source: git/kernel/gfan.cc @ 198a339

spielwiese
Last change on this file since 198a339 was 198a339, checked in by Martin Monerjan, 15 years ago
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1/*
2Compute the Groebner fan of an ideal
3Author: $Author: monerjan $
4Date: $Date: 2009-02-10 17:04:17 $
5Header: $Header: /exports/cvsroot-2/cvsroot/kernel/gfan.cc,v 1.9 2009-02-10 17:04:17 monerjan Exp $
6Id: $Id: gfan.cc,v 1.9 2009-02-10 17:04:17 monerjan Exp $
7*/
8
9#include "mod2.h"
10#include "kstd1.h"
11#include "intvec.h"
12#include "polys.h"
13#include "ideals.h"
14#include "kmatrix.h"
15
16#ifndef gfan_DEBUG
17#define gfan_DEBUG
18#endif
19
20ideal getGB(ideal inputIdeal)
21{
22        #ifdef gfan_DEBUG
23        printf("Now in getGB\n");
24        #endif
25
26        ideal gb;
27        gb=kStd(inputIdeal,NULL,testHomog,NULL); //Possible to call without testHomog/isHomog?
28        idSkipZeroes(gb); //Get rid of zero entries
29
30        return gb;
31}
32
33/****** getWallIneq computes the inequalities ***/
34/*INPUT_TYPE: ideal                             */
35/*RETURN_TYPE: matrix                           */
36/************************************************/
37void getWallIneq(ideal I)
38{
39        #ifdef gfan_DEBUG
40        printf("*** Computing Inequalities... ***\n");
41        #endif
42
43        //All variables go here - except ineq matrix
44        int lengthGB=IDELEMS(I);        // # of polys in the groebner basis
45        int pCompCount;                 // # of terms in a poly
46        poly aktpoly;
47        int numvar = pVariables;        // # of variables in a polynomial (or ring?)
48        int leadexp[numvar];            // dirty hack of exp.vects
49        int aktexp[numvar];
50        int cols,rows;                  // will contain the dimensions of the ineq matrix
51        // End of var declaration
52
53        printf("The Groebner basis has %i elements\n",lengthGB);
54        printf("The current ring has %i variables\n",numvar);
55        cols = numvar;
56
57        //Compute the # inequalities i.e. rows of the matrix
58        rows=0; //Initialization
59        for (int ii=0;ii<IDELEMS(I);ii++)
60        {
61                aktpoly=(poly)I->m[ii];
62                rows=rows+pLength(aktpoly)-1;
63        }
64        printf("rows=%i\n",rows);
65        printf("Will create a %i x %i - matrix to store inequalities\n",rows,cols);
66        int ineq[rows][cols];   // array of int vs matrix vs KMatrix ??? What's to use?
67        int aktmatrixrow=0;     // needed to store the diffs of the expvects in the rows of ineq
68
69        // We loop through each g\in GB
70        for (int i=0; i<IDELEMS(I); i++)
71        {
72                aktpoly=(poly)I->m[i];          //get aktpoly as i-th component of I
73                pCompCount=pLength(aktpoly);    //How many terms does aktpoly consist of?
74                printf("Poly No. %i has %i components\n",i,pCompCount);
75
76                int *v=(int *)omAlloc((numvar+1)*sizeof(int));
77                pGetExpV(aktpoly,v);    //find the exp.vect in v[1],...,v[n], use pNext(p)
78               
79                //Store leadexp for aktpoly
80                for (int kk=0;kk<numvar;kk++)
81                {
82                        leadexp[kk]=v[kk+1];
83                        printf("Leadexpcomp=%i\n",leadexp[kk]);
84                        //Since we need to know the difference of leadexp with the other expvects we do nothing here
85                        //but compute the diff below
86                }
87
88               
89                while (pNext(aktpoly)!=NULL) //move to next term until NULL
90                {
91                        aktpoly=pNext(aktpoly);
92                        pSetm(aktpoly);         //doesn't seem to help anything
93                        pGetExpV(aktpoly,v);
94                        for (int kk=0;kk<numvar;kk++)
95                        {
96//The ordering somehow gets lost here but this is acceptable, since we are only interested in the inequalities
97                                aktexp[kk]=v[kk+1];
98                                printf("aktexpcomp=%i\n",aktexp[kk]);
99                                ineq[aktmatrixrow][kk]=leadexp[kk]-aktexp[kk];  //dito
100                        }
101                        aktmatrixrow=aktmatrixrow+1;
102                }//while
103        } //for
104        #ifdef gfan_DEBUG
105        printf("Inequalitiy matrix\n");
106        for (int i=0;i<rows;i++)
107        {
108                for (int j=0;j<cols;j++)
109                {
110                        printf("%i ",ineq[i][j]);
111                }
112                printf("\n");
113        }
114        #endif
115        //res=(ideal)aktpoly;
116        //return res;
117}
118
119ideal gfan(ideal inputIdeal)
120{
121        #ifdef gfan_DEBUG
122        printf("Now in subroutine gfan\n");
123        #endif
124        ideal res;
125        matrix ineq; //Matrix containing the boundary inequalities
126
127        res=getGB(inputIdeal);
128        getWallIneq(res);
129        return res;
130}
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