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Ticket #13862: trac_13862-moves_3_constructors.patch

File trac_13862-moves_3_constructors.patch, 42.5 KB (added by ncohen, 7 years ago)

sage/graphs/generators/basic.py

# HG changeset patch
# User Nathann Cohen <nathann.cohen@gmail.com>
# Date 1356523694 -3600
# Node ID f728da1da8710218bc6ad6de05318d28ddac4e97
# Parent  3c8e3c18d3f23f9b05159f3aa10a01262468feb7
Split graph_generators into several files -- Moves 3 methods from families to basic

diff --git a/sage/graphs/generators/basic.py b/sage/graphs/generators/basic.py

-                      a
         sage: g.is_planar()
         True
     The Bucky Ball can also be created by extracting the 1-skeleton
+    The Bucky Ball can also be created by extracting the 1-skeleton
     of the Bucky Ball polyhedron, but this is much slower. ::
         sage: g = polytopes.buckyball().vertex_graph()
 …
         sage: g = graphs.BuckyBall()
         sage: g.plot(vertex_labels=False, vertex_size=10).show() # long time
     """
     edges = [(0, 2), (0, 48), (0, 59), (1, 3), (1, 9), (1, 58),
              (2, 3), (2, 36), (3, 17), (4, 6), (4, 8), (4, 12),
              (5, 7), (5, 9), (5, 16), (6, 7), (6, 20), (7, 21),
              (8, 9), (8, 56), (10, 11), (10, 12), (10, 20), (11, 27),
              (11, 47), (12, 13), (13, 46), (13, 54), (14, 15), (14, 16),
              (14, 21), (15, 25), (15, 41), (16, 17), (17, 40), (18, 19),
              (18, 20), (18, 26), (19, 21), (19, 24), (22, 23), (22, 31),
              (22, 34), (23, 25), (23, 38), (24, 25), (24, 30), (26, 27),
              (26, 30), (27, 29), (28, 29), (28, 31), (28, 35), (29, 44),
              (30, 31), (32, 34), (32, 39), (32, 50), (33, 35), (33, 45),
              (33, 51), (34, 35), (36, 37), (36, 40), (37, 39), (37, 52),
              (38, 39), (38, 41), (40, 41), (42, 43), (42, 46), (42, 55),
              (43, 45), (43, 53), (44, 45), (44, 47), (46, 47), (48, 49),
              (48, 52), (49, 53), (49, 57), (50, 51), (50, 52), (51, 53),
+    edges = [(0, 2), (0, 48), (0, 59), (1, 3), (1, 9), (1, 58),
+             (2, 3), (2, 36), (3, 17), (4, 6), (4, 8), (4, 12),
+             (5, 7), (5, 9), (5, 16), (6, 7), (6, 20), (7, 21),
+             (8, 9), (8, 56), (10, 11), (10, 12), (10, 20), (11, 27),
+             (11, 47), (12, 13), (13, 46), (13, 54), (14, 15), (14, 16),
+             (14, 21), (15, 25), (15, 41), (16, 17), (17, 40), (18, 19),
+             (18, 20), (18, 26), (19, 21), (19, 24), (22, 23), (22, 31),
+             (22, 34), (23, 25), (23, 38), (24, 25), (24, 30), (26, 27),
+             (26, 30), (27, 29), (28, 29), (28, 31), (28, 35), (29, 44),
+             (30, 31), (32, 34), (32, 39), (32, 50), (33, 35), (33, 45),
+             (33, 51), (34, 35), (36, 37), (36, 40), (37, 39), (37, 52),
+             (38, 39), (38, 41), (40, 41), (42, 43), (42, 46), (42, 55),
+             (43, 45), (43, 53), (44, 45), (44, 47), (46, 47), (48, 49),
+             (48, 52), (49, 53), (49, 57), (50, 51), (50, 52), (51, 53),
              (54, 55), (54, 56), (55, 57), (56, 58), (57, 59), (58, 59)
+             ]
     g = graph.Graph()
 …
     drawn at the top of the inner-circle, moving clockwise after that.
     The outer circle is drawn with the (n+1)th node at the top, then
     counterclockwise as well.
     EXAMPLES: Construct and show a circular ladder graph with 26 nodes
     ::
         sage: g = graphs.CircularLadderGraph(13)
         sage: g.show() # long time
     Create several circular ladder graphs in a Sage graphics array
     ::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
 …
     import networkx
     G = networkx.circular_ladder_graph(n)
     return graph.Graph(G, pos=pos_dict, name="Circular Ladder graph")
 def ClawGraph():
     """
     Returns a claw graph.
     A claw graph is named for its shape. It is actually a complete
     bipartite graph with (n1, n2) = (1, 3).
     PLOTTING: See CompleteBipartiteGraph.
     EXAMPLES: Show a Claw graph
     ::
         sage: (graphs.ClawGraph()).show() # long time
     Inspect a Claw graph
     ::
         sage: G = graphs.ClawGraph()
         sage: G
         Claw graph: Graph on 4 vertices
 …
 def CycleGraph(n):
     r"""
     Returns a cycle graph with n nodes.
     A cycle graph is a basic structure which is also typically called
     an n-gon.
     This constructor is dependent on vertices numbered 0 through n-1 in
     NetworkX ``cycle_graph()``
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, each cycle
     graph will be displayed with the first (0) node at the top, with
     the rest following in a counterclockwise manner.
     The cycle graph is a good opportunity to compare efficiency of
     filling a position dictionary vs. using the spring-layout algorithm
     for plotting. Because the cycle graph is very symmetric, the
     resulting plots should be similar (in cases of small n).
     Filling the position dictionary in advance adds O(n) to the
     constructor.
     EXAMPLES: Compare plotting using the predefined layout and
     networkx::
         sage: import networkx
+        sage: import networkx
         sage: n = networkx.cycle_graph(23)
         sage: spring23 = Graph(n)
         sage: posdict23 = graphs.CycleGraph(23)
         sage: spring23.show() # long time
         sage: posdict23.show() # long time
     We next view many cycle graphs as a Sage graphics array. First we
     use the ``CycleGraph`` constructor, which fills in the
     position dictionary::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
 …
         ...
         sage: G = sage.plot.graphics.GraphicsArray(j)
         sage: G.show() # long time
     Compare to plotting with the spring-layout algorithm::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
         ...    spr = networkx.cycle_graph(i+3)
+        ...    spr = networkx.cycle_graph(i+3)
         ...    k = Graph(spr)
         ...    g.append(k)
         ...
 …
         x = float(cos((pi/2) + ((2*pi)/n)*i))
         y = float(sin((pi/2) + ((2*pi)/n)*i))
         pos_dict[i] = (x,y)
     import networkx
+    import networkx
     G = networkx.cycle_graph(n)
     return graph.Graph(G, pos=pos_dict, name="Cycle graph")
+def CompleteGraph(n):
+    """
+    Returns a complete graph on n nodes.
+    A Complete Graph is a graph in which all nodes are connected to all
+    other nodes.
+    This constructor is dependent on vertices numbered 0 through n-1 in
+    NetworkX complete_graph()
+    PLOTTING: Upon construction, the position dictionary is filled to
+    override the spring-layout algorithm. By convention, each complete
+    graph will be displayed with the first (0) node at the top, with
+    the rest following in a counterclockwise manner.
+    In the complete graph, there is a big difference visually in using
+    the spring-layout algorithm vs. the position dictionary used in
+    this constructor. The position dictionary flattens the graph,
+    making it clear which nodes an edge is connected to. But the
+    complete graph offers a good example of how the spring-layout
+    works. The edges push outward (everything is connected), causing
+    the graph to appear as a 3-dimensional pointy ball. (See examples
+    below).
+    EXAMPLES: We view many Complete graphs with a Sage Graphics Array,
+    first with this constructor (i.e., the position dictionary
+    filled)::
+        sage: g = []
+        sage: j = []
+        sage: for i in range(9):
+        ...    k = graphs.CompleteGraph(i+3)
+        ...    g.append(k)
+        ...
+        sage: for i in range(3):
+        ...    n = []
+        ...    for m in range(3):
+        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
+        ...    j.append(n)
+        ...
+        sage: G = sage.plot.graphics.GraphicsArray(j)
+        sage: G.show() # long time
+    We compare to plotting with the spring-layout algorithm::
+        sage: import networkx
+        sage: g = []
+        sage: j = []
+        sage: for i in range(9):
+        ...    spr = networkx.complete_graph(i+3)
+        ...    k = Graph(spr)
+        ...    g.append(k)
+        ...
+        sage: for i in range(3):
+        ...    n = []
+        ...    for m in range(3):
+        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
+        ...    j.append(n)
+        ...
+        sage: G = sage.plot.graphics.GraphicsArray(j)
+        sage: G.show() # long time
+    Compare the constructors (results will vary)
+    ::
+        sage: import networkx
+        sage: t = cputime()
+        sage: n = networkx.complete_graph(389); spring389 = Graph(n)
+        sage: cputime(t)           # random
+.59203700000000126
+        sage: t = cputime()
+        sage: posdict389 = graphs.CompleteGraph(389)
+        sage: cputime(t)           # random
+.6680419999999998
+    We compare plotting::
+        sage: import networkx
+        sage: n = networkx.complete_graph(23)
+        sage: spring23 = Graph(n)
+        sage: posdict23 = graphs.CompleteGraph(23)
+        sage: spring23.show() # long time
+        sage: posdict23.show() # long time
+    """
+    pos_dict = {}
+    for i in range(n):
+        x = float(cos((pi/2) + ((2*pi)/n)*i))
+        y = float(sin((pi/2) + ((2*pi)/n)*i))
+        pos_dict[i] = (x,y)
+    import networkx
+    G = networkx.complete_graph(n)
+    return graph.Graph(G, pos=pos_dict, name="Complete graph")
+def CompleteBipartiteGraph(n1, n2):
+    """
+    Returns a Complete Bipartite Graph sized n1+n2, with each of the
+    nodes [0,(n1-1)] connected to each of the nodes [n1,(n2-1)] and
+    vice versa.
+    A Complete Bipartite Graph is a graph with its vertices partitioned
+    into two groups, V1 and V2. Each v in V1 is connected to every v in
+    V2, and vice versa.
+    PLOTTING: Upon construction, the position dictionary is filled to
+    override the spring-layout algorithm. By convention, each complete
+    bipartite graph will be displayed with the first n1 nodes on the
+    top row (at y=1) from left to right. The remaining n2 nodes appear
+    at y=0, also from left to right. The shorter row (partition with
+    fewer nodes) is stretched to the same length as the longer row,
+    unless the shorter row has 1 node; in which case it is centered.
+    The x values in the plot are in domain [0,maxn1,n2].
+    In the Complete Bipartite graph, there is a visual difference in
+    using the spring-layout algorithm vs. the position dictionary used
+    in this constructor. The position dictionary flattens the graph and
+    separates the partitioned nodes, making it clear which nodes an
+    edge is connected to. The Complete Bipartite graph plotted with the
+    spring-layout algorithm tends to center the nodes in n1 (see
+    spring_med in examples below), thus overlapping its nodes and
+    edges, making it typically hard to decipher.
+    Filling the position dictionary in advance adds O(n) to the
+    constructor. Feel free to race the constructors below in the
+    examples section. The much larger difference is the time added by
+    the spring-layout algorithm when plotting. (Also shown in the
+    example below). The spring model is typically described as
+    `O(n^3)`, as appears to be the case in the NetworkX source
+    code.
+    EXAMPLES: Two ways of constructing the complete bipartite graph,
+    using different layout algorithms::
+        sage: import networkx
+        sage: n = networkx.complete_bipartite_graph(389,157); spring_big = Graph(n)   # long time
+        sage: posdict_big = graphs.CompleteBipartiteGraph(389,157)                    # long time
+    Compare the plotting::
+        sage: n = networkx.complete_bipartite_graph(11,17)
+        sage: spring_med = Graph(n)
+        sage: posdict_med = graphs.CompleteBipartiteGraph(11,17)
+    Notice here how the spring-layout tends to center the nodes of n1
+    ::
+        sage: spring_med.show() # long time
+        sage: posdict_med.show() # long time
+    View many complete bipartite graphs with a Sage Graphics Array,
+    with this constructor (i.e., the position dictionary filled)::
+        sage: g = []
+        sage: j = []
+        sage: for i in range(9):
+        ...    k = graphs.CompleteBipartiteGraph(i+1,4)
+        ...    g.append(k)
+        ...
+        sage: for i in range(3):
+        ...    n = []
+        ...    for m in range(3):
+        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
+        ...    j.append(n)
+        ...
+        sage: G = sage.plot.graphics.GraphicsArray(j)
+        sage: G.show() # long time
+    We compare to plotting with the spring-layout algorithm::
+        sage: g = []
+        sage: j = []
+        sage: for i in range(9):
+        ...    spr = networkx.complete_bipartite_graph(i+1,4)
+        ...    k = Graph(spr)
+        ...    g.append(k)
+        ...
+        sage: for i in range(3):
+        ...    n = []
+        ...    for m in range(3):
+        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
+        ...    j.append(n)
+        ...
+        sage: G = sage.plot.graphics.GraphicsArray(j)
+        sage: G.show() # long time
+    Trac ticket #12155::
+        sage: graphs.CompleteBipartiteGraph(5,6).complement()
+        complement(Complete bipartite graph): Graph on 11 vertices
+    """
+    pos_dict = {}
+    c1 = 1 # scaling factor for top row
+    c2 = 1 # scaling factor for bottom row
+    c3 = 0 # pad to center if top row has 1 node
+    c4 = 0 # pad to center if bottom row has 1 node
+    if n1 > n2:
+        if n2 == 1:
+            c4 = (n1-1)/2
+        else:
+            c2 = ((n1-1)/(n2-1))
+    elif n2 > n1:
+        if n1 == 1:
+            c3 = (n2-1)/2
+        else:
+            c1 = ((n2-1)/(n1-1))
+    for i in range(n1):
+        x = c1*i + c3
+        y = 1
+        pos_dict[i] = (x,y)
+    for i in range(n1+n2)[n1:]:
+        x = c2*(i-n1) + c4
+        y = 0
+        pos_dict[i] = (x,y)
+    import networkx
+    from sage.graphs.graph import Graph
+    G = networkx.complete_bipartite_graph(n1,n2)
+    return Graph(G, pos=pos_dict, name="Complete bipartite graph")
+def CompleteMultipartiteGraph(l):
+    r"""
+    Returns a complete multipartite graph.
+    INPUT:
+    - ``l`` -- a list of integers : the respective sizes
+      of the components.
+    EXAMPLE:
+    A complete tripartite graph with sets of sizes
+    `5, 6, 8`::
+        sage: g = graphs.CompleteMultipartiteGraph([5, 6, 8]); g
+        Multipartite Graph with set sizes [5, 6, 8]: Graph on 19 vertices
+    It clearly has a chromatic number of 3::
+        sage: g.chromatic_number()
+    """
+    from sage.graphs.graph import Graph
+    g = Graph()
+    for i in l:
+        g = g + CompleteGraph(i)
+    g = g.complement()
+    g.name("Multipartite Graph with set sizes "+str(l))
+    return g
 def DiamondGraph():
     """
     Returns a diamond graph with 4 nodes.
     A diamond graph is a square with one pair of diagonal nodes
     connected.
     This constructor depends on NetworkX numeric labeling.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, the diamond
     graph is drawn as a diamond, with the first node on top, second on
     the left, third on the right, and fourth on the bottom; with the
     second and third node connected.
     EXAMPLES: Construct and show a diamond graph
     ::
         sage: g = graphs.DiamondGraph()
         sage: g.show() # long time
     """
 …
     import networkx
     G = networkx.diamond_graph()
     return graph.Graph(G, pos=pos_dict, name="Diamond Graph")
 def EmptyGraph():
     """
     Returns an empty graph (0 nodes and 0 edges).
     This is useful for constructing graphs by adding edges and vertices
     individually or in a loop.
     PLOTTING: When plotting, this graph will use the default
     spring-layout algorithm, unless a position dictionary is
     specified.
     EXAMPLES: Add one vertex to an empty graph and then show::
         sage: empty1 = graphs.EmptyGraph()
         sage: empty1.add_vertex()
         sage: empty1.show() # long time
     Use for loops to build a graph from an empty graph::
         sage: empty2 = graphs.EmptyGraph()
         sage: for i in range(5):
         ...    empty2.add_vertex() # add 5 nodes, labeled 0-4
 …
 def GridGraph(dim_list):
     """
     Returns an n-dimensional grid graph.
     INPUT:
     -  ``dim_list`` - a list of integers representing the
        number of nodes to extend in each dimension.
     PLOTTING: When plotting, this graph will use the default
     spring-layout algorithm, unless a position dictionary is
     specified.
     EXAMPLES::
         sage: G = graphs.GridGraph([2,3,4])
         sage: G.show()  # long time
     ::
         sage: C = graphs.CubeGraph(4)
         sage: G = graphs.GridGraph([2,2,2,2])
         sage: C.show()  # long time
 …
 def HouseGraph():
     """
     Returns a house graph with 5 nodes.
     A house graph is named for its shape. It is a triangle (roof) over a
     square (walls).
     This constructor depends on NetworkX numeric labeling.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, the house
     graph is drawn with the first node in the lower-left corner of the
 …
     and the fourth is in the upper-right corner connecting the roof to
     the wall. The fifth node is the top of the roof, connected only to
     the third and fourth.
     EXAMPLES: Construct and show a house graph
     ::
         sage: g = graphs.HouseGraph()
         sage: g.show() # long time
     """
 …
     import networkx
     G = networkx.house_graph()
     return graph.Graph(G, pos=pos_dict, name="House Graph")
 def HouseXGraph():
     """
     Returns a house X graph with 5 nodes.
     A house X graph is a house graph with two additional edges. The
     upper-right corner is connected to the lower-left. And the
     upper-left corner is connected to the lower-right.
     This constructor depends on NetworkX numeric labeling.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, the house X
     graph is drawn with the first node in the lower-left corner of the
 …
     and the fourth is in the upper-right corner connecting the roof to
     the wall. The fifth node is the top of the roof, connected only to
     the third and fourth.
     EXAMPLES: Construct and show a house X graph
     ::
         sage: g = graphs.HouseXGraph()
         sage: g.show() # long time
     """
 …
 def KrackhardtKiteGraph():
     """
     Returns a Krackhardt kite graph with 10 nodes.
     The Krackhardt kite graph was originally developed by David
     Krackhardt for the purpose of studying social networks. It is used
     to show the distinction between: degree centrality, betweeness
     centrality, and closeness centrality. For more information read the
     plotting section below in conjunction with the example.
     REFERENCES:
     - [1] Kreps, V. (2002). "Social Network Analysis".  [Online] Available:
       http://www.fsu.edu/~spap/water/network/intro.htm [2007,
       January 17]
     This constructor depends on NetworkX numeric labeling.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, the graph is
     drawn left to right, in top to bottom row sequence of [2, 3, 2, 1,
 …
     third row and have degree = 5. These nodes have the shortest path
     to all other nodes in the graph (i.e.: Closeness Centrality).
     Please execute the example for visualization.
     EXAMPLE: Construct and show a Krackhardt kite graph
     ::
         sage: g = graphs.KrackhardtKiteGraph()
         sage: g.show() # long time
     """
 …
 def LadderGraph(n):
     """
     Returns a ladder graph with 2\*n nodes.
     A ladder graph is a basic structure that is typically displayed as
     a ladder, i.e.: two parallel path graphs connected at each
     corresponding node pair.
     This constructor depends on NetworkX numeric labels.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, each ladder
     graph will be displayed horizontally, with the first n nodes
     displayed left to right on the top horizontal line.
     EXAMPLES: Construct and show a ladder graph with 14 nodes
     ::
         sage: g = graphs.LadderGraph(7)
         sage: g.show() # long time
     Create several ladder graphs in a Sage graphics array
     ::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
 …
 def LollipopGraph(n1, n2):
     """
     Returns a lollipop graph with n1+n2 nodes.
     A lollipop graph is a path graph (order n2) connected to a complete
     graph (order n1). (A barbell graph minus one of the bells).
     This constructor depends on NetworkX numeric labels.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, the complete
     graph will be drawn in the lower-left corner with the (n1)th node
     at a 45 degree angle above the right horizontal center of the
     complete graph, leading directly into the path graph.
     EXAMPLES: Construct and show a lollipop graph Candy = 13, Stick =
     ::
         sage: g = graphs.LollipopGraph(13,4)
         sage: g.show() # long time
     Create several lollipop graphs in a Sage graphics array
     ::
         sage: g = []
         sage: j = []
         sage: for i in range(6):
 …
         sage: G.show() # long time
     """
     pos_dict = {}
     for i in range(n1):
         x = float(cos((pi/4) - ((2*pi)/n1)*i) - n2/2 - 1)
         y = float(sin((pi/4) - ((2*pi)/n1)*i) - n2/2 - 1)
 …
         x = float(i - n1 - n2/2 + 1)
         y = float(i - n1 - n2/2 + 1)
         pos_dict[i] = (x,y)
     import networkx
     G = networkx.lollipop_graph(n1,n2)
     return graph.Graph(G, pos=pos_dict, name="Lollipop Graph")
 def PathGraph(n, pos=None):
     """
     Returns a path graph with n nodes. Pos argument takes a string
     which is either 'circle' or 'line', (otherwise the default is
     used). See the plotting section below for more detail.
     A path graph is a graph where all inner nodes are connected to
     their two neighbors and the two end-nodes are connected to their
     one inner neighbors. (i.e.: a cycle graph without the first and
     last node connected).
     This constructor depends on NetworkX numeric labels.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, the graph may
     be drawn in one of two ways: The 'line' argument will draw the
 …
     circle in a clockwise manner. By default (without an appropriate
     string argument) the graph will be drawn as a 'circle' if 10 n 41
     and as a 'line' for all other n.
     EXAMPLES: Show default drawing by size: 'line': n 11
     ::
         sage: p = graphs.PathGraph(10)
         sage: p.show() # long time
     'circle': 10 n 41
     ::
         sage: q = graphs.PathGraph(25)
         sage: q.show() # long time
     'line': n 40
     ::
         sage: r = graphs.PathGraph(55)
         sage: r.show() # long time
     Override the default drawing::
         sage: s = graphs.PathGraph(5,'circle')
         sage: s.show() # long time
     """
     pos_dict = {}
     # Choose appropriate drawing pattern
     circle = False
     if pos == "circle": circle = True
     elif pos == "line": circle = False
     # Otherwise use default by size of n
     elif 10 < n < 41: circle = True
     # Draw 'circle'
     if circle:
         for i in range(n):
 …
         rem = n%10 # remainder to appear on last row
         rows = n//10 # number of rows (not counting last row)
         lr = True # left to right
         for i in range(rows): # note that rows doesn't include last row
             y = -i
             for j in range(10):
                 if lr:
                     x = j
                 else:
+                else:
                     x = 9 - j
                 pos_dict[counter] = (x,y)
                 counter += 1
 …
         for j in range(rem): # last row
             if lr:
                 x = j
             else:
+            else:
                 x = 9 - j
             pos_dict[counter] = (x,y)
             counter += 1
 …
 def StarGraph(n):
     """
     Returns a star graph with n+1 nodes.
     A Star graph is a basic structure where one node is connected to
     all other nodes.
     This constructor is dependent on NetworkX numeric labels.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, each star
     graph will be displayed with the first (0) node in the center, the
     second node (1) at the top, with the rest following in a
     counterclockwise manner. (0) is the node connected to all other
     nodes.
     The star graph is a good opportunity to compare efficiency of
     filling a position dictionary vs. using the spring-layout algorithm
     for plotting. As far as display, the spring-layout should push all
     other nodes away from the (0) node, and thus look very similar to
     this constructor's positioning.
     EXAMPLES::
         sage: import networkx
     Compare the plots::
         sage: n = networkx.star_graph(23)
         sage: spring23 = Graph(n)
         sage: posdict23 = graphs.StarGraph(23)
         sage: spring23.show() # long time
         sage: posdict23.show() # long time
     View many star graphs as a Sage Graphics Array
     With this constructor (i.e., the position dictionary filled)
     ::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
 …
         ...
         sage: G = sage.plot.graphics.GraphicsArray(j)
         sage: G.show() # long time
     Compared to plotting with the spring-layout algorithm
     ::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
         ...    spr = networkx.star_graph(i+3)
+        ...    spr = networkx.star_graph(i+3)
         ...    k = Graph(spr)
         ...    g.append(k)
         ...
 …
 def WheelGraph(n):
     """
     Returns a Wheel graph with n nodes.
     A Wheel graph is a basic structure where one node is connected to
     all other nodes and those (outer) nodes are connected cyclically.
     This constructor depends on NetworkX numeric labels.
     PLOTTING: Upon construction, the position dictionary is filled to
     override the spring-layout algorithm. By convention, each wheel
     graph will be displayed with the first (0) node in the center, the
     second node at the top, and the rest following in a
     counterclockwise manner.
     With the wheel graph, we see that it doesn't take a very large n at
     all for the spring-layout to give a counter-intuitive display. (See
     Graphics Array examples below).
     EXAMPLES: We view many wheel graphs with a Sage Graphics Array,
     first with this constructor (i.e., the position dictionary
     filled)::
         sage: g = []
         sage: j = []
         sage: for i in range(9):
 …
         ...
         sage: G = sage.plot.graphics.GraphicsArray(j)
         sage: G.show() # long time
     Next, using the spring-layout algorithm::
         sage: import networkx
         sage: g = []
         sage: j = []
         sage: for i in range(9):
         ...    spr = networkx.wheel_graph(i+3)
+        ...    spr = networkx.wheel_graph(i+3)
         ...    k = Graph(spr)
         ...    g.append(k)
         ...
 …
         ...
         sage: G = sage.plot.graphics.GraphicsArray(j)
         sage: G.show() # long time
     Compare the plotting::
         sage: n = networkx.wheel_graph(23)
         sage: spring23 = Graph(n)
         sage: posdict23 = graphs.WheelGraph(23)
 …
         x = float(cos((pi/2) + ((2*pi)/(n-1))*(i-1)))
         y = float(sin((pi/2) + ((2*pi)/(n-1))*(i-1)))
         pos_dict[i] = (x,y)
     import networkx
+    import networkx
     G = networkx.wheel_graph(n)
     return graph.Graph(G, pos=pos_dict, name="Wheel graph")

sage/graphs/generators/families.py

diff --git a/sage/graphs/generators/families.py b/sage/graphs/generators/families.py

-                      a
         raise ValueError(
             "Invalid number of symbols to permute, n should be >= 1")
     if n == 1:
         from sage.graphs.generators.families import CompleteGraph
+        from sage.graphs.generators.basic import CompleteGraph
         return graph.Graph(CompleteGraph(n), name="Bubble sort")
     from sage.combinat.permutation import Permutations
     #create set from which to permute
 …
         G.add_edges([(v,(v-j)%n) for j in adjacency])
     return G
-def CompleteGraph(n):
-    """
-    Returns a complete graph on n nodes.
-    A Complete Graph is a graph in which all nodes are connected to all
-    other nodes.
-    This constructor is dependent on vertices numbered 0 through n-1 in
-    NetworkX complete_graph()
-    PLOTTING: Upon construction, the position dictionary is filled to
-    override the spring-layout algorithm. By convention, each complete
-    graph will be displayed with the first (0) node at the top, with
-    the rest following in a counterclockwise manner.
-    In the complete graph, there is a big difference visually in using
-    the spring-layout algorithm vs. the position dictionary used in
-    this constructor. The position dictionary flattens the graph,
-    making it clear which nodes an edge is connected to. But the
-    complete graph offers a good example of how the spring-layout
-    works. The edges push outward (everything is connected), causing
-    the graph to appear as a 3-dimensional pointy ball. (See examples
-    below).
-    EXAMPLES: We view many Complete graphs with a Sage Graphics Array,
-    first with this constructor (i.e., the position dictionary
-    filled)::
-        sage: g = []
-        sage: j = []
-        sage: for i in range(9):
-        ...    k = graphs.CompleteGraph(i+3)
-        ...    g.append(k)
-        ...
-        sage: for i in range(3):
-        ...    n = []
-        ...    for m in range(3):
-        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
-        ...    j.append(n)
-        ...
-        sage: G = sage.plot.graphics.GraphicsArray(j)
-        sage: G.show() # long time
-    We compare to plotting with the spring-layout algorithm::
-        sage: import networkx
-        sage: g = []
-        sage: j = []
-        sage: for i in range(9):
-        ...    spr = networkx.complete_graph(i+3)
-        ...    k = Graph(spr)
-        ...    g.append(k)
-        ...
-        sage: for i in range(3):
-        ...    n = []
-        ...    for m in range(3):
-        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
-        ...    j.append(n)
-        ...
-        sage: G = sage.plot.graphics.GraphicsArray(j)
-        sage: G.show() # long time
-    Compare the constructors (results will vary)
-    ::
-        sage: import networkx
-        sage: t = cputime()
-        sage: n = networkx.complete_graph(389); spring389 = Graph(n)
-        sage: cputime(t)           # random
-.59203700000000126
-        sage: t = cputime()
-        sage: posdict389 = graphs.CompleteGraph(389)
-        sage: cputime(t)           # random
-.6680419999999998
-    We compare plotting::
-        sage: import networkx
-        sage: n = networkx.complete_graph(23)
-        sage: spring23 = Graph(n)
-        sage: posdict23 = graphs.CompleteGraph(23)
-        sage: spring23.show() # long time
-        sage: posdict23.show() # long time
-    """
-    pos_dict = {}
-    for i in range(n):
-        x = float(cos((pi/2) + ((2*pi)/n)*i))
-        y = float(sin((pi/2) + ((2*pi)/n)*i))
-        pos_dict[i] = (x,y)
-    import networkx
-    G = networkx.complete_graph(n)
-    return graph.Graph(G, pos=pos_dict, name="Complete graph")
-def CompleteBipartiteGraph(n1, n2):
-    """
-    Returns a Complete Bipartite Graph sized n1+n2, with each of the
-    nodes [0,(n1-1)] connected to each of the nodes [n1,(n2-1)] and
-    vice versa.
-    A Complete Bipartite Graph is a graph with its vertices partitioned
-    into two groups, V1 and V2. Each v in V1 is connected to every v in
-    V2, and vice versa.
-    PLOTTING: Upon construction, the position dictionary is filled to
-    override the spring-layout algorithm. By convention, each complete
-    bipartite graph will be displayed with the first n1 nodes on the
-    top row (at y=1) from left to right. The remaining n2 nodes appear
-    at y=0, also from left to right. The shorter row (partition with
-    fewer nodes) is stretched to the same length as the longer row,
-    unless the shorter row has 1 node; in which case it is centered.
-    The x values in the plot are in domain [0,maxn1,n2].
-    In the Complete Bipartite graph, there is a visual difference in
-    using the spring-layout algorithm vs. the position dictionary used
-    in this constructor. The position dictionary flattens the graph and
-    separates the partitioned nodes, making it clear which nodes an
-    edge is connected to. The Complete Bipartite graph plotted with the
-    spring-layout algorithm tends to center the nodes in n1 (see
-    spring_med in examples below), thus overlapping its nodes and
-    edges, making it typically hard to decipher.
-    Filling the position dictionary in advance adds O(n) to the
-    constructor. Feel free to race the constructors below in the
-    examples section. The much larger difference is the time added by
-    the spring-layout algorithm when plotting. (Also shown in the
-    example below). The spring model is typically described as
-    `O(n^3)`, as appears to be the case in the NetworkX source
-    code.
-    EXAMPLES: Two ways of constructing the complete bipartite graph,
-    using different layout algorithms::
-        sage: import networkx
-        sage: n = networkx.complete_bipartite_graph(389,157); spring_big = Graph(n)   # long time
-        sage: posdict_big = graphs.CompleteBipartiteGraph(389,157)                    # long time
-    Compare the plotting::
-        sage: n = networkx.complete_bipartite_graph(11,17)
-        sage: spring_med = Graph(n)
-        sage: posdict_med = graphs.CompleteBipartiteGraph(11,17)
-    Notice here how the spring-layout tends to center the nodes of n1
-    ::
-        sage: spring_med.show() # long time
-        sage: posdict_med.show() # long time
-    View many complete bipartite graphs with a Sage Graphics Array,
-    with this constructor (i.e., the position dictionary filled)::
-        sage: g = []
-        sage: j = []
-        sage: for i in range(9):
-        ...    k = graphs.CompleteBipartiteGraph(i+1,4)
-        ...    g.append(k)
-        ...
-        sage: for i in range(3):
-        ...    n = []
-        ...    for m in range(3):
-        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
-        ...    j.append(n)
-        ...
-        sage: G = sage.plot.graphics.GraphicsArray(j)
-        sage: G.show() # long time
-    We compare to plotting with the spring-layout algorithm::
-        sage: g = []
-        sage: j = []
-        sage: for i in range(9):
-        ...    spr = networkx.complete_bipartite_graph(i+1,4)
-        ...    k = Graph(spr)
-        ...    g.append(k)
-        ...
-        sage: for i in range(3):
-        ...    n = []
-        ...    for m in range(3):
-        ...        n.append(g[3*i + m].plot(vertex_size=50, vertex_labels=False))
-        ...    j.append(n)
-        ...
-        sage: G = sage.plot.graphics.GraphicsArray(j)
-        sage: G.show() # long time
-    Trac ticket #12155::
-        sage: graphs.CompleteBipartiteGraph(5,6).complement()
-        complement(Complete bipartite graph): Graph on 11 vertices
-    """
-    pos_dict = {}
-    c1 = 1 # scaling factor for top row
-    c2 = 1 # scaling factor for bottom row
-    c3 = 0 # pad to center if top row has 1 node
-    c4 = 0 # pad to center if bottom row has 1 node
-    if n1 > n2:
-        if n2 == 1:
-            c4 = (n1-1)/2
-        else:
-            c2 = ((n1-1)/(n2-1))
-    elif n2 > n1:
-        if n1 == 1:
-            c3 = (n2-1)/2
-        else:
-            c1 = ((n2-1)/(n1-1))
-    for i in range(n1):
-        x = c1*i + c3
-        y = 1
-        pos_dict[i] = (x,y)
-    for i in range(n1+n2)[n1:]:
-        x = c2*(i-n1) + c4
-        y = 0
-        pos_dict[i] = (x,y)
-    import networkx
-    from sage.graphs.graph import Graph
-    G = networkx.complete_bipartite_graph(n1,n2)
-    return Graph(G, pos=pos_dict, name="Complete bipartite graph")
-def CompleteMultipartiteGraph(l):
-    r"""
-    Returns a complete multipartite graph.
-    INPUT:
-    - ``l`` -- a list of integers : the respective sizes
-      of the components.
-    EXAMPLE:
-    A complete tripartite graph with sets of sizes
-    `5, 6, 8`::
-        sage: g = graphs.CompleteMultipartiteGraph([5, 6, 8]); g
-        Multipartite Graph with set sizes [5, 6, 8]: Graph on 19 vertices
-    It clearly has a chromatic number of 3::
-        sage: g.chromatic_number()
-    """
-    from sage.graphs.graph import Graph
-    from sage.graphs.generators.families import CompleteGraph
-    g = Graph()
-    for i in l:
-        g = g + CompleteGraph(i)
-    g = g.complement()
-    g.name("Multipartite Graph with set sizes "+str(l))
-    return g
 def CubeGraph(n):
     r"""
     Returns the hypercube in `n` dimensions.
 …
         sage: set([g.laplacian_matrix(normalized=True).charpoly() for g in g_list])  # long time (7s on sage.math, 2011)
         set([x^8 - 8*x^7 + 4079/150*x^6 - 68689/1350*x^5 + 610783/10800*x^4 - 120877/3240*x^3 + 1351/100*x^2 - 931/450*x])
     """
+    from sage.graphs.generators.basic import CompleteGraph
     if len(partition)<1:
         raise ValueError, "partition must be a nonempty list of positive integers"
     n=q+sum(partition)
 …
         raise ValueError('The number of levels must be >= 1.')
     from sage.graphs.graph_plot import _circle_embedding
-    from sage.graphs.graph_plot import GraphGenerators
     # Creating the Balanced tree, which contains most edges already
     g = GraphGenerators().BalancedTree(2,k-1)
+    g = BalancedTree(2,k-1)
     g.name('Ringed Tree on '+str(k)+' levels')
     # We consider edges layer by layer

sage/graphs/generators/random.py

diff --git a/sage/graphs/generators/random.py b/sage/graphs/generators/random.py

-                      a
     if seed is None:
         seed = current_randstate().long_seed()
     if p == 1:
         from sage.graphs.generators.families import CompleteGraph
+        from sage.graphs.generators.basic import CompleteGraph
         return CompleteGraph(n)
     if method == 'networkx':

sage/graphs/graph_generators.py

diff --git a/sage/graphs/graph_generators.py b/sage/graphs/graph_generators.py

-                      a
      "CircularLadderGraph",
      "ClawGraph",
      "CycleGraph",
+     "CompleteBipartiteGraph",
+     "CompleteGraph",
+     "CompleteMultipartiteGraph",
      "DiamondGraph",
      "EmptyGraph",
      "Grid2dGraph",
 …
     ["BalancedTree",
      "BubbleSortGraph",
      "CirculantGraph",
-     "CompleteBipartiteGraph",
-     "CompleteGraph",
      "CubeGraph",
      "FibonacciTree",
      "FriendshipGraph",
 …
     BalancedTree           = staticmethod(sage.graphs.generators.families.BalancedTree)
     BubbleSortGraph        = staticmethod(sage.graphs.generators.families.BubbleSortGraph)
     CirculantGraph         = staticmethod(sage.graphs.generators.families.CirculantGraph)
-    CompleteGraph          = staticmethod(sage.graphs.generators.families.CompleteGraph)
-    CompleteBipartiteGraph = staticmethod(sage.graphs.generators.families.CompleteBipartiteGraph)
-    CompleteMultipartiteGraph = staticmethod(sage.graphs.generators.families.CompleteMultipartiteGraph)
     CubeGraph              = staticmethod(sage.graphs.generators.families.CubeGraph)
     DorogovtsevGoltsevMendesGraph = staticmethod(sage.graphs.generators.families.DorogovtsevGoltsevMendesGraph)
     FriendshipGraph        = staticmethod(sage.graphs.generators.families.FriendshipGraph)
 …
     CircularLadderGraph      = staticmethod(sage.graphs.generators.basic.CircularLadderGraph)
     ClawGraph                = staticmethod(sage.graphs.generators.basic.ClawGraph)
     CycleGraph               = staticmethod(sage.graphs.generators.basic.CycleGraph)
+    CompleteGraph            = staticmethod(sage.graphs.generators.basic.CompleteGraph)
+    CompleteBipartiteGraph   = staticmethod(sage.graphs.generators.basic.CompleteBipartiteGraph)
+    CompleteMultipartiteGraph= staticmethod(sage.graphs.generators.basic.CompleteMultipartiteGraph)
     DiamondGraph             = staticmethod(sage.graphs.generators.basic.DiamondGraph)
     EmptyGraph               = staticmethod(sage.graphs.generators.basic.EmptyGraph)
     Grid2dGraph              = staticmethod(sage.graphs.generators.basic.Grid2dGraph)

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