solve for polynomial equation runs endless

[Arnaud Usciati]

Hello,

I try to find solutions for : 8.99*x*(-x + 1)**1.9 + 3.1*(-x + 1)**2.1 - 3.1*(-x + 1)**2.9 == 0

I use >>> solve(8.99*x*(-x + 1)**1.9 + 3.1*(-x + 1)**2.1 - 3.1*(-x + 1)**2.9, x) but it runs endless !!!!

Any ideas to fix it ?

PS : sorry for my english, i'm french :)

[Aaron Meurer]

Is this in the latest version of SymPy? For me, it returns [0.0, 1.0] after a few seconds.

Aaron Meurer

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[Arnaud Usciati]

I use sympy-0.7.6.win32.

I tried it with a faster computer and it returns that : 

solve(8.99*x*(-x + 1)**1.9 + 3.1*(-x + 1)**2.1 - 3.1*(-x + 1)**2.9, x)

Traceback (most recent call last):

  File "<pyshell#0>", line 1, in <module>

    solve(8.99*x*(-x + 1)**1.9 + 3.1*(-x + 1)**2.1 - 3.1*(-x + 1)**2.9, x)

  File "C:\Python34\lib\site-packages\sympy\solvers\solvers.py", line 909, in solve

    solution = _solve(f[0], *symbols, **flags)

  File "C:\Python34\lib\site-packages\sympy\solvers\solvers.py", line 1218, in _solve

    u = unrad(f_num)

  File "C:\Python34\lib\site-packages\sympy\solvers\solvers.py", line 2885, in unrad

    neq = unrad(eq, *syms, cov=cov, dens=dens, n=len(rterms), rpt=rpt, take=_take)

  File "C:\Python34\lib\site-packages\sympy\solvers\solvers.py", line 2885, in unrad

    neq = unrad(eq, *syms, cov=cov, dens=dens, n=len(rterms), rpt=rpt, take=_take)

  File "C:\Python34\lib\site-packages\sympy\solvers\solvers.py", line 2781, in unrad

    eq = _mexpand(eq)

  File "C:\Python34\lib\site-packages\sympy\simplify\sqrtdenest.py", line 13, in _mexpand

    return expand_mul(expand_multinomial(expr))

  File "C:\Python34\lib\site-packages\sympy\core\function.py", line 2006, in expand_multinomial

    power_base=False, basic=False, multinomial=True, log=False)

  File "C:\Python34\lib\site-packages\sympy\core\cache.py", line 91, in wrapper

    retval = cfunc(*args, **kwargs)

  File "C:\Python34\lib\functools.py", line 458, in wrapper

    result = user_function(*args, **kwds)

  File "C:\Python34\lib\site-packages\sympy\core\expr.py", line 2871, in expand

    expr, hit = Expr._expand_hint(expr, hint, deep=deep, **hints)

  File "C:\Python34\lib\site-packages\sympy\core\expr.py", line 2804, in _expand_hint

    arg, arghit = Expr._expand_hint(arg, hint, **hints)

  File "C:\Python34\lib\site-packages\sympy\core\expr.py", line 2804, in _expand_hint

    arg, arghit = Expr._expand_hint(arg, hint, **hints)

  File "C:\Python34\lib\site-packages\sympy\core\expr.py", line 2812, in _expand_hint

    newexpr = getattr(expr, hint)(**hints)

  File "C:\Python34\lib\site-packages\sympy\core\power.py", line 819, in _eval_expand_multinomial

    expansion_dict = multinomial_coefficients(len(p), n)

  File "C:\Python34\lib\site-packages\sympy\ntheory\multinomial.py", line 145, in multinomial_coefficients

    return dict(multinomial_coefficients_iterator(m, n))

  File "C:\Python34\lib\site-packages\sympy\ntheory\multinomial.py", line 237, in multinomial_coefficients_iterator

    t1 = _tuple(t)

MemoryError

[Aaron Meurer]

Sorry, I must have tried in the git version, not 0.7.6. I see the same
thing in 0.7.6, but it works fine in the git master.

Aaron Meurer

> https://groups.google.com/d/msgid/sympy/9bb8b46d-d005-4c49-95c2-bbafdc05cdcc%40googlegroups.com.