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AMPL-Gurobi Parameter Reference
aggfill | amount of fill allowed during aggregation during Gurobi's presolve (default: -1) |
---|---|
aggregate | whether to use aggregation during Gurobi presolve:
|
ams_eps | relative tolerance for reporting alternate MIP solutions (default = no limit) |
ams_epsabs | absolute tolerance for reporting alternate MIP solutions (default = no limit) |
ams_limit | Limit on number of alternate MIP solutions written, with no limit when ams_limit = 0 (default). |
ams_mode | Search mode for MIP solutions when ams_stub is specified
to request finding several alternative solutions:
|
ams_stub | Stub for alternative MIP solutions, written to files with
names obtained by appending "1.sol", "2.sol", etc., to
ams_stub. The number of such files written is affected
by four keywords:
The number of alternative MIP solution files written is returned in suffix npool on the objective and problem. |
barconvtol | tolerance on the relative difference between the primal and dual objectives for stopping the barrier algorithm (default: 1e-8) |
barcorrectors | Limit on the number of central corrections done in each barrier iteration (default -1 = automatic choice) |
barhomogeneous | Whether to use the homogeneous barrier algorithm
(e.g., when lpmethod=2 or nodemethod=2 is specified):
The homogeneous barrier algorithm can detect infeasibility or unboundedness directly, without crossover, but is a bit slower than the nonhomogeneous barrier algorithm. |
bariterlim | Limit on the number of barrier iterations (default: 1000) |
barorder | Ordering used to reduce fill in sparse-matrix factorizations during the barrier algorithm:
|
barqcptol | convergence tolerance on the relative difference between primal and dual objective values for barrier algorithms when solving problems with quadratic constraints (default: 1e-6) |
basis | whether to use or return a basis:
|
basisdebug | whether to honor basis and solnsens when an optimal solution was not found:
|
bestbndstop | stop once the best bound on the objective value is at least as good as this value. |
bestbound | whether to return suffix .bestbound for the best known bound on the objective value:
The suffix is on the objective and problem and is +Infinity for minimization problems and -Infinity for maximization problems if there are no integer variables or if an integer feasible solution has not yet been found. |
bestobjstop | stop after a feasible solution with objective value at least as good as this value has been found. |
bqpcuts | Whether to enable Boolean Quadric Polytope cut generation:
|
branchdir | which child node to explore first when branching:
|
cliquecuts | clique cuts: overrides "cuts"; choices as for "cuts" |
cloudid | use Gurobi Instant Cloud with this "accessID". |
cloudkey | use Gurobi Instant Cloud with this "secretKey". Both cloudid and cloudkey are required. |
cloudpool | optional "machine pool" to use with Gurobi Instant Cloud. |
cloudpriority | Priority of Cloud job, an integer >= -100 and <= 100. Default 0. Jobs with priority 100 run immediately -- use caution when specifying this value. |
concurrentmip | how many independent MIP solves to allow at once when multiple threads are available. The available threads are divided as evenly as possible among the concurrent solves. (default: 1) |
covercuts | cover cuts: overrides "cuts"; choices as for "cuts" |
crossover | how to transform a barrier solution to a basic one:
|
crossoverbasis | strategy for initial basis construction during crossover:
|
cutagg | maximum number of constraint aggregation passes during cut generation (-1 = default = no limit); overrides "cuts" |
cutoff | If the optimal objective value is no better than cutoff, report "objective cutoff" and do not return a solution; default: -∞ for minimizing, +∞ for maximizing |
cutpasses | maximum number of cutting-plane passes to do during root-cut generation (default: -1 = automatic choice) |
cuts | global cut generation control, valid unless overridden by individual
cut-type controls:
|
degenmoves | limit on the number of degenerate simplex moves -- for use when too much time is taken after solving the initial root relaxation of a MIP problem and before cut generation or root heuristics have started. |
disconnected | Whether to exploit independent MIP sub-models:
|
dualreductions |
whether Gurobi's presolve should use dual reductions, which may be useful on a
well-posed problem but can prevent distinguishing whether a problem is
infeasible or unbounded:
|
feasrelax |
Whether to modify the problem into a feasibility
relaxation problem:
|
feasrelaxbigm | Value of "big-M" sometimes used with constraints when doing a feasibility relaxation (default: 1e6) |
feastol | primal feasibility tolerance (default: 1e-6) |
fixedmethod | Value of "method" to use when seeking a basis for MIP problems when "basis=2" or (the default) "basis=3" has been specified. Default: if "method" is 0 or 1 then "method" else 1. |
flowcover | flowcover cuts: overrides "cuts"; choices as for "cuts" |
flowpath | flowpath cuts: overrides "cuts"; choices as for "cuts" |
gomory | maximum number of Gomory cut passes during cut generation (-1 = default = no limit); overrides "cuts" |
gubcover | GUB cover cuts: overrides "cuts"; choices as for "cuts" |
heurfrac | fraction of time to spend in MIP heuristics (default: 0.05) |
iisfind | whether to return an IIS (via suffix .iis) when the problem is infeasible:
|
iismethod | which method to use when finding an IIS (irreducible infeasible set of
constraints, including variable bounds):
|
implied | implied cuts: overrides "cuts"; choices as for "cuts" |
improvegap | optimality gap below which the MIP solver switches from trying to improve the best bound to trying to find better feasible solutions (default: 0) |
improvetime | execution seconds after which the MIP solver switches from trying to improve the best bound to trying to find better feasible solutions (default: ∞) |
impstartnodes | number of MIP nodes after which the solution strategy will change from improving the best bound to finding better feasible solutions (default: 0) |
infproofcuts | whether to generate infeasibility proof cuts:
|
integrality | Setting this parameter to 1 requests the solver to work
harder at finding solutions that are still (nearly) feasible
when all integer variables are rounded to exact integral
values:
|
intfeastol | feasibility tolerance for integer variables (default: 1e-05) |
intstart | when there are integer variables, whether to use an initial guess (if available):
|
iterlim | iteration limit (default: no limit) |
kappa | Whether to return the estimated condition number (kappa) of
the optimal basis (default 0): sum of
The request is ignored when there is no optimal basis. |
lazy | whether to honor suffix .lazy on linear constraints in problems with binary or integer variables:
Lazy constraints are indicated with .lazy values of -1, 1, 2, or 3 and are ignored until a solution feasible to the remaining constraints is found. What happens next depends on the value of .lazy:
|
lbpen | See feasrelax |
logfile | name of file to receive log lines (default: none); implies outlev = 1. |
logfreq | number of seconds between log lines (default: 5) |
lpmethod | synonym for "method" |
maxmipsub | maximum number of nodes for RINS heuristic to explore on MIP problems (default: 500) |
method | Which algorithm to use for non-MIP problems or for the root
node of MIP problems:
|
minrelnodes | number of nodes for the Minimum Relaxation heuristic to explore at the MIP root node when a feasible solution has not been found by any other heuristic; default -1 = automatic choice. |
mipfocus | MIP solution strategy:
|
mipgap | maximum relative MIP optimality gap (default: 1e-4) |
mipgapabs | absolute MIP optimality gap (default: 1e-10) |
mipsep | MIPsep cuts: overrides "cuts"; choices as for "cuts" |
mipstart | whether to use initial guesses in problems with integer variables:
|
miqcpmethod | Method for solving mixed-integer quadratically constrained
(MIQCP) problems:
|
mircuts | MIR cuts: overrides "cuts"; choices as for "cuts" |
modkcuts | mod-k cuts: overrides "cuts"; choices as for "cuts" |
multiobj | whether to do multi-objective optimization:
When multiobj = 1 and several objectives are present, suffixes .objpriority, .objweight, .objreltol, and .objabstol on the objectives are relevant. Objectives with greater .objpriority values (integer 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 indicated by objno can be general; all others must be linear. Objective-specific convergence tolerances and method values may be assigned via keywords of the form obj_n_name, such as obj_1_method for the first objective. |
multiobjmethod | choice of optimization algorithm for lower-priority
objectives:
|
multiobjpre | how to apply Gurobi's presolve when doing
multi-objective optimization:
|
multprice_norm | choice of norm used in multiple pricing:
|
networkcuts | Network cuts: overrides "cuts"; choices as for "cuts" |
nodefiledir | directory where MIP tree nodes are written after memory for them exceeds nodefilestart (default: .) |
nodefilestart | gigabytes of memory to use for MIP tree nodes (default = ∞ - no limit, i.e., no node files written) |
nodelim | maximum MIP nodes to explore (default: no limit) |
nodemethod | algorithm used to solve relaxed MIP node problems:
|
nonconvex |
How to handle non-convex quadratic objectives and constraints:
|
norelheurtime | Limits the amount of time spent in the NoRel heuristic; see the description of norelheurwork for details. This parameter will introduce non determinism; use norelheurwork for deterministic results. Default 0. |
norelheurwork | Limits the amount of work spent in the NoRel heuristic. This heuristics searches for high-quality feasible solutions before solving the root relaxation. The work metrix is hard to define precisely, as it depends on the machine. Default 0. |
normadjust | synonym for multprice_norm |
numericfocus | how much to try detecting and managing numerical issues:
|
objno | objective to optimize:
|
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:
For maximization problems, ">= f(x)" is changed to "<= f(x)" in the description above. |
objscale | how to scale the objective:
|
opttol | optimality tolerance on reduced costs (default: 1e-6) |
outlev | whether to write Gurobi log lines (chatter) to stdout:
|
param | general way to specify values of both documented and undocumented Gurobi parameters; value should be a quoted string (delimited by ' or ") containing a parameter name, a space, and the value to be assigned to the parameter. Can appear more than once. Cannot be used to query current parameter values. |
paramfile | name of file (surrounded by 'single' or "double" quotes if the name contains blanks) of parameter names and values for them. Lines that start with # are ignored. Otherwise, each nonempty line should contain a name and a value, separated by a space. |
partitionplace | Whether and how to use the .partition suffix on variables
in the partition heuristic for MIP problems: sum of
Values of .partition determine how variables participate in the partition heuristic. Variables with
The partition heuristic is only run when partitionplace is between 1 and 31 and some variables have suitable .partition suffix values. |
perturb | magnitude of simplex perturbation (when needed; default: 2e-4) |
pivtol | Markowitz pivot tolerance (default: 7.8125e-3) |
pl_bigm | When some variables applear in piecewise-linear terms in the objective and AMPL's "option pl_lineraize 0" is specified, lower bounds of -pl_bigm are assumed for such variables that are not bounded below and upper bounds of +pl_bigm are assumed for such variables that are not bounded above. (Default = 1e6) |
pool_distmip | number of machines in the server pool (if specified by pool_servers) to use for solving each MIP instance |
pool_mip | number of independent MIP jobs (default 0) to generate and solve using the server pool (if specified by pool_servers); Gurobi automatically chooses different algorithm parameter values for each job |
pool_password | password for the server pool (if needed) |
pool_servers | comma-separated list of server names or IP addresses of machines in the server pool (default "" = none) |
pool_tunejobs | number of parallel tuning jobs (default 0) to run on the server (if specified by pool_servers); tuning results are not normalized by server performance, so tuning is most effective when all the servers in the server pool have similar performance characteristics |
poolgap | synonym for ams_eps |
poolabsgap | synonym for ams_epsabs |
poolsearchmode | synonym for ams_mode |
poolsolutions | synonym for ams_limit |
poolstub | synonym for ams_stub |
predeprow | whether Gurobi's presolve should remove linearly dependent constraint-matrix rows:
|
predual | whether gurobi's presolve should form the dual of a continuous model:
|
premiqcpform | For mixed-integer quadratically constrained (MIQCP) problems,
how Gurobi should transform quadratic constraints:
Choices 0 and 1 work with general quadratic constraints. Choices 1 and 2 only work with constraints of suitable forms. |
prepasses | limit on the number of Gurobi presolve passes:
|
preqlinearize | How Gurobi's presolve should treat quadratic problems:
|
presolve | whether to use Gurobi's presolve:
|
presos1bigm |
Big-M for converting SOS1 constraints to binary form:
|
presos2bigm |
Big-M for converting SOS2 constraints to binary form:
|
presparsify | whether Gurobi's presolve should use its sparsify reduction, which
sometimes gives significant problem-size reductions:
|
pricing | pricing strategy:
|
priorities | whether to use the variable.priority suffix with MIP problems.
When several branching candidates are available, a variable
with the highest .priority is chosen for the next branch.
Priorities are nonnegative integers, with a default priority of 0:
|
psdtol | maximum diagonal perturbation to correct indefiniteness in quadratic objectives (default: 1e-6) |
pumppasses | number of feasibility-pump passes to do after the MIP root when no other root heuristic found a feasible solution (default: -1) |
qcpdual |
Whether to compute dual variables when the problem has quadratic constraints (which can be expensive):
|
quad | whether simplex should use quad-precision:
|
rays | Whether to return suffix .unbdd if the objective is unbounded or suffix
.dunbdd if the constraints are infeasible:
|
relax | whether to enforce integrality:
|
relaxliftcuts |
Whether to enable relax-and-lift cut generation:
|
resultfile | name of a file of extra information written after completion of optimization. The name's suffix determines what is written:
|
return_mipgap | Whether to return mipgap suffixes or include mipgap values
(|objectve - best_bound|) in the solve_message: sum of
Default = 0. 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. |
rhspen | See feasrelax |
rins | how often to apply the RINS heuristic for MIP problems:
|
rltcuts |
Whether to enable generation of cuts by the Relaxation
Linearization Technique (RLT):
|
round | Whether to round integer variables to integral values before
returning the solution, and whether to report that GUROBI
returned noninteger values for integer values: sum of
|
round_reptol | Tolerance for reporting rounding of integer variables to integer values; see "round". Default = 1e-9. |
scale | whether to scale the problem:
|
seed | random number seed, affecting perturbations that may influence the solution path (default: 0) |
server | Comma-separated list of Gurobi compute servers, specified either by name or by IP address. (default: unspecified - solve according to license key) |
server_insecure | Whether to user "insecure mode" with the Gurobi Compute Server. Should be left at default value (0) unless an administrator specifies another value. |
server_password | Password (if needed) for specified Gurobi Compute Server(s) |
server_priority | Priority for Gurobi Compute Server(s) (default: 1; maximum 100) |
server_timeout | Report job as rejected by Gurobi Compute Server if the job is not started within server_timeout seconds (default: -1 = no limit) |
servers | synonym for "server" |
sifting | whether to use sifting within the dual simplex algorithm,
which can be useful when there are many more variables than
constraints:
|
siftmethod | algorithm to use for sifting with the dual simplex method:
|
simplex | synonym for method |
solnlimit | maximum MIP solutions to find (default: 2e9) |
solnsens | whether to return suffixes for solution sensitivities, i.e., ranges of values for which the optimal basis remains optimal: 0 = no (default) 1 = yes: suffixes return on variables are .sensobjlo = smallest objective coefficient .sensobjhi = greatest objective coefficient .senslblo = smallest variable lower bound .senslbhi = greatest variable lower bound .sensublo = smallest variable upper bound .sensubhi = greatest variable upper bound suffixes for constraints are .sensrhslo = smallest right-hand side value .sensrhshi = greatest right-hand side value For problems with integer variables and quadratic constraints, solnsens = 0 is assumed quietly. |
sos | whether to honor declared suffixes .sosno and .ref describing SOS sets:
|
sos2 | whether to tell Gurobi about SOS2 constraints for nonconvex piecewise-linear terms
|
startnodelimit | limit on how many branch-and-bound nodes to explore when
doing a partial MIP start:
|
submipcuts | sub-MIP cuts: overrides "cuts"; choices as for "cuts" |
submipnodes | limit on nodes explored by MIP-based heuristics, e.g., RINS. Default = 500. |
symmetry | MIP symmetry detection:
|
threads | maximum threads to use on MIP problems (default: 0 - maximum possible) |
timelim | limit on solve time (in seconds; default: no limit) |
timing | whether to report timing:
|
tunebase | base name for results of running Gurobi's search for better parameter settings. The search is run only when tuneparbase is specified. Results are written to files with names derived from tunebase by appending ".prm" if ".prm" does not occur in tuneparbase and inserting 1, 2, ... (for the first, second, ... set of parameter settings) before the right-most ".prm". The file with "1" inserted is the best set and the solve results returned are for this set. In a subsequent "solve;", you can use paramfile=... to apply the settings in results file ... . |
tuneoutput | amount of tuning output when tunebase is specified:
|
tuneresults | limit on the number of tuning result files to write when tunerbase is specified. The default (-1) is to write results for all parameter sets on the efficient frontier. |
tunetimelimit | time limit (in seconds) on tuning when tunebase is specified. (default: -1 = automatic choice of time limit) |
tunetrials | number of trials for each parameter set when tunebase is specified, each with a different random seed value. (default = 3) |
ubpen | See feasrelax |
varbranch | MIP branch variable selection strategy:
|
wantsol | solution report without -AMPL: sum of
|
warmstart |
Whether to use incoming primal and dual variable values
(if both are available) in a simplex warm start:
|
writeprob | name of a GUROBI-format file to be written (for debugging); must end in one of ".bas", ".lp", ".mps", ".prm", ".rew", ".rlp", ".sol", or for the "fixed" model used to recover a basis or dual values for problems with integer variables or quadratic constraints, ".fix_lp" or ".fix_mps"; the '_' will be replaced by '.' in the name of the file written for ".fix_lp" or ".fix_mps". Can appear more than once with different filenames. |
zerohalfcuts | zero-half cuts: overrides "cuts"; choices as for "cuts" |
zeroobjnodes | number of nodes for the zero objective heuristic to explore at the MIP root node when a feasible solution has not been found by any other heuristic (default: -1) |
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