(WIP) feat/heuristic-clique-oracle #150
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| def find_max_degree_node(self, graph, nodes): | ||
| """Returns greatest degree node out of list""" | ||
| max_degree_node = None | ||
| for node in nodes: |
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You can use python built-ins here. They are more readable and also faster! Something like:
max_degree_node = max(nodes, key=lambda node: graph.degree(node))
Not sure the above will work b/c I can't get this code running for some reason, but something similar should work :)
| # base case: find largest degree node in graph | ||
| max_degree_node = self.find_max_degree_node(graph, nodes) | ||
| if not max_degree_node: | ||
| raise Exception("### Did not find a node in the graph, no common estimates") |
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Does this ever trigger? It seems like if we have any nodes (as nodes are "inferred" from edges), we should have some node with a max degree.
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No it does not really ever get triggered. More just a check in case of empty graph-- But I already check before starting the search so I can safely remove this :)
| return heuristic_min_clique | ||
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| # remove neighbors that are not adjacent to the new max degree vertex | ||
| for node in max_degree_neighbors: |
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You can change this to a Python built-in. Something like difference_update
Read more here: https://docs.python.org/2/library/sets.html
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Oh cool. Yeah for sure, will refactor to use built-ins. Starting to get this whole python thing.. lol.
| nodes = graph.nodes() | ||
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| # if graph is empty, break out of function | ||
| if not nodes: |
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maybe, if not any(nodes):
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@seanavery Much like the Turan's oracle, I think this might be mildly "attackable." If I'm an attacker that controls some portion of the network w/ low weight validators, they can construct a high-degree connected node (that would be first chosen in the greedy search), that ends up not contributing to safety very much b/c of it's low weight. This disappears once you add in weight considerations! |
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@naterush Completely agree on vulnerability to attacks. i.e. A big hub and spoke resulting in a clique size of 2! Taking into account weight will make it much more expensive to perform such an attack. Still brainstorming on how to properly perform the greedy search w/ weight but i have some ideas. Going to work on rebasing this oracle-- cleaning up code and weight integration. |
Heuristic Clique Oracle
Right now, the functionality is appended to the CliqueOracle class. For testing, the oracle is being called from the blockchain view.
To run:
python casper.py rand --validators 10 --rounds 100Check console output to see it in action.This oracle does a greedy search in attempt to find a large clique quickly. It iterates through the graph favoring vertices with the largest degree until it can reduce a clique.
The current implementation does not take into account weight, which I plan on adding in.
The greedy algorithm can also be extended beyond a simple lookup to do a full search on the graph space.
For more details see #134