On Oct 23, 1:23 pm, Jaap Spies <[EMAIL PROTECTED]> wrote:
> Last year after less than two days I could finish
> a calculation and write to William:
>
>
>
> > -------- Original Message --------
> > Subject: dance(10)
> > Date: Thu, 09 Mar 2006 00:10:19 +0100
> > From: Jaap Spies <[EMAIL PROTECTED]>
> > To: William Stein <[EMAIL PROTECTED]>
>
> > William,
>
> > Some time ago, dance(10) finished:
>
> > sage: time dance(10)
> > [1, 90, 3405, 71040, 901152, 7225344, 36862960, 117340800, 221170456,
> > 220658800, 87396728]
> > h^10 - 35*h^9 + 675*h^8 - 8610*h^7 + 78435*h^6 - 523467*h^5 +
> > 2562525*h^4 - 9008160*h^3 + 21623220*h^2 - 31840760*h + 21750840
> > CPU times: user 141822.70 s, sys: 18387.03 s, total: 160209.74 s
> > Wall time: 165997.13
>
> > Jaap
>
> To day I got with sage-2.8.8.1:
>
> > sage: time dance(10)
>
> > ------------------------------------------------------------
> > Unhandled SIGSEGV: A segmentation fault 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).
> > ------------------------------------------------------------
>
> With sage -gdb:
>
> > sage: time dance(9)
> > h^9 - 27*h^8 + 414*h^7 - 4158*h^6 + 29421*h^5 - 148743*h^4 + 530796*h^3 -
> > 1276992*h^2 + 1866384*h - 1255608
> > CPU times: user 1786.82 s, sys: 23.05 s, total: 1809.87 s
> > Wall time: 1831.52
>
> > sage: time dance(10)
>
> > Program received signal SIGSEGV, Segmentation fault.
> > [Switching to Thread -1208523072 (LWP 30162)]
> > 0x0064d473 in strlen () from /lib/libc.so.6
> > (gdb)
>
> The program (see below) uses methods from sage.matrix.matrix2.pyx
>
> Jaap
Hello Jaap,
I am looking into this, but I am pressed for time until Thursday, so
don't expect any solution before that. It will take forever to
valgrind this anyway. If you still have that gdb session it would be
great to get a backtrace. I did run the code with smaller parameters,
i.e. dance(4) and dance(5), under valgrind and nothing popped up
there. So I am suspecting that the code might smash the stack with
large parameters, but that ought to be taken with a grain of salt
until I get a backtrace and some valgrind output
Cheers,
Michael
>
> ##########################################################################
> # Copyright (C) 2006 Jaap Spies, [EMAIL PROTECTED]
> #
> # Distributed under the terms of the GNU General Public License (GPL):
> #
> # http://www.gnu.org/licenses/
> ##########################################################################
>
> """
> Usage from sage
>
> sage: attach 'dancing.sage'
>
> sage: dance(4)
> h^4 - 2*h^3 + 9*h^2 - 8*h + 6
>
> """
>
> # use variable 'h' in the polynomial ring over the rationals
>
> h = QQ['h'].gen()
>
> def dance(m):
> """
> Generates the polynomial solutions of the Dancing School Problem
> Based on a modification of theorem 7.2.1 from Brualdi and Ryser,
> Combinatorial Matrix Theory.
>
> See NAW 5/7 nr. 4 december 2006 p. 285
>
> INPUT: integer m
>
> OUTPUT: polynomial in 'h'
>
> EXAMPLE:
> sage: dance(4)
> h^4 - 2*h^3 + 9*h^2 - 8*h + 6
>
> AUTHOR: Jaap Spies (2006)
> """
> n = 2*m-2
> M = MatrixSpace(ZZ, m, n)
> A = M([0 for i in range(m*n)])
> for i in range(m):
> for j in range(n):
> if i > j or j > i + n - m:
> A[i,j] = 1
> rv = A.rook_vector()
> # print rv
> s = sum([(-1)^k*rv[k]*falling_factorial(m+h-k, m-k) for k in range(m+1)])
> print s
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