Macaulay2 » Documentation
Packages » Macaulay2Doc » commutative algebra » Gröbner bases » computing Groebner bases » gb » GroebnerBasis » mingens(GroebnerBasis)
next | previous | forward | backward | up | index | toc

# mingens(GroebnerBasis) -- (partially constructed) minimal generator matrix

- Function: mingens
- Usage:
    `mingens G`
- Inputs:
  - G, a Gröbner basis
- Optional inputs:
  - Strategy => ..., default value null, a Strategy option value
- Outputs:
  - whose columns form a (partially computed) minimal generating set, a matrix

## Description

Every GroebnerBasis computation in Macaulay2 computes a generator matrix, in the process of constructing the Gröbner basis. If the original ideal or module is homogeneous, then the columns of this matrix form a minimal set of generators. In the inhomogeneous case, the columns generate, and an attempt is made to keep the size of the generating set small.

If the Gröbner basis is only partially constructed, the returned result will be a partial answer. In the graded case this set can be extended to a minimal set of generators for the ideal or module.

    i1 : R = QQ[a..f]

    o1 = R

    o1 : PolynomialRing

    i2 : M = genericSymmetricMatrix(R,a,3)

    o2 = | a b c |
         | b d e |
         | c e f |

                 3      3
    o2 : Matrix R  <-- R

    i3 : I = minors(2,M)

                   2                                                  2
    o3 = ideal (- b  + a*d, - b*c + a*e, - c*d + b*e, - b*c + a*e, - c  + a*f, -
         ------------------------------------------------------------------------
                                                 2
         c*e + b*f, - c*d + b*e, - c*e + b*f, - e  + d*f)

    o3 : Ideal of R

    i4 : G = gb(I, PairLimit=>5)

    o4 = GroebnerBasis[status: PairLimit; all S-pairs handled up to degree 1]

    o4 : GroebnerBasis

    i5 : mingens G

    o5 = | e2-df ce-bf cd-be |

                 1      3
    o5 : Matrix R  <-- R

    i6 : mingens I

    o6 = | e2-df ce-bf cd-be c2-af bc-ae b2-ad |

                 1      6
    o6 : Matrix R  <-- R

## See also

- GroebnerBasis -- the class of all Gröbner bases
- gb -- compute a Gröbner basis
- genericSymmetricMatrix -- make a generic symmetric matrix
- minors -- ideal generated by minors

## Ways to use this method:

- mingens(GroebnerBasis) -- (partially constructed) minimal generator matrix

The source of this document is in /build/macaulay2-88fgJW/macaulay2-1.25.11+ds/M2/Macaulay2/packages/Macaulay2Doc/functions/mingens-doc.m2:138:0.