Changeset f3094a in git for libpolys/polys/monomials/p_polys.cc

Timestamp:

Jul 23, 2012, 5:29:18 PM (11 years ago)

Author:

Oleksandr Motsak <motsak@…>

Branches:

(u'jengelh-datetime', 'ceac47cbc86fe4a15902392bdbb9bd2ae0ea02c6')(u'spielwiese', '2234726c50d679d6664181a5c72f75a6fd64a787')

Children:

6779bb431ba1eced98b7cb0e1fed5fbfef1f0244

Parents:

98223c2d11013c57837511c1adb1ef9a16193b3d

git-author:

Oleksandr Motsak <motsak@mathematik.uni-kl.de>2012-07-23 17:29:18+02:00

git-committer:

Oleksandr Motsak <motsak@mathematik.uni-kl.de>2012-07-25 15:25:07+02:00

Message:

moved the definition of p_GetShortExpVector(poly, ring) to p_polys.cc

File:

• libpolys/polys/monomials/p_polys.cc (modified) (2 diffs)

libpolys/polys/monomials/p_polys.cc

@@ -10 +10 @@
 
 
-
 #include "config.h"
+
+#include <ctype.h>
+
+#include <omalloc/omalloc.h>
+
 #include <misc/auxiliary.h>
 
-#include <ctype.h>
-#include <omalloc/omalloc.h>
 #include <misc/options.h>
 #include <misc/intvec.h>
@@ -4091 +4093 @@
   }
 }
+
+/***************************************************************
+ *
+ * Storage Managament Routines
+ *
+ ***************************************************************/
+
+
+static inline unsigned long GetBitFields(long e,
+                                         unsigned int s, unsigned int n)
+{
+#define Sy_bit_L(x)     (((unsigned long)1L)<<(x))
+  unsigned int i = 0;
+  unsigned long  ev = 0L;
+  assume(n > 0 && s < BIT_SIZEOF_LONG);
+  do
+  {
+    assume(s+i < BIT_SIZEOF_LONG);
+    if (e > (long) i) ev |= Sy_bit_L(s+i);
+    else break;
+    i++;
+  }
+  while (i < n);
+  return ev;
+}
+
+// Short Exponent Vectors are used for fast divisibility tests
+// ShortExpVectors "squeeze" an exponent vector into one word as follows:
+// Let n = BIT_SIZEOF_LONG / pVariables.
+// If n == 0 (i.e. pVariables > BIT_SIZE_OF_LONG), let m == the number
+// of non-zero exponents. If (m>BIT_SIZEOF_LONG), then sev = ~0, else
+// first m bits of sev are set to 1.
+// Otherwise (i.e. pVariables <= BIT_SIZE_OF_LONG)
+// represented by a bit-field of length n (resp. n+1 for some
+// exponents). If the value of an exponent is greater or equal to n, then
+// all of its respective n bits are set to 1. If the value of an exponent
+// is smaller than n, say m, then only the first m bits of the respective
+// n bits are set to 1, the others are set to 0.
+// This way, we have:
+// exp1 / exp2 ==> (ev1 & ~ev2) == 0, i.e.,
+// if (ev1 & ~ev2) then exp1 does not divide exp2
+unsigned long p_GetShortExpVector(poly p, const ring r)
+{
+  assume(p != NULL);
+  if (p == NULL) return 0;
+  unsigned long ev = 0; // short exponent vector
+  unsigned int n = BIT_SIZEOF_LONG / r->N; // number of bits per exp
+  unsigned int m1; // highest bit which is filled with (n+1)
+  unsigned int i = 0, j=1;
+
+  if (n == 0)
+  {
+    if (r->N <2*BIT_SIZEOF_LONG)
+    {
+      n=1;
+      m1=0;
+    }
+    else
+    {
+      for (; j<=(unsigned long) r->N; j++)
+      {
+        if (p_GetExp(p,j,r) > 0) i++;
+        if (i == BIT_SIZEOF_LONG) break;
+      }
+      if (i>0)
+        ev = ~((unsigned long)0) >> ((unsigned long) (BIT_SIZEOF_LONG - i));
+      return ev;
+    }
+  }
+  else
+  {
+    m1 = (n+1)*(BIT_SIZEOF_LONG - n*r->N);
+  }
+
+  n++;
+  while (i<m1)
+  {
+    ev |= GetBitFields(p_GetExp(p, j,r), i, n);
+    i += n;
+    j++;
+  }
+
+  n--;
+  while (i<BIT_SIZEOF_LONG)
+  {
+    ev |= GetBitFields(p_GetExp(p, j,r), i, n);
+    i += n;
+    j++;
+  }
+  return ev;
+}
+
 /***************************************************************
  *