Initializing help system before first use

xpress.constraint

Description
Class representing linear, quadratic, and nonlinear constraints.
Attributes
name 
Name of the constraint.
type 
Type of the constraint, one of:
xpress.leq 
a ≤ constraint;
xpress.eq 
an equality constraint;
xpress.geq 
a ≥ constraint;
xpress.rng 
a range constraint;
xpress.nonbinding 
a free constraint.
rhs 
Right-hand side of the constraint.
rhsrange 
Right-hand side range value for the constraint.
index 
Index of the constraint in the Optimization problem. None for constraints that have not yet been added to a problem (and for unlinked constraints).
lb 
Lower bound on the constraint expression (read-only).
ub 
Upper bound on the constraint expression (read-only).
Constructors
c = xpress.constraint(constraint=None, body=None, lb=-xpress.infinity, ub=xpress.infinity, type=None, rhs=None, name='', rhsrange=None)

Constructor detail
xpress.constraint
Synopsis
c = xpress.constraint(constraint=None, body=None, lb=-xpress.infinity, ub=xpress.infinity, type=None, rhs=None, name='', rhsrange=None)
Arguments
constraint 
The constraint, written as a ==, <=, or >= condition between two expressions. Variables can appear on either or both sides of the sign. Example: x1 + 2 * x2 <= 4
body 
An expression indicating the function to be constrained between lb and ub or by rhs with an assigned type. It should not be used when constraint is defined. Example: 3 * x1 + x2
lb 
Lower bound on body.
ub 
Upper bound on body.
type 
Type of the constraint, one of:
xpress.leq 
for ≤ constraints;
xpress.eq 
for equality constraints;
xpress.geq 
for ≥ constraints;
xpress.rng 
for range constraints.
rhs 
Right-hand side of the constraint if type is defined. It may not be specified if lb or ub are.
name 
Name of the constraint.
rhsrange 
Right-hand side range of the constraint. rhs argument must also be specified. It may not be specified if lb or ub are.
Example
Constraint declared without the explicit constructor: 
myconstr = x1 + x2 * (x2 + 1) <= 4
One or more constraints (or lists of constraints) can be added to a problem via the addConstraint method: 
m.addConstraint(myconstr)
m.addConstraint(v1 + v2 <= 3)
m.addConstraint(x[i] + y[i] <= 2 for i in range(10))
The constraint constructor argument is provided so that constraints defined with an inequality can be assigned a name: 
myconstr = xp.constraint(x1 + x2 * (x2 + 1) <= 4, name='myconstr')
In order to help formulate compact problems, the Sum operator of the xpress module can be used to express sums of expressions. Its argument is a list of expressions (linear or quadratic): 
m.addConstraint(xp.Sum([y[i]    for i in range(10)]) <= 1)
m.addConstraint(xp.Sum([x[i]**2 for i in range(9)])  <= x[9])
See also
problem.addConstraint.

Parent Topic Xpress base classes

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