#16497: Rounding problem with CBC and gurobi LP solvers
-------------------------------------+-------------------------------------
Reporter: tmonteil | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: packages: | Resolution:
optional | Merged in:
Keywords: | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | 7c2fb38a2ae24e8c59c5fce8dc0c42967a6ef7c2
u/tmonteil/rounding_problem_with_cbc| Stopgaps:
Dependencies: |
-------------------------------------+-------------------------------------
Old description:
> Running `make ptestlong` with CBC package installed leads to the
> following doctest errors:
>
> {{{
> File "src/doc/en/thematic_tutorials/linear_programming.rst", line 442, in
> doc.en.thematic_tutorials.linear_programming
> Failed example:
> p.solve()
> Expected:
> 2.0
> Got:
> 1.0
> }}}
>
> {{{
> File "src/sage/graphs/graph.py", line 3215, in
> sage.graphs.graph.Graph.minimum_outdegree_orientation
> Failed example:
> max(o.out_degree()) == ceil((4*3)/(3+4))
> Expected:
> True
> Got:
> False
> }}}
>
> {{{
> File "src/sage/numerical/optimize.py", line 777, in
> sage.numerical.optimize.binpacking
> Failed example:
> all([ (v in b1 or v in b2 or v in b3) for v in values ])
> Expected:
> True
> Got:
> False
> }}}
New description:
Running `make ptestlong` with CBC package installed leads to the following
doctest errors:
{{{
File "src/doc/en/thematic_tutorials/linear_programming.rst", line 442, in
doc.en.thematic_tutorials.linear_programming
Failed example:
p.solve()
Expected:
2.0
Got:
1.0
}}}
{{{
File "src/sage/graphs/graph.py", line 3215, in
sage.graphs.graph.Graph.minimum_outdegree_orientation
Failed example:
max(o.out_degree()) == ceil((4*3)/(3+4))
Expected:
True
Got:
False
}}}
{{{
File "src/sage/numerical/optimize.py", line 777, in
sage.numerical.optimize.binpacking
Failed example:
all([ (v in b1 or v in b2 or v in b3) for v in values ])
Expected:
True
Got:
False
}}}
The problem seems to come from `get_variable_value` method in the CBC
backend that does not round its result when the variable is binary.
Actually, the same problems exists for integer variables in both gurobi
and CBC backends (at least), but no doctest detects it.
--
Comment (by tmonteil):
New commits:
||[http://git.sagemath.org/sage.git/commit/?id=bc1cc7d411fd805879f3c179b6dfaf28c69fe5fc
bc1cc7d]||{{{first attempt inspired from gurobi_backend}}}||
||[http://git.sagemath.org/sage.git/commit/?id=7c2fb38a2ae24e8c59c5fce8dc0c42967a6ef7c2
7c2fb38]||{{{16497 : fix the integer case for gurobi and cplex}}}||
--
Ticket URL: <http://trac.sagemath.org/ticket/16497#comment:3>
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