#11526: count_points() error for generic schemes. (includes patch)
------------------------------------------+---------------------------------
Reporter: mmarco | Owner: AlexGhitza
Type: defect | Status: positive_review
Priority: major | Milestone: sage-4.8
Component: algebraic geometry | Keywords:
Work_issues: | Upstream: N/A
Reviewer: Johan Bosman, Julian Rueth | Author: Miguel Marco,
davideklund, Frithjof Schulze
Merged: | Dependencies:
------------------------------------------+---------------------------------
Changes (by newvalueoldvalue):
* status: needs_review => positive_review
* reviewer: => Johan Bosman, Julian Rueth
* author: Miguel Marco => Miguel Marco, davideklund, Frithjof Schulze
Old description:
> sage raises an error when trying to count the number of points of a
> subscheme of an affine scheme.
>
> See, for instance:
>
> {{{
> sage: F=FiniteField(3)
> sage: R.<x,y>=F[]
> sage: A=AffineSpace(F,2)
> sage: I=R.ideal(x^2-y^2-1)
> sage: S=A.subscheme(I)
> sage: S.count_points(2)
>
>
> ---------------------------------------------------------------------------
> NameError Traceback (most recent call
> last)
>
> /home/mmarco/sage-4.6.2/<ipython console> in <module>()
>
> /usr/lib64/python2.7/site-packages/sage/schemes/generic/scheme.py in
> count_points(self, n)
> 531 F1 = GF(q**i, name='z')
> 532 S1 = self.base_extend(F1)
> --> 533 a.append(len(S1.rational_points()))
> 534 return(a)
> 535
>
> /usr/lib64/python2.7/site-
> packages/sage/schemes/generic/algebraic_scheme.py in
> rational_points(self, F, bound)
> 1129 raise TypeError, "Unable to enumerate points over
> %s."%F
> 1130 try:
> -> 1131 return X.points()
> 1132 except TypeError:
> 1133 raise TypeError, "Unable to enumerate points over
> %s."%F
>
> /usr/lib64/python2.7/site-packages/sage/schemes/generic/homset.py in
> points(self, B)
> 162 except TypeError:
> 163 raise TypeError, "Domain of argument must be of the
> form Spec(S)."
> --> 164 if is_RationalField(R) or R == Z:
> 165 if not B > 0:
> 166 raise TypeError, "A positive bound B (= %s) must
> be specified."%B
>
> NameError: global name 'Z' is not defined
> }}}
>
> '''Apply:'''
> [attachment:trac_11526_bugfix_with_docstring.patch]
New description:
sage raises an error when trying to count the number of points of a
subscheme of an affine scheme.
See, for instance:
{{{
sage: F=FiniteField(3)
sage: R.<x,y>=F[]
sage: A=AffineSpace(F,2)
sage: I=R.ideal(x^2-y^2-1)
sage: S=A.subscheme(I)
sage: S.count_points(2)
---------------------------------------------------------------------------
NameError Traceback (most recent call
last)
/home/mmarco/sage-4.6.2/<ipython console> in <module>()
/usr/lib64/python2.7/site-packages/sage/schemes/generic/scheme.py in
count_points(self, n)
531 F1 = GF(q**i, name='z')
532 S1 = self.base_extend(F1)
--> 533 a.append(len(S1.rational_points()))
534 return(a)
535
/usr/lib64/python2.7/site-
packages/sage/schemes/generic/algebraic_scheme.py in rational_points(self,
F, bound)
1129 raise TypeError, "Unable to enumerate points over
%s."%F
1130 try:
-> 1131 return X.points()
1132 except TypeError:
1133 raise TypeError, "Unable to enumerate points over
%s."%F
/usr/lib64/python2.7/site-packages/sage/schemes/generic/homset.py in
points(self, B)
162 except TypeError:
163 raise TypeError, "Domain of argument must be of the
form Spec(S)."
--> 164 if is_RationalField(R) or R == Z:
165 if not B > 0:
166 raise TypeError, "A positive bound B (= %s) must
be specified."%B
NameError: global name 'Z' is not defined
}}}
'''Apply:'''
[attachment:trac_11526_final.patch]
--
Comment:
Apply trac_11526_final.patch
Tested against sage-4.8.alpha3 and doctests pass.
[attachment:trac_11526_final.patch] is identical to
[trac_11526_bugfix_with_docstring.2.patch] except for the commit message
which I replaced with something that makes hopefully more sense to
somebody who does not know this ticket.
We still don't have a docstring for
!SchemeHomset?_projective_coordinates_ring.points() but I guess that is
acceptable since there wasn't any before and it's not implemented anyway.
I'm unsure if "Reviewers" should only mention the person who clicked
"positive review" or everybody who was part of the review process. Anyway,
I added some authors and reviewers, I hope nobody minds.
Btw. davideklund, your name is not in the AccountNamesMappedtoRealNames on
the trac wiki start page.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11526#comment:7>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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