Sage Reference Manual: Numerical Optimization - Mirrors

Sage Reference Manual: Numerical Optimization, Release 6.1.1
base_ring()
Return the base ring.
OUTPUT:
A ring. The coefficients that the chosen solver supports.
EXAMPLES:
sage: p = MixedIntegerLinearProgram(solver=’GLPK’)
sage: p.base_ring()
Real Double Field
sage: p = MixedIntegerLinearProgram(solver=’ppl’)
sage: p.base_ring()
Rational Field
constraints(indices=None)
Returns a list of constraints, as 3-tuples.
INPUT:
•indices – select which constraint(s) to return
OUTPUT:
–If indices = None, the method returns the list of all the constraints.
–If indices is an integer i, the method returns constraint i.
–If indices is a list of integers, the method returns the list of the corresponding constraints.
Each constraint is returned as a triple lower_bound, (indices, coefficients),
upper_bound. For each of those entries, the corresponding linear function is the one associating
to variable indices[i] the coefficient coefficients[i], and 0 to all the others.
lower_bound and upper_bound are numerical values.
EXAMPLE:
First, let us define a small LP:
sage: p = MixedIntegerLinearProgram()
sage: p.add_constraint(p[0] - p[2], min = 1, max = 4)
sage: p.add_constraint(p[0] - 2*p[1], min = 1)
To obtain the list of all constraints:
sage: p.constraints()
# not tested
[(1.0, ([1, 0], [-1.0, 1.0]), 4.0), (1.0, ([2, 0], [-2.0, 1.0]), None)]
Or constraint 0 only:
sage: p.constraints(0)
# not tested
(1.0, ([1, 0], [-1.0, 1.0]), 4.0)
A list of constraints containing only 1:
sage: p.constraints([1]) # not tested
[(1.0, ([2, 0], [-2.0, 1.0]), None)]
TESTS:
As the ordering of the variables in each constraint depends on the solver used, we define a short function
reordering it before it is printed. The output would look the same without this function applied:
16 Chapter 2. Mixed integer linear programming