = new InputParameter ("k", (int) 5 , "Maximum number of admissible paths per demand" , 1 , Integer.MAX_VALUE); 051 private InputParameter shortestPathType = new InputParameter ("shortestPathType", "#select# hops km" , "Criteria to compute the shortest path. Valid values: 'hops' or 'km'"); 052 private InputParameter nonBifurcatedRouting = new InputParameter ("nonBifurcatedRouting", false , "True if the routing is constrained to be non-bifurcated"); 053 private InputParameter optimizationTarget = new InputParameter ("optimizationTarget", "#select# min-av-num-hops minimax-link-utilization maximin-link-idle-capacity min-av-network-delay min-av-network-blocking" , "Type of optimization target. Choose among minimize the average number of hops, minimize the highest link utilization, maximize the lowest link idle capacity, minimize the average end-to-end network delay including queueing (M/M/1 estimation) and propagation delays, and minimize the average network blocking assuming independent Erlang-B blocking in each link, load sharing model"); 054 private InputParameter maxLengthInKm = new InputParameter ("maxLengthInKm", (double) 2000 , "Paths longer than this are considered not admissible. A non-positive number means this limit does not exist"); 055 private InputParameter solverName = new InputParameter ("solverName", "#select# glpk ipopt xpress cplex", "The solver name to be used by JOM. GLPK and IPOPT are free, XPRESS and CPLEX commercial. GLPK, XPRESS and CPLEX solve linear problems w/w.o integer contraints. IPOPT is can solve nonlinear problems (if convex, returns global optimum), but cannot handle integer constraints"); 056 private InputParameter solverLibraryName = new InputParameter ("solverLibraryName", "" , "The solver library full or relative path, to be used by JOM. Leave blank to use JOM default."); 057 private InputParameter maxSolverTimeInSeconds = new InputParameter ("maxSolverTimeInSeconds", (double) -1 , "Maximum time granted to the solver to solve the problem. If this time expires, the solver returns the best solution found so far (if a feasible solution is found)"); 058 private InputParameter binaryRatePerTrafficUnit_bps = new InputParameter ("binaryRatePerTrafficUnit_bps", (double) 1E6 , "Binary rate equivalent to one traffic unit (used only in average network delay minimization formulation)." , 0 , false , Double.MAX_VALUE , true); 059 private InputParameter averagePacketLengthInBytes = new InputParameter ("averagePacketLengthInBytes", (double) 500 , "Average packet length in bytes (used only in average network delay minimization formulation)." , 0 , false , Double.MAX_VALUE , true); 060 061 @Override 062 public String executeAlgorithm(NetPlan netPlan, Map<String, String> algorithmParameters, Map<String, String> net2planParameters) 063 { 064 /* Initialize all InputParameter objects defined in this object (this uses Java reflection) */ 065 InputParameter.initializeAllInputParameterFieldsOfObject(this, algorithmParameters); 066 if (solverName.getString ().equalsIgnoreCase("ipopt") && nonBifurcatedRouting.getBoolean()) throw new Net2PlanException ("With IPOPT solver, the routing cannot be constrained to be non-bifurcated"); 067 068 /* Initialize variables */ 069 final int E = netPlan.getNumberOfLinks(); 070 final int D = netPlan.getNumberOfDemands(); 071 final double PRECISION_FACTOR = Double.parseDouble(net2planParameters.get("precisionFactor")); 072 if (E == 0 || D == 0) throw new Net2PlanException("This algorithm requires a topology with links and a demand set"); 073 074 /* Remove all unicast routed traffic. Any multicast routed traffic is kept */ 075 netPlan.removeAllUnicastRoutingInformation(); 076 netPlan.setRoutingTypeAllDemands(RoutingType.SOURCE_ROUTING); 077 078 /* Add all the k-shortest candidate routes to the netPlan object carrying no traffic */ 079 final DoubleMatrix1D linkCostVector = shortestPathType.getString().equalsIgnoreCase("hops")? DoubleFactory1D.dense.make (E , 1.0) : netPlan.getVectorLinkLengthInKm(); 080 netPlan.addRoutesFromCandidatePathList(netPlan.computeUnicastCandidatePathList(linkCostVector , k.getInt(), maxLengthInKm.getDouble(), -1, -1, -1, -1, -1 , null)); 081 final int P = netPlan.getNumberOfRoutes(); 082 083 /* Create the optimization problem object (JOM library) */ 084 OptimizationProblem op = new OptimizationProblem(); 085 086 /* Set some input parameters to the problem */ 087 op.setInputParameter("u_e", netPlan.getVectorLinkSpareCapacity(), "row"); /* for each link, its unused capacity (the one not used by any mulitcast trees) */ 088 op.setInputParameter("A_dp", netPlan.getMatrixDemand2RouteAssignment()); /* 1 in position (d,p) if demand d is served by path p, 0 otherwise */ 089 op.setInputParameter("A_ep", netPlan.getMatrixLink2RouteAssignment()); /* 1 in position (e,p) if link e is traversed by path p, 0 otherwise */ 090 op.setInputParameter("h_d", netPlan.getVectorDemandOfferedTraffic(), "row"); /* for each demand, its offered traffic */ 091 op.setInputParameter("h_p", netPlan.getVectorRouteOfferedTrafficOfAssociatedDemand () , "row"); /* for each path, the offered traffic of its demand */ 092 093 /* Write the problem formulations */ 094 if (optimizationTarget.getString ().equals ("min-av-num-hops")) 095 { 096 op.setInputParameter("l_p", netPlan.getVectorRouteNumberOfLinks() , "row"); /* for each path, the number of traversed links */ 097 op.addDecisionVariable("xx_p", nonBifurcatedRouting.getBoolean() , new int[] { 1, P }, 0, 1); /* the FRACTION of traffic of demand d(p) that is carried by p */ 098 099 op.setObjectiveFunction("minimize", "sum (l_p .* h_p .* xx_p)"); /* sum of the traffic in the links, proportional to the average number of hops */ 100 op.addConstraint("A_dp * xx_p' == 1"); /* for each demand, the 100% of the traffic is carried (summing the associated paths) */ 101 op.addConstraint("A_ep * (h_p .* xx_p)' <= u_e'"); /* the traffic in each link cannot exceed its capacity */ 102 } 103 else if (optimizationTarget.getString ().equals ("minimax-link-utilization")) 104 { 105 op.addDecisionVariable("xx_p", nonBifurcatedRouting.getBoolean(), new int[] { 1, P }, 0, 1); /* the FRACTION of traffic of demand d(p) that is carried by p */ 106 op.addDecisionVariable("rho", false, new int[] { 1, 1 }, 0, 1); /* worse case link utilization */ 107 op.setObjectiveFunction("minimize", "rho"); 108 op.addConstraint("A_dp * xx_p' == 1"); /* for each demand, the 100% of the traffic is carried (summing the associated paths) */ 109 op.addConstraint("A_ep * (h_p .* xx_p)' <= rho * u_e'"); /* the traffic in each link cannot exceed its capacity. sets rho as the worse case utilization */ 110 } 111 else if (optimizationTarget.getString ().equals ("maximin-link-idle-capacity")) 112 { 113 op.addDecisionVariable("xx_p", nonBifurcatedRouting.getBoolean() , new int[] { 1, P }, 0, 1); /* the FRACTION of traffic of demand d(p) that is carried by p */ 114 op.addDecisionVariable("u", false, new int[] { 1, 1 }, 0, Double.MAX_VALUE); /* worse case link idle capacity */ 115 op.setObjectiveFunction("maximize", "u"); 116 op.addConstraint("A_dp * xx_p' == 1"); /* for each demand, the 100% of the traffic is carried (summing the associated paths) */ 117 op.addConstraint("A_ep * (h_p .* xx_p)' <= -u + u_e'"); /* the traffic in each link cannot exceed its capacity. sets u as the worse case idle capacity */ 118 } 119 else if (optimizationTarget.getString ().equals ("min-av-network-delay")) 120 { 121 if (!solverName.getString ().equalsIgnoreCase("ipopt") || nonBifurcatedRouting.getBoolean()) throw new Net2PlanException ("This is a convex non linear model: please use IPOPT solver. The routing cannot be constrained to be non-bifurcated"); 122 op.setInputParameter("d_e_secs", netPlan.getVectorLinkPropagationDelayInMiliseconds().assign (DoubleFunctions.mult (0.001)) , "row"); 123 op.setInputParameter("L", averagePacketLengthInBytes.getDouble() * 8); /* average packet length in bits */ 124 op.setInputParameter("R", binaryRatePerTrafficUnit_bps.getDouble()); /* binary rate per traffic unit */ 125 op.addDecisionVariable("xx_p", false , new int[] { 1, P }, 0, 1); /* the FRACTION of traffic of demand d(p) that is carried by p */ 126 op.addDecisionVariable("y_e", false, new int[] { 1, E }, DoubleUtils.zeros(E), netPlan.getVectorLinkCapacity().toArray()); /* traffic in the links (already limited to the link capacity) */ 127 op.setObjectiveFunction("minimize", "sum( y_e .* (d_e_secs + (L./R) * (1 ./ (u_e - y_e))) )"); 128 op.addConstraint("A_dp * xx_p' == 1"); /* for each demand, the 100% of the traffic is carried (summing the associated paths) */ 129 op.addConstraint("A_ep * (h_p .* xx_p)' == y_e'"); /* sets y_e as the traffic in link e */ 130 } 131 else if (optimizationTarget.getString ().equals ("min-av-network-blocking")) 132 { 133 if (!solverName.getString ().equalsIgnoreCase("ipopt") || nonBifurcatedRouting.getBoolean()) throw new Net2PlanException ("This is a convex non linear model: please use IPOPT solver. The routing cannot be constrained to be non-bifurcated"); 134 op.addDecisionVariable("xx_p", false , new int[] { 1, P }, 0, 1); /* the FRACTION of traffic of demand d(p) that is carried by p */ 135 op.addDecisionVariable("y_e", false, new int[] { 1, E }, DoubleUtils.zeros(E), netPlan.getVectorLinkCapacity().toArray()); /* traffic in the links (already limited to the link capacity) */ 136 op.setObjectiveFunction("minimize", "sum(y_e .* erlangB(y_e, u_e))"); 137 op.addConstraint("A_dp * xx_p' == 1"); /* for each demand, the 100% of the traffic is carried (summing the associated paths) */ 138 op.addConstraint("A_ep * (h_p .* xx_p)' == y_e'"); /* sets y_e as the traffic in link e */ 139 } 140 else throw new Net2PlanException ("Unknown optimization target " + optimizationTarget.getString()); 141 142 143 op.solve(solverName.getString (), "solverLibraryName", solverLibraryName.getString () , "maxSolverTimeInSeconds" , maxSolverTimeInSeconds.getDouble ()); 144 145 /* If no solution is found, quit */ 146 if (op.feasibleSolutionDoesNotExist()) throw new Net2PlanException("The problem has no feasible solution"); 147 if (!op.solutionIsFeasible()) throw new Net2PlanException("A feasible solution was not found"); 148 149 /* Save the solution found in the netPlan object */ 150 final DoubleMatrix1D h_p = netPlan.getVectorRouteOfferedTrafficOfAssociatedDemand(); 151 final DoubleMatrix1D xx_p = DoubleFactory1D.dense.make (op.getPrimalSolution("xx_p").to1DArray()); 152 final DoubleMatrix1D x_p = xx_p.copy().assign (h_p , DoubleFunctions.mult); 153 netPlan.setVectorRouteCarriedTrafficAndOccupiedLinkCapacities(x_p , x_p); 154 netPlan.removeAllRoutesUnused(PRECISION_FACTOR); // routes with zero traffic (or close to zero, with PRECISION_FACTOR tolerance) 155 156 return "Ok!: The solution found is guaranteed to be optimal: " + op.solutionIsOptimal() + ". Number routes = " + netPlan.getNumberOfRoutes(); 157 } 158 159 @Override 160 public String getDescription() 161 { 162 return "Given a network topology, the capacities in the links, and a set unicast traffic demands, this algorithm permits computing the optimum routing of the traffic (that is, the set of routes carrying the traffic of the demands) solving flow-path formulations, that start computing a set of admissible paths, and then solve the routing problem over them. Through a set of input parameters, the user can choose among different optimization targets and constraints."; 163 } 164 165 166 @Override 167 public List<Triple<String, String, String>> getParameters() 168 { 169 /* Returns the parameter information for all the InputParameter objects defined in this object (uses Java reflection) */ 170 return InputParameter.getInformationAllInputParameterFieldsOfObject(this); 171 } 172}