reduce_evalue.c

   1 #include <polylib/polylibgmp.h>
   2
   3 /*------------------------------------------------------------*/
   4 /* int eequal (e1, e2)                                        */
   5 /*      e1, e2 : pointers to evalues                          */
   6 /* returns 1 (true) if they are equal, 0 (false) if not       */
   7 /*------------------------------------------------------------*/
   8 static int eequal(evalue *e1,evalue *e2) {
   9
  10   int i;
  11   enode *p1, *p2;
  12
  13   if (value_ne(e1->d,e2->d))
  14     return 0;
  15
  16   /* e1->d == e2->d */
  17   if (value_notzero_p(e1->d)) {
  18     if (value_ne(e1->x.n,e2->x.n))
  19       return 0;
  20
  21     /* e1->d == e2->d != 0  AND e1->n == e2->n */
  22     return 1;
  23   }
  24
  25   /* e1->d == e2->d == 0 */
  26   p1 = e1->x.p;
  27   p2 = e2->x.p;
  28   if (p1->type != p2->type) return 0;
  29   if (p1->size != p2->size) return 0;
  30   if (p1->pos  != p2->pos) return 0;
  31   for (i=0; i<p1->size; i++)
  32     if (!eequal(&p1->arr[i], &p2->arr[i]) )
  33       return 0;
  34   return 1;
  35 } /* eequal */
  36
  37 /*------------------------------------------------------------*/
  38 /* void reduce_evalue ( e )                                   */
  39 /*       e : pointer to an evalue                             */
  40 /*------------------------------------------------------------*/
  41 void reduce_evalue (evalue *e) {
  42
  43   enode *p;
  44   int i, j, k;
  45
  46   if (value_notzero_p(e->d))
  47     return;     /* a rational number, its already reduced */
  48   if(!(p = e->x.p))
  49     return;     /* hum... an overflow probably occured */
  50
  51   /* First reduce the components of p */
  52   for (i=0; i<p->size; i++)
  53     reduce_evalue(&p->arr[i]);
  54
  55   if (p->type==periodic) {
  56
  57     /* Try to reduce the period */
  58     for (i=1; i<=(p->size)/2; i++) {
  59       if ((p->size % i)==0) {
  60
  61         /* Can we reduce the size to i ? */
  62         for (j=0; j<i; j++)
  63           for (k=j+i; k<e->x.p->size; k+=i)
  64             if (!eequal(&p->arr[j], &p->arr[k])) goto you_lose;
  65
  66             /* OK, lets do it */
  67             for (j=i; j<p->size; j++) free_evalue_refs(&p->arr[j]);
  68             p->size = i;
  69             break;
  70
  71 you_lose:   /* OK, lets not do it */
  72             continue;
  73          }
  74       }
  75
  76       /* Try to reduce its strength */
  77     if (p->size == 1) {
  78       value_clear(e->d);
  79       memcpy(e,&p->arr[0],sizeof(evalue));
  80       free(p);
  81     }
  82   }
  83   else if (p->type==polynomial) {
  84
  85     /* Try to reduce the degree */
  86     for (i=p->size-1;i>=0;i--) {
  87       if (value_one_p(p->arr[i].d) && value_zero_p(p->arr[i].x.n))
  88
  89         /* Zero coefficient */
  90         continue;
  91       else
  92         break;
  93     }
  94     if (i==-1) p->size = 1;
  95     else if (i+1<p->size) p->size = i+1;
  96
  97     /* Try to reduce its strength */
  98     if (p->size == 1) {
  99       value_clear(e->d);
 100       memcpy(e,&p->arr[0],sizeof(evalue));
 101       free(p);
 102     }
 103   }
 104 } /* reduce_evalue */