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Add weights to digraph

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Because in some cases (e.g. partitioning) the order is needed,
add weights to the digraph to get an (somewhat) stable
topological sort.

Change-Id: I5ef1acc6338ac93c593faa0eafe26cbed42ed887
Signed-off-by: Andreas Florath <andreas@florath.net>
This commit is contained in:
Andreas Florath 2017-05-20 06:41:27 +00:00
parent 9eb71a1fe0
commit 45272343c5
3 changed files with 120 additions and 19 deletions
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70
diskimage_builder/graph/digraph.py
View File

@ -12,6 +12,7 @@
# License for the specific language governing permissions and limitations
# under the License.
#
import bisect
class Digraph(object):
@ -20,6 +21,32 @@ class Digraph(object):
Each node of the digraph must have a unique name.
"""
class Edge(object):
"""Directed graph edge.
The digraph has weighted edges. This class holds the weight and
a reference to the node.
"""
def __init__(self, node, weight):
self.__node = node
self.__weight = weight
def __eq__(self, other):
return self.__weight == other.get_weight() \
and self.__node == other.get_node()
def __lt__(self, other):
return self.__weight < other.get_weight()
def get_node(self):
"""Return the (pointed to) node"""
return self.__node
def get_weight(self):
"""Return the edge's weight"""
return self.__weight
class Node(object):
"""Directed graph node.
@ -35,33 +62,38 @@ class Digraph(object):
computed.
"""
self.__name = name
self.__incoming = set()
self.__outgoing = set()
self.__incoming = []
self.__outgoing = []
def __repr__(self):
return "<Node [%s]>" % self.__name
def get_name(self):
"""Returns the name of the node."""
return self.__name
def add_incoming(self, node):
def add_incoming(self, node, weight):
"""Add node to the incoming list."""
bisect.insort(self.__incoming, Digraph.Edge(node, weight))
self.__incoming.add(node)
def add_outgoing(self, node):
"""Add node to the incoming list."""
self.__outgoing.add(node)
def add_outgoing(self, node, weight):
"""Add node to the outgoing list."""
bisect.insort(self.__outgoing, Digraph.Edge(node, weight))
def get_iter_outgoing(self):
"""Return an iterator over the outgoing nodes."""
return iter(self.__outgoing)
return iter([x.get_node() for x in self.__outgoing])
def has_incoming(self):
"""Returns True if the node has incoming edges"""
return self.__incoming
@staticmethod
def __as_named_list(inlist):
"""Return given list as list of names."""
return map(lambda x: x.get_name(), inlist)
return [x.get_node().get_name() for x in inlist]
def get_outgoing_as_named_list(self):
"""Return the names of all outgoing nodes as a list."""
@ -105,7 +137,7 @@ class Digraph(object):
"exists" % node.get_name())
self._named_nodes[anode.get_name()] = anode
def create_edge(self, anode, bnode):
def create_edge(self, anode, bnode, weight=0):
"""Creates an edge from a to b - both must be nodes."""
assert issubclass(anode.__class__, Digraph.Node)
@ -114,8 +146,8 @@ class Digraph(object):
assert anode == self._named_nodes[anode.get_name()]
assert bnode.get_name() in self._named_nodes.keys()
assert bnode == self._named_nodes[bnode.get_name()]
anode.add_outgoing(bnode)
bnode.add_incoming(anode)
anode.add_outgoing(bnode, weight)
bnode.add_incoming(anode, weight)
def get_iter_nodes_values(self):
"""Returns the nodes dict to the values.
@ -144,7 +176,7 @@ class Digraph(object):
rval[node.get_name()] = node.get_outgoing_as_named_list()
return rval
def topological_sort(dg):
def topological_sort(self):
"""Digraph topological search.
This algorithm is based upon a depth first search with
@ -169,7 +201,9 @@ class Digraph(object):
tsort.insert(0, node)
# The 'main' function of the topological sort
for node in dg.get_iter_nodes_values():
for node in self.get_iter_nodes_values():
if node.has_incoming():
continue
visit(node)
return tsort
@ -189,6 +223,6 @@ def node_list_to_node_name_list(node_list):
"""Converts a node list into a list of the corresponding node names."""
node_name_list = []
for n in node_list:
node_name_list.append(n.get_name())
for node in node_list:
node_name_list.append(node.get_name())
return node_name_list

20
diskimage_builder/tests/functional/test_graph.py
View File

@ -121,3 +121,23 @@ class TestDigraph(testtools.TestCase):
self.assertTrue(False)
except RuntimeError:
pass
def test_iter_outgoing_weight_01(self):
"""Tests iter_outgoing in a graph with weights"""
digraph = Digraph()
node0 = Digraph.Node("R")
digraph.add_node(node0)
node1 = Digraph.Node("A")
digraph.add_node(node1)
node2 = Digraph.Node("B")
digraph.add_node(node2)
node3 = Digraph.Node("C")
digraph.add_node(node3)
digraph.create_edge(node0, node1, 1)
digraph.create_edge(node0, node2, 2)
digraph.create_edge(node0, node3, 3)
self.assertEqual([node1, node2, node3],
list(node0.get_iter_outgoing()))

49
diskimage_builder/tests/functional/test_graph_toposort.py
View File

@ -12,9 +12,11 @@
# License for the specific language governing permissions and limitations
# under the License.
import testtools
from diskimage_builder.graph.digraph import Digraph
from diskimage_builder.graph.digraph import digraph_create_from_dict
from diskimage_builder.graph.digraph import node_list_to_node_name_list
import testtools
class TestTopologicalSearch(testtools.TestCase):
@ -67,3 +69,48 @@ class TestTopologicalSearch(testtools.TestCase):
self.assertTrue(tnames.index('A') < tnames.index('B'))
self.assertTrue(tnames.index('B') < tnames.index('C'))
self.assertTrue(tnames.index('D') < tnames.index('E'))
def test_tsort_006(self):
"""Complex digraph with weights"""
digraph = Digraph()
node0 = Digraph.Node("R")
digraph.add_node(node0)
node1 = Digraph.Node("A")
digraph.add_node(node1)
node2 = Digraph.Node("B")
digraph.add_node(node2)
node3 = Digraph.Node("C")
digraph.add_node(node3)
node4 = Digraph.Node("B1")
digraph.add_node(node4)
node5 = Digraph.Node("B2")
digraph.add_node(node5)
node6 = Digraph.Node("B3")
digraph.add_node(node6)
digraph.create_edge(node0, node1, 1)
digraph.create_edge(node0, node2, 2)
digraph.create_edge(node0, node3, 3)
digraph.create_edge(node2, node4, 7)
digraph.create_edge(node2, node5, 14)
digraph.create_edge(node2, node6, 21)
tsort = digraph.topological_sort()
tnames = node_list_to_node_name_list(tsort)
# Also here: many possible solutions
self.assertTrue(tnames.index('R') < tnames.index('A'))
self.assertTrue(tnames.index('R') < tnames.index('B'))
self.assertTrue(tnames.index('R') < tnames.index('C'))
self.assertTrue(tnames.index('B') < tnames.index('B1'))
self.assertTrue(tnames.index('B') < tnames.index('B2'))
self.assertTrue(tnames.index('B') < tnames.index('B3'))
# In addition in the weighted graph the following
# must also hold:
self.assertTrue(tnames.index('B') < tnames.index('A'))
self.assertTrue(tnames.index('C') < tnames.index('B'))
self.assertTrue(tnames.index('B2') < tnames.index('B1'))
self.assertTrue(tnames.index('B3') < tnames.index('B2'))