GRBConstr#

GRBConstr#

Gurobi constraint object. Constraints are always associated with a particular model. You create a constraint object by adding a constraint to a model (using GRBModel.AddConstr), rather than by using a GRBConstr constructor.

Example:
// Create variables
GRBVar x = model.AddVar(0.0, GRB.INFINITY, 0.0, GRB.CONTINUOUS, "x");
GRBVar y = model.AddVar(0.0, GRB.INFINITY, 0.0, GRB.CONTINUOUS, "y");
// Add linear constraint x + y = 0 with name c1
GRBConstr constr = model.AddConstr(x + y == 0, "c1");

The methods on constraint objects are used to get and set constraint attributes. For example, constraint right-hand sides can be queried by calling Get (GRB.DoubleAttr.RHS). It can also be queried more directly using constr.RHS where constr is a GRBConstr object. Note, however, that it is generally more efficient to query attributes for a set of constraints at once. This is done using the attribute query method on the GRBModel object (GRBModel.Get).

The full list of attributes can be found in the Attributes section of this document. Examples of how to query and set attributes can also be found in this section.

char Get(GRB.CharAttr attr)#

Query the value of a char-valued attribute.

Parameters:

attr – The attribute being queried.

Returns:

The current value of the requested attribute.

Example:
// Get constraint sense
char sense = constr.Get(GRB.CharAttr.Sense);
double Get(GRB.DoubleAttr attr)#

Query the value of a double-valued attribute.

Parameters:

attr – The attribute being queried.

Returns:

The current value of the requested attribute.

Example:
// Get RHS
double rhs = constr.Get(GRB.DoubleAttr.RHS);
int Get(GRB.IntAttr attr)#

Query the value of an int-valued attribute.

Parameters:

attr – The attribute being queried.

Returns:

The current value of the requested attribute.

Example:
// Get CBasis value
int cbasis = constr.Get(GRB.IntAttr.CBasis);
string Get(GRB.StringAttr attr)#

Query the value of a string-valued attribute.

Parameters:

attr – The attribute being queried.

Returns:

The current value of the requested attribute.

Example:
// Get constraint name
string name = constr.Get(GRB.StringAttr.ConstrName);
int Index#

This property returns the current index, or order, of the constraint in the underlying constraint matrix.

Note that the index of a constraint may change after subsequent model modifications.

Returns:

-2: removed, -1: not in model, otherwise: index of the constraint in the model

Example:
int index = constr.Index;
bool SameAs(GRBConstr constr2)#

Check whether two constraint objects refer to the same constraint.

Parameters:

constr2 – The other constraint.

Returns:

Boolean result indicates whether the two constraint objects refer to the same model constraint.

Example:
// Compare to a second constraint
bool isSame = constr.SameAs(constr2);
void Set(GRB.CharAttr attr, char newvalue)#

Set the value of a char-valued attribute.

Parameters:

  • attr – The attribute being modified.

  • newvalue – The desired new value of the attribute.

Example:
// Set constraint sense
constr.Set(GRB.CharAttr.Sense, '>');
void Set(GRB.DoubleAttr attr, double newvalue)#

Set the value of a double-valued attribute.

Parameters:

  • attr – The attribute being modified.

  • newvalue – The desired new value of the attribute.

Example:
// Set RHS
constr.Set(GRB.DoubleAttr.RHS, 2.0);
void Set(GRB.IntAttr attr, int newvalue)#

Set the value of an int-valued attribute.

Parameters:

  • attr – The attribute being modified.

  • newvalue – The desired new value of the attribute.

Example:
// Set CBasis value
constr.Set(GRB.IntAttr.CBasis, 0);
void Set(GRB.StringAttr attr, string newvalue)#

Set the value of a string-valued attribute.

Parameters:

  • attr – The attribute being modified.

  • newvalue – The desired new value of the attribute.

Example:
// Set constraint name
constr.Set(GRB.StringAttr.ConstrName, "newName");