Status: Accepted
Owner: smichr
CC: mattpap
Labels: Type-Defect Priority-Medium polys
New issue 2087 by smichr: solver treats a nonlinear expression as linear
and mis-solves a true nonlinear system; fixed in polys11 but slow
http://code.google.com/p/sympy/issues/detail?id=2087
The following is the wrong solution to the equation set:
a=solve([x+x*y-3,y+x*y-4]);a
{x: 3, y: 1}
Although this satisfies the second equation, it does not satisfy the first.
In solve, this is identified as being linear since:
Poly(x+x*y-3).is_linear
True
If mixed terms are tested for in the multi-equation handling portion of
solve then the correct solution is obtained.
BUT for the nonlinear system
[-10 + x + y**2, 20 - y + x*y + x**2] the wrong solution is obtained from
solve_poly_system and it takes almost longer to solve than it does to solve
the system manually with sympy and confirm the correctness of the solution.
Everything is corrected in polys11 --is_linear returns False for the
example from above, and the right answers are obtained for both systems,
but it takes an excruciatingly long time to obtain the solution to this
relatively trivial system -- even with simplified=False. There's got to be
some better way to use polys to obtain a solution.
--
You received this message because you are subscribed to the Google Groups
"sympy-issues" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/sympy-issues?hl=en.
