ILOG CPLEX 11.0 User's Manual

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not correct that problem either. In short, the tuning tool does not magically eliminate allperformance bottlenecks. However, if you understand the performance issues of your model,the tuning tool can help you discern parameter settings that lead to faster solving time.The recommended practice with the tuning tool is to solve your model first with defaultsettings and to consider the results before invoking the tuning tool. Your analysis of thoseresults directs you toward the next step. The following sections sketch typical scenarios forworking effectively with the tuning tool and outline what to expect from the tuing tool.◆ If ILOG CPLEX Solves Your Problem to Optimality on page 162◆ If ILOG CPLEX Finds Solutions But Does Not Prove Optimality on page 162◆ Tuning and Time Limits on page 163◆ Tuning Results on page 163If ILOG CPLEX Solves Your Problem to OptimalityIf ILOG CPLEX solves your problem to optimality, you may still want to apply the tuningtool to discover whether you can solve the model faster. In such a case, bear in mind that thetuning tool performs several optimization runs as it goes about its work. These optimizationruns may take six to eight times longer than the default run that produced your optimalresults. If that projected time (six to eight times longer than the initial default run) seems toolong for your purpose, then consider setting a general time limit by means of the parameterTiLim, CPX_PARAM_TILIM or consider setting a specific tuning time limit per problem, peroptimization, by means of the parameter TuningTiLim, CPX_PARAM_TUNINGTILIM.Example: Time Limits on Tuning in the Interactive Optimizer on page 164 illustrates thisapproach through time limits more fully.If ILOG CPLEX Finds Solutions But Does Not Prove OptimalityIn the case where ILOG CPLEX finds solutions for your model but does not proveoptimality in your initial run before invoking the tuning tool, you will likely want to set thetime limit per model. See Tuning and Time Limits on page 163 for more about that idea.In situations where ILOG CPLEX does not solve your model to optimality for a reason otherthan a time limit, you should address that reason before you apply the tuning tool.For example, if your initial run results in an out-of-memory error, consider setting thememory emphasis parameter (MemoryEmphasis (bool), CPX_PARAM_MEMORYEMPHASIS(int)). Then create a file in which you specify a fixed setting of that parameter for thetuning tool to respect. Pass that file to the tuning tool with your model. Fixing Parametersand Tuning Multiple Models in the Interactive Optimizer on page 165 illustrates thisapproach.162 ILOG CPLEX 11.0 — USER’ S MANUAL
Tuning and Time LimitsThe tuning process is affected by two time limit parameters.The overall time limit for the tuning process is set with the general time limit parameter(TiLim, CPX_PARAM_TILIM) .Tuning consists of a series of optimizations of each of the problems to be tuned. The timelimit on each of these optimizations is specified by the tuning time limit parameter(TuningTiLim, CPX_PARAM_TUNINGTILIM). The default value of this parameter is set to avalue much smaller than the default value of the overall time limit, so as to avoid runs ofindeterminate length.The per-problem, per-optimization time limit can also be set using the general time limitparameter (TiLim, CPX_PARAM_TILIM) in a fixed parameter set. Fixing Parameters andTuning Multiple Models in the Interactive Optimizer on page 165 explains more about thatapproach. You would want to set the per-problem, per-optimization time limit in this way ifyou are using a time limit in your usual (non-tuning) runs of the models.Tuning ResultsThe tuning tool selects the best suite of parameter settings based on the performance times ofthe several optimizations of the model or models. Because theperformance times cannot bemeasured exactly, the results of tuning can differ from one tuning run to another if the timesfor the individual optimizations are close.Invoking the Tuning ToolThe tuning tool is available in all components of ILOG CPLEX: Concert Technology,Callable Library, and Interactive Optimizer.In Concert Technology, you invoke the tuning tool through these methods:◆◆◆IloCplex::tuneParam in the C++ API; see also the example ilotuneset.cpp;IloCplex.tuneParam in the Java API; see also the example TuneSet.java;Cplex.TuneParam in the .NET API; see also the example TuneSet.cs orTuneSet.vb.The tool is also part of the Callable Library (C API) through separate routines for tuning asingle model or a group of models. For more detail about the C routine for tuning a singlemodel or a group of models, see Tuning Models in the Callable Library (C API) onpage 166. For a sample application, see examples/src/cplex/tuneset.c.ILOG CPLEX 11.0 — USER’ S MANUAL 163
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ILOG CPLEX 11.0User’s ManualSepte
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C O N T E N T STable of ContentsILO
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Building the Model by Column . . .
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Program Description . . . . . . . .
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Cholesky Factor in the Log File . .
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Examples: QCP . . . . . . . . . . .
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Chapter 18 Using Piecewise Linear F
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Representing the Data. . . . . . .
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Reading and Writing MPS Files . . .
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Protected Variables in Presolve Red
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P R E F A C EMeet ILOG CPLEXILOG CP
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When a linear optimization problem
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◆◆◆◆implemented in ILOG CPL
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Solution Pool: Generating and Keepi
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Table 1ExamplesExample Source File
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◆◆◆◆◆◆Overview of the A
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Wolsey, Laurence A., Integer Progra
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C H A P T E R1ILOG Concert Technolo
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Compiling and LinkingCompilation an
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The class IloNumVar provides method
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IloModel object itself and added to
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Table 1.1 Concert Technology Modeli
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Choosing an OptimizerSolving the ex
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Table 1.4 on page 55 summarizes the
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Dynamic control of the solution pro
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However, querying solution values v
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parameter for the getQuality method
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model2.add(model1);model2.add(IloCo
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Example: Optimizing the Diet Proble
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Concert Technology, as demonstrated
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method IloModel::add returns the mo
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Licenses in a Java ApplicationILOG
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Models that consist only of such co
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The special case of linear expressi
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IloObjective obj = cplex.add(cplex.
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Solving the ModelOnce you have crea
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IloCplex cplex = new IloCplex();Ilo
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IloCplex.setParam(IloCplex.IntParam
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Thus, the suggested method for sett
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Basis InformationWhen solving an LP
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where A is a sparse matrix. A spars
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The example starts by evaluating th
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IloMPModeler.setLinearCoefs, and Il
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◆What is the purpose (the objecti
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Step 3Create the modelGo to the com
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Step 9Add nutritional constraintsGo
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Step 14Display the solutionGo to th
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Step 18Enclose the application in t
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C H A P T E R4ILOG CPLEX Callable L
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Page 113 and 114: ◆◆If data already exist in MPS,
Page 115 and 116: For example, let’s look at the sy
Page 117 and 118: As you modify a problem object thro
Page 119 and 120: However, ILOG CPLEX updates the nam
Page 121 and 122: whether an optimization should be a
Page 123 and 124: Callable Library have names greater
Page 125 and 126: ◆CPXsetstrparam accepts arguments
Page 127 and 128: Here’s another way to visualize a
Page 129 and 130: program—can discover the length o
Page 131: Part IIProgramming ConsiderationsTh
Page 134 and 135: ◆ Test Data on page 135◆ Choose
Page 136 and 137: ◆ Use the MIP optimizer if the pr
Page 138 and 139: Choose Clarity First, Efficiency La
Page 140 and 141: 1. If you can reproduce the behavio
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Page 144 and 145: Understanding File FormatsThe refer
Page 146 and 147: definitions that it finds. The firs
Page 148 and 149: ◆◆IloXmlReader creates a reader
Page 150 and 151: Controlling Message ChannelsIn both
Page 152 and 153: more calls to the message handling
Page 154 and 155: Concert Technology Message Channels
Page 156 and 157: Types of ILM Runtime LicensesILM ru
Page 158 and 159: char *inststr = NULL;char *envstr =
Page 160 and 161: The registerLicense Method for Java
Page 164 and 165: In the Interactive Optimizer, you c
Page 166 and 167: For models not in the current worki
Page 168 and 169: ◆◆In the .NET API, pass an inst
Page 171 and 172: C H A P T E R9Solving LPs: Simplex
Page 173 and 174: The symbolic names for these settin
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Page 177 and 178: solution; but examination of soluti
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Page 181 and 182: Table 9.5 PPriInd Parameter Setting
Page 183 and 184: ILOG CPLEX ignores the coefficients
Page 185 and 186: Numeric DifficultiesILOG CPLEX is d
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Page 189 and 190: automatically perturbs the variable
Page 191 and 192: 4. Consider alternate scalings.You
Page 193 and 194: smaller in absolute value than the
Page 195 and 196: exceptions are caught as well, and
Page 197 and 198: C H A P T E R10Solving LPs: Barrier
Page 199 and 200: The ILOG CPLEX Barrier Optimizer is
Page 201 and 202: And then you call the solution rout
Page 203 and 204: Here is an example of a log file fo
Page 205 and 206: If solution values are large in abs
Page 207 and 208: Normalized errors, for example, rep
Page 209 and 210: ◆ workmem in the Interactive Opti
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choice of starting-point heuristic
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To see the current value of the col
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C H A P T E R11Solving Network-Flow
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◆◆l a , the lower bound, sets t
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of the objective function calculate
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then ILOG CPLEX will carry out such
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-a 1 + a 2 - a 8 - a 9 + a 14 = 0-
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C H A P T E R12Solving Problems wit
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convex QPs, Q must be positive semi
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A similar Java program using Concer
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◆ qp indicates that you want ILOG
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RootAlg parameter (QPMETHOD in the
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ilolpex1.cpp counterpart. Here the
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C H A P T E R13Solving Problems wit
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Figure 13.2y(0, 1)(-1, 0)d(1, 0)xc(
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Detecting Problem TypeILOG CPLEX de
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COLUMNSMARK0000 'MARKER''INTORG'C15
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C180 R100 159C180 R119 200C180 R120
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QMATRIXC158 C158 1C158 C189 0.5C189
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◆From the Callable Library, use t
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Part IVDiscrete OptimizationThis pa
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Stating a MIP ProblemA mixed intege
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sections does not matter. To enter
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◆milp, miqp, or miqcpindicating t
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1. finding a succession of improvin
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easonable amount of computation tim
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If the solution to the relaxation s
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anches taken so far in this dive. S
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directives about the order in which
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◆ Parameters Affecting Cuts on pa
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◆●●IloCplex.getNcuts in the J
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Relaxation Induced Neighborhood Sea
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Table 14.10Parameters for Controlli
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Library). If this process succeeds,
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After you have solved a MIP, you wi
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Table 14.13Settings of the MIP Disp
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ILOG CPLEX also logs its addition o
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◆ Parent specifies the NodeID of
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parameter settings are also worth c
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When you set a MIP cutoff value, IL
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memory. It also includes several op
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◆◆●●at problem modification
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◆In the Callable Library, use the
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●●Then call CPXprimopt to optim
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◆ The Incumbent and the Solution
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c17: x1 - y11 >= 0c18: x1 - y21 >=
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Populating the Solution PoolILOG CP
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NodesCuts/Node Left Objective IInf
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Note: The parameter to limit the nu
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Example: Using Populate after MIP O
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Limitations Due to Numeric Difficul
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Examining the Solution PoolIn the I
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For a sample of these methods or ro
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◆◆In the Callable Library (C AP
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Then display the objective value of
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◆ If you want to filter solutions
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●●●In the C++ API, use the me
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NAME locationRNGFILTER f2 -inf 0tra
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continuous, a model containing one
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◆The routine setPriorities sets t
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What Are Semi-Continuous Variables?
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With that model, now the applicatio
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Piecewise Linearity in ILOG CPLEXSo
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Reminder: It may help you understan
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overlaps with an endpoint of two ot
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Figure 18.4400003000020000100000Fig
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in demand; in terms of this model,
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348 ILOG CPLEX 11.0 — USER’ S M
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What Are Logical Constraints?For IL
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◆◆Cplex.NotCplex.IfThenAgain, t
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In Concert Technology applications,
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Describing the ProblemThe problem i
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Notice that how much to use and buy
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Then use a for-loop to add the cons
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These lines (the action of the if-s
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Describing the ProblemThe problem i
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Stating Precedence ConstraintsIn ea
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Solving the ProblemAn emphasis on f
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What Is Column Generation?In colloq
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Solving this model with all columns
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Likewise, the application adds an a
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Pattern Generator ModelThe submodel
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Complete ProgramYou can see the ent
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your problem formulation caused thi
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To control the types of reductions
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What Is Unboundedness?Any class of
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Callable Library use the advanced r
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the conflict to arrive at a minimal
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the IIS finder can, and often more.
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Then you will see results like thes
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Now view the entire conflict with t
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The constraints in conflict with th
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If a model contains more than one c
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Immediately after that statement, i
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◆ Groups in the Conflict Refiner
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The infeasibility on which FeasOpt
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Now the following lines invoke Feas
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suggests decreasing the upper bound
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C H A P T E R28User-Cut and Lazy-Co
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However, there is an important dist
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◆◆Through the routine CPXreadco
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Here is an example of an MPS file e
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C H A P T E R29Using GoalsThis chap
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How Goals Are Implemented in Branch
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In the Java API, a Fail goal is ret
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This return statement returns an An
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The Goal StackTo understand how goa
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soon as they are enclosed in a goal
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The global cut goal for lhs[i] ≤
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If a node has multiple evaluators a
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As this example is an extension of
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C H A P T E R30Using Optimization C
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Reference Documents about Informati
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Query or Diagnostic CallbacksQuery
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● Cplex.DisjunctiveCutCallback in
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◆◆●●Cplex.HeuristicCallback
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It is not customary to write such a
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IloCplex::Callback mycallback = cpl
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Here is the previous sample of code
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◆◆cbdata, a pointer to ILOG CPL
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conventions of the Interactive Opti
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een added, it can be deleted by cal
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Interaction Between Callbacks and I
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C H A P T E R31Goals and Callbacks:
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The only functionality that is not
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C H A P T E R32Advanced Presolve Ro
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once. All of the node relaxation so
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- 5x1, + x2 ≤ 0 2y1, + y2, ≥ 1x
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problem, the problem has a presolve
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Modifying a ProblemThis section bri
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C H A P T E R33Advanced MIP Control
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value strictly greater than one. It
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Cut CallbackThe next example we con
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problem. Since branching involves a
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C H A P T E R34Parallel OptimizersT
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Threads and Performance Considerati
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3. Call the parallel optimizer with
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optimizer turns out to be the faste
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0 0 3383.7784 16 4505.0000 Cuts: 35
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I N D E XIndexAabsolute objective d
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ole in converting LP to network flo
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emoving from basis (C++ API) 62repr
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CPX_PARAM_PCPX_PARAM_POLISHTIMEsolu
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CPXcreateprob 467CPXcreateprob rout
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CPXwcpxwarning message channel 151C
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empty goal 431, 435end methodIloEnv
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getDuals method (Java API) 88getMax
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emove method (Java API) 94IloModele
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ecords singularities 188relocating
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from 218head 218sink 219source 219s
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control callbacks and 453query call
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primal reduction 385primal simplex
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eturn statusBounded (Java API) 81Er
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solvingdiet problem (Java API) 82mo
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arrier 208WorkMem 293WorkMem parame
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