Changeset 659036 in git for Singular/ipshell.cc

Timestamp:

Jul 15, 2010, 9:19:45 PM (14 years ago)

Author:

Frank Seelisch <seelisch@…>

Branches:

(u'spielwiese', '17f1d200f27c5bd38f5dfc6e8a0879242279d1d8')

Children:

0f35158095f640c6aeef13c0631e9b146fc2fd5b

Parents:

81ececf82600f3e46a20998d8379da4cfd3c8b30

Message:

fixed criterion when to use Z/2^n implementation and when Z/m; previous version used Z/m for 2^31 / 2^63 resp.; new version will still use Z/2^n in this case

git-svn-id: file:///usr/local/Singular/svn/trunk@13028 2c84dea3-7e68-4137-9b89-c4e89433aadc

File:

• Singular/ipshell.cc (modified) (2 diffs)

Singular/ipshell.cc

@@ -1974 +1974 @@
   {
     R->ch = R->ringflagb;
-    if ((mpz_cmp_ui(R->ringflaga, 2) == 0) && (R->ringflagb + 2 <= 8*sizeof(NATNUMBER)))
-    {
+    if ((mpz_cmp_ui(R->ringflaga, 2) == 0) && (R->ringflagb < 8*sizeof(NATNUMBER)))
+    {
+      /* this branch should be active for ringflagb = 2..31 resp. 2..63;
+         note that 2^31 resp 2^63 is the largest power of 2 that fits into
+         an unsigned long */
       R->ringtype = 1;       // Use Z/2^ch
     }
@@ -4758 +4761 @@
     {
       ch = ringflagb;
-      if ((mpz_cmp_ui(ringflaga, 2) == 0) && (ringflagb + 2 <= 8*sizeof(NATNUMBER)))
-      {
+      if ((mpz_cmp_ui(ringflaga, 2) == 0) && (ringflagb < 8*sizeof(NATNUMBER)))
+      {
+        /* this branch should be active for ringflagb = 2..31 resp. 2..63;
+           note that 2^31 resp 2^63 is the largest power of 2 that fits into
+           an unsigned long */
         ringtype = 1;       // Use Z/2^ch
       }