Error when taking radical of an ideal in characteristic 2

[KSchwede]

I'm not sure if the problem is not enough units and for some reason
things break, or what.

I'm using Macaulay2 1.3.1 (although I also tried this on a machine I
have still running version 1.2)

I'm looking at the following ring

R := ZZ/2[x,y,z,u,v]

and the following ideal

I := ideal(z^2 + x*y*z + x^2*y + x*y^2, u^2 + x*u + x, v^2 + y*v + y)

when I take

"radical I"

I get

"i3 : radical I
convertFacCF2NTLGF2X: coefficient not immidiate! : a_7^2*a_6

Process M2 exited abnormally with code 1"

Does anyone have any thoughts or suggestions? (it also looks like
there's a misspelling in the error message as well).

Karl

[Douglas Leonard]

If you're desperate for an answer in char 2 (where the bug seems to be),
try:

R=ZZ/2[x,y,z]
S=R[u,v]
I=ideal(z^2+x*y*z+x^2*y+x*y^2,u^2+x*u+x,v^2+y*v+y)
G=gens gb I
radical(I)

If you're just reporting this bug for reporting purposes, I'm not the
one to be answering.

Doug

>>> KSchwede <ksch...@gmail.com> 03/12/10 11:52 AM >>>

R := ZZ/2[x,y,z,u,v]

and the following ideal

when I take

"radical I"

I get

Karl

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[Dan Grayson]

The error message comes from Singular Libfac, the library from
Singular written by Michael Messollen that computes characteristic
series. It might be a bug in that library, since if I try replacing 2
by 101, there is no problem like this. So, I've added a bug report in
Macaulay2/bugs/dan on my development branch. For now, if the work-
around found by Doug Leonard does it for you, I'll leave the bug
report at lowish priority.

[KSchwede]

Thanks for the help all. We did have another way to think about it,
but it is nice to check things.

It's not surprising to me that this ring is much weirder in
characteristic 2 than in char 101 though (it has some strange
ramification going on with other rings), perhaps the ramification is
too wild :-)

There isn't any great priority on this from my point of view.