Provided by: gfan_0.3dfsg-1.1_amd64 bug


       Gfan - program for computing with Groebner fans


       This is a program for computing all reduced Groebner bases of a polynomial ideal. It takes
       a generating set for the ideal as input. By default the enumeration is done by  an  almost
       memoryless  reverse  search.  If  the ideal is symmetric the symmetry option is useful and
       enumeration will be done up to symmetry using a breadth first search. The program needs  a
       starting  Groebner basis to do its computations. If the -g option is not specified it will
       compute one using Buchberger's algorithm.


              /usr/bin/gfan [options]


       -g     Tells the program that the input is already a Groebner basis (with the initial term
              of  each  polynomial  being the first ones listed). Use this option if it takes too
              much time to compute the starting (standard degree  lexicographic)  Groebner  basis
              and the input is already a Groebner basis.

               Tells  the  program  to  read in generators for a group of symmetries (subgroup of
              $S_n$) after having read in the ideal. The program  checks  that  the  ideal  stays
              fixed  when  permuting  the  variables  with  respect to elements in the group. The
              program uses breadth first search to compute the set of reduced Groebner  bases  up
              to symmetry with respect to the specified subgroup.

       -e     Echo. Output the generators for the symmetry group.

              Only  do breadth first search on cones with their interior intersecting a specified
              subspace. The subspace is given by a list of hyperplane normals at the end  of  the
              input.  The  intersection  of the hyperplanes is the subspace being specified. Note
              that the set of Groebner cones intersecting the subspace could be disconnected  and
              that only one connected component is computed. Works only together with --symmetry.

              When  using  --symmetry  this option will disable the check that the group read off
              from the input actually is a symmetry group with respect to the input ideal.