Function GMP::Instance::GetAttributeValue(GMP, attr, objNo)

GMP::Instance::GetAttributeValue

The function GMP::Instance::GetAttributeValue can be used to get the value of certain solver attributes, related to solving a generated mathematical program.

GMP::Instance::GetAttributeValue(
     GMP,            ! (input) a generated mathematical program
     attr,           ! (input) a string expression
     [objNo]         ! (input, optional) an integer expression
     )

Arguments

GMP

An element in AllGeneratedMathematicalPrograms.

attr

A string that holds the name of the attribute.

objNo

A nonnegative scalar value specifying the objective number in a multi-objective optimization problem. The default value is 0.

Return Value

In case of success, the function returns the attribute value. Otherwise it returns UNDF.

Note

  • The attribute name is case-insensitive.

  • This function is only supported by CPLEX and Gurobi.

  • This function cannot be called inside a callback procedure.

Attributes

The table below shows the model attributes supported by CPLEX and Gurobi.

Attribute

CPLEX

Gurobi

Description

ObjCon

✔

✔

Objective constant/offset

NumStart

✔

✔

Number of MIP starts (MIP only)

NumObj

✔

✔

Number of objectives

The table below shows the solution attributes supported by CPLEX and Gurobi.

Attribute

CPLEX

Gurobi

Description

ObjVal

✔

✔

Objective value

ObjBound

✔

✔

Best bound (MIP only)

MIPGap

✔

✔

Relative MIP gap (MIP only)

Runtime

✔

✔

Runtime in seconds

Work

✔

✔

Work or deterministic time

MaxMemUsed

✔

Maximum amount (in GB) of memory used

MemUsed

✔

Current amount (in GB) of memory used

SolCount

✔

Number of solutions (MIP only)

IterCount

✔

✔

Number of simplex iterations

BarIterCount

✔

✔

Number of barrier iterations

NodeCount

✔

✔

Number of branch-and-cut nodes (MIP only)

OpenNodeCount

✔

✔

Number of open branch-and-cut nodes (MIP only)

NodeInt

✔

Node number of the best solution (MIP only)

The table below shows the solution quality attributes supported by CPLEX and Gurobi.

Attribute

CPLEX

Gurobi

Description

MaxVio

✔

✔

Maximum unscaled violation

IntVio

✔

✔

Maximum integrality violation

Kappa

✔

✔

Estimated condition number

KappaExact

✔

✔

Exact condition number

KappaMax

✔

Highest condition number (MIP only)

KappaAttention

✔

Score of numerical difficulties (MIP only)

KappaStable

✔

Percentage of stable simplex bases (MIP only)

KappaSuspicious

✔

Percentage of suspicious simplex bases (MIP only)

KappaUnstable

✔

Percentage of unstable simplex bases (MIP only)

KappaIllposed

✔

Percentage of ill-posed simplex bases (MIP only)

The table below shows the attributes for multi-objective optimization supported by CPLEX and Gurobi. These attributes can be used to retrieve model or solution information for each subproblem solved, as specified by the objNo argument.

Attribute

CPLEX

Gurobi

Description

ObjNPriority

✔

✔

Objective priority

ObjNCon

✔

Objective constant/offset

ObjVal / ObjNVal

✔

✔

Objective value

ObjBound / ObjPassNObjBound

✔

✔

Best bound (MIP only)

MIPGap / ObjPassNMIPGap

✔

✔

Relative MIP gap (MIP only)

Runtime / ObjPassNRuntime

✔

✔

Runtime in seconds

Work / ObjPassNWork

✔

✔

Work or deterministic time

Status / ObjPassNStatus

✔

✔

Solution status

NodeCount / ObjPassNNodeCount

✔

✔

Number of branch-and-cut nodes (MIP only)

OpenNodeCount / ObjPassNOpenNodeCount

✔

✔

Number of open branch-and-cut nodes (MIP only)

IterCount / ObjPassNIterCount

✔

✔

Number of simplex iterations

BarIterCount

✔

Number of barrier iterations

For Gurobi also other model and solution attributes are supported. For a complete list; see: Model attributes. Attributes with type string are not supported by this function.

Example

In the example below two multi-objectives are specified, each with its own priority. Therefore two subproblems are solved; one for each objective. Below we retrieve the (relative) MIP gap for both subproblems. We also retrieve the total runtime by the solver.

myGMP := GMP::Instance::Generate( MP );

GMP::Column::SetAsMultiObjective( myGMP, TotalDist, 2, 1.0 );
GMP::Column::SetAsMultiObjective( myGMP, TotalTime, 1, 1.0 );

GMP::Instance::Solve( myGMP );

gap1 := GMP::Instance::GetAttributeValue( myGMP, "MIPGap", 1 );
gap2 := GMP::Instance::GetAttributeValue( myGMP, "MIPGap", 2 );

runtime := GMP::Instance::GetAttributeValue( myGMP, "Runtime" );

See also