#4622: Bug in variety()
---------------------------------+------------------------------------------
Reporter: SimonKing | Owner: malb
Type: defect | Status: new
Priority: major | Milestone: sage-3.2.1
Component: commutative algebra | Keywords: variety triang.lib
---------------------------------+------------------------------------------
Reported by Alex Raichev at http://groups.google.com/group/sage-
support/browse_thread/thread/39b5eeeddebd1910
Slightly simplifying Alex's example, we have
{{{
sage: R.<w,z>= PolynomialRing(QQ,2,order='lex')
sage: F= 19 -20*z -20*w +5*z^2 +14*z*w +5*w^2 -2*z^2*w -2*z*w^2 +z^2*w^2
sage: G= (w*z-1)*F
sage: I=ideal([G]+G.gradient())
sage: I=ideal(I.groebner_basis())
sage: I
Ideal (w^2 - 2*w - 17/5*z^4 + 434/25*z^3 - 817/25*z^2 + 672/25*z - 179/25,
w*z - w + 33/28*z^4 - 433/70*z^3 + 869/70*z^2 - 839/70*z + 641/140, z^5 -
27/5*z^4 + 56/5*z^3 - 56/5*z^2 + 27/5*z - 1) of Multivariate Polynomial
Ring in w, z over Rational Field
sage: I.variety()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
...
}}}
I repeat the command `I.variety()`, because then the Traceback provides
one bit more of information:
{{{
sage: I.variety()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/home/king/Projekte/Cohom/CAS/fullBens/src/<ipython console> in <module>()
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/rings/polynomial/multi_polynomial_ideal.pyc in variety(self,
ring)
1528 P = self.ring()
1529 if ring is not None: P = P.change_ring(ring)
-> 1530 T = self.triangular_decomposition('singular:triangLfak')
1531
1532 V = []
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/rings/polynomial/multi_polynomial_ideal.pyc in
triangular_decomposition(self, algorithm, singular)
777 Tbar = Ibar.triangL()
778 elif algorithm == "singular:triangLfak":
--> 779 Tbar = Ibar.triangLfak()
780 elif algorithm == "singular:triangM":
781 Tbar = Ibar.triangM()
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/interfaces/expect.pyc in __call__(self, *args, **kwds)
1248
1249 def __call__(self, *args, **kwds):
-> 1250 return self._obj.parent().function_call(self._name,
[self._obj] + list(args), kwds)
1251
1252 def help(self):
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/interfaces/expect.pyc in function_call(self, function, args,
kwds)
1168
1169 return self.new("%s(%s)"%(function, ",".join([s.name() for
s in args]+
-> 1170
['%s=%s'%(key,value.name()) for key, value in kwds.items()])))
1171
1172 def call(self, function_name, *args, **kwds):
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/interfaces/expect.pyc in new(self, code)
1028
1029 def new(self, code):
-> 1030 return self(code)
1031
1032
###################################################################
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/interfaces/singular.pyc in __call__(self, x, type)
591 x = str(x)[1:-1]
592
--> 593 return SingularElement(self, type, x, False)
594
595
/home/king/SAGE/devel/sage-3.1.4/local/lib/python2.5/site-
packages/sage/interfaces/singular.pyc in __init__(self, parent, type,
value, is_name)
1007 except (RuntimeError, TypeError, KeyboardInterrupt),
x:
1008 self._session_number = -1
-> 1009 raise TypeError, x
1010 else:
1011 self._name = value
TypeError: Singular error:
// ** redefining zerlegt
? wrong range[2] in ideal/module(1)
? error occurred in triang.lib::Erw_ggt_oT line 509: `parameter poly f;
parameter poly g; parameter int v; parameter ideal T; `
? wrong type declaration. type 'help poly;'
? leaving triang.lib::Erw_ggt_oT
? `f` is undefined
? error occurred in triang.lib::Erw_ggt_oT line 511: ` poly p1 = f;`
? expected poly-expression. type 'help poly;'
? leaving triang.lib::Erw_ggt_oT
skipping text from `;` error at token `)`
? leaving triang.lib::invertieren_oT
? leaving triang.lib::normieren_oT
? leaving triang.lib::Erw_ggt_oT
? leaving triang.lib::invertieren_oT
? leaving triang.lib::invertieren
? leaving triang.lib::triangLbas
? leaving triang.lib::triangLfak
}}}
Some observations:
* There is a slight inconvenience, but not yet a bug: Singular apparently
defines a name `zerlegt` and does not properly kill it. The following line
in the Traceback only occurs when running `I.variety()` for the second
time.
{{{
TypeError: Singular error:
// ** redefining zerlegt
}}}
* The Traceback continues
{{{
? wrong range[2] in ideal/module(1)
? error occurred in triang.lib::Erw_ggt_oT line 509: `parameter poly f;
parameter poly g; parameter int v; parameter ideal T; `
? wrong type declaration. type 'help poly;'
}}}
hence, it looks like it was tried to address the second generator of an
ideal or module in Singular, in order to assign it to either `f` or `g` to
the arguments of the function `Erw_ggt_oT` in `triang.lib` -- which failed
since the ideal or module only has a single generator.
* Does that error come from a bug in Sage or a bug in Singular's
`triang.lib`? It seems to me it is in `triang.lib`, since the Traceback
ends with
{{{
? leaving triang.lib::Erw_ggt_oT
? `f` is undefined
? error occurred in triang.lib::Erw_ggt_oT line 511: ` poly p1 = f;`
? expected poly-expression. type 'help poly;'
? leaving triang.lib::Erw_ggt_oT
skipping text from `;` error at token `)`
? leaving triang.lib::invertieren_oT
? leaving triang.lib::normieren_oT
? leaving triang.lib::Erw_ggt_oT
? leaving triang.lib::invertieren_oT
? leaving triang.lib::invertieren
? leaving triang.lib::triangLbas
? leaving triang.lib::triangLfak
}}}
and AFAIK only `triangLfak` is directly called by Sage, the rest (in
particular the failing call of `Erw_ggt_oT`) happens internally in
`triang.lib`.
But even if it is a Singular issue, Michael Abshoff asked me to post it
here, so I did.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4622>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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