On Fri, Jul 17, 2009 at 9:13 AM, David Joyner<wdjoy...@gmail.com> wrote:
> On Thu, Jul 16, 2009 at 5:19 AM, Martin
> Albrecht<m...@informatik.uni-bremen.de> wrote:
>>
>> On Thursday 16 July 2009, David Joyner wrote:
>>> On Wed, Jul 15, 2009 at 7:31 PM, Kiran Kedlaya<ksk...@gmail.com> wrote:
>>> > One pet complaint that you might bring up with the Singular team: I
>>>
>>> Speaking of pet complaints, can you ask if they will at some point fix
>>> the bugs in the Riemann-Roch computations in the Brill-Noether routines?
>>> To be honest, I have not checked them recently but as of a few years
>>> ago they were unreliable. The Sage module sage/coding/ag_codes.py
>>> (from 2006) is waiting for some Singular routines to be fixed I think.
>>> I do not know of an open source correct and functional implementation of
>>> any general algorithm to compute a basis for a Riemann-Roch space
>>> of a curve over a finite field.
>>
>> Hi David,
>>
>> this is now
>>
>> http://www.singular.uni-kl.de:8002/trac/ticket/153
>>
>> Would you mind giving concrete examples there?
>
>
> Thanks for creating it.
>
> I've looked through my emails from 2006 and cannot find a trace of the
> examples I had then. I vaguely remember a certain example which would
I just found this email from William Stein written in early 2006:
Date: Fri, 27 Jan 2006 15:05:20 -0500 216 of 280
From: William Stein <wst...@ucsd.edu>
Subject: Re: more riemann_roch_basis woes
To: David Joyner <w...@usna.edu>
David,
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.
William
> be getting different answers on different runs when trying to compute
> Riemann-Roch spaces. William might remember better since his memory
> is about a million times better than mine.
>
> It is also possible that the bug submission form back then was via some
> sort of web based forum, http://www.singular.uni-kl.de/request_form.html,
> in which case they might have a copy of the email
> on their website.
>
>
>>
>> Cheers,
>> Martin
>>
>> --
>> 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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