Parameter Groups

To provide some guidance on this page, we have classified the parameters into a number of categories. Some parameters are part of multiple categories. Those categories are:

• Termination parameters which set the stopping conditions for algorithms;

• Tolerance parameters which control solution quality requirements;

• Logging and I/O parameters which control logging behavior as well as input and output files;

• Algorithmic control parameters for Presolve, Simplex, Barrier, Scaling, MIP, MIP Cuts, and Numerics;

• Tuning parameters which control parameter tuning strategies for grbtune and the tune API calls;

• Solution Pool parameters which control how the solver searches for and stores additional solutions other than the best available one;

• Multi-Objective parameters which control some aspects when working with multiple objectives;

• Parameters for configuring aspects of remote optimization and licensing: Parallel and Distributed Computing, Instant Cloud, Compute Server, Cluster Manager, Token Server, Web License Service; and

• Other parameters that do not fit directly into one of the other categories.

The tables below link to the full detail of each parameter’s effect in the Parameter Reference section.

Termination

These parameters affect the termination of the algorithms. If the algorithm exceeds any of these limits, it will terminate and report a non-optimal termination status (see the Status Code section for further details). Note that the algorithm won’t necessarily stop the moment it hits the specified limit. The termination check may occur well after the limit has been exceeded.

Parameter name	Purpose
BarIterLimit	Barrier iteration limit
BestBdStop	Best objective bound to stop
BestObjStop	Best objective value to stop
Cutoff	Objective cutoff
IterationLimit	Simplex iteration limit
MemLimit	Memory limit
NodeLimit	MIP node limit
SoftMemLimit	Soft memory limit
SolutionLimit	MIP feasible solution limit
TimeLimit	Time limit
WorkLimit	Work limit

A few termination parameters can be modified from a callback with the corresponding callback methods. Those are: TimeLimit, WorkLimit, NodeLimit, and BarIterLimit. This makes it easier to implement custom termination criteria that, for example, set a time limit based on dynamic solving process data like the current incumbent objective value.

Tolerances

These parameters control the allowable feasibility or optimality violations.

Parameter name	Purpose
BarConvTol	Barrier convergence tolerance
BarQCPConvTol	Barrier QCP convergence tolerance
FeasibilityTol	Primal feasibility tolerance
IntFeasTol	Integer feasibility tolerance
MarkowitzTol	Threshold pivoting tolerance
MIPGap	Relative MIP optimality gap
MIPGapAbs	Absolute MIP optimality gap
OptimalityTol	Dual feasibility tolerance
PSDTol	Positive semi-definite tolerance

Logging

These parameters control the logging information.

Parameter name	Purpose
CSClientLog	Controls logging for Compute Server and the Web License Service (WLS)
DisplayInterval	Frequency at which log lines are printed
LogFile	Log file name
LogToConsole	Console logging
OutputFlag	Solver output control

I/O

These parameters can be used to read or write information.

Parameter name	Purpose
InputFile	File to be read before optimization commences
JSONSolDetail	Controls the level of detail stored in generated JSON solution
Record	Enable API call recording
ResultFile	Result file written upon completion of optimization
SolFiles	Location to store intermediate solution files

Presolve

These parameters control the operation of the presolve algorithms.

Parameter name	Purpose
AggFill	Allowed fill during presolve aggregation
Aggregate	Presolve aggregation control
DualReductions	Disables dual reductions in presolve
PreCrush	Allows presolve to translate constraints on the original model to equivalent constraints on the presolved model
PreDepRow	Presolve dependent row reduction
PreDual	Presolve dualization
PreMIQCPForm	Format of presolved MIQCP model
PrePasses	Presolve pass limit
PreQLinearize	Presolve Q matrix linearization
Presolve	Presolve level
PreSOS1BigM	Controls largest coefficient in SOS1 reformulation
PreSOS1Encoding	Controls SOS1 reformulation
PreSOS2BigM	Controls largest coefficient in SOS2 reformulation
PreSOS2Encoding	Controls SOS2 reformulation
PreSparsify	Presolve sparsify reduction

Simplex

These parameters control the operation of the simplex algorithms.

Parameter name	Purpose
InfUnbdInfo	Generate additional info for infeasible/unbounded models
IterationLimit	Simplex iteration limit
LPWarmStart	Warm start usage in simplex
Method	Define method, e.g., Simplex, to solve continuous models
NetworkAlg	Network simplex algorithm
NormAdjust	Simplex pricing norm
PerturbValue	Simplex perturbation magnitude
Quad	Quad precision computation in simplex
Sifting	Sifting within dual simplex
SiftMethod	LP method used to solve sifting sub-problems
SimplexPricing	Simplex variable pricing strategy

Barrier

These parameters control the operation of the barrier solver.

Parameter name	Purpose
BarConvTol	Barrier convergence tolerance
BarCorrectors	Central correction limit
BarHomogeneous	Barrier homogeneous algorithm
BarIterLimit	Barrier iteration limit
BarOrder	Barrier ordering algorithm
BarQCPConvTol	Barrier QCP convergence tolerance
Crossover	Barrier crossover strategy
CrossoverBasis	Crossover initial basis construction strategy
Method	Define method, e.g., Barrier, to solve continuous models
QCPDual	Compute dual variables for QCP models

Scaling

These parameters control the operation of the simplex algorithms and the barrier solver.

Parameter name	Purpose
ObjScale	Objective scaling
ScaleFlag	Model scaling

MIP

These parameters control the operation of the MIP algorithms.

Parameter name	Purpose
BranchDir	Branch direction preference
ConcurrentJobs	Enables distributed concurrent solver
ConcurrentMethod	Chooses continuous solvers to run concurrently
ConcurrentMIP	Enables concurrent MIP solver
ConcurrentSettings	Create concurrent environments from a list of .prm files
DegenMoves	Degenerate simplex moves
Disconnected	Disconnected component strategy
DistributedMIPJobs	Enables the distributed MIP solver
Heuristics	Turn MIP heuristics up or down
ImproveStartGap	Trigger solution improvement
ImproveStartNodes	Trigger solution improvement
ImproveStartTime	Trigger solution improvement
IntegralityFocus	Set the integrality focus
LazyConstraints	Programs that add lazy constraints must set this parameter
MinRelNodes	Minimum relaxation heuristic control
MIPFocus	Set the focus of the MIP solver
MIQCPMethod	Method used to solve MIQCP models
NLPHeur	Controls the NLP heuristic for non-convex quadratic models
NodefileDir	Directory for MIP node files
NodefileStart	Memory threshold for writing MIP tree nodes to disk
NodeLimit	MIP node limit
NodeMethod	Method used to solve MIP node relaxations
NonConvex	Control how to deal with non-convex quadratic programs
NoRelHeurTime	Limits the amount of time (in seconds) spent in the NoRel heuristic
NoRelHeurWork	Limits the amount of work performed by the NoRel heuristic
OBBT	Controls aggressiveness of optimality-based bound tightening
PartitionPlace	Controls when the partition heuristic runs
PumpPasses	Feasibility pump heuristic control
RINS	RINS heuristic
SolFiles	Location to store intermediate solution files
SolutionLimit	MIP feasible solution limit
SolutionNumber	Sub-optimal MIP solution retrieval
StartNodeLimit	Node limit for MIP start sub-MIP
StartNumber	Set index of MIP start
SubMIPNodes	Nodes explored by sub-MIP heuristics
Symmetry	Symmetry detection
VarBranch	Branch variable selection strategy
ZeroObjNodes	Zero objective heuristic control

The PumpPasses parameter can be modified from a callback with the corresponding callback methods.

MIP Cuts

These parameters affect the generation of MIP cutting planes. In all cases, a value of -1 corresponds to an automatic setting, which allows the solver to determine the appropriate level of aggressiveness in the cut generation. Unless otherwise noted, settings of 0, 1, and 2 correspond to no cut generation, conservative cut generation, or aggressive cut generation, respectively. The Cuts parameter provides global cut control, affecting the generation of all cuts. This parameter also has a setting of 3, which corresponds to very aggressive cut generation. The other parameters override the global Cuts parameter (so setting Cuts to 2 and CliqueCuts to 0 would generate all cut types aggressively, except clique cuts which would not be generated at all).

Parameter name	Purpose
BQPCuts	BQP cut generation
Cuts	Global cut generation control
CliqueCuts	Clique cut generation
CoverCuts	Cover cut generation
CutAggPasses	Constraint aggregation passes performed during cut generation
CutPasses	Root cutting plane pass limit
DualImpliedCuts	Dual implied bound cut generation
FlowCoverCuts	Flow cover cut generation
FlowPathCuts	Flow path cut generation
GomoryPasses	Root Gomory cut pass limit
GUBCoverCuts	GUB cover cut generation
ImpliedCuts	Implied bound cut generation
InfProofCuts	Infeasibility proof cut generation
LiftProjectCuts	Lift-and-project cut generation
MIPSepCuts	MIP separation cut generation
MIRCuts	MIR cut generation
MixingCuts	Mixing cut generation
ModKCuts	Mod-k cut generation
NetworkCuts	Network cut generation
ProjImpliedCuts	Projected implied bound cut generation
PSDCuts	PSD cut generation
RelaxLiftCuts	Relax-and-lift cut generation
RLTCuts	RLT cut generation
StrongCGCuts	Strong-CG cut generation
SubMIPCuts	Sub-MIP cut generation
ZeroHalfCuts	Zero-half cut generation

Numerics

These parameters can help to handle numerically challenging problems.

Parameter name	Purpose
BarHomogeneous	Barrier homogeneous algorithm
IntegralityFocus	Set the integrality focus
NumericFocus	Set the numerical focus

Tuning

These parameters control the operation of the parameter tuning tool.

Parameter name	Purpose
TuneBaseSettings	Comma-separated list of base parameter settings
TuneCleanup	Enables a tuning cleanup phase
TuneCriterion	Specify tuning criterion
TuneDynamicJobs	Enables distributed tuning using a dynamic set of workers
TuneJobs	Enables distributed tuning using a static set of workers
TuneMetric	Metric to aggregate results into a single measure
TuneOutput	Tuning output level
TuneParams	Comma-separated list of JSON files defining the parameters to be considered for tuning
TuneResults	Number of improved parameter sets returned
TuneTargetMIPGap	A target gap to be reached
TuneTargetTime	A target runtime in seconds to be reached
TuneTimeLimit	Time limit for tuning
TuneTrials	Perform multiple runs on each parameter set to limit the effect of random noise
TuneUseFilename	Use model file names as model names

Multiple Solutions

These parameters allow you to modify the behavior of the MIP search in order to find more than one solution to a MIP model.

Parameter name	Purpose
PoolGap	Relative gap for solutions in pool
PoolGapAbs	Absolute gap for solutions in pool
PoolSearchMode	Choose the approach used to find additional solutions
PoolSolutions	Number of solutions to keep in pool

Multiple Objectives

These parameters can be relevant when working with multiple objectives.

Parameter name	Purpose
MultiObjMethod	Warm-start method to solve for subsequent objectives
MultiObjPre	Initial presolve on multi-objective models
MultiObjSettings	Create multi-objective settings from a list of .prm files
ObjNumber	Set index of multi-objectives

Parallel and Distributed Computing

Parameters that are used to control the number of threads and our distributed parallel algorithms (distributed MIP, distributed concurrent, and distributed tuning).

Parameter name	Purpose
ConcurrentJobs	Enables distributed concurrent solver
ConcurrentMIP	Enables concurrent MIP solver
ConcurrentSettings	Create concurrent environments from a list of .prm files
DistributedMIPJobs	Enables the distributed MIP solver
Threads	Number of parallel threads to use
ThreadLimit	Specifies a thread limit when starting an environment
TuneJobs	Enables distributed tuning
WorkerPassword	Password for distributed worker cluster
WorkerPool	Distributed worker cluster

Instant Cloud

Parameters that are used to launch Gurobi Instant Cloud instances.

Parameter name	Purpose
CloudAccessID	Access ID for Gurobi Instant Cloud
CloudHost	Host for the Gurobi Cloud entry point
CloudSecretKey	Secret Key for Gurobi Instant Cloud
CloudPool	Cloud pool to use for Gurobi Instant Cloud instance

Compute Server

Parameters that are used to configure and launch Gurobi Compute Server jobs. You will normally set these in your license file, but you have the option of setting them through these parameters instead (by first constructing an empty environment). Refer to the Gurobi Remote Services Reference Manual for more information.

Parameter name	Purpose
ComputeServer	Name of a node in the Remote Services cluster
CSClientLog	Controls logging
CSPriority	Job priority for Remote Services job
CSQueueTimeout	Queue timeout for new jobs
CSRouter	Router node for Remote Services cluster
CSGroup	Group placement request for cluster
CSIdleTimeout	Idle time before Compute Server kills a job
CSTLSInsecure	Use insecure mode in Transport Layer Security (TLS)
JobID	Job ID of current job
ServerPassword	Client password for Remote Services cluster (or token server)
ServerTimeout	Network timeout interval

Cluster Manager

Parameters that are used to configure and launch Gurobi Cluster Manager. You will normally set these in your license file, but you have the option of setting them through these parameters instead (by first constructing an empty environment). Refer to the Gurobi Remote Services Reference Manual for more information.

Parameter name	Purpose
CSAPIAccessID	Access ID for Gurobi Cluster Manager
CSAPISecret	Secret key for Gurobi Cluster Manager
CSAppName	Application name of the batches or jobs
CSAuthToken	Token used internally for authentication
CSBatchMode	Controls Batch-Mode optimization
CSClientLog	Controls logging
CSManager	URL for the Cluster Manager
Username	User name to use when connecting to the Cluster Manager

Token Server

Parameters that are used to launch jobs that check out tokens from a token server. You will normally set these in your license file, but you have the option of setting them through these parameters instead (by first constructing an empty environment).

Parameter name	Purpose
ServerPassword	Client password for token server (or Remote Services cluster)
TokenServer	Name of your token server
TSPort	Token server port number

Web License Service

Parameters that are used to launch jobs that use the Web License Service (WLS). You will normally set these in your license file, but you have the option of setting them through these parameters instead (by first constructing an empty environment).

Parameter name	Purpose
CSClientLog	Controls logging
LicenseID	License ID
WLSAccessID	WLS access ID
WLSSecret	WLS secret
WLSToken	WLS token
WLSTokenDuration	WLS token duration
WLSTokenRefresh	Relative WLS token refresh interval

Other

Other parameters.

Parameter name	Purpose
FeasRelaxBigM	Big-M value for feasibility relaxations
FuncPieceError	Error allowed for PWL translation of function constraint
FuncPieceLength	Piece length for PWL translation of function constraint
FuncPieceRatio	Controls whether to under- or over-estimate function values in PWL approximation
FuncPieces	Sets strategy for PWL function approximation
FuncMaxVal	Maximum value for x and y variables in function constraints
FuncNonlinear	Chooses the approximation approach used to handle function constraints
IgnoreNames	Indicates whether to ignore names provided by users
IISMethod	IIS method
ScenarioNumber	Set index of scenario in multi-scenario models
Seed	Modify the random number seed
SolutionTarget	Specify the solution target for LP
UpdateMode	Change the behavior of lazy updates

Callback settable parameters

A few parameters can be modified from within a callback with the corresponding callback methods. This makes it easier to implement custom termination criteria that, for example, set a time limit based on dynamic solving process data like the current incumbent objective value. How to do that for the different APIs is illustrated here.

Note

In case of a remote server, the change of a parameter from within a callback may not be taken into account immediately.

Parameter name	Purpose
BarIterLimit	Barrier iteration limit
NodeLimit	MIP node limit
PumpPasses	Feasibility pump heuristic control
TimeLimit	Time limit
WorkLimit	Work limit