#16553: Clean IncidenceStructure
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Reporter: vdelecroix | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.3
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: | Reviewers:
Authors: Nathann Cohen, | Work issues:
Vincent Delecroix | Commit:
Report Upstream: N/A | 9be78f42a2e26008661462f6db66b5646849ee76
Branch: public/16553v2 | Stopgaps:
Dependencies: |
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Comment (by ncohen):
Yo !
> - It makes sense to translate everything on {0,...,n-1} internally. It
will save a lot of pain.
+1
> - For the blocks we can put it into a fixed datastructure: i.e. a sparse
incidence matrix (that way even the blocks are numbered). Sparse integer
matrices have methods
> {{{
> def _nonzero_positions_by_row(self, copy=True)
> def _nonzero_positions_by_column(self, copy=True)
> }}}
> It is a bit stupid for our purpose to use GMP integers... but at least
these are fast methods.
>
> What do you think of getting rid of the attribute `._blocks` and use
only `._incidence_matrix`.
I don't like it, because I don't trust complicated datatypes. What do we
earn by storing this as a matrix ? I expect it to be heavier (because it
has to remember the '1' in each cell, it is not meant to be a binary
matrix) and less practical (we iterate on the blocks all day long)..
The best data structure for this is a bipartite graph, isn't it ?
But even then, I personally prefer simple data types. Otherwise we will
constantly do work on list of lists, translate everything to a
matrix/graph, then export everything to list of lists, then build another
incidence structure ...
What do you think ?
Nathann
Nathann
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Ticket URL: <http://trac.sagemath.org/ticket/16553#comment:99>
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