On Fri, Oct 30, 2009 at 9:17 AM, Martin Albrecht
<m...@informatik.uni-bremen.de> wrote:
>
> Hi,
>
> this e-mail by Frank on libsingular-devel leads to the following question: do
> we want to set the random seed of Singular by default at Sage/Singular start-
> up? From what I gather from randstate.pyx we don't do that even for NTL.
>
> I would vote for setting the random seed to all 'subsystems' by default by
> Sage's randstate whenever these 'subsystems' are initialised.
+1
I agree with you.
Thank you for following up with this Martin. I very much want
a Riemann-Roch space basis computation to work in Sage!
>
> Cheers,
> Martin
>
>
> ---------- Forwarded Message ----------
> Subject: [libsingular-devel] Riemann-Roch computations in the Brill-Noether
> routines
> Date: Friday 30 October 2009
> From: Frank Seelisch <seeli...@mathematik.uni-kl.de>
> To: libsingular-de...@googlegroups.com
>
>
>
> Hi everybody,
>
> this deals with the problem in SINGULAR's "brnoeth.lib" you have
> reported some time ago; see the below snippet from a mail from William
> Stein to David Joyner.
>
> As far as we understand correctly, the problem seems to be that SAGE
> wants to have stable results when calling this piece of SINGULAR code?
> But "brnoeth.lib" uses randomly chosen points; so there is some kind of
> indeterminacy in there. (I hope that is what your problem really is about.)
>
> We suggest to use a random seed, e.g., to pass on the random seed that
> you use in SAGE to SINGULAR. This can either be done via the SINGULAR
> command
> system("random", mySeedAsAnInt);
> or directly in C by assigning the SINGULAR-internal variable
> siseed = mySeedAsAnInt;
>
> When providing the random seed this way, SINGULAR will procude the same
> sequence of random numbers on all platforms.
>
> I hope this resolves your problem!
>
> Regards,
> Frank
>
> =========================================================================
>
> Thanks for the Singular-ish version via evals. I wrote the following
> pure-Singular version, which you can put in a file "rrbasis.lib" and
> load into singular with
>
> < "rrbasis.lib";
>
> (or you can just paste it in):
>
> LIB "brnoeth.lib";
> kill X, X2,R,G,LG;
> ring R=11,(x,y),lp;
> list X = Adj_div(x^7 + y^7 - 1);
> def X2 = NSplaces(1,X);
> def X3 = extcurve(1,X2);
> def RR =X3[1][5];
> setring RR;
> print("POINTS");
> print(POINTS);
> /* PROBLEM -- this G defined a different divisor every time the
> this code is run!!! Need a way to compute G from a list of points */
> intvec G=(10,-1,0,0,9,0,0,0,0,0,0,0,0,0);
> def R = X2[1][2];
> setring R;
> list LG = BrillNoether(G,X2);
> print(LG);
>
> It gives random answers since the G has a different meaning every time
> the function is run.
>
>
>
>
> --
> name: Martin Albrecht
> _pgp: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8EF0DC99
> _otr: 47F43D1A 5D68C36F 468BAEBA 640E8856 D7951CCF
> _www: http://www.informatik.uni-bremen.de/~malb
> _jab: martinralbre...@jabber.ccc.de
>
>
> >
>
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