2007/7/30, Martin Albrecht <[EMAIL PROTECTED]>:
>
> Hi Didier,
>
> I hope you don't mind that I have some remarks about your patches
Not at all! I am just poking my way through the multivariate code and
any input from someone more knowledgeable than me would be greatly
appreciated.
>
> The R.random_element method on the other hand seems to be specialized for
> MPolynomial_polydict only, i.e. you'd loose the speed advantage of
> MPolynomial_libsingular by constructing an MPolynomial_polydict in any case.
Is there a way to construct a multivariate polynomial from a
dictionary? That's what I was shooting for, but I'm getting it doesn't
always work. Example:
Base ring is RR:
{{{
sage: # Works fine
sage: from sage.rings.polynomial.polydict import PolyDict
sage: R.<x,y,z> = MPolynomialRing(RR,3,order='grevlex')
sage: D= PolyDict( {(1, 1, 1): 1, (0, 0, 1): 1/2, (0, 1, 0): 9, (0, 1,
1): -3/8, (0, 0, 0): 3/4})
sage: R(D)
x*y*z - 3/8*y*z + 9*y + 1/2*z + 3/4
}}}
Base ring is QQ (this fails):
{{{
sage: R.<x,y,z> = MPolynomialRing(QQ,3,order='grevlex')
sage: R(D)
---------------------------------------------------------------------------
<type 'exceptions.TypeError'> Traceback (most recent call last)
/home/dfdeshom/custom/sage/devel/sage-multi-random/<ipython console>
in <module>()
/home/dfdeshom/custom/sage/devel/sage-multi-random/multi_polynomial_libsingular.pyx
in multi_polynomial_libsingular.MPolynomialRing_libsingular.__call__()
/home/dfdeshom/custom/sage/local/lib/python2.5/site-packages/sage/rings/rational_field.py
in __call__(self, x, base)
172 if isinstance(x, sage.rings.rational.Rational):
173 return x
--> 174 return sage.rings.rational.Rational(x, base)
175
176 def construction(self):
/home/dfdeshom/custom/sage/devel/sage-multi-random/rational.pyx in
rational.Rational.__init__()
/home/dfdeshom/custom/sage/devel/sage-multi-random/rational.pyx in
rational.Rational.__set_value()
<type 'exceptions.TypeError'>: Unable to coerce PolyDict with
representation {(0, 0, 0): 3/4, (0, 1, 1): -3/8, (0, 1, 0): 9, (1, 1,
1): 1, (0, 0, 1): 1/2} (<type
'sage.rings.polynomial.polydict.PolyDict'>) to Rational
}}}
Is this a bug, or am I not using this correctly?
didier
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