Overview ..............111
Creating, renaming, relocating log files ....111
Closing log files ...........112
Controlling message channels ........112
Overview..............112
Output channels in the Interactive Optimizer 112
Callable Library routines for message channels 113
Example: Callable Library message channels . . 114
Concert Technology message channels ....115
Chapter 8. Timing interface .....117
Using the timing interface .........117
Chapter 9. Tuning tool .......119
Meet the tuning tool ...........119
Overview..............119
If CPLEX solves your problem to optimality . . 119
If CPLEX finds solutions but does not prove
optimality .............119
Tuning and time limits .........120
Tuning results ............120
Invoking the tuning tool..........120
Example: time limits on tuning in the Interactive
Optimizer ..............121
Fixing parameters and tuning multiple models in
the Interactive Optimizer .........122
Invoking the tuning tool in the Interactive
Optimizer .............122
Fixed parameters to respect .......122
Files of models to tune .........123
Tuning models in the Callable Library (C API) . . 123
Callbacks for tuning ...........124
Terminating a tuning session ........124
Part 3. Continuous optimization 127
Chapter 10. Solving LPs: simplex
optimizers .............129
Introducing the primal and dual optimizers . . . 129
Choosing an optimizer for your LP problem . . . 129
Overview of LP optimizers ........129
Automatic selection of an optimizer .....130
Dual simplex optimizer .........131
Primal simplex optimizer ........131
Network optimizer ..........131
Barrier optimizer ...........131
Sifting optimizer ...........131
Concurrent optimizer..........132
Parameter settings and optimizer choice . . . 132
Tuning LP performance ..........132
Introducing performance tuning for LP models 132
Preprocessing ............133
Starting from an advanced basis ......135
Simplex parameters ..........136
Diagnosing performance problems ......139
Lack of memory ...........139
Numeric difficulties ..........141
Diagnosing LP infeasibility .........145
Infeasibility reported by LP optimizers ....145
Coping with an ill-conditioned problem or
handling unscaled infeasibilities ......146
Interpreting solution quality .......147
Finding a conflict ...........149
Repairing infeasibility: FeasOpt ......150
Examples: using a starting basis in LP optimization 150
Overview..............150
Example ilolpex6.cpp ..........150
Example lpex6.c ...........151
Chapter 11. Solving LPs: barrier
optimizer .............153
Introducing the barrier optimizer .......153
Barrier simplex crossover .........154
Differences between barrier and simplex optimizers 154
Using the barrier optimizer.........155
Special options in the Interactive Optimizer . . . 156
Controlling crossover...........156
Using SOL file format ..........156
Interpreting the barrier log file .......156
Accessing and managing the log file of the
barrier optimizer ...........156
Sample log file from the barrier optimizer . . . 157
Sample log file from the augmented system
solver ...............157
Preprocessing in the log file .......158
Nonzeros in lower triangle of A*A' in the log
file ................158
Ordering-algorithm time in the log file ....158
Cholesky factor in the log file .......159
Iteration progress in the log file ......159
Infeasibility ratio in the log file ......159
Understanding solution quality from the barrier LP
optimizer...............160
Tuning barrier optimizer performance .....161
Overview of parameters for tuning the barrier
optimizer..............161
Memory emphasis: letting the optimizer use
disk for storage............163
Preprocessing ............164
Detecting and eliminating dense columns . . . 164
Choosing an ordering algorithm ......165
Using a starting-point heuristic ......165
Overcoming numeric difficulties .......166
Default behavior of the barrier optimizer with
respect to numeric difficulty .......166
Numerical emphasis settings .......166
Difficulties in the quality of solution.....167
Difficulties during optimization ......168
Difficulties with unbounded problems ....169
Diagnosing infeasibility reported by barrier
optimizer...............170
Chapter 12. Solving network-flow
problems .............171
Choosing an optimizer: network considerations 171
Formulating a network problem .......171
Example: network optimizer in the Interactive
Optimizer ..............172
Network flow problem description .....172
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