source: git/Singular/maps.cc @ e20214

/****************************************
*  Computer Algebra System SINGULAR     *
****************************************/
/* $Id: maps.cc,v 1.15 1999-07-13 15:06:52 Singular Exp $ */
/*
* ABSTRACT - the mapping of polynomials to other rings
*/

#include "mod2.h"
#include "tok.h"
#include "febase.h"
#include "polys.h"
#include "numbers.h"
#include "ipid.h"
#include "ring.h"
#include "ideals.h"
#include "matpol.h"
#include "mmemory.h"
#include "kstd1.h"
#include "lists.h"
#include "longalg.h"
#include "maps.h"

#define MAX_MAP_DEG 128

/*2
* copy a map
*/
map maCopy(map theMap)
{
  int i;
  map m=(map)idInit(IDELEMS(theMap),0);
  for (i=IDELEMS(theMap)-1; i>=0; i--)
      m->m[i] = pCopy(theMap->m[i]);
  m->preimage=mstrdup(theMap->preimage);
  return m;
}


/*2
* return the image of var(v)^pExp, where var(v) maps to p
*/
poly maEvalVariable(poly p, int v,int pExp,matrix s)
{
  if (pExp==1)
    return pCopy(p);

  poly res;

  if((s!=NULL)&&(pExp<MAX_MAP_DEG))
  {
    int j=2;
    poly p0=p;
    // find starting point
    if(MATELEM(s,v,1)==NULL)
    {
      MATELEM(s,v,1)=pCopy(p/*theMap->m[v-1]*/);
    }
    else
    {
      while((j<=pExp)&&(MATELEM(s,v,j)!=NULL))
      {
        j++;
      }
      p0=MATELEM(s,v,j-1);
    }
    // multiply
    for(;j<=pExp;j++)
    {
      p0=MATELEM(s,v,j)=pMult(pCopy(p0/*MATELEM(s,v,j-1)*/),
                              pCopy(p/*theMap->m[v-1]*/));
    }
    res=pCopy(p0/*MATELEM(s,v,pExp)*/);
  }
  else //if ((p->next!=NULL)&&(p->next->next==NULL))
  {
    res=pPower(pCopy(p),pExp);
  }
  return res;
}

poly maEvalMonom(map theMap, poly p,ring preimage_r,matrix s)
{
    poly q=pOne();
    pSetCoeff(q,nMap(pGetCoeff(p)));

    int i;
    for(i=preimage_r->N; i>0; i--)
    {
      int pExp=pRingGetExp(preimage_r, p,i);
      if (pExp != 0)
      {
        if (theMap->m[i-1]!=NULL)
        {
          poly p1=theMap->m[i-1];
          poly pp=maEvalVariable(p1,i,pExp,s);
          q = pMult(q,pp);
        }
        else
        {
          pDelete(&q);
          break;
        }
      }
    }
    int modulComp = pRingGetComp(preimage_r, p);
    if (q!=NULL) pSetCompP(q,modulComp);
  return q;
}

poly maEval(map theMap, poly p,ring preimage_r,matrix s)
{
  poly result = NULL;
  int i;

//  for(i=1; i<=preimage_r->N; i++)
//  {
//    pTest(theMap->m[i-1]);
//  }
//  while (p!=NULL)
//  {
//    poly q=maEvalMonom(theMap,p,preimage_r,s);
//    result = pAdd(result,q);
//    pIter(p);
//  }
  if (p!=NULL)
  {
    int l = pLength(p)-1;
    poly* monoms;
    if (l>0)
    {
      monoms = (poly*) Alloc(l*sizeof(poly));

      for (i=0; i<l; i++)
      {
        monoms[i]=maEvalMonom(theMap,p,preimage_r,s);
        pIter(p);
      }
    }
    result=maEvalMonom(theMap,p,preimage_r,s);
    if (l>0)
    {
      for(i = l-1; i>=0; i--)
      {
        result=pAdd(result, monoms[i]);
      }
      Free((ADDRESS)monoms,l*sizeof(poly));
    }
    if (currRing->minpoly!=NULL) result=pMult(result,pOne());
  }
  pTest(result);
  return result;
}

/*2
*shifts the variables between minvar and maxvar of p  \in p_ring to the
*first maxvar-minvar+1 variables in the actual ring
*be carefull: there is no range check for the variables of p
*/
static poly pChangeSizeOfPoly(ring p_ring, poly p,int minvar,int maxvar)
{
  int i;
  poly result = NULL,resultWorkP;
  number n;

  if (p==NULL) return result;
  else result = pInit();
  resultWorkP = result;
  while (p!=NULL)
  {
    for (i=minvar;i<=maxvar;i++)
      pSetExp(resultWorkP,i-minvar+1,pRingGetExp(p_ring,p,i));
    pSetComp(resultWorkP,pRingGetComp(p_ring,p));
    n=nCopy(pGetCoeff(p));
    pSetCoeff(resultWorkP,n);
    pSetm(resultWorkP);
    pIter(p);
    if (p!=NULL)
    {
      pNext(resultWorkP) = pInit();
      pIter(resultWorkP);
    }
  }
  return result;
}


/*2
*returns the preimage of id under theMap,
*if id is empty or zero the kernel is computed
*/
ideal maGetPreimage(ring theImageRing, map theMap, ideal id)
{
  int i,j,sizeofpoly;
  int ordersize;
  poly p,pp,q;
  ideal temp1;
  ideal temp2;
  short  ** wv;
#define blockmax 5
  int orders[blockmax],block0[blockmax], block1[blockmax];
  int imagepvariables = theImageRing->N;
  ring sourcering = currRing;
  int N = pVariables+imagepvariables;
  sip_sring tmpR;

  memset(block0, 0,sizeof(block0));
  memset(block1, 0,sizeof(block1));
  memset(orders, 0,sizeof(orders));
  if (theImageRing->OrdSgn == 1) orders[0] = ringorder_dp;
  else orders[0] = ringorder_ls;
  block1[0] = imagepvariables;
  block0[0] = 1;
  /*
  *if (sourcering->order[blockmax])
  *{
  *  if (sourcering->OrdSgn == 1) orders[1] = ringorder_dp;
  *  else orders[1] = ringorder_ls;
  *  block1[1] = N;
  *}
  *else
  */
  {
    i=0;
    while(sourcering->order[i])
    {
      orders[i+1] = sourcering->order[i];
      block0[i+1] = sourcering->block0[i]+imagepvariables;
      block1[i+1] = sourcering->block1[i]+imagepvariables;
      i++;
    }
  }
  ordersize=i+1;
  wv = (short **) Alloc0(ordersize * sizeof(short **));
  for (i--;i!=0 ;i--) wv[i+1] = sourcering->wvhdl[i];
  tmpR = *currRing;
  tmpR.N = N;
  tmpR.order = orders;
  tmpR.block0 = block0;
  tmpR.block1 = block1;
  tmpR.wvhdl = wv;
  rComplete(&tmpR);

  // change to new ring
  rChangeCurrRing(&tmpR, FALSE);
  sizeofpoly = mmGetSpecSize();
  if (id==NULL)
    j = 0;
  else
    j = IDELEMS(id);
  temp1 = idInit(sourcering->N+j,1);
  for (i=0;i<sourcering->N;i++)
  {
    if ((i<IDELEMS(theMap)) && (theMap->m[i]!=NULL))
    {
      p = pChangeSizeOfPoly(theImageRing, theMap->m[i],1,imagepvariables);
      q = p;
      while (pNext(q)) pIter(q);
      pNext(q) = pOne();
      pIter(q);
    }
    else
      q = p = pOne();
    pGetCoeff(q)=nNeg(pGetCoeff(q));
    pSetExp(q,i+1+imagepvariables,1);
    pSetm(q);
    temp1->m[i] = p;
  }
  for (i=sourcering->N;i<sourcering->N+j;i++)
  {
    temp1->m[i] = pChangeSizeOfPoly(theImageRing,
                                    id->m[i-sourcering->N],1,imagepvariables);
  }
  // we ignore here homogenity - may be changed later:
  temp2 = kStd(temp1,NULL,isNotHomog,NULL);
  idDelete(&temp1);
  for (i=0;i<IDELEMS(temp2);i++)
  {
    if (pLowVar(temp2->m[i])<imagepvariables) pDelete(&(temp2->m[i]));
  }

  // let's get back to the original ring
  rChangeCurrRing(sourcering, FALSE);
  temp1 = idInit(5,1);
  j = 0;
  for (i=0;i<IDELEMS(temp2);i++)
  {
    p = temp2->m[i];
    temp2->m[i]=NULL;
    if (p!=NULL)
    {
      q = pChangeSizeOfPoly(&tmpR, p,imagepvariables+1,N);
      if (j>=IDELEMS(temp1))
      {
        pEnlargeSet(&(temp1->m),IDELEMS(temp1),5);
        IDELEMS(temp1)+=5;
      }
      temp1->m[j] = q;
      j++;
      while (p!=NULL)
      {
        pp = pNext(p);
        Free((ADDRESS)p,sizeofpoly);
        p = pp;
      }
    }
  }
  idDelete(&temp2);
  Free((ADDRESS) wv, ordersize*sizeof(short **));
  idSkipZeroes(temp1);
  return temp1;
}

void maFindPerm(char **preim_names, int preim_n, char **preim_par, int preim_p,
                char **names,       int n,       char **par,       int nop,
                int * perm, int *par_perm, int ch)
{
  int i,j;
  /* find correspondig vars */
  for (i=0; i<preim_n; i++)
  {
    for(j=0; j<n; j++)
    {
      if (strcmp(preim_names[i],names[j])==0)
      {
        if (BVERBOSE(V_IMAP))
          Print("// var %s: nr %d -> nr %d\n",preim_names[i],i+1,j+1);
        /* var i+1 from preimage ring is var j+1  (index j+1) from image ring */
        perm[i+1]=j+1;
        break;
      }
    }
    if ((perm[i+1]==0)&&(par!=NULL)
        // do not consider par of Fq
         && (ch < 2))
    {
      for(j=0; j<nop; j++)
      {
        if (strcmp(preim_names[i],par[j])==0)
        {
          if (BVERBOSE(V_IMAP))
            Print("// var %s: nr %d -> par %d\n",preim_names[i],i+1,j+1);
          /* var i+1 from preimage ring is par j+1 (index j) from image ring */
          perm[i+1]=-(j+1);
        }
      }
    }
  }
  if (par_perm!=NULL)
  {
    for (i=0; i<preim_p; i++)
    {
      for(j=0; j<n; j++)
      {
        if (strcmp(preim_par[i],names[j])==0)
        {
          if (BVERBOSE(V_IMAP))
            Print("// par %s: par %d -> nr %d\n",preim_par[i],i+1,j+1);
          /* var i+1 from preimage ring is var j+1  (index j+1) from image ring */
          par_perm[i]=j+1;
          break;
        }
      }
      if ((par!=NULL) && (par_perm[i]==0))
      {
        for(j=0; j<nop; j++)
        {
          if (strcmp(preim_par[i],par[j])==0)
          {
            if (BVERBOSE(V_IMAP))
              Print("// par %s: nr %d -> par %d\n",preim_par[i],i+1,j+1);
            /* var i+1 from preimage ring is par j+1 (index j) from image ring */
            par_perm[i]=-(j+1);
          }
        }
      }
    }
  }
}

/*2
* embeds poly p from the subring r into the current ring
*/
poly maIMap(ring r, poly p)
{
  /* the simplest case:*/
  if(r==currRing) return pCopy(p);
  nSetMap(rInternalChar(r),r->parameter,rPar(r),r->minpoly);
  int *perm=(int *)Alloc0((r->N+1)*sizeof(int));
  //int *par_perm=(int *)Alloc0(rPar(r)*sizeof(int));
  maFindPerm(r->names,r->N, r->parameter, r->P,
             currRing->names,currRing->N,currRing->parameter, currRing->P,
             perm,NULL, currRing->ch);
  poly res=pPermPoly(p,perm,r/*,par_perm,rPar(r)*/);
  Free((ADDRESS)perm,(r->N+1)*sizeof(int));
  //Free((ADDRESS)par_perm,rPar(r)*sizeof(int));
  return res;
}

/*3
* find the max. degree in one variable, but not larger than MAX_MAP_DEG
*/
static int maMaxDeg_Ma(ideal a,ring preimage_r)
{
  int i,j;
  int N = preimage_r->N;
  poly p;
  int *m=(int *)Alloc0(N*sizeof(int));

  for (i=MATROWS(a)*MATCOLS(a)-1;i>=0;i--)
  {
    p=a->m[i];
    //pTest(p); // cannot test p because it is from another ring
    while(p!=NULL)
    {
      for(j=N-1;j>=0;j--)
      {
        m[j]=max(m[j],pRingGetExp(preimage_r, p,j+1));
        if (m[j]>=MAX_MAP_DEG)
        {
          i=MAX_MAP_DEG;
          goto max_deg_fertig_id;
        }
      }
      pIter(p);
    }
  }
  i=m[0];
  for(j=N-1;j>0;j--)
  {
    i=max(i,m[j]);
  }
max_deg_fertig_id:
  Free((ADDRESS)m,N*sizeof(int));
  return i;
}

/*3
* find the max. degree in one variable, but not larger than MAX_MAP_DEG
*/
static int maMaxDeg_P(poly p,ring preimage_r)
{
  int i,j;
  int N = preimage_r->N;
  int *m=(int *)Alloc0(N*sizeof(int));

//  pTest(p);
  while(p!=NULL)
  {
    for(j=N-1;j>=0;j--)
    {
      m[j]=max(m[j],pRingGetExp(preimage_r,p,j+1));
      if (m[j]>=MAX_MAP_DEG)
      {
        i=MAX_MAP_DEG;
        goto max_deg_fertig_p;
      }
    }
    pIter(p);
  }
  i=m[0];
  for(j=N-1;j>0;j--)
  {
    i=max(i,m[j]);
  }
max_deg_fertig_p:
  Free((ADDRESS)m,N*sizeof(int));
  return i;
}

/*2
* maps the expression w to res,
* switch what: MAP_CMD: use theMap for mapping, N for preimage ring
*              FETCH_CMD: use pOrdPoly for mapping
*              IMAP_CMD: use perm for mapping, N for preimage ring
*              default: map only poly-structures,
*                       use perm and par_perm, N and P,
*/
BOOLEAN maApplyFetch(int what,map theMap,leftv res, leftv w, ring preimage_r,
                     int *perm, int *par_perm, int P)
{
  int i;
  int N = preimage_r->N;
  //Print("N=%d ",N);
  //if (perm!=NULL) for(i=1;i<=N;i++) Print("%d -> %d ",i,perm[i]);
  //PrintS("\n");
  //Print("P=%d ",P);
  //if (par_perm!=NULL) for(i=0;i<P;i++) Print("%d -> %d ",i,par_perm[i]);
  //PrintS("\n");
  void *data=w->Data();
  res->rtyp = w->rtyp;
  switch (w->rtyp)
  {
    case NUMBER_CMD:
      if (P!=0)
      {
        res->data=(void *)naPermNumber((number)data,par_perm,P);
        res->rtyp=POLY_CMD;
        if (currRing->minpoly!=NULL)
          res->data=(void *)pMult((poly)res->data,pOne());
      }
      else
      {
        res->data=(void *)nMap((number)data);
        if (currRing->minpoly!=NULL)
        {
          number a=(number)res->data;
          number b=nInit(1);
          number c=nMult(a,b);
          nDelete(&a);
          nDelete(&b);
          res->data=(void *)c;
        }
      }
      break;
    case POLY_CMD:
    case VECTOR_CMD:
      if (what==FETCH_CMD)
        res->data=(void *)pFetchCopy(preimage_r, (poly)data);
      else if (what==IMAP_CMD)
        res->data=(void *)pPermPoly((poly)data,perm,preimage_r,par_perm,P);
      else /*if (what==MAP_CMD)*/
      {
        matrix s=mpNew(N,maMaxDeg_P((poly)data, preimage_r));
        res->data=(void *)maEval(theMap,(poly)data,preimage_r,s);
        idDelete((ideal *)&s);
      }
      if (currRing->minpoly!=NULL)
        res->data=(void *)pMult((poly)res->data,pOne());
      pTest((poly)res->data);
      break;
    case MODUL_CMD:
    case MATRIX_CMD:
    case IDEAL_CMD:
    case MAP_CMD:
    {
      int C=((matrix)data)->cols();
      int R;
      if (w->rtyp==MAP_CMD) R=1;
      else R=((matrix)data)->rows();
      matrix m=mpNew(R,C);
      char *tmpR=NULL;
      if(w->rtyp==MAP_CMD)
      {
        tmpR=((map)data)->preimage;
        ((matrix)data)->rank=((matrix)data)->rows();
      }
      if (what==FETCH_CMD)
      {
        for (i=R*C-1;i>=0;i--)
        {
          m->m[i]=pFetchCopy(preimage_r,((ideal)data)->m[i]);
          pTest(m->m[i]);
        }
      }
      else if (what==IMAP_CMD)
      {
        for (i=R*C-1;i>=0;i--)
        {
          m->m[i]=pPermPoly(((ideal)data)->m[i],perm,preimage_r,par_perm,P);
          pTest(m->m[i]);
        }
      }
      else /* if(what==MAP_CMD) */
      {
        matrix s=mpNew(N,maMaxDeg_Ma((ideal)data,preimage_r));
        for (i=R*C-1;i>=0;i--)
        {
          m->m[i]=maEval(theMap,((ideal)data)->m[i],preimage_r,s);
          pTest(m->m[i]);
        }
        idDelete((ideal *)&s);
      }
      if (currRing->minpoly!=NULL)
      {
        for (i=R*C-1;i>=0;i--)
        {
          m->m[i]=pMult(m->m[i],pOne());
          pTest(m->m[i]);
        }
      }
      if(w->rtyp==MAP_CMD)
      {
        ((map)data)->preimage=tmpR;
        ((map)m)->preimage=mstrdup(tmpR);
      }
      else
      {
        m->rank=((matrix)data)->rank;
      }
      res->data=(char *)m;
      break;
    }
    case LIST_CMD:
    {
      lists l=(lists)data;
      lists ml=(lists)Alloc(sizeof(slists));
      ml->Init(l->nr+1);
      for(i=0;i<=l->nr;i++)
      {
        if (((l->m[i].rtyp>BEGIN_RING)&&(l->m[i].rtyp<END_RING))
        ||(l->m[i].rtyp==LIST_CMD))
        {
          if (maApplyFetch(what,theMap,&ml->m[i],&l->m[i],
                           preimage_r,perm,par_perm,P))
          {
            ml->Clean();
            Free((ADDRESS)ml,sizeof(slists));
            res->rtyp=0;
            return TRUE;
          }
        }
        else
        {
          ml->m[i].Copy(&l->m[i]);
        }
      }
      res->data=(char *)ml;
      break;
    }
    default:
    {
      return TRUE;
    }
  }
  return FALSE;
}