Changeset a8b44d in git

Timestamp:

Mar 21, 2011, 3:55:47 PM (12 years ago)

Author:

Frank Seelisch <seelisch@…>

Branches:

(u'jengelh-datetime', 'ceac47cbc86fe4a15902392bdbb9bd2ae0ea02c6')(u'spielwiese', 'a800fe4b3e9d37a38c5a10cc0ae9dfa0c15a4ee6')

Children:

9cd697732c2adbda992d49885d226fc966966251

Parents:

f4a33e267c2b5be378ef1fc5426935bee8f1e4d9

Message:

changed div check in Z/m, and command simplify over rings

git-svn-id: file:///usr/local/Singular/svn/trunk@14022 2c84dea3-7e68-4137-9b89-c4e89433aadc

Files:

• doc/reference.doc (modified) (previous)
• kernel/ideals.cc (modified) (4 diffs)
• kernel/polys.cc (modified) (4 diffs)
• kernel/polys.h (modified) (1 diff)
• kernel/polys1.cc (modified) (1 diff)
• kernel/rmodulon.cc (modified) (1 diff)

kernel/ideals.cc

@@ -299 +299 @@
 
 //
-// Delete id[j], if Lm(j) == Lm(i) and j > i
+// Delete id[j], if Lm(j) == Lm(i) and both LC(j), LC(i) are units and j > i
 //
 void idDelLmEquals(ideal id)
@@ -312 +312 @@
       {
         if ((id->m[j] != NULL)
-        && pLmEqual(id->m[i], id->m[j]))
+        && pLmEqual(id->m[i], id->m[j])
+#ifdef HAVE_RINGS
+        && nIsUnit(pGetCoeff(id->m[i])) && nIsUnit(pGetCoeff(id->m[j]))
+#endif
+        )
         {
           pDelete(&id->m[j]);
@@ -321 +325 @@
 }
 
+//
+// delete id[j], if LT(j) == coeff*mon*LT(i) and vice versa, i.e.,
+// delete id[i], if LT(i) == coeff*mon*LT(j)
+//
 void idDelDiv(ideal id)
 {
@@ -333 +341 @@
         if (id->m[j]!=NULL)
         {
-          if(pDivisibleBy(id->m[i], id->m[j]))
+#ifdef HAVE_RINGS
+          if (rField_is_Ring(currRing))
           {
-            pDelete(&id->m[j]);
-          }
-          else if(pDivisibleBy(id->m[j], id->m[i]))
+            if (pDivisibleByRingCase(id->m[i], id->m[j]))
+            {
+              pDelete(&id->m[j]);
+            }
+            else if (pDivisibleByRingCase(id->m[j], id->m[i]))
           {
             pDelete(&id->m[i]);
             break;
           }
+          }
+          else
+          {
+#endif
+          /* the case of a ground field: */
+          if (pDivisibleBy(id->m[i], id->m[j]))
+          {
+            pDelete(&id->m[j]);
+          }
+          else if (pDivisibleBy(id->m[j], id->m[i]))
+          {
+            pDelete(&id->m[i]);
+            break;
+          }
+#ifdef HAVE_RINGS
+          }
+#endif          
         }
       }

kernel/polys.cc

@@ -99 +99 @@
 * assumes that the head term of b is a multiple of the head term of a
 * and return the multiplicant *m
+* Frank's observation: If LM(b) = LM(a)*m, then we may actually set
+* negative(!) exponents in the below loop. I suspect that the correct
+* comment should be "assumes that LM(a) = LM(b)*m, for some monomial m..."
 */
 poly pDivide(poly a, poly b)
@@ -130 +133 @@
   p_Test(q, r);
   return q;
+}
+#endif
+
+static void printNumber(const number z)
+{
+  if (nIsZero(z)) printf("number = 0\n");
+  else
+  {
+    poly p = pOne();
+    pSetCoeff(p, nCopy(z));
+    pSetm(p);
+    printf("number = %s\n", pString(p));
+    pDelete(&p);
+  }
+}
+
+#ifdef HAVE_RINGS
+/* TRUE iff LT(f) | LT(g) */
+BOOLEAN pDivisibleByRingCase(poly f, poly g)
+{
+  int exponent;
+  for(int i = (int)pVariables; i; i--)
+  {
+    exponent = pGetExp(g, i) - pGetExp(f, i);
+    if (exponent < 0) return FALSE;
+  }
+  return nDivBy(pGetCoeff(g), pGetCoeff(f));
 }
 #endif
@@ -567 +597 @@
 
 /*2
-*divides p1 by its leading coefficient
+* divides p1 by its leading coefficient if it is a unit
+* (this will always be true over fields; but not over coefficient rings)
 */
 void pNorm(poly p1)
@@ -574 +605 @@
   if (rField_is_Ring(currRing))
   {
-    Werror("pNorm not possible in the case of coefficient rings.");
-  }
-  else
+    if (!nIsUnit(pGetCoeff(p1))) return;
+  }
 #endif
   if (p1!=NULL)

kernel/polys.h

@@ -169 +169 @@
 // tests (see polys-impl.cc )
 #define pGetShortExpVector(a)   p_GetShortExpVector(a, currRing)
+#ifdef HAVE_RINGS
+/* divisibility check over ground ring (which may contain zero divisors);
+   TRUE iff LT(f) divides LT(g), i.e., LT(f)*c*m = LT(g), for some
+   coefficient c and some monomial m;
+   does not take components into account */
+BOOLEAN pDivisibleByRingCase(poly f, poly g);
+#endif
 
 /***************************************************************

kernel/polys1.cc

@@ -1720 +1720 @@
   if (rField_is_Ring(currRing))
   {
-    if ((pLength(p1) == 1) && (nEqual(pGetCoeff(p1), pGetCoeff(p2))))
-      return TRUE;
-    if (!nIsUnit(pGetCoeff(p2))) return FALSE;
+    if (!nDivBy(pGetCoeff(p1), pGetCoeff(p2))) return FALSE;
   }
 #endif

kernel/rmodulon.cc

@@ -270 +270 @@
 }
 
-BOOLEAN nrnDivBy (number a,number b)
+BOOLEAN nrnDivBy (number a, number b)
 {
   if (a == NULL)
-    return mpz_divisible_p(currRing->nrnModul, (int_number) b);
+    return mpz_divisible_p(currRing->nrnModul, (int_number)b);
   else
-    return mpz_divisible_p((int_number) a, (int_number) b);
-  /*
-  number bs = nrnGcd(a, b, currRing);
-  mpz_tdiv_q((int_number) bs, (int_number) b, (int_number) bs);
-  bool res = nrnIsUnit(bs);
-  nrnDelete(&bs, NULL);
-  return res;
-  */
+  { /* b divides a iff b/gcd(a, b) is a unit in the given ring: */
+    number n = nrnGcd(a, b, currRing);
+    mpz_tdiv_q((int_number)n, (int_number)b, (int_number)n);
+    bool result = nrnIsUnit(n);
+    nrnDelete(&n, NULL);
+    return result;
+  }
 }