Initializing help system before first use

xpress.constraint

Purpose

Class for linear, quadratic, and nonlinear constraints.


Synopsis
c = xpress.constraint (constraint=None, body=None, lb=-xpress.infinity, ub=xpress.infinity, sense=None, rhs=None, name='')
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 sense. It should not be used when constraint is defined. Example: 3 * x1 + x2
lb 
Lower bound on body.
ub 
Upper bound on body.
sense 
Sign of the constraint: one of xpress.leq, xpress.eq, xpress.geq, or xpress.rng.
rhs 
Right-hand side of the constraint if sense is defined. It may not be specified if lb or ub are.
name 
Name of the constraint (string).
Example
Constraint declared without the explicit constructor: 
myconstr = x1 + x2 * (x2 + 1) <= 4
One or more constraints (or arrays 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))
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])
Further information
1. Parameters lb, ub, and rhs must be constant.
2. A constraint can be specified more naturally as a condition on a linear or quadratic expression:
3. When handling variables or expressions, it is advised to use the Sum operator in the Xpress module rather than the native Python operator, for reasons of efficiency.
Related topics
problem.addConstraint.

Parent Topic Xpress base classes

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