Merge branch 'master' of git+ssh://metalzone.distorted.org.uk/~mdw/public-git/catacomb/

[u/mdw/catacomb] / gfreduce.c

diff --git a/gfreduce.c b/gfreduce.c
index 929c46c..bdf3579 100644 (file)
--- a/gfreduce.c
+++ b/gfreduce.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: gfreduce.c,v 1.3 2004/03/23 15:19:32 mdw Exp $
+ * $Id$
  *
  * Efficient reduction modulo sparse binary polynomials
  *
@@ -27,20 +27,6 @@
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: gfreduce.c,v $
- * Revision 1.3  2004/03/23 15:19:32  mdw
- * Test elliptic curves more thoroughly.
- *
- * Revision 1.2  2004/03/21 22:52:06  mdw
- * Merge and close elliptic curve branch.
- *
- * Revision 1.1.2.1  2004/03/21 22:39:46  mdw
- * Elliptic curves on binary fields work.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include <mLib/alloc.h>
@@ -98,7 +84,8 @@ DA_DECL(instr_v, gfreduce_instr);
 void gfreduce_create(gfreduce *r, mp *p)
 {
   instr_v iv = DA_INIT;
-  unsigned long d, dw;
+  unsigned long d;
+  unsigned dw;
   mpscan sc;
   unsigned long i;
   gfreduce_instr *ip;
@@ -162,8 +149,8 @@ void gfreduce_create(gfreduce *r, mp *p)
       w = ww;
       wi = DA_LEN(&iv);
     }
-    INSTR(GFRI_LSL, (i - d)%MPW_BITS);
-    if ((i - d)%MPW_BITS)
+    INSTR(GFRI_LSL, (MPW_BITS + i - d)%MPW_BITS);
+    if ((MPW_BITS + i - d)%MPW_BITS)
       f |= f_lsr;
   }
   wl = DA_LEN(&iv);
@@ -351,7 +338,7 @@ int gfreduce_trace(gfreduce *r, mp *x)
     y = gfreduce_do(r, t, t);
     y = gf_add(y, y, x);
   }
-  rc = !MP_ISZERO(y);
+  rc = !MP_ZEROP(y);
   mp_drop(spare);
   mp_drop(y);
   return (rc);
@@ -423,7 +410,7 @@ mp *gfreduce_quadsolve(gfreduce *r, mp *d, mp *x)
        z = gf_add(z, z, t);
        w = gf_add(w, w, rho);
       }
-      if (!MP_ISZERO(w))
+      if (!MP_ZEROP(w))
        break;
       MP_DROP(z);
       MP_DROP(w);
@@ -463,13 +450,19 @@ mp *gfreduce_exp(gfreduce *gr, mp *d, mp *a, mp *e)
   mp *spare = (e->f & MP_BURN) ? MP_NEWSEC : MP_NEW;
 
   MP_SHRINK(e);
-  if (!MP_LEN(e))
+  MP_COPY(a);
+  if (MP_ZEROP(e))
     ;
-  else if (MP_LEN(e) < EXP_THRESH)
-    EXP_SIMPLE(x, a, e);
-  else
-    EXP_WINDOW(x, a, e);
+  else {
+    if (MP_NEGP(e))
+      a = gf_modinv(a, a, gr->p);
+    if (MP_LEN(e) < EXP_THRESH)
+      EXP_SIMPLE(x, a, e);
+    else
+      EXP_WINDOW(x, a, e);
+  }
   mp_drop(d);
+  mp_drop(a);
   mp_drop(spare);
   return (x);
 }