#14229: Remove vacuous solutions from solve
-------------------------------+--------------------------------------------
Reporter: ppurka | Owner: burcin
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-5.10
Component: symbolics | Resolution:
Keywords: | Work issues: port to upstream
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Changes (by ppurka):
* status: needs_review => needs_work
* work_issues: => port to upstream
Old description:
> Sometimes solve and its variants tend to report vacuous solutions. A
> recent one from [http://ask.sagemath.org/question/2324/how-to-print-out-
> maxima-commands-being-used-by ask.sagemath] is the following:
> {{{
> sage: x,y = var('x,y')
> sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
> [[x == 0, 1 < y, 0 != 0], [x == 0, y < 0, 0 != 0]]
> }}}
>
> Shouldn't we remove these meaningless solutions? The attached patch
> contains a potential solution. If it seems reasonable, then similar
> changes could be introduced in `solve_ineq`.
>
> The output of the above command after this patch is as expected:
> {{{
> sage: x,y = var('x,y')
> sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
> []
> }}}
New description:
Sometimes solve and its variants tend to report vacuous solutions. A
recent one from [http://ask.sagemath.org/question/2324/how-to-print-out-
maxima-commands-being-used-by ask.sagemath] is the following:
{{{
sage: x,y = var('x,y')
sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
[[x == 0, 1 < y, 0 != 0], [x == 0, y < 0, 0 != 0]]
}}}
Shouldn't we remove these meaningless solutions? The attached patch
contains a potential solution. If it seems reasonable, then similar
changes could be introduced in `solve_ineq`.
The output of the above command after this patch is as expected:
{{{
sage: x,y = var('x,y')
sage: solve([x^2*y^2 <= x^2*y, x^2*y^2 > x^2*y],[x,y])
[]
}}}
----
If you can translate this to maxima proper, please feel free to do so and
submit a patch upstream.
--
Comment:
If someone knows how to translate this to maxima, please feel free to put
this upstream. Thanks! [ I can not spend time in learning maxima right
now. :( ]
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14229#comment:6>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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