#15060: The empty graph once again
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Reporter: darij | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-5.12
Component: combinatorics | Resolution:
Keywords: graphs, border cases, bitset, | Merged in:
memleak | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Changes (by darij):
* cc: sagecombinat (removed)
* cc: sage-combinat (added)
* keywords: graphs, border cases, memleak => graphs, border cases, bitset,
memleak
Old description:
> {{{
> sage: Graph({}).is_connected()
> True
> }}}
> If my understanding of good terminology is correct, this should not be
> the case (see http://ncatlab.org/nlab/show/too+simple+to+be+simple ).
> Note that {{{Graph({}).is_tree()}}} correctly returns {{{False}}}.
>
> Another issue is that
> {{{
> Graph({}).is_triangle_free()
> }}}
> seems to allocate lots of RAM and possibly die with a MemoryError (it did
> so on the Sage cell server; on my machine I had to ctrl-alt-del the VM).
> The culprit seems to be {{{Bitset(capacity=0)}}}. If I see other issues
> caused by this, I'll open up a new ticket for this.
New description:
{{{
sage: Graph({}).is_connected()
True
}}}
If my understanding of good terminology is correct, this should not be the
case (see http://ncatlab.org/nlab/show/too+simple+to+be+simple ). Note
that {{{Graph({}).is_tree()}}} correctly returns {{{False}}}.
Another issue is that
{{{
Graph({}).is_triangle_free()
}}}
seems to allocate lots of RAM and possibly die with a MemoryError (it did
so on the Sage cell server; on my machine I had to ctrl-alt-del the VM).
The culprit seems to be {{{Bitset(capacity=0)}}}. It looks like
{{{is_triangle_free}}} is the only method ever using the
{{{Bitset(capacity=X)}}} construction, so I'm not opening up a new ticket
for this.
--
--
Ticket URL: <http://trac.sagemath.org/ticket/15060#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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