Hello Markus,
we have massively rewritten and refactor the new Letterplace in recent years. I doubt, that the ordering you use was properly supported in older versions. The behavior as above, i.e. saying "degree bound is ..., but at least ... is needed" appears only with monomal orderings, which are not compatible with the length of the words (like usual degree left/right lex).
My recommendations:
1) Have a close look at
https://www.singular.uni-kl.de/Manual/l ... ng_801.htm for the exact description of the supported orderings.
We use Singular classical lp, dp etc names only as placeholders,
they encode the specific orderings as described in the manual.
No other system except us can do non-length-compatible orderings properly, so the message (and the behavior) as above is a part of the price to pay.
2) keep activated
Code:
option(redTail);
3) have a look at how the polynomials in your input are ordered (Singular automatically orders them according to the monomial ordering) - with your ordering the polynomials look as
Code:
I[1]=z-y*x+x*y
I[2]=y*y*y+x*y*z-x*x*x*x*x*x
so any operation on y's in the second will increase the degree of the trailing x's and nothing can be done here.
4) Instead, try other ordering and also other order of variables in addition:
Code:
...
ring r = 0,(x,y,z),(a(1,2,3),dp);
...
I;
>I[1]=-y*x+x*y+z
>I[2]=-x*x*x*x*x*x+y*y*y+x*y*z
twostd(I); //gives 40 elements
Also,
Code:
...
r = 0,(z,y,x),(a(3,2,1),dp);
...
resulted in the finite answer.
All the best,
Viktor Levandovskyy
mwageringel wrote:
Hi everyone,
when trying to compute Gröbner bases of ideals in letterplace rings with weighted orderings, the computation always fails with an error:
Code:
LIB "freegb.lib";
ring r = 0,(x,y,z),wp(1,2,3);
def R = freeAlgebra(r, 22);
setring R;
ideal I = x*y+z-y*x, x*y*z-x^6+y^3;
ideal J = twostd(I);
// ? degree bound of Letterplace ring is 22, but at least 23 is needed for this multiplication
As far as I understand, the computation should not go beyond the degree bound here, but return the result up to the degree bound instead. Any help in resolving this problem would be appreciated.
This came up in Sage trac #25993. Sage wraps an older version of Singular's letterplace functionality which does not exist anymore in the current version of Singular, and I have difficulties making the above example work with the current version of Singular.
Thank you,
Markus