#7720: Digraph.reverse() should be rewritten more efficiently ( not hard )
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Reporter: ncohen | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone: sage-4.3.1
Component: graph theory | Keywords:
Work_issues: | Author:
Upstream: N/A | Reviewer:
Merged: |
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Comment(by rlm):
In case of a `SparseGraph`, the `SparseGraphBackend` has `self._cg` and
`self._cg_rev`. They can merely be swapped. In the case of a `NetworkX`
graph, I believe their digraphs have `succ` and `pred` dictionaries
storing the adjacency information. These could also be swapped. For
`DenseGraphs`, this is equivalent to switching between row ordering and
column ordering in bitsets, which is inevitably costly.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7720#comment:1>
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