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xpress.sos

Description
Class representing special ordered set (SOS) constraints. A SOS constraint is a modeling tool for constraining a small number of consecutive variables in a vector to be nonzero.
Constructors
s = xpress.sos(indices, weights, type=1, name='') (deprecated)
Related topics
problem.addSOS.

Constructor detail
xpress.sos
Synopsis
s = xpress.sos(indices, weights, type=1, name='') (deprecated)
Use problem.addSOS to add linked SOS constraints to the problem instead.
Arguments
indices 
List of variables composing the SOS.
weights 
List of weights (one per variable). These define the order for SOS2 constraints and may be used in branching for both types.
type 
Type of SOS. Can be 1 (default) or 2.
name 
Name of the SOS.
Description
1. Weights must be sufficiently distinct (see the SOSREFTOL control in the Optimizer manual).
2. Unlinked SOS constraints are not tied to a problem but may exist globally in a Python program. In order for them to be included into a problem, they have to be explicitly added to that problem using problem.addSOS. Unlinked SOS constraints are deprecated.
Example
The following are example declarations of SOS: 
x = [xp.var() for _ in range(10)]
set1 = xp.sos(x, [0.5 + i*0.1 for i in range(10)], type=2)
v1, v2 = xp.vars(2)
set2 = xp.sos([v1, v2], [2, 5], 2, "mysos")
One or more SOS can be added to a problem via the addSOS method: 
n = 10
w = [xp.var() for i in range(n)]
p = xp.problem(w)
p.addSOS([
  xp.sos([w[i], w[i+1]], [2,3])
  for i in range(n-1)
])

Parent Topic Xpress base classes

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