This is probably a late comment,
but genus() in Singular is also known for containing bugs,
see tickets
http://www.singular.uni-kl.de:8002/trac/ticket/259,
http://www.singular.uni-kl.de:8002/trac/ticket/469
Jack
Am Dienstag, 23. November 2010 11:56:20 UTC+1 schrieb Martin Albrecht:
>
> On Tuesday 23 November 2010, VictorMiller wrote:
> > Thanks! Then perhaps Sage should raise an exception when it gets back
> > genus -1 from singular.
>
> Here's what Hannes Schönemann from the Singular team replied to me when I
> reported this on [libsingular-devel]:
>
> """
> Singular uses (currently) 32bit int on all platforms.
> Here our overflow detection represents -1 as a result of a subtraction
> as 4294967295.
> Fix (in Singular/iparith.cc, routine jjMINUS_I):
> --- iparith.cc (Revision 13661)
> +++ iparith.cc (Arbeitskopie)
> @@ -697,14 +697,18 @@
> }
> static BOOLEAN jjMINUS_I(leftv res, leftv u, leftv v)
> {
> - unsigned int a=(unsigned int)(unsigned long)u->Data();
> - unsigned int b=(unsigned int)(unsigned long)v->Data();
> + void *ap=u->Data(); void *bp=v->Data();
> + int aa=(int)(long)ap;
> + int bb=(int)(long)bp;
> + int cc=aa-bb;
> + unsigned int a=(unsigned int)(unsigned long)ap;
> + unsigned int b=(unsigned int)(unsigned long)bp;
> unsigned int c=a-b;
> if (((Sy_bit(31)&a)!=(Sy_bit(31)&b))&&((Sy_bit(31)&a)!=(Sy_bit(31)&c)))
> {
> WarnS("int overflow(-), result may be wrong");
> }
> - res->data = (char *)((long)c);
> + res->data = (char *)((long)cc);
> return jjPLUSMINUS_Gen(res,u,v);
> }
> """
>
> It seems with the new patch the overflow would at least be detected? Can
> you
> give it a try?
>
> 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://martinralbrecht.wordpress.com/
> _jab: martinr...@jabber.ccc.de <javascript:>
>
>
--
You received this message because you are subscribed to the Google Groups
"sage-support" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sage-support+unsubscr...@googlegroups.com.
To post to this group, send email to sage-support@googlegroups.com.
Visit this group at http://groups.google.com/group/sage-support.
For more options, visit https://groups.google.com/groups/opt_out.
