#4364: major bug in singular polynomial GCD (?)
---------------------------------+------------------------------------------
Reporter: was | Owner: malb
Type: defect | Status: new
Priority: major | Milestone: sage-3.2
Component: commutative algebra | Resolution:
Keywords: |
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Old description:
> This looks like maybe a serious bug in Singular's GCD:
>
> {{{
> sage: def f(n):
> ....: p = next_prime(n)
> ....: a = GF(p)(1)
> ....: b = GF(p)(1)
> ....: E = EllipticCurve([a, b])
> ....: ret = E.multiplication_by_m(2)
> ....: return ret
> ....:
> sage: f(next_prime(2^30-41))
>
> Program received signal SIGABRT, Aborted.
> [Switching to Thread -1210337072 (LWP 6522)]
> 0xffffe410 in __kernel_vsyscall ()
> (gdb)
> (gdb) bt
> #0 0xffffe410 in __kernel_vsyscall ()
> #1 0xb7de5df0 in raise () from /lib/tls/i686/cmov/libc.so.6
> #2 0xb7de7641 in abort () from /lib/tls/i686/cmov/libc.so.6
> #3 0xb7b6ff12 in global_NTL_error_callback (s=0xb7a3c8c8
> "zz_pContext: modulus too big", context=0x0) at src/stdsage.c:42
> #4 0xb79f9ef7 in NTL::Error (s=0xb7a3c8c8 "zz_pContext: modulus too
> big") at tools.c:38
> #5 0xb79a26db in zz_pInfoT (this=0xa1be668, NewP=1073741827,
> maxroot=25) at lzz_p.c:15
> #6 0xb79a280e in zz_pContext (this=0xbfa40744, p=1073741827,
> maxroot=25) at lzz_p.c:157
> #7 0xb47649c5 in gcd_poly_p ([EMAIL PROTECTED], [EMAIL PROTECTED]) at
> cf_gcd.cc:852
> #8 0xb47660b8 in gcd_poly ([EMAIL PROTECTED], [EMAIL PROTECTED]) at
> cf_gcd.cc:538
> #9 0xb4766ca3 in gcd ([EMAIL PROTECTED], [EMAIL PROTECTED]) at cf_gcd.cc:776
> #10 0xb45dd1f1 in singclap_gcd (f=0xb445e220, g=0xb445e324) at
> clapsing.cc:230
> #11 0xb4849286 in
> __pyx_pf_4sage_5rings_10polynomial_28multi_polynomial_libsingular_23MPolynomial_libsingular_gcd
> (__pyx_v_self=0xb7c80acc, __pyx_args=0xa1d158c, __pyx_kwds=0x0)
> at sage/rings/polynomial/multi_polynomial_libsingular.cpp:23491
> }}}
New description:
This looks like maybe a serious bug in Singular's GCD:
On *32-bit* Linux or OS X we have this (it works fine on 64-bit):
{{{
sage: def f(n):
....: p = next_prime(n)
....: a = GF(p)(1)
....: b = GF(p)(1)
....: E = EllipticCurve([a, b])
....: ret = E.multiplication_by_m(2)
....: return ret
....:
sage: f(next_prime(2^30-41))
Program received signal SIGABRT, Aborted.
[Switching to Thread -1210337072 (LWP 6522)]
0xffffe410 in __kernel_vsyscall ()
(gdb)
(gdb) bt
#0 0xffffe410 in __kernel_vsyscall ()
#1 0xb7de5df0 in raise () from /lib/tls/i686/cmov/libc.so.6
#2 0xb7de7641 in abort () from /lib/tls/i686/cmov/libc.so.6
#3 0xb7b6ff12 in global_NTL_error_callback (s=0xb7a3c8c8
"zz_pContext: modulus too big", context=0x0) at src/stdsage.c:42
#4 0xb79f9ef7 in NTL::Error (s=0xb7a3c8c8 "zz_pContext: modulus too
big") at tools.c:38
#5 0xb79a26db in zz_pInfoT (this=0xa1be668, NewP=1073741827,
maxroot=25) at lzz_p.c:15
#6 0xb79a280e in zz_pContext (this=0xbfa40744, p=1073741827,
maxroot=25) at lzz_p.c:157
#7 0xb47649c5 in gcd_poly_p ([EMAIL PROTECTED], [EMAIL PROTECTED]) at
cf_gcd.cc:852
#8 0xb47660b8 in gcd_poly ([EMAIL PROTECTED], [EMAIL PROTECTED]) at
cf_gcd.cc:538
#9 0xb4766ca3 in gcd ([EMAIL PROTECTED], [EMAIL PROTECTED]) at cf_gcd.cc:776
#10 0xb45dd1f1 in singclap_gcd (f=0xb445e220, g=0xb445e324) at
clapsing.cc:230
#11 0xb4849286 in
__pyx_pf_4sage_5rings_10polynomial_28multi_polynomial_libsingular_23MPolynomial_libsingular_gcd
(__pyx_v_self=0xb7c80acc, __pyx_args=0xa1d158c, __pyx_kwds=0x0)
at sage/rings/polynomial/multi_polynomial_libsingular.cpp:23491
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4364#comment:2>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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