Singular

The example given above does not lead to an error.
But the development continues: now the new primdec.lib requires also
the new version of ring.lib for changeordTo.

Is there now a bug in primdec.lib with something such as changeordTo?
Try the example for given integralBasis to see if you get the same error I did.

True, the problem was that the simplification was using larger and larger maps
which led to huge computation times.
A re-ordering of the variables to consider for simplifications helps
(independend of characateristic).
Get a new primdec.lib from
[url]
https://github.com/Singular/Sources/blob/spielwiese/Singular/LIB/primdec.lib
[/url]

Well I tried ctrl-c,
then ctrl-c ctrl-c gives me only the choices
(a)bort current command, (q)uit, (r)estart Singular or (c)ontinue?

Then I tried this in Singular instead of ESingular to finally get the print backtrace(b) option.

But this seems to be characteristic independent.

ring r=0,(y,x),dp;
ideal i=y31+y12x17-2y6x27+x37;
list nor=normal(i);nor;

seems to hang at the same command

iwork=phi(iwork)

To find out where it is hanging: press ctrl-c and you will be asked
[code]
// ** Interrupt at cmd:`$INVALID$` in line:' iwork=phi(iwork);'
abort after this command(a), abort immediately(r), print backtrace(b), continue(c) or quit Singular(q) ?
[/code]
Answering with b presents the backtrace.
The problem here is that the routine simplifyIdeal from primdec.lib
does not work in char 2.
To fix it, substitute simplifyIdeal by
[code]
static proc simplifyIdeal(ideal i)
{
ASSUME(1, hasFieldCoefficient(basering) );
ASSUME(1, not isQuotientRing(basering) ) ;
ASSUME(1, hasGlobalOrdering(basering) ) ;

def r=basering;

int j,k;
map phi;
poly p;

ideal iwork=i;
ideal imap1=maxideal(1);
ideal imap2=maxideal(1);

if (char(r)!=2)
{
for(j=1;j<=nvars(basering);j++)
{
for(k=1;k<=ncols(i);k++)
{
if(deg(iwork[k]/var(j))==0)
{
p=-1/leadcoef(iwork[k]/var(j))*iwork[k];
imap1[j]=p+2*var(j);
phi=r,imap1;
iwork=phi(iwork);
iwork=subst(iwork,var(j),0);
iwork[k]=var(j);
imap1=maxideal(1);
imap2[j]=-p;
break;
}
}
}
}
return(iwork,imap2);
}
[/code]

LIB "normal.lib";
ring r=2,(y,x),wp(37,31);
ideal i=y31+y12x17+x37;
list nor=normal(i);nor;

has been running for maybe 200 hours (3.7 GB),
on this problem that can almost be done by hand.
It takes my QthPower algorithm maybe 9 seconds in M2.
How can I rerun this and trace what is taking so much time?
[I assume it is a kernel computation, though it could be a GB computation.]