Changeset a74143 in git for libpolys

Timestamp:

Jan 6, 2012, 9:47:51 PM (12 years ago)

Author:

Oleksandr Motsak <motsak@…>

Branches:

(u'spielwiese', 'fe61d9c35bf7c61f2b6cbf1b56e25e2f08d536cc')

Children:

31f1850ad6697d9acd155b53fa63f9e1a648ed9c

Parents:

4b38e3cc9992129dd4ef044c1d2cc7e55f93b134

git-author:

Oleksandr Motsak <motsak@mathematik.uni-kl.de>2012-01-06 21:47:51+01:00

git-committer:

Oleksandr Motsak <motsak@mathematik.uni-kl.de>2012-01-06 21:59:37+01:00

Message:

inverse computation over Zp

CHG: simplified extGCD in nvInvMod (due to Burcin)

TODO: there should better be only one such function: nvInvMod vs InvMod

File:

• libpolys/coeffs/modulop.cc (modified) (5 diffs)

libpolys/coeffs/modulop.cc

@@ -153 +153 @@
 
 #ifdef HAVE_DIV_MOD
+
 #ifdef USE_NTL_XGCD
+
 //ifdef HAVE_NTL // in ntl.a
 //extern void XGCD(long& d, long& s, long& t, long a, long b);
@@ -160 +162 @@
 NTL_CLIENT
 #endif
+
 #endif
 
@@ -748 +751 @@
 
 
-long nvInvMod(long a, const coeffs R)
-{
+inline long nvInvMod(long a, const coeffs R)
+{
+#ifdef HAVE_DIV_MOD
+  return InvMod(a, R);
+#else
+/// TODO: use "long InvMod(long a, const coeffs R)"?!
+  
    long  s;
 
-   long  u, v, u0, v0, u1, v1, u2, v2, q, r;
-
-   u1=1; v1=0;
-   u2=0; v2=1;
-   u = a; v = R->ch;
+   long  u, u0, u1, u2, q, r; // v0, v1, v2, 
+
+   u1=1; // v1=0;
+   u2=0; // v2=1;
+   u = a;
+
+   long v = R->ch;
 
    while (v != 0)
@@ -765 +775 @@
       v = r;
       u0 = u2;
-      v0 = v2;
-      u2 =  u1 - q*u2;
-      v2 = v1- q*v2;
+//      v0 = v2;
+      u2 = u1 - q*u2;
+//      v2 = v1 - q*v2;
       u1 = u0;
-      v1 = v0;
+//      v1 = v0;
    }
 
@@ -777 +787 @@
       return s + R->ch;
    else
-      return s;
+     return s;
+#endif
 }