Sage Reference Manual: Numerical Optimization - Mirrors

Sage Reference Manual: Numerical Optimization, Release 6.1.1
sage: vertices = [None for i in range(3)]
sage: gbe.add_vertices(vertices)
[’0’, ’1’, ’2’]
sage: gbe.set_vertex_demand(’0’, 2)
sage: gbe.get_vertex(’0’)[’rhs’]
2.0
sage: gbe.set_vertex_demand(’3’, 2)
Traceback (most recent call last):
...
KeyError: ’Vertex 3 does not exist.’
set_vertices_demand(pairs)
Sets the parameters of selected vertices.
INPUT:
•pairs – A list of pairs (vertex, demand) associating a demand to each vertex. For more
information, see the documentation of set_vertex_demand().
EXAMPLE:
sage: from sage.numerical.backends.glpk_graph_backend import GLPKGraphBackend
sage: gbe = GLPKGraphBackend()
sage: vertices = [None for i in range(3)]
sage: gbe.add_vertices(vertices)
[’0’, ’1’, ’2’]
sage: gbe.set_vertices_demand([(’0’, 2), (’1’, 3), (’3’, 4)])
sage: sorted(gbe.get_vertex(’1’).items())
[(’cut’, 0), (’es’, 0.0), (’ls’, 0.0), (’pi’, 0.0), (’rhs’, 3.0)]
vertices()
Returns the list of all vertices
Note: Changing elements of the list will not change anything in the the graph.
Note: If a vertex in the graph does not have a name / label it will appear as None in the resulting list.
EXAMPLE:
sage: from sage.numerical.backends.glpk_graph_backend import GLPKGraphBackend
sage: gbe = GLPKGraphBackend()
sage: verts = ["A", "B", "C"]
sage: gbe.add_vertices(verts)
sage: a = gbe.vertices(); a
[’A’, ’B’, ’C’]
sage: a.pop(0)
’A’
sage: gbe.vertices()
[’A’, ’B’, ’C’]
write_ccdata(fname)
Writes the graph to a text file in DIMACS format.
Writes the data to plain ASCII text file in DIMACS format. A discription of the DIMACS format can be
found at http://dimacs.rutgers.edu/Challenges/.
INPUT:
90 Chapter 5. LP Solver backends