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       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


              /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.

Gfan Groebner fan package   VersionMay32008                            GFAN(1)