#19649: Crash in pari polroots()
--------------------------------------------+-------------------------
Reporter: kedlaya | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.10
Component: interfaces | Resolution:
Keywords: pari, polynomials, roots | Merged in:
Authors: Jeroen Demeyer | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
--------------------------------------------+-------------------------
Changes (by {'newvalue': u'Jeroen Demeyer', 'oldvalue': ''}):
* author: => Jeroen Demeyer
Old description:
> We've seen weird issues with pari.polroots before (e.g., #2418); this may
> be related. (Observed in Sage 6.9, on multiple platforms.)
> {{{
> sage: polRing.<x> = PolynomialRing(ZZ)
> sage: j = (x+1)^2 * (x-1)^7 * (x^2-x+1)^5
> sage: l = j.roots(CC)
> ---------------------------------------------------------------------------
> SignalError Traceback (most recent call
> last)
> <ipython-input-106-2450a50ef70a> in <module>()
> ----> 1 l = j.roots(CC)
>
> /home/kedlaya/sage-
> complete/src/sage/rings/polynomial/polynomial_element.pyx in
> sage.rings.polynomial.polynomial_element.Polynomial.roots
> (/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/rings/polynomial/polynomial_element.c:53329)()
> 6344 real_field = RealField(L.prec())
> 6345
> -> 6346 return self.change_ring(real_field).roots(ring=L,
> multiplicities=multiplicities, algorithm=algorithm)
> 6347 elif is_pAdicRing(L) or is_pAdicField(L):
> 6348 p = L.prime()
>
> /home/kedlaya/sage-
> complete/src/sage/rings/polynomial/polynomial_element.pyx in
> sage.rings.polynomial.polynomial_element.Polynomial.roots
> (/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/rings/polynomial/polynomial_element.c:50813)()
> 6251 if not input_arbprec:
> 6252 self = self.change_ring(CC if input_complex
> else RR)
> -> 6253 ext_rts = pari(self.monic()).polroots(precision =
> L.prec())
> 6254
> 6255 if output_complex:
>
> /home/kedlaya/sage-complete/src/sage/libs/pari/gen.pyx in
> sage.libs.pari.gen.gen.polroots
> (/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/libs/pari/gen.c:133557)()
> 8236 from sage.misc.superseded import deprecation
> 8237 deprecation(16997, 'The flag argument to polroots()
> is deprecated and not used anymore')
> -> 8238 pari_catch_sig_on()
> 8239 return P.new_gen(cleanroots(self.g,
> prec_bits_to_words(precision)))
> 8240
>
> /home/kedlaya/sage-complete/src/sage/ext/interrupt/interrupt.pyx in
> sage.ext.interrupt.interrupt.sig_raise_exception
> (/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/ext/interrupt/interrupt.c:1356)()
> 108 if msg == NULL:
> 109 msg = "Segmentation fault"
> --> 110 raise SignalError(msg)
> 111
> 112 raise SystemError("unknown signal number %s"%sig)
>
> SignalError: Segmentation fault
> }}}
New description:
We've seen weird issues with pari.polroots before (e.g., #2418); this may
be related. (Observed in Sage 6.9, on multiple platforms.)
{{{
sage: polRing.<x> = PolynomialRing(ZZ)
sage: j = (x+1)^2 * (x-1)^7 * (x^2-x+1)^5
sage: l = j.roots(CC)
---------------------------------------------------------------------------
SignalError Traceback (most recent call
last)
<ipython-input-106-2450a50ef70a> in <module>()
----> 1 l = j.roots(CC)
/home/kedlaya/sage-
complete/src/sage/rings/polynomial/polynomial_element.pyx in
sage.rings.polynomial.polynomial_element.Polynomial.roots
(/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/rings/polynomial/polynomial_element.c:53329)()
6344 real_field = RealField(L.prec())
6345
-> 6346 return self.change_ring(real_field).roots(ring=L,
multiplicities=multiplicities, algorithm=algorithm)
6347 elif is_pAdicRing(L) or is_pAdicField(L):
6348 p = L.prime()
/home/kedlaya/sage-
complete/src/sage/rings/polynomial/polynomial_element.pyx in
sage.rings.polynomial.polynomial_element.Polynomial.roots
(/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/rings/polynomial/polynomial_element.c:50813)()
6251 if not input_arbprec:
6252 self = self.change_ring(CC if input_complex
else RR)
-> 6253 ext_rts = pari(self.monic()).polroots(precision =
L.prec())
6254
6255 if output_complex:
/home/kedlaya/sage-complete/src/sage/libs/pari/gen.pyx in
sage.libs.pari.gen.gen.polroots
(/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/libs/pari/gen.c:133557)()
8236 from sage.misc.superseded import deprecation
8237 deprecation(16997, 'The flag argument to polroots() is
deprecated and not used anymore')
-> 8238 pari_catch_sig_on()
8239 return P.new_gen(cleanroots(self.g,
prec_bits_to_words(precision)))
8240
/home/kedlaya/sage-complete/src/sage/ext/interrupt/interrupt.pyx in
sage.ext.interrupt.interrupt.sig_raise_exception
(/home/kedlaya/Downloads/sage-6.9/src/build/cythonized/sage/ext/interrupt/interrupt.c:1356)()
108 if msg == NULL:
109 msg = "Segmentation fault"
--> 110 raise SignalError(msg)
111
112 raise SystemError("unknown signal number %s"%sig)
SignalError: Segmentation fault
}}}
Equivalent GP session:
{{{
gp> \p10
realprecision = 19 significant digits (10 digits displayed)
gp> polroots((x+1)^2 * (x-1)^7 * (x^2-x+1)^5 * 1.0)
*** at top-level: polroots((x+1)^2*(x-
*** ^--------------------
*** polroots: bug in PARI/GP (Segmentation Fault), please report.
}}}
--
--
Ticket URL: <http://trac.sagemath.org/ticket/19649#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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