#16755: PPL LP solver does not accept rationals
--------------------------------------+------------------------
Reporter: jdemeyer | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: linear programming | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by jdemeyer:
Old description:
> This should work (even though PPL doesn't seem to provide an interface
> for inputting rationals, we need some manual rescaling):
> {{{
> sage: p = MixedIntegerLinearProgram(solver="PPL")
> sage: x = p.new_variable(nonnegative=True)
> sage: p.add_constraint(x[0] + x[1] <= 1/2)
> sage: p.set_objective(x[0])
> sage: p.solve()
> ---------------------------------------------------------------------------
> TypeError Traceback (most recent call
> last)
> <ipython-input-10-082b726ace8d> in <module>()
> ----> 1 p.solve()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/numerical/mip.so in
> sage.numerical.mip.MixedIntegerLinearProgram.solve
> (build/cythonized/sage/numerical/mip.c:10574)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/numerical/backends/ppl_backend.so in
> sage.numerical.backends.ppl_backend.PPLBackend.solve
> (build/cythonized/sage/numerical/backends/ppl_backend.c:5346)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/numerical/backends/ppl_backend.so in
> sage.numerical.backends.ppl_backend.PPLBackend.init_mip
> (build/cythonized/sage/numerical/backends/ppl_backend.c:2284)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/libs/ppl.so in sage.libs.ppl.Linear_Expression.__richcmp__
> (build/cythonized/sage/libs/ppl.cpp:17640)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/libs/ppl.so in sage.libs.ppl._make_Constraint_from_richcmp
> (build/cythonized/sage/libs/ppl.cpp:23124)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/libs/ppl.so in sage.libs.ppl.Linear_Expression.__cinit__
> (build/cythonized/sage/libs/ppl.cpp:15675)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/rings/integer.so in sage.rings.integer.Integer.__init__
> (build/cythonized/sage/rings/integer.c:7650)()
>
> /usr/local/src/sage-config/local/lib/python2.7/site-
> packages/sage/rings/rational.so in sage.rings.rational.Rational._integer_
> (build/cythonized/sage/rings/rational.c:20851)()
>
> TypeError: no conversion of this rational to integer
> }}}
New description:
Inputting rationals in MILP constraints or objective functions should work
for the PPL interface (even though PPL doesn't seem to provide an
interface for inputting rationals, we need some manual rescaling):
{{{
sage: p = MixedIntegerLinearProgram(solver="PPL")
sage: x = p.new_variable(nonnegative=True)
sage: p.add_constraint(x[0] + x[1] <= 1/2)
sage: p.set_objective(x[0])
sage: p.solve()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
<ipython-input-10-082b726ace8d> in <module>()
----> 1 p.solve()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/numerical/mip.so in
sage.numerical.mip.MixedIntegerLinearProgram.solve
(build/cythonized/sage/numerical/mip.c:10574)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/numerical/backends/ppl_backend.so in
sage.numerical.backends.ppl_backend.PPLBackend.solve
(build/cythonized/sage/numerical/backends/ppl_backend.c:5346)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/numerical/backends/ppl_backend.so in
sage.numerical.backends.ppl_backend.PPLBackend.init_mip
(build/cythonized/sage/numerical/backends/ppl_backend.c:2284)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/libs/ppl.so in sage.libs.ppl.Linear_Expression.__richcmp__
(build/cythonized/sage/libs/ppl.cpp:17640)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/libs/ppl.so in sage.libs.ppl._make_Constraint_from_richcmp
(build/cythonized/sage/libs/ppl.cpp:23124)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/libs/ppl.so in sage.libs.ppl.Linear_Expression.__cinit__
(build/cythonized/sage/libs/ppl.cpp:15675)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/rings/integer.so in sage.rings.integer.Integer.__init__
(build/cythonized/sage/rings/integer.c:7650)()
/usr/local/src/sage-config/local/lib/python2.7/site-
packages/sage/rings/rational.so in sage.rings.rational.Rational._integer_
(build/cythonized/sage/rings/rational.c:20851)()
TypeError: no conversion of this rational to integer
}}}
--
--
Ticket URL: <http://trac.sagemath.org/ticket/16755#comment:7>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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