cfCharSetsUtil.cc

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/*****************************************************************************\
 * Computer Algebra System SINGULAR
\*****************************************************************************/
/** @file cfCharSetsUtil.cc
 *
 * This file provides utility functions to compute characteristic sets
 *
 * @note some of the code is code from libfac or derived from code from libfac.
 * Libfac is written by M. Messollen. See also COPYING for license information
 * and README for general information on characteristic sets.
 *
 * @authors Martin Lee
 *
 **/
/*****************************************************************************/
 
#include "config.h"
 
#include "canonicalform.h"
#include "cf_algorithm.h"
#include "cfCharSetsUtil.h"
 
#define __ARRAY_INIT__ -1
 
// the maximal degree of polys in PS wrt. variable x
int
degpsmax (const CFList & PS, const Variable & x,
          Intarray & A, Intarray & C)
{
  int varlevel= level(x);
  if (A[varlevel] != __ARRAY_INIT__)
    return A[varlevel];
  int max= 0, temp, count= 0;
 
  for (CFListIterator i= PS; i.hasItem(); i++)
  {
    temp= degree (i.getItem(), x);
    if (temp > max)
    {
      max= temp;
      count = 0;
    }
    if (temp == max)
      count += max;  // we count the number of polys
  }
  A[varlevel]= max;
  C[varlevel]= count;
  return max;
}
 
// the minimal non-zero degree of polys in PS wrt. x
// returns 0 if variable x doesn't occure in any of the polys
int
degpsmin (const CFList & PS, const Variable & x, Intarray & A, Intarray & B,
          Intarray & C, Intarray & D)
{
  int varlevel= level(x);
  if (B[varlevel] != __ARRAY_INIT__ )
    return B[varlevel];
  int min= degpsmax (PS, x, A, C), temp, count= 0;
 
  if (min == 0)
  {
    B[varlevel]= min;
    D[varlevel]= min;
    return min;
  }
  else
  {
    for (CFListIterator i= PS; i.hasItem(); i++)
    {
      temp= degree (i.getItem(), x);
      if (temp < min && temp != 0)
      {
        min= temp;
        count= 0;
      }
      if (temp == min)
        count += min; // we count the number of polys
    }
  }
  B[varlevel]= min;
  D[varlevel]= count;