I am writing a program to study the puiseux expansion of a curve
singularity, focusing on the real branches. Doing so, i have
encountered an error, that strangely appears only at some particular
case. The error is triggered by something as simple as making a
substitution on a polynomial. I have tried to make the same by direct
evaluation and by means of a ring morphism, with the same result.
To reproduce it:
R.<x,y>=QQ[]
f=x^5+8*x^4-2*x^2*y^2-y^3+2*y^4
X=f.discriminant(y).univariate_polynomial().roots(AA)[1][0]
Y=f(X,y).univariate_polynomial().roots(AA)[0][0]
g=f(x+X,y+Y)
S.<a,t>=QQbar[]
p=g(t^2,a*t)
res=[i[0] for i in p.polynomial(t).coefficients()[0].roots()]
dic={x.change_ring(AA):x^2,y.change_ring(AA):res[0]*x+x*y}
g.subs(dic)
---------------------------------------------------------------------------
PariError Traceback (most recent call
last)
/home/mmarco/<ipython console> in <module>()
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/
polynomial/multi_polynomial_element.pyc in subs(self, fixed, **kw)
975 elif fixed and fixed.has_key(variables[i]):
976 variables[i] = fixed[variables[i]]
--> 977 return self(tuple(variables))
978
979 def monomials(self):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/
polynomial/multi_polynomial_element.pyc in __call__(self, *x, **kwds)
154 y = K(0)
155 for (m,c) in self.element().dict().iteritems():
--> 156 y += c*misc.mul([ x[i]**m[i] for i in range(n) if
m[i] != 0])
157 return y
158
/usr/local/sage/local/lib/python2.6/site-packages/sage/structure/
element.so in sage.structure.element.ModuleElement.__iadd__ (sage/
structure/element.c:8285)()
/usr/local/sage/local/lib/python2.6/site-packages/sage/structure/
coerce.so in sage.structure.coerce.CoercionModel_cache_maps.bin_op
(sage/structure/coerce.c:6630)()
/usr/local/sage/local/lib/python2.6/site-packages/sage/structure/
element.so in sage.structure.element.ModuleElement.__iadd__ (sage/
structure/element.c:8264)()
/usr/local/sage/local/lib/python2.6/site-packages/sage/structure/
element.so in sage.structure.element.ModuleElement._add_ (sage/
structure/element.c:8117)()
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/
polynomial/multi_polynomial_element.pyc in _add_(self, right)
212 def _add_(self, right):
213 #return self.parent()(self.__element +
right.__element)
--> 214 return self.__class__(self.parent(),self.__element +
right.__element)
215
216 def _sub_(self, right):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/
polynomial/polydict.so in
sage.rings.polynomial.polydict.PolyDict.__add__ (sage/rings/polynomial/
polydict.c:7503)()
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/
polynomial/polydict.so in
sage.rings.polynomial.polydict.PolyDict.__init__ (sage/rings/
polynomial/polydict.c:1781)()
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in __eq__(self, other)
3049 if self is other: return True
3050 if other._descr.is_rational() and
other._descr.rational_value() == 0:
-> 3051 return not self.__nonzero__()
3052 if self._descr.is_rational() and
self._descr.rational_value() == 0:
3053 return not other.__nonzero__()
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in __nonzero__(self)
3081 if self._value.prec() < 128:
3082 self._more_precision()
-> 3083 return self.__nonzero__()
3084
3085 # Sigh...
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in __nonzero__(self)
3084
3085 # Sigh...
-> 3086 self.exactify()
3087 return self.__nonzero__()
3088
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
2739 od = self._descr
2740 if od.is_exact(): return
-> 2741 self._set_descr(self._descr.exactify())
2742
2743 def _set_descr(self, new_descr):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
5891 left = self._left
5892 right = self._right
-> 5893 left.exactify()
5894 right.exactify()
5895 gen =
left._exact_field().union(right._exact_field())
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
2739 od = self._descr
2740 if od.is_exact(): return
-> 2741 self._set_descr(self._descr.exactify())
2742
2743 def _set_descr(self, new_descr):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
5891 left = self._left
5892 right = self._right
-> 5893 left.exactify()
5894 right.exactify()
5895 gen =
left._exact_field().union(right._exact_field())
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
2739 od = self._descr
2740 if od.is_exact(): return
-> 2741 self._set_descr(self._descr.exactify())
2742
2743 def _set_descr(self, new_descr):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
5891 left = self._left
5892 right = self._right
-> 5893 left.exactify()
5894 right.exactify()
5895 gen =
left._exact_field().union(right._exact_field())
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
2739 od = self._descr
2740 if od.is_exact(): return
-> 2741 self._set_descr(self._descr.exactify())
2742
2743 def _set_descr(self, new_descr):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
5892 right = self._right
5893 left.exactify()
-> 5894 right.exactify()
5895 gen =
left._exact_field().union(right._exact_field())
5896 left_value = gen(left._exact_value())
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
2739 od = self._descr
2740 if od.is_exact(): return
-> 2741 self._set_descr(self._descr.exactify())
2742
2743 def _set_descr(self, new_descr):
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in exactify(self)
5166 newpol_sage_y = QQy(newpol_sage)
5167
-> 5168 red_elt, red_back, red_pol =
do_polred(newpol_sage_y)
5169
5170 new_nf = NumberField(red_pol, name='a',
check=False)
/usr/local/sage/local/lib/python2.6/site-packages/sage/rings/qqbar.pyc
in do_polred(poly)
1206 assert(best is not None)
1207 parent = poly.parent()
-> 1208 rev = parent(best_elt.Mod(pari_poly).modreverse().lift())
1209 return parent(best_elt), rev, parent(best)
1210
/usr/local/sage/local/lib/python2.6/site-packages/sage/libs/pari/
gen.so in sage.libs.pari.gen._pari_trap (sage/libs/pari/gen.c:49380)()
PariError: (5)
I guess it is a bug (in Pari, or in our interface?) but i know
basically nothing about pari, so i wanted to ask first.
Any clue?
--
You received this message because you are subscribed to the Google Groups
"sage-devel" group.
To post to this group, send email to sage-devel@googlegroups.com.
To unsubscribe from this group, send email to
sage-devel+unsubscr...@googlegroups.com.
Visit this group at http://groups.google.com/group/sage-devel?hl=en.
