Sage Reference Manual: Numerical Optimization - Mirrors

Sage Reference Manual: Numerical Optimization, Release 6.1.1
sage: gbe.add_vertices(verts)
sage: gbe.delete_vertex("A")
sage: gbe.vertices()
[’D’]
sage: gbe.delete_vertex("A")
Traceback (most recent call last):
...
RuntimeError: Vertex A does not exist.
delete_vertices(verts)
Removes vertices from the graph.
Trying to delete a non existing vertex will raise an exception.
INPUT:
•verts – iterable container containing names (as str) of the vertices to delete
EXAMPLE:
sage: from sage.numerical.backends.glpk_graph_backend import GLPKGraphBackend
sage: gbe = GLPKGraphBackend()
sage: verts = ["A", "B", "C", "D"]
sage: gbe.add_vertices(verts)
sage: v_d = ["A", "B"]
sage: gbe.delete_vertices(v_d)
sage: gbe.vertices()
[’C’, ’D’]
sage: gbe.delete_vertices(["C", "A"])
Traceback (most recent call last):
...
RuntimeError: Vertex A does not exist.
sage: gbe.vertices()
[’C’, ’D’]
edges()
Returns a list of all edges in the graph
OUTPUT:
A list of triples representing the edges of the graph.
EXAMPLE:
sage: from sage.numerical.backends.glpk_graph_backend import GLPKGraphBackend
sage: gbe = GLPKGraphBackend()
sage: edges = [("A", "B", {"low":0.0, "cap":10.0, "cost":5})]
sage: edges.append(("B", "C"))
sage: gbe.add_edges(edges)
sage: for ed in gbe.edges():
... print ed[0], ed[1], ed[2][’cost’]
A B 5.0
B C 0.0
get_edge(u, v)
Returns an edge connecting two vertices.
Note: If multiple edges connect the two vertices only the first edge found is returned.
INPUT:
86 Chapter 5. LP Solver backends