Attributes

To query and modify properties of a COPT model is through the attribute interface. A variety of different attributes are available, and they can be associated with solutions, or the model.

Problem related

Problem related attributes provide the relevant information of the model composition and description. The names and descriptions of these attributes are summarized below.

Table 14 Problem related attributes

Name	Type	Description
Cols	Integer	Number of variables (columns) in the problem
Bins	Integer	Number of binary variables
Ints	Integer	Number of integer variables
PSDCols	Integer	Number of PSD variables in the problem
Rows	Integer	Number of constraints (rows) in the problem
Indicators	Integer	Number of indicator constraints
Soss	Integer	Number of SOS constraints
Cones	Integer	Number of Second-Order-Cone constraints
ExpCones	Integer	Number of exponential cone constraints
AffineCones	Integer	Number of affine cone constraints
QConstrs	Integer	Number of quadratic constraints
PSDConstrs	Integer	Number of PSD constraints
LMIConstrs	Integer	Number of LMI (Linear Matrix Inequalities) constraints
NLConstrs	Integer	Number of nonlinear expression constraints in the model
Elems	Integer	Number of non-zero elements in the coefficient matrix
QElems	Integer	Number of non-zero quadratic elements in the quadratic objective function
PSDElems	Integer	Number of PSD terms in objective function
NLElems	Integer	Number of nonlinear expression terms in the objective of the model
SymMats	Integer	Number of symmetric matrices in the problem
MultiObjs	Integer	Number of objectives in a multi-objective model
ObjSense	Integer	The optimization direction
ObjConst	Double	The constant part of the objective function
HasQObj	Integer	Whether the problem has quadratic terms in its objective
HasPSDObj	Integer	Whether the problem has PSD terms in its objective
HasNLObj	Integer	Whether the problem has nonlinear terms in its objective
IsMIP	Integer	Whether the problem is a MIP
MinElem	Double	Minimum absolute value of the non-zero elements of the coefficient matrix in the linear constraints
MaxElem	Double	Maximum absolute value of the non-zero elements of the coefficient matrix in the linear constraints
MinBound	Double	Minimum absolute value of the non-zero variable bounds
MaxBound	Double	Maximum absolute value of the non-zero variable bounds
MinRHS	Double	Minimum absolute value of the non-zero bounds (right-hand sides) of the linear constraints
MaxRHS	Double	Maximum absolute value of the non-zero bounds (right-hand sides) of the linear constraints
MinCost	Double	Minimum absolute value of the non-zero linear objective costs
MaxCost	Double	Maximum absolute value of the non-zero linear objective costs
MinQElem	Double	Minimum absolute value of the non-zero quadratic elements of the quadratic constraints
MaxQElem	Double	Maximum absolute value of the non-zero quadratic elements of the quadratic constraints
MinQLElem	Double	Minimum absolute value of the non-zero linear elements of the quadratic constraints
MaxQLElem	Double	Maximum absolute value of the non-zero linear elements of the quadratic constraints
MinQRHS	Double	Minimum absolute value of the non-zero right-hand sides of the quadratic constraints
MaxQRHS	Double	Maximum absolute value of the non-zero right-hand sides of the quadratic constraints
MinQCost	Double	Minimum absolute value of the non-zero quadratic objective costs
MaxQCost	Double	Maximum absolute value of the non-zero quadratic objective costs

• Cols

  Integer attribute.

  Number of variables (columns) in the problem.

• Bins

  Integer attribute.

  Number of binary variables.

• Ints

  Integer attribute.

  Number of integer variables.

• PSDCols

  Integer attribute.

  Number of PSD variables in the problem.

• Rows

  Integer attribute.

  Number of constraints (rows) in the problem.

• Indicators

  Integer attribute.

  Number of indicator constraints.

• Soss

  Integer attribute.

  Number of SOS constraints.

• Cones

  Integer attribute.

  Number of Second-Order-Cone constraints.

• ExpCones

  Integer attribute.

  Number of exponential cone constraints.

• AffineCones

  Integer attribute.

  Number of affine cone constraints.

• QConstrs

  Integer attribute.

  Number of quadratic constraints.

• PSDConstrs

  Integer attribute.

  Number of PSD constraints.

• LMIConstrs

  Integer attribute.

  Number of LMI (Linear Matrix Inequalities) constraints.

• NLConstrs

  Integer attribute.

  The number of nonlinear expression constraints in the model.

• Elems

  Integer attribute.

  Number of non-zero elements in the coefficient matrix.

• QElems

  Integer attribute.

  Number of non-zero quadratic elements in the quadratic objective function.

• PSDElems

  Integer attribute.

  Number of PSD terms in objective function.

• NLElems

  Integer attribute.

  The number of nonlinear expression terms in the objective of the model.

• SymMats

  Integer attribute.

  Number of symmetric matrices in the problem.

• MultiObjs

  Integer attribute.

  Number of objectives in a multi-objective model.

• ObjSense

  Integer attribute.

  The optimization direction.

• ObjConst

  Double attribute.

  The constant part of the objective function.

• HasQObj

  Integer attribute.

  Whether the problem has quadratic terms in its objective.

• HasPSDObj

  Integer attribute.

  Whether the problem has PSD terms in its objective.

• HasNLObj

  Integer attribute.

  Whether the problem has nonlinear terms in its objective.

• IsMIP

  Integer attribute.

  Whether the problem is a MIP.

• MinElem

  Double attribute.

  Minimum absolute value of the non-zero elements of the coefficient matrix in the linear constraints.

• MaxElem

  Double attribute.

  Maximum absolute value of the non-zero elements of the coefficient matrix in the linear constraints.

• MinBound

  Double attribute.

  Minimum absolute value of the non-zero variable bounds.

  Bounds equal to zero and infinite bounds are not taken into account. A bound is treated as infinite when its absolute value reaches the infinite-bound value used by COPT, which is 1e30 by default.

• MaxBound

  Double attribute.

  Maximum absolute value of the non-zero variable bounds.

  Please refer to MinBound for details.

• MinRHS

  Double attribute.

  Minimum absolute value of the non-zero bounds (right-hand sides) of the linear constraints.

  In COPT, a linear constraint is defined by a lower and an upper bound rather than by a single right-hand side, and both bounds are taken into account. A ranged constraint therefore contributes two values, while a constraint with a single sense contributes only its finite bound. Bounds equal to zero and infinite bounds are not taken into account.

• MaxRHS

  Double attribute.

  Maximum absolute value of the non-zero bounds (right-hand sides) of the linear constraints.

  Please refer to MinRHS for details.

• MinCost

  Double attribute.

  Minimum absolute value of the non-zero linear objective costs.

• MaxCost

  Double attribute.

  Maximum absolute value of the non-zero linear objective costs.

• MinQElem

  Double attribute.

  Minimum absolute value of the non-zero quadratic elements of the quadratic constraints.

  This attribute describes the quadratic constraints. For the quadratic objective function, whose elements are counted by QElems, see MinQCost and MaxQCost.

• MaxQElem

  Double attribute.

  Maximum absolute value of the non-zero quadratic elements of the quadratic constraints.

  Please refer to MinQElem for details.

• MinQLElem

  Double attribute.

  Minimum absolute value of the non-zero linear elements of the quadratic constraints.

• MaxQLElem

  Double attribute.

  Maximum absolute value of the non-zero linear elements of the quadratic constraints.

• MinQRHS

  Double attribute.

  Minimum absolute value of the non-zero right-hand sides of the quadratic constraints.

  Unlike a linear constraint, a quadratic constraint is defined by a single right-hand side together with a sense. Right-hand sides equal to zero and infinite right-hand sides are not taken into account.

• MaxQRHS

  Double attribute.

  Maximum absolute value of the non-zero right-hand sides of the quadratic constraints.

  Please refer to MinQRHS for details.

• MinQCost

  Double attribute.

  Minimum absolute value of the non-zero quadratic objective costs.

  Coefficients are reported as supplied to the model, without applying any additional factor.

• MaxQCost

  Double attribute.

  Maximum absolute value of the non-zero quadratic objective costs.

  Please refer to MinQCost for details.

Note

The attributes from MinElem to MaxQCost describe the problem as it was last loaded into the solver. Because model modifications are buffered, they return 0.0 before the model is first loaded, and their previous values after any later modification. Load the model before querying them, for example by solving or updating it.

A value of 0.0 is also returned when the model contains no elements of the corresponding kind: all quadratic attributes do so for a model with neither quadratic constraints nor a quadratic objective function. Use QConstrs and HasQObj to tell the two cases apart.

These attributes are retrieved from the original problem, and will therefore generally differ from the ranges of coefficients printed in the solver log, which are those of the problem actually passed to the solver, after presolving, scaling and reformulation.

Solution related

Solution related attributes provide the relevant information of the solution composition and description. The names and descriptions of these attributes are summarized below.

Table 15 Solution related attributes

Name	Type	Description
Status	Integer	Optimization status
LpStatus	Integer	(deprecated) The LP status
MipStatus	Integer	(deprecated) The MIP status
HasSol	Integer	Whether a solution is available
HasLpSol	Integer	(deprecated) Whether LP solution is available
HasMipSol	Integer	(deprecated) Whether MIP solution is available
HasBasis	Integer	Whether LP basis is available
HasSensitivity	Integer	Whether sensitivity analysis results are available for LP problem
HasDualFarkas	Integer	Whether the dual Farkas of an infeasible LP problem is available
HasPrimalRay	Integer	Whether the primal ray of an unbounded LP problem is available
HasFeasRelaxSol	Integer	Whether feasibility LP-relaxation solution is available
HasIIS	Integer	Whether IIS is available
IsMinIIS	Integer	Whether the computed IIS is minimal
IISCols	Integer	Number of bounds of columns in IIS
IISRows	Integer	Number of rows in IIS
IISSOSs	Integer	Number of SOS constraints in IIS
IISIndicators	Integer	Number of indicator constraints in IIS
SimplexIter	Integer	Number of simplex iterations performed
BarrierIter	Integer	Number of barrier iterations performed
PDLPIter	Integer	Number of first-order method (PDLP) iterations performed
NodeCnt	Integer	Number of explored nodes
PoolSols	Integer	Number of solutions in solution pool
TuneResults	Integer	Number of parameter tuning results
ObjVal	Double	Current best objective value
ObjBound	Double	Current best bound on the optimal objective value
LpObjVal	Double	(deprecated) Optimal objective value for continuous convex optimization problem
BestObj	Double	(deprecated) Current best objective value for MIP
BestBnd	Double	(deprecated) Current best bound for MIP
BestGap	Double	Current best relative gap for MIP
FeasRelaxObj	Double	Feasibility relaxation objective value
SolvingTime	Double	The time spent for the optimization (in seconds)
MemPeak	Double	Peak memory usage (MB) for the optimization

• Status

  Integer attribute.

  Optimization status.

  Please refer to General Constants: Solution status for possible values.

• LpStatus

  Integer attribute.

  The LP status.

  Deprecated. Use Status instead.

• MipStatus

  Integer attribute.

  The MIP status.

  Deprecated. Use Status instead.

• HasSol

  Integer attribute.

  Whether a solution is available.

• HasLpSol

  Integer attribute.

  Whether LP solution is available.

  Deprecated. Use HasSol instead.

• HasMipSol

  Integer attribute.

  Whether MIP solution is available.

  Deprecated. Use HasSol instead.

• HasBasis

  Integer attribute.

  Whether LP basis is available.

• HasSensitivity

  Integer attribute.

  Whether sensitivity analysis results are available for LP problem.

• HasDualFarkas

  Integer attribute.

  Whether the dual Farkas of an infeasible LP problem is available.

• HasPrimalRay

  Integer attribute.

  Whether the primal ray of an unbounded LP problem is available.

• HasFeasRelaxSol

  Integer attribute.

  Whether feasibility LP-relaxation solution is available.

• HasIIS

  Integer attribute.

  Whether IIS is available.

• IsMinIIS

  Integer attribute.

  Whether the computed IIS is minimal.

• IISCols

  Integer attribute.

  Number of bounds of columns in IIS.

• IISRows

  Integer attribute.

  Number of rows in IIS.

• IISSOSs

  Integer attribute.

  Number of SOS constraints in IIS.

• IISIndicators

  Integer attribute.

  Number of indicator constraints in IIS.

• SimplexIter

  Integer attribute.

  Number of simplex iterations performed.

• BarrierIter

  Integer attribute.

  Number of barrier iterations performed.

• PDLPIter

  Integer attribute.

  Number of first-order method (PDLP) iterations performed.

• NodeCnt

  Integer attribute.

  Number of explored nodes.

• PoolSols

  Integer attribute.

  Number of solutions in solution pool.

• TuneResults

  Integer attribute.

  Number of parameter tuning results.

• ObjVal

  Double attribute.

  Current best objective value. When Status is OPTIMAL, this is the optimal objective value.

• ObjBound

  Double attribute.

  Current best bound on the optimal objective value.

• LpObjVal

  Double attribute.

  Optimal objective value for continuous convex optimization problem.

  Deprecated. Use ObjVal instead.

• BestObj

  Double attribute.

  Current best objective value for MIP.

  Deprecated. Use ObjVal instead.

• BestBnd

  Double attribute.

  Current best bound for MIP.

  Deprecated. Use ObjBound instead.

• BestGap

  Double attribute.

  Current best relative gap for MIP.

• FeasRelaxObj

  Double attribute.

  Feasibility relaxation objective value.

• SolvingTime

  Double attribute.

  The time spent for the optimization (in seconds).

• MemPeak

  Double attribute.

  Peak memory usage (MB) for the optimization.

Note

It is recommended to use Status, HasSol, ObjVal and ObjBound instead of the attributes marked (deprecated) above, as they provide a unified interface for querying the solution status, whether a solution is available, and optimal objective value across all supported problem types, including linear programming, integer programming, and convex/non-convex optimization problems.

Methods for accessing attributes

In different programming interfaces, the ways to access attributes are slightly different. For details, please refer to the corresponding chapters for each programming language API:

• C API: C API Functions: Accessing attributes

• C++ API: C++ API Reference: Attributes

• C# API: C# API Reference: Attributes

• Java API: Java API Reference: Attributes

• Python API: Python API Reference: Attributes