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Gurobi Optimizer Reference Manual
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  • Optimizer Reference Manual

Concepts

  • Modeling Components
    • Variables
    • Constraints
    • Objectives
    • Tolerances and Ill Conditioning
  • API Usage
  • Environments
    • Session boundaries
    • Configuration parameters (Empty environment)
    • Algorithmic parameters
    • Concurrent environments
    • Multi-objective environments
  • Attributes
    • Attribute Types
    • Attribute Examples
  • Parameters
    • Parameter Groups
    • Parameter Guidelines
    • Parameter Examples
  • Logging
    • Header
    • Simplex Logging
    • Barrier Logging
    • Sifting Logging
    • MIP Logging
    • Solution Pool and Multi-Scenario Logging
    • Multi-Objective Logging
    • Distributed MIP Logging
    • IIS Logging
  • Numerical Issues
    • Avoid Rounding of Input
    • Real Numbers are not Real
    • Tolerances and User-Scaling
    • Does my Model have Numerical Issues?
    • Solver Parameters to Manage Numerical Issues
    • Instability and the Geometry of Optimization Problems
    • Source Code Examples:

Features

  • Batch Optimization
  • Concurrent Optimizer
  • Gurobi Instant Cloud
  • Infeasibility Analysis
  • Multiple Objectives
  • Multiple Scenarios
  • Parameter Tuning Tool
  • Recording API Calls
  • Solution Pool

Reference

  • Release Notes for Gurobi 10.0
    • Additions, Changes and Removals
    • Supported Platforms
    • Fixed issues in this Release
  • C API
    • Overview
    • Environment Creation and Destruction
    • Model Creation and Modification
    • Model Solution
    • Model Queries
    • Input/Output
    • Attribute Management
    • Parameter Management
    • Monitoring Progress - Logging and Callbacks
    • Modifying Solver Behavior - Callbacks
    • Batch Requests
    • Error Handling
    • Parameter Tuning
    • Advanced simplex routines
  • C++ API
    • Overview
    • GRBEnv
    • GRBModel
    • GRBVar
    • GRBConstr
    • GRBQConstr
    • GRBSOS
    • GRBGenConstr
    • GRBExpr
    • GRBLinExpr
    • GRBQuadExpr
    • GRBTempConstr
    • GRBColumn
    • GRBCallback
    • GRBException
    • GRBBatch
    • Overloaded Operators
    • Enums
  • Java API
    • Overview
    • GRBEnv
    • GRBModel
    • GRBVar
    • GRBConstr
    • GRBQConstr
    • GRBSOS
    • GRBGenConstr
    • GRBExpr
    • GRBLinExpr
    • GRBQuadExpr
    • GRBColumn
    • GRBCallback
    • GRBException
    • GRBBatch
    • GRB
  • .NET API
    • Overview
    • GRBEnv
    • GRBModel
    • GRBVar
    • GRBConstr
    • GRBQConstr
    • GRBSOS
    • GRBGenConstr
    • GRBExpr
    • GRBLinExpr
    • GRBQuadExpr
    • GRBTempConstr
    • GRBColumn
    • Overloaded Operators
    • GRBCallback
    • GRBException
    • GRBBatch
    • GRB
  • Python API
    • Overview
    • Global Functions
    • Model
    • Var
    • MVar
    • Constr
    • MConstr
    • MQConstr
    • QConstr
    • SOS
    • GenConstr
    • LinExpr
    • QuadExpr
    • GenExpr
    • MLinExpr
    • MQuadExpr
    • TempConstr
    • Column
    • Callbacks
    • GurobiError
    • Env
    • Batch
    • GRB
    • tuplelist
    • tupledict
    • General Constraint Helper Functions
  • MATLAB API
    • Overview
    • Common Arguments
    • Solving a Model
    • Input/Output
    • Using Gurobi within MATLAB's Problem-Based Optimization
    • Setting up the Gurobi MATLAB interface
  • R API
    • Overview
    • Common Arguments
    • Solving a Model
    • Input/Output
    • Installing the R package
  • Gurobi Command-Line Tool
  • Attribute Reference
    • Model Attributes
    • Variable Attributes
    • Linear Constraint Attributes
    • SOS Attributes
    • Quadratic Constraint Attributes
    • General Constraint Attributes
    • Quality Attributes
    • Multi-objective Attributes
    • Multi-Scenario Attributes
    • Batch Attributes
  • Parameter Reference
  • Numeric Codes
    • Optimization Status Codes
    • Batch Status Codes
    • Callback Codes
    • Error Codes
  • File Formats
    • Model File Formats
    • Solution File Formats
    • Other File Formats
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Warning

You are reading the documentation for Gurobi version 10.0, an older release. Please see version 12.0 for documentation of the current Gurobi release.

Header#

When you solve a model, the first part of the resulting log contains basic information about the model you are solving and the machine you are solving it on. You will first see a line that looks like this:

Thread count: 4 physical cores, 8 logical processors, using up to 8 threads

This shows the number of physical cores and logical processors in the machine. The latter may be larger than the former due to Simultaneous Multi Threading (SMT), which allows one physical core to appear as multiple logical processors. This log line also shows the maximum number of threads that the solver will use in this instance. This depends on the number of (logical) processors in the machine, but also on the number requested (through the Threads parameter), and for some license types on the number enabled by your license.

Next you will see summary information about the model you are solving:

Optimize a model with 755 rows, 2756 columns and 8937 nonzeros
Model fingerprint: 0x22935346
Variable types: 0 continuous, 2756 integer (0 binary)

The first line shows the size of the model. The second shows the model fingerprint, which is a hash value that takes into account the values of all attributes of all components of the model. The intent is that models that differ in any way will most always have different fingerprints. The last log line above provides additional information about variable integrality (for MIP models).

The final portion of the header contains statistics about the constraint matrix:

Coefficient statistics:
  Matrix range     [1e+00, 1e+04]
  Objective range  [1e+00, 1e+04]
  Bounds range     [1e+00, 1e+00]
  RHS range        [1e+00, 1e+04]

This information gives a very rough indication of whether you can expect numerical issues when solving your model. Please consult the numerical guidelines section to learn more.

The format of the remainder of the log depends on the algorithm that is invoked (simplex, barrier, sifting, branch-and-cut, or IIS).

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Last updated on May 09, 2025