Changeset 1b38b23 in git

Timestamp:

Jul 15, 2010, 1:30:23 PM (13 years ago)

Author:

Frank Seelisch <seelisch@…>

Branches:

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

Children:

5046ce577e8d17d17d4ae4e6b0d19f1fa941849c

Parents:

d56cdae01f2cd4bd0d5e6cf03bbe3672345b236d

Message:

bug fix (old ticket #200 and new bug report by Martin Albrecht as of July 14, 2010) by Anne und Frank

git-svn-id: file:///usr/local/Singular/svn/trunk@13012 2c84dea3-7e68-4137-9b89-c4e89433aadc

File:

• kernel/kbuckets.cc (modified) (3 diffs)

kernel/kbuckets.cc

@@ -1103 +1103 @@
   number rn;
 
+  /* we shall reduce bucket=bn*lm+... by p1=an*t+a1 where t=lm(p1)
+     and an,bn shall be defined further down only if lc(p1)!=1
+     we already know: an|bn and t|lm */
   if(a1==NULL)
   {
@@ -1114 +1117 @@
 //StringSetS("##### an = "); nWrite(an); PrintS(StringAppend("\n"));
 //StringSetS("##### bn = "); nWrite(bn); PrintS(StringAppend("\n"));
+    /* ksCheckCoeff: divide out gcd from an and bn: */
     int ct = ksCheckCoeff(&an, &bn);
+    /* the previous command returns ct=0 or ct=2 iff an!=1
+       note: an is now 1 or -1 */
+
+    /* setup factor for p1 which cancels leading terms */
     p_SetCoeff(lm, bn, bucket->bucket_ring);
     if ((ct == 0) || (ct == 2))
     {
-      kBucket_Mult_n(bucket, an);
-#ifdef HAVE_RINGS
-      if (rField_is_Ring(bucket->bucket_ring))
-        lm = p_Mult_nn(lm, an, bucket->bucket_ring);
-#endif
+      /* next line used to be here before but is WRONG:
+      kBucket_Mult_n(bucket, an); 
+        its use would result in a wrong sign for the tail of bucket
+        in the reduction */
+
+      /* correct factor for cancelation by changing sign if an=-1 */
+      lm = p_Mult_nn(lm, an, bucket->bucket_ring);
     }
     rn = an;
@@ -1162 +1172 @@
   }
   #endif
+
   kBucket_Minus_m_Mult_p(bucket, lm, a1, &l1, spNoether);