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Gröbner Walk


A Gröbner walk is an algorithm that converts a Gröbner basis of a polynomial ideal for one monomial order into a Gröbner basis of the same ideal for another monomial order (Collart et al. 1997). It follows a path through the polyhedral cones of the Gröbner fan. At a shared face, a basis conversion for the corresponding initial ideal is lifted to a basis for the original ideal. This replaces one large conversion by a succession of smaller conversions. The method applies to ideals of positive Krull dimension as well as zero Krull dimension (Tran 2000).

A usual weight path has the form

 w(t)=(1-t)u+tv,

where 0<=t<=1 and u and v represent the starting and target monomial orders for the ideal. For example, for I=<x^2-y^3>, the path w(t)=(1+2t,1) crosses 2w_1=3w_2 at t=1/4. The leading term changes from y^3 in the reduced Gröbner basis {y^3-x^2} to x^2 in {x^2-y^3}.

In practice, conversion can make it useful to compute a basis in an easier monomial order before converting to lexicographic order when solving polynomial equations (Trott 2006). This is a possible computational advantage, rather than a guarantee that every conversion is faster. The generic Gröbner walk replaces explicit numerical perturbations of the weight path by comparisons of vectors using monomial orders (Fukuda et al. 2007).


See also

Gröbner Basis, Gröbner Fan, Monomial Order

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References

Amrhein, B.; Gloor, O.; and Küchlin, W. "On the Walk." Theor. Comput. Sci. 187, 179-202, 1997. https://doi.org/10.1016/S0304-3975(97)00064-9.Collart, S.; Kalkbrener, M.; and Mall, D. "Converting Bases with the Gröbner Walk." J. Symb. Comput. 24, 465-469, 1997. https://doi.org/10.1006/jsco.1996.0145.Fukuda, K.; Jensen, A. N.; Lauritzen, N.; and Thomas, R. "The Generic Gröbner Walk." J. Symb. Comput. 42, 298-312, 2007. https://doi.org/10.1016/j.jsc.2006.09.004.Tran, Q.-N. "A Fast Algorithm for Gröbner Basis Conversion and Its Applications." J. Symb. Comput. 30, 451-467, 2000. https://doi.org/10.1006/jsco.1999.0416.Trott, M. "Polynomials in Equations." §1.2.2 in The Mathematica GuideBook for Symbolics. New York: Springer-Verlag, 2006. https://doi.org/10.1007/0-387-28815-5. https://www.mathematicaguidebooks.org/.

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Gröbner Walk

Cite this as:

Weisstein, Eric W. "Gröbner Walk." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/GroebnerWalk.html

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