#16490: Create a linear programming backend for cvxopt
-------------------------------------+-------------------------------------
Reporter: ingolfured | Owner: ingolfured
Type: enhancement | Status: new
Priority: minor | Milestone: sage-6.3
Component: linear | Resolution:
programming | Merged in:
Keywords: | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | 2fc6f054ae7f6faa36782ba85829540c15e3720b
u/ingolfured/create_a_linear_programming_backend_for_cvxopt| Stopgaps:
Dependencies: |
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Comment (by ncohen):
Yo !
> > You put cvxopt before gurobi in the ordering of LP solvers: this list
is meant to be "use the fastest solver available installed on this
computer". Is CVXOPT faster than Gurobi ?
>
> This list for making the most suitable for the task solver the default.
No, this list is a linear ordering that makes Sage's default the first
solver that can be called and that appears in the list. If CVXOPT is the
second, and as it is available by default, then none of the others will
ever become the default. And unless you tell me that CVXOPT is faster than
gurobi it should appear afterwards.
> > 1) It is useless to put anything after a solver which is installed by
default
>
> huh?
>
> >
> > 2) PPL cannot really be a "default solver" as it misses the important
feature of being able to solve integer linear programs.
>
> We have discussed this in April:
> let me quote your email dated 22.04.14:
>
> > > DP 1) I'd like this:
>
> > > DP sage:
sage.numerical.backends.generic_backend.default_mip_solver(solver='PPL')
>
> > > DP to work...
>
> > NC Well. PPL is just missing from the list of keywords, it should only
be
>
> > NC added there. Can you write the patch ? I will review it, it takes
ten
>
> > NC seconds.
I don't see what you intend by quoting me against myself. Just read the
code :
{{{
if solver is None:
if default_solver is not None:
return default_solver
else:
for s in ["Cplex", "Cvxopt", "Gurobi", "Coin", "Glpk", "Ppl"]:
try:
default_mip_solver(s)
return s
except ValueError:
pass
}}}
If CPLEX is available, Cplex will be used. If CVXOPT is available, it will
be used. And CVXOPT is always available, so none of the others LP will
ever be used.
If you want to be able to make CVXOPT the default solver all you need is
this part of your branch
{{{
elif solver == "Cvxopt":
try:
from sage.numerical.backends.cvxopt_backend import
CVXOPTBackend
default_solver = solver
except ImportError:
raise ValueError("CVXOPT is not available. Please refer to the
documentation to install it.")
}}}
Touching the list changes the "automatically defined" default solver of
Sage. And as the code shows, by puting cvxopt second you may as well
remove anything that appears after it. Similarly, it's useless to put
anything after Glpk. In the current state the function will only test
Cplex and CVXOPT.
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/16490#comment:22>
Sage <http://www.sagemath.org>
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