Changeset 798f721 in git for kernel/gfan.cc

Timestamp:

Mar 31, 2009, 11:59:14 AM (15 years ago)

Author:

Martin Monerjan

Branches:

(u'spielwiese', '17f1d200f27c5bd38f5dfc6e8a0879242279d1d8')

Children:

2b7bb5d62530e14bffcd668b38aba478016be940

Parents:

19567be673a59b344557c01d516e211ba26b36c3

Message:

Started work on facet::flip(ideal I, facet *f) method to compute the groebner basis
on the other side of a flippable facet.
Is there a kernel implementation to check the rank of a matrix?


git-svn-id: file:///usr/local/Singular/svn/trunk@11608 2c84dea3-7e68-4137-9b89-c4e89433aadc

File:

• kernel/gfan.cc (modified) (5 diffs)

kernel/gfan.cc

@@ -2 +2 @@
 Compute the Groebner fan of an ideal
 $Author: monerjan $
-$Date: 2009-03-30 14:07:21 $
-$Header: /exports/cvsroot-2/cvsroot/kernel/gfan.cc,v 1.24 2009-03-30 14:07:21 monerjan Exp $
-$Id: gfan.cc,v 1.24 2009-03-30 14:07:21 monerjan Exp $
+$Date: 2009-03-31 09:59:14 $
+$Header: /exports/cvsroot-2/cvsroot/kernel/gfan.cc,v 1.25 2009-03-31 09:59:14 monerjan Exp $
+$Id: gfan.cc,v 1.25 2009-03-31 09:59:14 monerjan Exp $
 */
 
@@ -17 +17 @@
 #include "kmatrix.h"
 #include "fast_maps.h"  //Mapping of ideals
+#include "maps.h"
 #include "iostream.h"   //deprecated
 
@@ -76 +77 @@
                         fNormal->show();
                 }
+                
+                /** \brief The Groebner basis on the other side of a shared facet
+                *
+                * In order not to have to compute the flipped GB twice we store the basis we already get
+                * when identifying search facets. Thus in the next step of the reverse search we can 
+                * just copy the old cone and update the facet and the gcBasis
+                */
+                ideal flibGB;           //The Groebner Basis on the other side, computed via gcone::flip
                 
                 bool isFlippable;       //flippable facet? Want to have cone->isflippable.facet[i]
@@ -278 +287 @@
                 }//method getConeNormals(ideal I)       
                 
-                void flip();            //Compute "the other side"
+                /** \brief Compute the Groebner Basis on the other side of a shared facet 
+                *
+                * Implements algorithm 4.3.2 from Anders' thesis.
+                * As shown there it is not necessary to compute an interior point. The knowledge of the facet normal
+                * suffices. A term \f$ x^\gamma \f$ of \f$ g \f$ is in \f$  in_\omega(g) \f$ iff \f$ \gamma - leadexp(g)\f$
+                * is parallel to \f$ leadexp(g) \f$
+                * Checking for parallelity is done by computing the rank of the matrix consisting of the vectors in question.
+                * Another possibility would be to compute an interior point of the facet and taking all terms having the same
+                * weight with respect to this interior point.
+                *\param ideal, facet
+                */
+                void flip(ideal I, facet *f)            //Compute "the other side"
+                {
+                        /*1st step: Compute the initial ideal*/
+                        map mapping;
+                        idhdl h;
+                        ideal image;
+                        mapping=IDMAP(h);
+                        image=idInit(1,1);
+                        image=maGetPreimage(currRing,mapping,image);                    
+                }
                                 
                 /** \brief Compute a Groebner Basis
@@ -354 +383 @@
         gcAct->getGB(inputIdeal);
         gcAct->getConeNormals(gcAct->gcBasis);  //hopefully compute the normals
+        
         /*Now it is time to compute the search facets, respectively start the reverse search.
-        But since we are in the root all facets should be search facets.
+        But since we are in the root all facets should be search facets. IS THIS TRUE?
         MIND: AS OF NOW, THE LIST OF FACETS IS NOT PURGED OF NON-FLIPPAPLE FACETS
         */