本文整理汇总了Python中cnfformula.cnf.CNF.sparse_mapping方法的典型用法代码示例。如果您正苦于以下问题：Python CNF.sparse_mapping方法的具体用法？Python CNF.sparse_mapping怎么用？Python CNF.sparse_mapping使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类cnfformula.cnf.CNF的用法示例。
在下文中一共展示了CNF.sparse_mapping方法的1个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Python代码示例。
示例1: GraphPigeonholePrinciple
# 需要导入模块: from cnfformula.cnf import CNF [as 别名]
# 或者: from cnfformula.cnf.CNF import sparse_mapping [as 别名]
def GraphPigeonholePrinciple(graph,functional=False,onto=False):
"""Graph Pigeonhole Principle CNF formula
The graph pigeonhole principle CNF formula, defined on a bipartite
graph G=(L,R,E), claims that there is a subset E' of the edges such that
every vertex on the left size L has at least one incident edge in E' and
every edge on the right side R has at most one incident edge in E'.
This is possible only if the graph has a matching of size |L|.
There are different variants of this formula, depending on the
values of `functional` and `onto` argument.
- PHP(G): each left vertex can be incident to multiple edges in E'
- FPHP(G): each left vertex must be incident to exaclty one edge in E'
- onto-PHP: all right vertices must be incident to some vertex
- matching: E' must be a perfect matching between L and R
Arguments:
- `graph` : bipartite graph
- `functional`: add clauses to enforce at most one edge per left vertex
- `onto`: add clauses to enforce that any right vertex has one incident edge
Remark: the graph vertices must have the 'bipartite' attribute
set. Left vertices must have it set to 0 and the right ones to
1. A KeyException is raised otherwise.
"""
def var_name(p,h):
return 'p_{{{0},{1}}}'.format(p,h)
if functional:
if onto:
formula_name="Graph matching"
else:
formula_name="Graph functional pigeonhole principle"
else:
if onto:
formula_name="Graph onto pigeonhole principle"
else:
formula_name="Graph pigeonhole principle"
gphp=CNF()
gphp.header="{0} formula for graph {1}\n".format(formula_name,graph.name)
Left, _ = bipartite_sets(graph)
for p in Left:
for h in neighbors(graph,p):
gphp.add_variable(var_name(p,h))
clauses=gphp.sparse_mapping( graph,
var_name=var_name,
complete = True,
injective = True,
functional = functional,
surjective = onto)
for c in clauses:
gphp.add_clause(c,strict=True)
return gphp