#12533: arbitrary precision LP solver backend
-------------------------------------------+--------------------------------
Reporter: dimpase | Owner: ncohen
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.1
Component: linear programming | Resolution:
Keywords: arbitrary precision, LP | Work issues: see the latest
comments
Report Upstream: N/A | Reviewers: David Coudert,
Nathann Cohen
Authors: | Merged in:
Dependencies: 12553 | Stopgaps:
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Changes (by vbraun):
* status: needs_review => needs_work
* dependencies: => 12553
Comment:
Generally speaking, looks good! There are a few nitpicks:
In #12553, I modified the PPL classes to derive from `SageObject`. This'll
make it play nicer with the rest of Sage. Correspondingly you should
override `_repr_`, not `__repr__`. Also needs to dump the actual
information of the `MIP_problem` or its useless in other doctests.
Speaking of which, the method needs a doctest. Also, in English you'd say
"A MIP" not "An MIP", but really the output should be more specific.
All expensive operations (that need to solve a LP, say) must be wrapped in
`sig_on/sig_off` blocks. Be careful with exceptions thrown, use
try/finally if necessary. Otherwise you'll get into expensive but
untinterruptable computations...
Can we have a few less empty lines? No need for an empty line before and
after the """ closing the docstring.
The INPUT: section should be formatted like
{{{
- ``number`` (integer) -- description.
}}}
You often have only a single "-" between type and description.
Coverage should be 100%:
{{{
[vbraun@volker-desktop hg]$ sage -coverage
sage/numerical/backends/ppl_backend.pyx
----------------------------------------------------------------------
sage/numerical/backends/ppl_backend.pyx
ERROR: Please add a `TestSuite(s).run()` doctest.
SCORE sage/numerical/backends/ppl_backend.pyx: 72% (24 of 33)
Missing documentation:
* int add_variable(self, lower_bound=0.0, upper_bound=None,
binary=False, continuous=True, integer=False, obj=0.0, name=None) except
-1: """ Add a variable. This amounts to adding a new column to the matrix.
By default, the variable is both positive and real. It has not been
implemented for selecting the variable type yet. INPUT: - ``lower_bound``
- the lower bound of the variable (default: 0) - ``upper_bound`` - the
upper bound of the variable (default: ``None``) - ``binary`` - ``True`` if
the variable is binary (default: ``False``). - ``continuous`` - ``True``
if the variable is binary (default: ``True``). - ``integer`` - ``True`` if
the variable is binary (default: ``False``). - ``obj`` - (optional)
coefficient of this variable in the objective function (default: 0.0) -
``name`` - an optional name for the newly added variable (default:
``None``). OUTPUT: The index of the newly created variable EXAMPLE:: sage:
from sage.numerical.backends.generic_backend import get_solver sage: p =
get_solver(solver = "PPL") sage: p.ncols() 0 sage: p.add_variable() 0
sage: p.ncols() 1 sage: p.add_variable(lower_bound=-2.0) 1 sage:
p.add_variable(name='x',obj=1.0) 2 sage: p.col_name(2) 'x' sage:
p.objective_coefficient(2) 1.00000000000000 """ for i in
range(len(self.Matrix)):
* int add_variables(self, int n, lower_bound=0.0,
upper_bound=None, binary=False, continuous=True, integer=False, obj=0.0,
names=None) except -1: """ Add ``n`` variables. This amounts to adding new
columns to the matrix. By default, the variables are both positive and
real. It has not been implemented for selecting the variable type yet.
INPUT: - ``n`` - the number of new variables (must be > 0) -
``lower_bound`` - the lower bound of the variable (default: 0) -
``upper_bound`` - the upper bound of the variable (default: ``None``) -
``binary`` - ``True`` if the variable is binary (default: ``False``). -
``continuous`` - ``True`` if the variable is binary (default: ``True``). -
``integer`` - ``True`` if the variable is binary (default: ``False``). -
``obj`` - (optional) coefficient of all variables in the objective
function (default: 0.0) - ``names`` - optional list of names (default:
``None``) OUTPUT: The index of the variable created last. EXAMPLE:: sage:
from sage.numerical.backends.generic_backend import get_solver sage: p =
get_solver(solver = "PPL") sage: p.ncols() 0 sage: p.add_variables(5) 4
sage: p.ncols() 5 sage: p.add_variables(2, lower_bound=-2.0,
names=['a','b']) 6 """ for k in range(n):
* int solve(self) except -1: """ Solve the problem. .. NOTE::
This method raises ``MIPSolverException`` exceptions when the solution can
not be computed for any reason (none exists, or the LP solver was not able
to find it, etc...) EXAMPLE:: sage: from
sage.numerical.backends.generic_backend import get_solver sage: p =
get_solver(solver = "PPL") sage: p.add_linear_constraints(5, 0, None)
sage: p.add_col(range(5), range(5)) sage: p.solve() 0 sage:
p.objective_coefficient(0,1) sage: p.solve() Traceback (most recent call
last):
Missing doctests:
* set_variable_type(self, int variable, int vtype):
* set_verbosity(self, int level):
* double get_objective_value(self):
* double get_variable_value(self, int variable):
* write_lp(self, char * name):
* write_mps(self, char * name, int modern):
}}}
Finally, the ticket description should say which patch to apply for the
sanity of the release manager.
Also, `ptrrsn_1` should put his name on the trac author list
(http://trac.sagemath.org) and populate the Author: field on the ticket.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12533#comment:47>
Sage <http://www.sagemath.org>
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