On May 25, 2011, at 3:01 AM, Mateusz Paprocki wrote:
> Hi,
>
> On 25 May 2011 10:43, Aaron S. Meurer <asmeu...@gmail.com> wrote:
> What happens if you make it use an algebraic domain, i.e., set extension=True?
>
> That's a good suggestion. Usually polys (domains or whatever else) in not the
> problem (unless there is some bug and there are still quite a few there), but
> the way the module is used. We can't expect that polys will work in all
> contexts without fine tuning (see sympy/polys/polyoptions.py). polys are
> optimized for symbolic manipulation (simplification etc.) so in other
> contexts you may need to override the defaults. Look for example into
> gosper_normal() in sympy/concrete/gosper.py (the first line). Two options
> (field and extension) had to be specified to adjust polys behavior to make it
> useful in the context of Gosper's algorithm. Similar thing happens in
> solve(). Unfortunately solve() was updated to use polys properly.
>
> btw.
>
> Did you notice this odd printing (- -):
>
> In [37]: F = [(x - 5)**2 + (y - 5)**2 - 4, -(-x + 5)*(-x - 2*2**(1/S(2)) + 5)
> - (-y + 5)*(-y + 5)]
>
> In [38]: F
> Out[38]:
> ⎡ 2 2 ⎛ ⎽⎽⎽ ⎞ 2⎤
> ⎣(x - 5) + (y - 5) - 4, - -(x - 5)⋅⎝-x - 2⋅╲╱ 2 + 5⎠ - (-y + 5) ⎦
I bisected this, and it shouldn't be any surprise what caused it:
commit b8d6252ea115032f7da8c46aca60af0b6a75fd36
Author: Ronan Lamy <ronan.l...@normalesup.org>
Date: Thu Jan 13 23:43:00 2011 +0000
Set keep_sign = True
I created http://code.google.com/p/sympy/issues/detail?id=2425 for this.
Aaron Meurer
>
>
> Aaron Meurer
>
> On May 24, 2011, at 10:14 PM, smichr wrote:
>
> > One of the problems I am running into with polys is this:
> >
> >>>> p1,p2=[(x - 5)**2 + (y - 5)**2 - 4, -(-x + 5)*(-x - 2*2**(1/
> > S(2)) + 5) - (-y
> > + 5)*(-y + 5)]
> >>>> solve([p1,p2])
> > Traceback (most recent call last):
> > File "<stdin>", line 1, in <module>
> > File "sympy\solvers\solvers.py", line 236, in solve
> > solution = _solve(f, *symbols, **flags)
> > File "sympy\solvers\solvers.py", line 607, in _solve
> > soln = solve_poly_system(polys)
> > File "sympy\solvers\polysys.py", line 45, in solve_poly_system
> > return solve_generic(polys, opt)
> > File "sympy\solvers\polysys.py", line 179, in solve_generic
> > result = solve_reduced_system(polys, opt.gens, entry=True)
> > File "sympy\solvers\polysys.py", line 149, in
> > solve_reduced_system
> > raise NotImplementedError("only zero-dimensional systems
> > supported (finite n
> > umber of solutions)")
> > NotImplementedError: only zero-dimensional systems supported
> > (finite number of s
> > olutions)
> >
> > The two expressions end up getting different domains:
> > [Poly(x**2 - 10*x + y**2 - 10*y + 46, x, y, domain='ZZ'),
> > Poly(-x**2 + (-2*2**(1 /2) + 10)*x - y**2 + 10*y - 50 +
> > 10*2**(1/2), x, y, domain='EX')]
> >
> > If I get rid of the sqrt(2) then the domains are both ZZ and it works.
> >>>> p2
> > -(-x + 5)*(-x - 2*2**(1/2) + 5) - (-y + 5)**2
> >>>> _.subs(sqrt(2),2)
> > (-x + 1)*(x - 5) - (-y + 5)**2
> >>>> solve([p1,_])
> > [(4, -3**(1/2) + 5), (4, 3**(1/2) + 5)]
> >
> > What's the best way to make solve flexible so it will handle this?
> >
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>
> Mateusz
>
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