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Dec 30, 2009, 12:37:19 AM12/30/09

to sage-support

Here is the code:

----------------------------------------------------------------------

| Sage Version 4.2.1, Release Date: 2009-11-14 |

| Type notebook() for the GUI, and license() for information. |

----------------------------------------------------------------------

sage: q = 3

sage: F.<a> = FiniteField(q)

sage: P.<T> = PolynomialRing(F)

sage: PP.<z> = PolynomialRing(P)

sage: time (z + 1)^81

CPU times: user 0.17 s, sys: 0.00 s, total: 0.17 s

Wall time: 0.17 s

z^81 + 1

sage: time (2*z + 1)^81

CPU times: user 0.17 s, sys: 0.00 s, total: 0.17 s

Wall time: 0.17 s

2*z^81 + 1

sage: time (2*T*z + 1)^81

CPU times: user 0.17 s, sys: 0.00 s, total: 0.18 s

Wall time: 0.18 s

2*T^81*z^81 + 1

sage: time (z^3 + T*z)^81

CPU times: user 1.00 s, sys: 0.00 s, total: 1.00 s

Wall time: 1.00 s

z^243 + T^81*z^81

sage: time (z^3 + T*z)^(81*3)

CPU times: user 6.49 s, sys: 0.03 s, total: 6.51 s

Wall time: 6.51 s

z^729 + T^243*z^243

sage: time (z^3 + T*z)^(3^6)

CPU times: user 71.92 s, sys: 0.06 s, total: 71.98 s

Wall time: 72.38 s

z^2187 + T^729*z^729

sage: time (z^3 + T*z)^(3^7)

^CException KeyboardInterrupt: KeyboardInterrupt() in

'sage.rings.polynomial.polynomial_zmod_flint.get_cparent' ignored

^C

------------------------------------------------------------

Unhandled SIGFPE: An unhandled floating point exception occured in

SAGE.

This probably occured because a *compiled* component

of SAGE has a bug in it (typically accessing invalid memory)

or is not properly wrapped with _sig_on, _sig_off.

You might want to run SAGE under gdb with 'sage -gdb' to debug this.

SAGE will now terminate (sorry).

------------------------------------------------------------

Dec 30, 2009, 6:07:42 AM12/30/09

to sage-support

Hi Alex!

On 30 Dez., 06:37, Alex P <alexvpetr...@gmail.com> wrote:

> Here is the code:

>

> ----------------------------------------------------------------------

> | Sage Version 4.2.1, Release Date: 2009-11-14 |

> | Type notebook() for the GUI, and license() for information. |

> ----------------------------------------------------------------------

> sage: q = 3

> sage: F.<a> = FiniteField(q)

> sage: P.<T> = PolynomialRing(F)

> sage: PP.<z> = PolynomialRing(P)

[...]

> sage: time (z^3 + T*z)^(3^7)

> ^CException KeyboardInterrupt: KeyboardInterrupt() in

> 'sage.rings.polynomial.polynomial_zmod_flint.get_cparent' ignored

> ^C

>

> ------------------------------------------------------------

> Unhandled SIGFPE: An unhandled floating point exception occured in

> SAGE.

> This probably occured because a *compiled* component

> of SAGE has a bug in it (typically accessing invalid memory)

> or is not properly wrapped with _sig_on, _sig_off.

> You might want to run SAGE under gdb with 'sage -gdb' to debug this.

> SAGE will now terminate (sorry).

> ------------------------------------------------------------

That's certainly a bug. I created a ticket for it:

http://trac.sagemath.org/sage_trac/ticket/7794

As it is defined, PP is a polynomial ring in one variable over a

polynomial ring in one variable.

Would it be a good thing to automatically convert this into a

polynomial ring with *two* variables? What do people think? If you

have an opinion about it, you might also comment on

http://trac.sagemath.org/sage_trac/ticket/7580, where I do those

conversions for Infinite Polynomial Rings.

Note that Alex' example reveals another bug, this time in

MPolynomialRing_libsingular:

sage: F.<a> = FiniteField(3)

sage: P.<T,z> = PolynomialRing(F)

sage: type(P)

<type

'sage.rings.polynomial.multi_polynomial_libsingular.MPolynomialRing_libsingular'>

sage: (z^3 + T*z)^(81*3) # immediate answer

z^729 + T^243*z^243

sage: (z^3 + T*z)^(2^20)

/home/king/SAGE/sage-4.3/local/bin/sage-sage: line 206: 20889

Segmentation fault sage-ipython "$@" -i

This was without Ctrl-C.

Certainly there should be no segfault. If anything, there should an

error be raised.

I made this another ticket, http://trac.sagemath.org/sage_trac/ticket/7795

Thanks for the report!

Simon

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