Opened 6 years ago

Closed 6 years ago

#4364 closed defect (fixed)

[with patch, positive review] major bug in singular polynomial GCD (?)

Reported by: was Owned by: malb
Priority: major Milestone: sage-3.3
Component: commutative algebra Keywords:
Cc: Merged in:
Authors: Reviewers:
Report Upstream: Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description (last modified by was)

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 (f=@0xbfa40908, g=@0xbfa40904) at cf_gcd.cc:852
#8  0xb47660b8 in gcd_poly (f=@0xbfa40b4c, g=@0xbfa40b50) at cf_gcd.cc:538
#9  0xb4766ca3 in gcd (f=@0xbfa40b4c, g=@0xbfa40b50) 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

Attachments (1)

trac_4364.patch (4.5 KB) - added by malb 6 years ago.

Download all attachments as: .zip

Change History (6)

comment:1 Changed 6 years ago by mabshoff

This is actually an uncaught error in NTL:

zz_pContext: modulus too big

This then likely segfaults libSingular.

Cheers,

Michael

comment:2 Changed 6 years ago by was

  • Description modified (diff)

comment:3 Changed 6 years ago by malb

  • Summary changed from major bug in singular polynomial GCD (?) to [with patch, needs review] major bug in singular polynomial GCD (?)

Changed 6 years ago by malb

comment:4 Changed 6 years ago by was

  • Summary changed from [with patch, needs review] major bug in singular polynomial GCD (?) to [with patch, positive review] major bug in singular polynomial GCD (?)

comment:5 Changed 6 years ago by mabshoff

  • Milestone changed from sage-3.4.1 to sage-3.3
  • Resolution set to fixed
  • Status changed from new to closed

Merged in Sage 3.3.alpha3.

Cheers,

Michael

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