# CPLEX Options¶

```
ampl: option solver cplex; # change the solver
ampl: option cplex_options 'option1=value1 option2=value2'; # specify options
ampl: solve; # solve the problem
```

Solver options obtained with `$ cplex -=`

.

```
absmipgap Absolute mixed-integer optimality gap tolerance
(for difference between current best integer solution
and optimal value of LP relaxation). Default 0.
advance Whether to use advance basis information (initial
primal and dual variable values and basis indicators).
Default 1 (yes).
aggcutlim Bound on the number of constraints aggregated to
generate flow-cover and mixed-integer-rounding cuts;
default = 3.
aggfill Synonym for "agglim".
agglim Variables that appear in more than agglim rows
(default 10) will not be substituted away by the
"aggregate" algorithm.
aggregate Whether to make substitutions to reduce the number of
rows: 0 ==> no; n > 0 ==> apply aggregator n times.
Default -1 ==> automatic choice.
aggtol Pivot tolerance for aggregating. It seldom needs
fiddling. Default = .05; must be in [1e-10, .99].
autoopt Single-word phrase: use CPLEX's automatic choice of
optimizer (currently dualopt for LPs).
autopt Synonym for "autoopt".
auxrootthreads Controls the number of threads used for auxiliary
chores when solving the root node of a MIP problem.
When N threads are available (possibly limited by
"threads"), auxrootthreads must be less than N.
Possible values:
0 = automatic choice (default)
n < N: use N-n threads for the root node and
n threads for auxiliary chores.
backtrack Tolerance (> 0, default 0.9999) for when to backtrack
during branch & bound. Low values tend to pure
best-bound search. High values (> 1) tend to pure
depth-first search. Values less than the default
are often good when subproblems are expensive.
baralg How to start the barrier algorithm:
0 (default) = 1 for MIP subproblems, else 3
1 = infeasibility-estimate start
2 = infeasibility-constant start
3 = standard start.
barcorr Limit on centering corrections in each iteration
of the barrier algorithm:
-1 = decide automatically (default)
nonnegative = at most that many.
bardisplay Specifies how much the barrier algorithm chatters:
0 = no output (default)
1 = one line per iteration
2 = more output.
bargrowth Tolerance for detecting unbounded faces in the
barrier algorithm: higher values make the test
for unbounded faces harder to satisfy.
Default = 1e12.
bariterlim Maximum barrier iterations allowed (default 2^31 - 1).
barobjrange Limit on the absolute objective value before the
barrier algorithm considers the problem unbounded.
Default = 1e20.
baropt Single-word phrase: use the barrier algorithm
(unless there are discrete variables).
barstart Barrier starting-point algorithm:
1 = assume dual is 0 (default)
2 = estimate dual
3 = average of primal estimate, 0 dual
4 = average of primal and dual estimates.
barstartalg Synonym for "barstart".
basis_cond Whether to show the condition number of the simplex
basis in the solve_message and to return its value
in the problem.basis_cond and objective.basis_cond
suffixes. (Default = 0 = no; 1 = yes).
bbinterval For nodeselect = 2, select the best-bound node,
rather than the best-estimate node, every
bbinterval iterations (default 7); 0 means
always use the best-estimate node.
benders_feascut_tol Tolerance for violations of feasibility cuts in Benders
algorithm. Default = 1e-6.
benders_optcut_tol Tolerance for violations of optimality cuts in Benders
algorithm. Default = 1e-6.
benders_strategy How to decompose the problem for Benders algorithm:
-1 = do not apply Benders algorithm
0 = automatic choice (default): if suffix benders
is present on variables, variables that have
.benders = 0 go into the master and CPLEX
assigns other variables to workers; otherwise
integer variables go into the master and
continuous variables into workers
1 = use suffix benders to determine which variables
are for the master (.benders = 0) and which
for workers (.benders = n > 0 ==> worker n
2 = similar to 0, but suffix benders is required
3 = similar to 0, but ignore suffix benders (if
present).
benders_worker Designate the algorithm that CPLEX applies to solve the
subproblems when using Benders decomposition:
0 = automatic (default)
1 = primal simplex
2 = dual simplex
3 = network simplex
4 = barrier algorithm
5 = sifting algorithm.
bendersopt Single-word phrase: use Benders algorithm.
Both integer and continuous variables must be present.
bestbound Single-word phrase requesting return of suffix
.bestbound on the objective and problem for the
best known bound on the objective value. For MIP
problems with .bestnode value from a feasible node
(see below), .bestbound = .bestnode.
bestnode Single-word phrase requesting return of suffix
.bestnode on the objective and problem for the
objective value at the best feasible MIP node.
For non-MIP problems and for MIP problems for which
a feasible node has not yet been found, this value
is +Infinity for minimization problems and -Infinity
for maximization problems.
boundstr Whether to use bound strengthening in solving MIPs:
-1 (default) = automatic choice
0 = never
1 = always.
bqpcuts Whether to generate boolean quadratic polytope (BQP)
cuts for nonconvex QP amd MIQP problems when solved
to optimality:
-1 = do not generate BQP cuts
0 = automatic choice (default)
1 = generate BQP cuts moderateely
2 = generate BQP cuts agressively
3 = generate BQP cuts very agressively.
branch Branching direction for integer variables:
-1 = down, 0 = algorithm decides, 1 = up; default = 0.
branchdir Synonym for "branch".
cliquecuts Synonym for "cliques".
cliques Whether to use clique cuts in solving MIPs:
-1 = never
0 = automatic choice (default)
1, 2, 3 = ever more aggressive generation.
clocktype Kind of times CPLEX reports during the solution
process:
0 = automatic choice
1 = CPU time
2 = wall clock time (total elapsed time = default)
coeffreduce Whether to use coefficient reduction when
preprocessing MIPS:
-1 = automatic choice (default)
0 = no
1 = reduce only integral coefficients
2 = reduce all potential coefficients
3 = reduce aggressively with tiling.
comptol Convergence tolerance for barrier algorithm:
the algorithm stops when the relative
complementarity is < bartol (default 1e-8).
concurrent Single-word phrase: with CPLEX versions >= 8
and when hardware and licensing permit, try
several methods in parallel.
concurrentopt Synonym for "concurrent".
conflictalg Choice of algorithm used by the CPLEX's conflict
refiner:
0 = automatic choice (default)
1 = fast
2 = propagate
3 = presolve
4 = IIS
5 = limited solve
6 = full solve.
Settings 1, 2, and 3 are fast but may not discard
many constraints; 5 and 6 work harder at this.
Setting 4 searches for an Irreducible Infeasible
Set of linear constraints (e.g., ignoring quadratic
constraints).
conflictdisplay What to report when the conflict finder is working:
0 = nothing
1 = summary (default)
2 = detailed display.
covercuts Synonym for "covers".
covers Whether to use cover cuts in solving MIPs:
-1 = never
0 = automatic choice (default)
1, 2, 3 = ever more aggressive generation.
cpumask Whether and how to bind threads to cores
on systems where this is possible:
off = no CPU binding
auto = automatic binding (default).
Values other than "off" and "auto" must be a
hexadecimal string (digits 0-9 and a-f, ignoring
case, so values A-F and a-f are treated alike).
The lowest order bit is for the first logical CPU.
For example, "a5" and "A5" indicate that CPUs 0, 2,
5, and 7 are available for binding to threads, since
hex value a5 = 2^7 + 2^5 + 2^2 + 2^0.
crash Crash strategy (used to obtain starting basis);
possible values = -1, 0, 1; default = 1.
The best setting is problem-dependent and
can only be found by experimentation.
0 completely ignores the objective.
crossover Causes the barrier algorithm to be run (in the
absence of discrete variables) and specifies
whether to "crossover" to an optimal simplex
basis afterwards:
0 = no crossover
1 = crossover with primal simplex
(default for baropt)
2 = crossover with dual simplex.
cutpass Number of passes permitted when generating MIP
cutting plane:
-1 = none
0 = automatic choice (default)
positive = at most that many passes.
cutsfactor Limit on MIP cuts added:
> 1 ==> (cutsfactor-1)*m, where m
is the original number of rows (after presolve);
< 0 ==> no limit;
0 <= cutsfactor <= 1 ==> no MIP cuts
Default = -1 (no limit).
cutstats 0 or 1 (default 0): Whether the solve_message report
the numbers and kinds of cuts used.
datacheck debug option; possible values:
0 = no data checking (default)
1 = issue warnings
2 = try to "assist" by warning about bad scaling.
dense Synonym for "densecol".
densecol If positive, minimum nonzeros in a column for
the barrier algorithm to consider the column dense.
If 0 (default), this tolerance is selected
automatically.
dependency Whether to use CPLEX's presolve dependency checker:
-1 = automatic choice (default)
0 = no
1 = turn on only at start of preprocessing
2 = turn on only at end of preprocessing
3 = turn on at both start and end of
preprocessing.
dettimelim Time limit in platform-dependent "ticks".
Default = 1e75. See timing.
dgradient Pricing algorithm for dual simplex (default 0):
0 = choose automatically
1 = standard dual pricing
2 = steepest-edge pricing
3 = steepest-edge pricing in slack space
4 = steepest-edge with unit initial norms
5 = devex pricing.
disjcuts Whether to generate MIP disjunctive cuts:
-1 = no
0 = automatic choice (default)
1, 2, 3 = ever more aggressive generation.
display Frequency of displaying LP progress information:
0 (default) = never
1 = each factorization
2 = each iteration.
doperturb 1 means initially perturb the problem (by an
amount governed by "perturbation", which is
described below). 0 (default) means let the
algorithm decide. Setting doperturb to 1
is occasionally helpful for highly degenerate
problems.
dparam Used with syntax "dparam=n=d" (no spaces), where n
is a decimal integer, the number of a CPLEX "double"
(i.e., floating-point valued) parameter. If d is a
decimal floating-point value, assign d to "double"
parameter n. If d is ?, report the current value of
"double" parameter n. This facility provides a way
to modify "double" parameters that have not (yet)
been assigned a keyword.
droptol If droptol > 0 is specified, linear constraint
and objective coefficients less than droptol in
magnitude are treated as zero.
dual Single-word phrase: solve the dual problem.
dualopt Single-word phrase: use a dual simplex algorithm.
dualratio If neither "primal" nor "dual" was specified and
"dual" is possible (e.g., no integer variables and
no node and arc declarations), choose between
"primal" and "dual" as follows.
Let m = number of rows, n = number of columns;
if m - n > dualthresh > 0 or m > dualratio*n,
solve the dual; otherwise solve the primal.
Defaults: dualthresh = 0, dualratio = 3.
dualthresh See dualratio.
eachcutlim Limit on the number of cuts of each time.
Default = 2100000000.
endbasis "endbasis foo" writes the final basis to
file "foo" (in BAS format).
endsol File for writing the final solution as an XML file.
feasibility Amount by which basic variables can violate
their bounds. Default = 1e-6; possible
values are between 1e-9 and 0.1.
feasopt For infeasible problems, whether to find a feasible
point for a relaxed problem (see feasoptobj):
0 = no (default)
1 = find a relaxed feasible point
2 = find a "best" solution among the relaxed
feasible points.
feasoptobj Objective for "feasopt":
1 = minimize the sum of constraint and variable
bound relaxations (default)
2 = minimize the number of constraint and variable
bounds relaxed (a MIP problem, generally
harder than feasoptobj = 1)
3 = minimize the sum of squares of constraint and
variable bound relaxations.
file Synonym for "writeprob".
finalmipalg Specify the algorithm to solve the final LP
obtained by fixing all integer variables at
their integer values:
0 = automatic (default)
1 = primal simplex
2 = dual simplex
3 = network simplex
4 = barrier
5 = sifting (not applicable to QP)
6 = concurrent optimizer.
flowcuts Whether to use flow cuts in solving MIPs:
-1 = never
0 = automatic choice (default)
1, 2 = ever more aggressive use.
flowpathcuts Whether to generate MIP flow-path cuts:
-1 = no
0 = automatic choice (default)
1, 2 = ever more aggressive generation.
fpheur Whether to use the feasibility pump heuristic on MIP
problems:
-1 = no
0 = automatic choice (default)
1 = yes, focus on finding a feasible solution
2 = yes, focus on finding a good objective
value at a feasible solution.
fraccand Limit on number of candidate variables when
generating Gomory cuts for MIP problems:
default = 200.
fraccuts Whether to generate MIP fractional Gomory
cuts:
-1 = no
0 = decide automatically (default)
1 = generate moderately
2 = generate aggressively.
fracpass Limit on number of passes to generate MIP
fractional Gomory cuts:
0 = automatic choice (default)
positive = at most that many passes.
fractionalcuts Synonym for "fracpass".
growth Synonym for "bargrowth".
gubcuts Whether to use GUB cuts in solving MIPs:
-1 = never
0 = automatic choice (default)
1, 2 = ever more aggressive generation.
heureffort Whether to increase ( > 1) or decrease ( < 1) efforts
spent on heuristics during MIP solvers;
heureffort = 0 ==> suppress all MIP heuristics.
heurfreq How often to apply "node heuristics" for MIPS:
-1 = never
0 = automatic choice (default)
n > 0 = every n nodes.
heuristicfreq Synonym for "heurfreq".
iisfind Whether to find and return an IIS (irreducible
infeasible set of variables and constraints) if
the problem is infeasible:
0 = no (default)
1 = find an IIS.
IIS details are returned in suffix .iis, which
assumes one of the values "non" for variables
and constraints not in the IIS; "low" for
variables or inequality constraint bodies whose lower
bounds are in the IIS; "upp" for variables and
inequality constraint bodies whose upper bounds are
in the IIS; and "fix" for equality constraints that
are in the IIS.
impliedcuts Whether to use implied cuts in solving MIPs:
-1 = never
0 = automatic choice (default)
1, 2 = ever more aggressive use.
incompat How to treat parameter settings that CPLEX finds
incompatible:
0 = quietly ignore incompatibilities
1 = report and ignore them (default)
2 = reject them, refusing to solve.
For example, CPLEX regards the polishafter_* parameters
introduced in CPLEX 11.2 as incompatible with the older
polishtime parameter.
integrality Amount by which an integer variable can differ
from the nearest integer and still be considered
feasible. Default = 1e-5; must be in [1e-9, 0.5].
(The upper bound was not enforced prior to CPLEX 11.)
intwarntol Do not warn about perturbations to "integer"
variables to make them integers when the maximum
perturbation is at most intwarntol (default 1e-9);
see "round".
iparam Used with syntax "iparam=n=i" (no spaces), where n
is a decimal integer, the number of a CPLEX integer
parameter. If i is a decimal integer, assign i to
integer parameter n. If i is ?, report the current
value of integer parameter n. This facility provides
a way to modify integer parameters that have not (yet)
been assigned a keyword.
iterations Limit on total LP iterations; default 2^31 - 1.
iterlim Synonym for "iterations".
lazy Whether to recognize suffix .lazy on constraints
(new for CPLEX 10): sum of
1 ==> treat .lazy = 1 as lazy constraint
2 ==> treat .lazy = 2 as user cut
Default lazy = 3 ==> treat both. (Suffix .lazy on
constraints is ignored if not 0, 1, or 2 modulo 3.)
lbheur Whether to use a local branching heuristic in an
attempt to improve new incumbents found during a
MIP search. (Default = 0 = no; 1 = yes.)
limitperturb Synonym for "perturblimit".
localimpliedcuts Whether to generate locally valid implied bound
cuts for MIP problems:
-1 ==> no
0 ==> automatic choice (default)
1 ==> yes, moderately
2 ==> yes, aggressively
3 ==> yes, very aggressively.
logfile Name of file to receive all CPLEX messages.
lowercutoff For maximization problems involving integer
variables, skip any branch whose LP relaxation's
optimal value is less than lowercutoff. Warning:
if lowercutoff is too large, the problem will
appear infeasible. Default = -1e75.
lowerobj Stop minimizing when the objective value
goes below lowerobj. Default = -1e75.
lowerobjlim Synonym for "lowerobj".
lpdisplay Synonym for "display".
lpiterlim Synonym for "iterations".
lptimelim Synonym for "time".
markowitz Pivot tolerance; default = 0.01; must be between
0.0001 and 0.99999. Bigger values may improve
numerical properties of the solution (and may
take more time).
maximize Single-word phrase: maximize the objective,
regardless of model specifications.
mcfcuts Whether to use multi-commodity flow (MCF) cuts:
-1 = no
0 = let CPLEX decide (default)
1 = generate a modest number of MCS cuts
2 = generate MCS cuts aggressively.
memoryemphasis Whether to compress data to reduce the memory used,
which may make some information (e.g., basis condition)
unavailable:
0 = no (default)
1 = yes.
minimize Single-word phrase: minimize the objective,
regardless of model specifications.
mipalg Algorithm used on mixed-integer subproblems:
0 = automatic choice (default)
1 = primal simplex
2 = dual simplex
3 = network simplex
4 = barrier
5 = sifting.
For MIQP problems (quadratic objective, linear
constraints), settings other than 3 and 5 are treated
as 0. For MIQCP problems (quadratic objective and
constraints), all settings are treated as 4.
mipalgorithm Synonym for "mipalg".
mipbasis Whether to compute a basis and dual variables for MIP
problems when endbasis is not specified:
-1 = default (described below)
0 = no
1 = yes
This keyword is new with driver version 20040716.
When endbasis is specified, mipbasis=1 is assumed.
Otherwise, when mipbasis=0 is specified for a MIP
problem, no solver-status values for variables are
returned to AMPL. The default is to assume 1 unless
a quadratic objective or constraint is present, in
which case qcdual is assumed if quadratic constraints
are present and 0 is assumed otherwise (as finding a
basis can be time consuming).
mipcrossover Crossover method used when using the barrier
method for MIP subproblems:
-1 = no crossover
0 (default) = automatic choice
1 = primal
2 = dual.
mipcuts Sets all ten of cliques, covers, disjcuts,
flowcuts, flowpathcuts, fraccuts, gubcuts,
impliedcuts, mircuts and zerohalfcuts to the
specified value.
mipdisplay Frequency of displaying branch-and-bound
information (for optimizing integer variables):
0 (default) = never
1 = each integer feasible solution
2 = every "mipinterval" nodes
3 = every "mipinterval" nodes plus
information on LP relaxations
(as controlled by "display")
4 = same as 2, plus LP relaxation info
5 = same as 2, plus LP subproblem info.
mipemphasis How to balance seeking seeking
feasibility versus optimality when solving a MIP:
0 = balance optimality and feasibility (default)
1 = emphasize feasibility over optimality
2 = emphasize optimality over feasibility
3 = emphasize moving the best bound
4 = emphasize finding hidden feasible solutions
5 = emphasize finding good feasible solutions sooner.
mipgap Relative tolerance for optimizing integer
variables: stop if
abs((best bound) - (best integer))
< mipgap * (1 + abs(best bound)).
Default = 1e-4; must be between 1e-9 and 1.
mipinterval Frequency of node logging for mipdisplay >= 2.
Default = 0 ==> automatic choice. Values n > 0 ==>
every n nodes and every new incumbent; n < 0 ==> less
frequently the more negative n is.
mipkappa For MIP problems, whether to compute the "MIP kappa",
which summarizes the condition numbers of the optimal
bases seen while solving the problem:
-1 = no
0 = automatic choice (default)
1 = compute for a sample of subproblems
2 = compute for all subproblems (possibly expensive).
mipordertype Synonym for "ordertype".
mipsearch Search strategy for mixed-integer problems, new
in CPLEX 11:
0 = automatic choice (default)
1 = traditional branch and cut
2 = dynamic search.
mipsolutions Stop branch-and-bound for integer variables
after finding "mipsolutions" feasible solutions.
Default = 2^31 - 1.
mipstart Synonym for "mipstartvalue".
mipstartalg For problems with integer variables, which algorithm
to use in solving the initial MIP subproblem:
0 = automatic choice (default)
1 = primal simplex
2 = dual simplex
3 = network simplex
4 = barrier
5 = sifting
6 = concurrent (several at once, if possible).
For MIQP problems (quadratic objective, linear
constraints), setting 5 is treated as 0 and 6 as 4.
For MIQCP problems (quadratic objective & constraints),
all settings are treated as 4.
mipstartstatus Whether to use incoming variable and constraint
statuses if the problem has integer variables:
0 = no
1 = yes (default).
mipstartvalue Whether to use initial guesses in problems with
integer variables:
0 = no.
1 = yes (default), automatic choice of algorithm.
2 = withdrawn and now treated as 0.
3 = effort level = CPX_MIPSTART_CHECKFEAS, which
fails if the starting point is infeasiable.
4 = effort level = CPX_MIPSTART_SOLVEFIXED, which
solves the fixed problem specified by the starting
guess.
5 = effort level = CPX_MIPSTART_SOLVEMIP, which
causes a subMIP problem to be solved; "submipnodelim"
limits the number of nodes explored.
6 = effort level = CPX_MIPSTART_REPAIR, which causes
an attempt to repair an infeasible starting guess;
"repairtries" tells how often to attempt a repair, and
"submipnodelim" limits the number of nodes explored.
7 = effort level = CPX_MIPSTART_NOCHECK, under which
the starting guess is simply assumed to be feasiable.
mipsubalg Synonym for "mipalg".
miqcpstrat Strategy for solving quadratically-constrained MIPs
(MIQCP problems):
0 = automatic choice (default)
1 = solve a quadratically-constrained node
relaxation (QCP) at each node
2 = solve an LP node relaxation at each node.
mircuts Whether to generate MIP rounding cuts:
-1 = no
0 = automatic choice (default)
1 = moderate generation
2 = aggressive generation.
modisplay how much to report during multiobjective optimization:
0 = nothing
1 = summary after each subproblem (default)
2 = subproblem logs as well as summaries.
multiobj whether to do multi-objective optimization:
0 = no (default)
1 = yes
When multiobj = 1 and several linear objectives are
present, suffixes .objpriority, .objweight, .objreltol,
and .objabstol on the objectives are relevant.
Objectives with greater (integer) .objpriority values
have higher priority. Objectives with the same
.objpriority are weighted by .objweight. Objectives
with positive .objabstol or .objreltol are allowed to
be degraded by lower priority objectives by amounts not
exceeding the .objabstol (absolute) and .objreltol
(relative) limits. The objective must all be linear.
Objective-specific values may be assigned via keywords
of the form obj_n_name, such as obj_1_pricing to
specify "pricing" for the first objective. If no
.objweight values are provided, 1. is assumed for all.
Similarly, if no .objpriority values are given, 1 is
assumed for all. For .objreltol and .objabstol, if
no values are given, all are assumed to be 0.
nameround Whether to mangle variable and constraint names
by turning [ and ] into ( and ), respectively:
0 = no (default)
1 = yes.
This only matters if you specify endbasis=...
or startbasis=... or perhaps writeprob=something.lp
and have instructed AMPL to write .row and .col files.
(It is usually better to let AMPL's status facilities
convey basis information.) An alternative under Unix
is to use the "tr" command to make the above changes
if they are needed.
netdisplay Which objective value to show when using the
network simplex algorithm with display > 0
or netopt=3:
0 = none
1 = true objective
2 = penalized objective (default).
netfeasibility Feasibility tolerance for the network simplex
algorithm. Default = 1e-6; possible values are
between 1e-11 and 1e-1.
netfind Algorithm for finding embedded networks:
1 = extract only the natural network
2 = use reflection scaling (default)
3 = use general scaling.
netfinder Synonym for "netfind".
netiterations Limit on network simplex iterations.
Default = large (e.g., 2^31 - 1).
netopt 0 means never invoke the network optimizer.
1 (default) means invoke the network optimizer
only if the model had node and arc declarations.
2 means always invoke the network optimizer
(unless there are integer variables); the network
optimizer may be able to find and exploit an
embedded network.
3 is similar to 2, but sets CPLEX's LPMethod
to CPX_ALG_NET rather than explicitly invoking
the network optimizer. This might make a
difference if CPLEX's presolve makes relevant
reductions.
netoptimality Tolerance for optimality of reduced costs in the
network simplex algorithm. Default 1e-6; must be
between 1e-11 and 1e-1.
netpricing How to price in the network simplex algorithm:
0 = automatic choice (default)
1 = partial pricing
2 = multiple partial pricing
3 = multiple partial pricing with sorting.
node Synonym for "nodes".
nodecuts Decides whether or not cutting planes are separated
at the nodes of the branch-and-bound tree:
-1 = do not generate node cuts
0 = automatic (default)
1 = generate moderately
2 = generate aggressively
3 = genertate very aggresively.
nodefile Whether to save node information in a temporary file:
0 = no
1 (default) = compressed node file in memory
2 = node file on disk
3 = compressed node file on disk.
nodefiledir Synonym for workfiledir. Prior to CPLEX 7.1,
this directory is just for node information files.
nodelim Synonym for "nodes".
nodes Stop branch-and-bound for integer variables
after "nodes" LP relaxations. Default = 2^31 - 1;
nodes = 0 ==> complete processing at the root (create
cuts, apply heuristics at root);
1 ==> allow branching from root: create but do not
solve nodes.
nodesel Strategy for choosing next node while optimizing
integer variables:
0 = depth-first search;
1 = breadth-first search (default);
2 = best-estimate search;
3 = alternate best-estimate search.
nodeselect Synonym for "nodesel".
nosolve Stop after loading the problem and honoring any
"writeprob" or "writemipstart" directives.
numericalemphasis Whether to try to improve numerical accuracy (at a
possible cost of time or memory):
0 = no (default)
1 = yes.
objdifference Amount added to (for maximizing) or subtracted
from (for minimizing) the best (so far) feasible
objective value while optimizing integer variables.
Subsequent nodes will be ignored if their LP
relaxations have optimal values worse than this
sum. Default = 0. Positive values may speed
the search -- and may cause the optimal solution
to be missed.
objno 1 (default) = first objective, 2 = second, etc.;
0 ==> no objective: just find a feasible point.
objrep Whether to replace
minimize obj: v;
with
minimize obj: f(x)
when variable v appears linearly in exactly one
constraint of the form
s.t. c: v >= f(x);
or
s.t. c: v == f(x);
Possible objrep values:
0 = no
1 = yes for v >= f(x)
2 = yes for v == f(x) (default)
3 = yes in both cases
For maximization problems, ">= f(x)" is changed to
"<= f(x)" in the description above. This is new
with driver version 20130622.
optimality Tolerance for optimality of reduced costs.
Default 1e-6; must be between 1e-9 and 1e-1.
optimize Synonym for "primal".
ordering Ordering algorithm used by the barrier algorithm
0 = automatic choice (default)
1 = approximate minimum degree
2 = approximate minimum fill
3 = nested dissection.
ordertype How to generate default priorities for integer
variables when no .priority suffix is specified:
0 = do not generate priorities (default)
1 = use decreasing costs
2 = use increasing bound range
3 = use coefficient count.
outlev Synonym for "display".
parallelmode Parallel optimization mode:
-1 = opportunistic mode
0 = automatic: let CPLEX decide (default)
1 = deterministic mode.
paramfile File containing param settings to import. The file
is read and settings in it echoed when the keyword
is processed.
paramfileprm File containing param settings in CPLEX PRM format
to import. The file is read without echoing settings
in it when the keyword is processed.
perturb Synonym for "doperturb".
perturbation Amount by which to perturb variable bounds
when perturbing problems (see "doperturb").
Default 1e-6; must be positive.
perturbconst Synonym for "perturbation".
perturblim Number of stalled simplex iterations before the
problem is perturbed. Default = 0 = automatic.
perturblimit Synonym for "perturblim".
pgradient Pricing algorithm for primal simplex (default 0):
-1 = reduced-cost pricing
0 = hybrid reduced-cost and Devex pricing
1 = Devex pricing
2 = steepest-edge pricing
3 = steepest-edge with slack initial norms
4 = full pricing.
plconpri Priority (default 1) for SOS2 constraints for nonconvex
piecewise-linear terms in constraints.
plobjpri Priority (default 2) for SOS2 constraints for nonconvex
piecewise-linear terms in objectives.
polishafter_absmipgap Start polishing integer solutions after the
absolute mixed-integer optimality gap is at most
polishafter_absmipgap. Default 1e-6.
polishafter_intsol Start polishing integer solutions after the
finding polishafter_intsol integer-feasible
solutions. Default 2^31 - 1.
polishafter_mipgap Start polishing integer solutions after the
relative mixed-integer optimality gap is at most
polishafter_mipgap. Default 0.
polishafter_nodes Start polishing integer solutions after the
processing polishafter_nodes nodes.
Default 2^31 - 1.
polishafter_time Start polishing integer solutions after finding
at least one integer feasible solution and spending
polishafter_time CPU seconds seeking integer
solutions. Default 1e75.
polishafter_timedet Start polishing integer solutions after finding
at least one integer feasible solution and spending
polishafter_time "ticks" seeking integer solutions.
Default 1e75.
poolagap Solutions with objective worse in absolute value by
poolgap than the best solution are not kept in the
solution pool; see poolstub. Default 1e75.
poolcapacity Number of solutions to keep in solution pool;
see poolstub. Default 2100000000.
pooldual Whether to return dual values (corresponding to fixed
integer variables) for MIP and MIQP problems in the
solution pool:
0 = no (default)
1 = yes (which takes extra computation)
poolgap Solutions with objective worse in a relative sense by
poolgap than the best solution are not kept in the
solution pool; see poolstub. Default 1e75.
poolintensity How hard to try adding MIP solutions to the solution
pool. Useful only if poolstub is specified. Default 0
is treated as 1 if poolstub is specified without
populate, or 2 if populate is specified. Larger values
(3 or 4) cause more additions to the solution pool,
possibly consuming considerable time; poolintensity 4
tries to generate all MIP solutions, which could be a
very large number.
poolreplace Policy for replacing solutions in the solution pool if
more than poolcapacity solutions are generated:
0 = FIFO (first-in, first-out); default
1 = Keep best solutions
2 = Keep most diverse solutions.
poolstub Stub for solution files in the MIP solution pool.
New in CPLEX 11 and meaningful only if some variables
are integer or binary. A pool of alternate MIP
solutions is computed if poolstub is specified, and the
solutions that remain in the solution pool (after some
are replaced if more than poolcapacity solutions are
found) are written to files
(poolstub & '1') ... (poolstub & |solution pool|),
where |solution pool| is the number of solutions in the
solution pool. That is, file names are obtained by
appending 1, 2, ... |solution pool| to poolstub. The
value of |solution pool| is returned in suffix npool
on the objective and problem.
populate Whether to run CPLEX's "populate" algorithm in an
attempt to add more solutions to the MIP solution pool.
0 = no; just keep solutions found during the
initial solve
1 = run "populate" after finding a MIP solution
2 = run "populate" instead of seeking a single
best solution.
See poolstub.
populatelim Limit on number of solutions added to the solution pool
by the populate algorithm. See poolstub and populate.
Default 20.
predual Whether CPLEX's presolve phase should present the
CPLEX solution algorithm with the primal (-1) or
dual (1) problem or (default = 0) should decide
which automatically. Specifying "predual=1" often
gives better performance than specifying just "dual",
but sometimes "dual predual=1" is still better.
prelinear Whether CPLEX's presolve should do full reductions
or only linear ones. Default = 1 = full.
prepass Limit on number of CPLEX presolve passes.
Default = -1 = decide limit automatically.
prereduce Kinds of reductions permitted during CPLEX presolve:
0 = none
1 = only primal
2 = only dual
3 = both primal and dual (default).
prereformulations Reformulations applied during CPLEX presolve:
0 = none
1 = allow reformulations that interphere with
crushing forms
2 = allow reformulations that interphere with
uncrushing forms
3 = all reformulations (default).
prerelax Whether to use CPLEX's presolve on the initial LP
relaxation of a MIP:
-1 = automatic choice (default)
0 = no
1 = yes.
presolve 0 or 1 (default 1): Whether to run CPLEX's presolve
algorithm.
presolvedual Synonym for "predual".
presolvenode -1, 0, or 1 (default 0): Whether to run CPLEX's
presolve at each node of the MIP branch-and-bound
tree: -1 = no; 1 = yes; 0 = automatic choice.
presos1reform Control the reformulation of SOS of type 1:
-1 = no reformulation
0 = automatic (default)
1 = reformulate as linear constraints, with a
reformulation which is logarithmic in the
size of the SOSs.
presos2reform Control the reformulation of SOS of type 2:
-1 = no reformulation
0 = automatic (default)
1 = reformulate as linear constraints, with a
reformulation which is logarithmic in the
size of the SOSs.
prestats 0 or 1 (default 0): Whether to include summary
statistics (if nonzero) for CPLEX's "aggregate" and
"presolve" algorithms in the solve_message.
pretunefile File to which nondefault keyword settings are written
before tuning; written whether or not tunefile or
tunefilecpx is specified.
pretunefileprm File to which nondefault keyword settings are written
in CPLEX PRM format before tuning; written whether or
not tunefile or tunefileprm is specified. Includes
some display settings suppressed by pretunefile.
pricing Size of pricing candidate list (for partial pricing).
0 (default) means the algorithm decides.
primal Single-word phrase: solve the primal problem.
primalopt Use the primal simplex algorithm.
priorities Whether to consider priorities for MIP branching:
0 = no
1 = yes (default).
probe Whether to do variable probing when solving MIPs
(which sometimes dramatically affects performance,
for better or worse):
-1 = no
0 = automatic choice (default)
1, 2, or 3 = ever more probing.
probetime Limit in seconds on time spent probing.
Default = 1e75.
probetimedet Limit in "ticks" on time spent probing.
Default = 1e75.
qcdmax Limit on k*n*n for computing duals for quadratically
constrained problems, where k = number of quadratic
constraints and n = number of variables. Default = 1e9.
qcdual Whether to compute dual variable values for problems
with quadratic constraints. Default = 1 (for "yes").
This may be expensive if there are many quadratic
constraints. Specifying qcdual=0 suppresses the
computation.
qcpconvergetol Convergence tolerance on relative complementarity for
problems with quadratic constraints. Default = 1e-7.
qctol1 Tolerance on a quadratic inequality constraint's slack.
After CPLEX has returned a solution, dual values are
deduced for "active" quadratic constraints.
Default 1e-5; a negative value is quietly treated as 0.
qctol2 Tolerance on the maxnorm of the gradient of an
"active" quadratic constraint (see qctol1): if the
maxnorm is no more than qctol2, the gradient is
considered to vanish and dual value 0 is deduced.
Default 1e-5; a negative value is quietly treated as 0.
qctol3 Tolerance on the reduction during QR factorization of
the maxnorm of an "active" constraint's gradient
(see qctol1) for the constraint to be considered
independent of the other active quadratic constraints.
Dual value 0 is deduced for dependent constraints.
Default 1e-5; a negative value is quietly treated as 0.
qpmethod Choice of algorithm for a continuous quadratic
programming problem:
0 = automatic choice (default)
1 = primal simplex
2 = dual simplex
3 = network simplex
4 = barrier algorithm
6 = concurrent optimizer.
qtolin Whether to to linearize products of bounded variables
in quadratic objectives:
-1 = automatic choice (default)
0 = no
1 = yes.
rays Whether to return suffix .unbdd when the objective is
unbounded or suffix .dunbdd when the constraints are
infeasible:
0 = neither
1 = just .unbdd
2 = just .dunbdd
3 = both (default)
To get .dunbdd, you may need to specify presolve=0
in $cplex_options.
readbasis BAS file containing starting basis.
readsol File (previously written by an endsol directive) for
reading the starting point. This is for debugging
and is normally not used.
readvector VEC file containing starting point for barrier alg.
Deprecated; use "readsol" instead.
record Whether to record CPLEX library calls for debugging use
by IBM in a file with an automatically chosen name of
the form cplexXXXXXXX.db:
0 = no (default)
1 = yes.
refactor LP iterations between refactorizing the basis.
0 (default) means the algorithm decides.
relax Single-word phrase: ignore integrality.
relaxpresolve Synonym for "prerelax".
relobjdif Synonym for "relobjdiff".
relobjdiff If the objdifference parameter is 0,
relobjdiff times the absolute value of the objective
value is added to (for maximizing) or subtracted
from (for minimizing) the best (so far) feasible
objective value while optimizing integer variables.
Subsequent nodes will be ignored if their LP
relaxations have optimal values worse than this
sum. Default = 0. Positive values may speed
the search -- and may cause the optimal solution
to be missed.
relpresolve Synonym for "prerelax".
repairtries How many times to try to repair in infeasible
MIP starting guess:
-1 = none
0 = automatic choice (default)
> 0 = that many times.
repeatpresolve Whether to repeat CPLEX's presolve at MIP nodes:
-1 = automatic choice (default)
0 = no
1 = presolve again ignoring cuts
2 = presolve again considering cuts
3 = presolve again considering cuts and
allowing new root cuts.
reqconvex Whether to require a quadratic model to be convex:
0 = automatic choice (default)
1 = require convexity
2 = do not require convexity; just look
for a local solution
3 = globally solve if noncovex.
resolve Whether to re-solve the problem with CPLEX's
presolve turned off when it reports the problem
to be infeasible or unbounded. Re-solving may
take extra time but should determine whether the
problem is infeasible or unbounded.
0 = no
1 = yes (default).
return_mipgap Whether to return mipgap suffixes or include
mipgap values in the solve_message: sum of
1 = return relmipgap suffix
2 = return absmipgap suffix
4 = suppress mipgap values in solve_message
The suffixes are on the objective and problem;
returned suffix values are +Infinity if no integer-
feasible solution has been found, in which case no
mipgap values are reported in the solve_message.
Default = 0. See also bestbound and bestnode above.
rinsheur Relaxation INduced neighborhood Search HEURistic
for MIP problems:
-1 = none
0 = automatic choice of interval (default)
n (for n > 0) = every n nodes.
rltcuts Whether to use RLT (Reformulation Linearization
Technique) cuts:
-1 = no
0 = automatic choice (default)
1 = generate RLT cuts moderately
2 = generate RLT cuts aggressively
3 = generate RLT cuts very aggressively
round Whether to round integer variables to integral
values before returning the solution, and whether
to report that CPLEX returned noninteger values
for integer values (default 1): sum of
1 ==> round nonintegral integer variables
2 ==> do not modify solve_result
4 ==> do not modify solve_message
8 ==> modify solve_result and solve_message
even if maxerr < intwarntol (default 1e-9).
Modifications take place only if CPLEX assigned
nonintegral values to one or more integer variables.
scale How to scale the problem:
-1 = no scaling
0 (default) = equilibration
1 = a more aggressive scheme that sometimes helps.
seed Seed for random number generator used internally
by CPLEX. Use "seed=?" to see the default, which
depends on the CPLEX release.
sensitivity Single-word phrase: return sensitivity information for
the objective (in suffixes .up for the largest value
of a variable's cost coefficient or constraint's
right-hand side before the optimal basis changes,
.down for the smallest such value, and .current for
the current cost coefficient or right-hand side).
siftingopt Synonym for "siftopt".
siftopt Single-word phrase: on LPs with CPLEX versions >= 8,
solve ever larger sequences of subproblems until the
whole LP is solved.
simplexsifting Whether to allow the simplex algorithm to use sifting
when appropriate:
0 = no
1 = yes (default).
singular Maximum number of times CPLEX should try to
repair the basis when it encounters singularities.
Default = 10.
singularlim Synonym for "singular".
solutionlim Synonym for "mipsolutions".
solutiontype Whether to seek a basic solution when solving an LP:
0 = automatic choice (default)
1 = yes
2 = no (just seek a primal-dual pair).
sos 0 or 1 (default 1): Whether to honor declared
suffixes .sosno and .ref describing SOS sets.
Each distinct nonzero .sosno value designates an SOS
set, of type 1 for positive .sosno values and of type
2 for negative values. The .ref suffix contains
corresponding reference values.
sos2 0 or 1 (default 1): Whether to tell CPLEX about SOS2
constraints for nonconvex piecewise-linear terms.
sparam Used with syntax "sparam=n=str" (no spaces), where n
is a decimal integer, the number of a CPLEX string
parameter. If str is ?, report the current value of
string parameter n. Otherwise, if str is a quoted
string or a sequence of nonblank characters, assign
str to string parameter n. This facility provides a
way to modify string parameters that have not (yet)
been assigned a keyword.
splitcuts Whether to use lift-and-project cuts on MIP problems
(new for CPLEX 12.5.1):
-1 = no
0 = automatic choice (default)
1 = moderate use
2 = aggressive use
3 = very aggressive use.
startalg Synonym for "mipstartalg".
startalgorithm Synonym for "mipstartalg".
startbasis "startbasis foo" reads the initial basis
(in BAS format) from file "foo".
startsol Synonym for "readsol".
startvector Synonym for "readvector".
strongcand Length of the candidate list for "strong branching"
when solving MIPs: default 10.
strongit Number of simplex iterations on each variable in
the candidate list during strong branching.
Default = 0 = automatic choice.
subalg Synonym for "mipalg".
subalgorithm Synonym for "mipalg".
submipalg Choice of algorithm used to solve the subproblems
of a subMIP: not a subproblem, but an auxiliary MIP
that CPLEX sometimes forms and solves, e.g., when
* dealing with a partial MIP start
* repairing an infeasible MIP start
* using the RINS heuristic
* branching locally
* polishing a solution.
Possible values (when appropriate):
0 = automatic choice (default)
1 = primal simplex
2 = dual simplex
3 = network simplex (not for MIQPs)
4 = barrier
5 = sifting (0 is used for MIQPs).
Only 0 is allowed for MIQCPs.
submipnodelim Limit on nodes searched by relaxation induced
neighborhood search (RINS) heuristic for MIP
problems and for processing of MIP starting values.
Default = 500.
submipscale Rarely used choice of scaling for auxiliary subMIPs
(described with "submipalg"):
-1 = no scaling
0 = equilibration scaling (default)
1 = more aggressive scaling.
submipstartalg Rarely used choice of algorithm for the initial
relaxation of a subMIP (described with "submipalg"):
0 = automatic choice (default)
1 = primal simplex
2 = dual simplex
3 = network simplex
4 = barrier
5 = sifting (0 is used for MIQPs)
6 = concurrent (dual, barrier and primal in
opportunistic mode; dual and barrier in
deterministic mode; 4 is used for MIPQs).
Only 0 is allowed for MIQCPs.
symmetry Whether to break symmetry during
preprocessing of MIP problems:
-1 = automatic choice (default)
0 = no
1 = moderate effort
2 = more effort
3 = still more effort
4 = even more effort (new in CPLEX 11)
5 = more effort than 4 (new in CPLEX 11).
threads Default maximum number of threads for any of
the parallel CPLEX optimizers (limited also
by licensing). Default = 1 prior to CPLEX 11,
or 0 (use maximum threads available) starting
with CPLEX 11. May be overridden, prior to
CPLEX 11, by more specific limits, such as
barthreads or mipthreads.
time Time limit in seconds; default = 1e75.
timelimit Synonym for "time".
timing Whether to write times in seconds or "ticks" to
stdout or stderr: sum of
1 = write time in seconds to stdout
2 = write time in seconds to stderr
4 = write time in "ticks" to stdout
8 = write time in "ticks" to stderr
16 = write number of logical cores to stdout
32 = write number of logical cores to stderr.
Default = 0.
tranopt Synonym for "dualopt".
treelimit Synonym for "treememory".
treememlim Synonym for "treememory".
treememory Max. megabytes of memory (default 1e75) to use for
branch-and-bound tree.
tunedisplay How much to print during tuning:
0 = nothing
1 = minimal printing (default)
2 = show parameters being tried
3 = exhaustive printing.
tunefile Name of file for tuning results. If specified, CPLEX
will experiment with parameter settings that would
make the solution faster. This can significantly
increase execution time of the current invocation, but
the settings it finds might save time in future runs.
tunefileprm Name of file for tuning results in CPLEX PRM format.
If specified, CPLEX will experiment with parameter
settings as described for "tunefile".
tunefix List of keywords not to tune, enclosed in quotes
(" or ') or separated by commas without white space
if more than one.
tunefixfile Name of file containing keywords not to tune.
(There is no PRM format alternative.) Merged with
tunefix specification (if any).
tunerepeat How many times to perturb the problem during tuning.
Default = 1.
tunetime Limit (in seconds) on tuning time; meaningful
if < time. Default = 1e75.
tunetimedet Limit (in "ticks") on tuning time; meaningful
if < time. Default = 1e75.
uppercutoff For minimization problems involving integer
variables, skip any branch whose LP relaxation's
optimal value is more than uppercutoff. Warning:
if uppercutoff is too small, the problem will
appear infeasible. Default = 1e75.
upperobj Stop maximizing when the objective value
goes above upperobj. Default = 1e75.
upperobjlim Synonym for "upperobj".
varsel Strategy for selecting the next branching
variable during integer branch-and-bound:
-1 = branch on variable with smallest
integer infeasibility
0 = algorithm decides (default)
1 = branch on variable with largest
integer infeasibility
2 = branch based on pseudo costs
3 = strong branching
4 = branch based on pseudo reduced costs.
varselect Synonym for "varsel".
version Single-word phrase: show the current version.
wantsol solution report without -AMPL: sum of
1 = write .sol file
2 = print primal variable values
4 = print dual variable values
8 = do not print solution message
warninglimit Limit on the number of warnings per issue
given when "datacheck=2" is specified. Default = 10.
workfiledir Directory where CPLEX creates a temporary
subdirectory for temporary files, e.g., for
node information and Cholesky factors.
workfilelim Maximum size in megabytes for in-core work "files".
Default 2048.
writebasis Synonym for "endbasis".
writemipstart [Debug option] The name of a file to which the MIP
starting guess (if any) is written in ".mst" format.
If there is no MIP start, an empty file is written.
writeprob Name of file to which the problem is written
in a format determined by the name's suffix:
.sav = binary SAV file;
.mps = MPS file, original names;
.lp = LP file, original names;
.rmp = MPS file, generic names;
.rew = MPS file, generic names;
.rlp = LP file, generic names.
SAV and LP formats are peculiar to CPLEX.
writesol Synonym for "endsol".
zerohalfcuts Whether to generate zero-half cuts for MIP problems:
-1 = no
0 = automatic choice (default): continue
generating until new cuts are not helpful
1 = generate zero-half cuts moderately
2 = generate zero-half cuts aggressively.
```