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Fix combinatorial blowup in ConstraintGraphFactory._recurse() from missing negative-memoization #177

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Fix combinatorial blowup in ConstraintGraphFactory._recurse() from missing negative-memoization #177

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34 changes: 17 additions & 17 deletions src/pyhpp/manipulation/constraint_graph_factory.py
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Original file line number Diff line number Diff line change
Expand Up @@ -249,23 +249,18 @@ class GraphFactoryAbstract(ABC):
The first node is defined by the empty set. The graph is built recursiveley
as follows:

if the set of grasps defining the node is not allowed (method \\link
For any pair \\f$(g,h)\\f$ of available grippers and available handles,
\\li if the resulting set of grasps is allowed (method \\link
constraint_graph_factory.GraphFactoryAbstract.graspIsAllowed
graspIsAllowed \\endlink), return.

Otherwise, for any pair \\f$(g,h)\f$ of available grippers and available
handles,
\\li build a new state by adding grasp \\f$(g,h)\\f$ to the current set of
grasps (method
\\link constraint_graph_factory.GraphFactoryAbstract.makeState
makeState\\endlink),
\\li build a transition from the current state to the new state (method \\link
constraint_graph_factory.GraphFactoryAbstract.makeTransition
makeTransition \\endlink)
\\li build a loopTransition from the current state to itself (method \\link
constraint_graph_factory.GraphFactoryAbstract.makeLoopTransition
makeLoopTransition \\endlink)
\\li repeat the two above states to the new state.
graspIsAllowed \\endlink), build a new state (method \\link
constraint_graph_factory.GraphFactoryAbstract.makeState
makeState\\endlink) and a transition from the current state (method
\\link constraint_graph_factory.GraphFactoryAbstract.makeTransition
makeTransition \\endlink),
\\li regardless of whether the next set of grasps is allowed, recurse into
it if it has not been visited before (to support non-monotonic filter
rules). A rejected set of grasps is memoized so its subtree is never
re-explored from a different parent path.
"""

def __init__(self):
Expand All @@ -283,6 +278,9 @@ def __init__(self):

self.states = dict()
self.transitions = set()
# Recursion-visited memo for all nGrasps, accepted or rejected.
# Separate from self.states, which only holds created State objects.
self._visitedGrasps = set()
# # the handle names
self.handles = tuple() # strings
# # the gripper names
Expand Down Expand Up @@ -507,7 +505,9 @@ def _recurse(self, grippers, handles, grasps, depth):
nGrasps = grasps[:isg] + (ish,) + grasps[isg + 1 :]

nextIsAllowed = self.graspIsAllowed(nGrasps)
isNewState = not self._existState(nGrasps)
isNewState = nGrasps not in self._visitedGrasps
if isNewState:
self._visitedGrasps.add(nGrasps)
if nextIsAllowed:
nnext = self._makeState(nGrasps, depth + 1)

Expand Down