X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/b817bfc642225b8c3c0b6a7e42d1fb949b61a606..ffec48800022b6872951eca188d2ceedef8dd5c8:/gfreduce.c

diff --git a/gfreduce.c b/gfreduce.c
index ae31d5c..01ca678 100644
--- a/gfreduce.c
+++ b/gfreduce.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: gfreduce.c,v 1.5 2004/04/08 01:36:15 mdw Exp $
+ * $Id$
  *
  * Efficient reduction modulo sparse binary polynomials
  *
@@ -90,7 +90,7 @@ void gfreduce_create(gfreduce *r, mp *p)
   unsigned long i;
   gfreduce_instr *ip;
   unsigned f = 0;
-  size_t w, ww, wi, wl, ll;
+  size_t w, ww, wi, wl, ll, bb;
 
   /* --- Sort out the easy stuff --- */
 
@@ -121,6 +121,7 @@ void gfreduce_create(gfreduce *r, mp *p)
   wi = DA_LEN(&iv);
   f = 0;
   ll = 0;
+  bb = MPW_BITS - dw;
   for (i = 0, mp_scan(&sc, p); mp_step(&sc) && i < d; i++) {
     if (!mp_bit(&sc))
       continue;
@@ -149,8 +150,8 @@ void gfreduce_create(gfreduce *r, mp *p)
       w = ww;
       wi = DA_LEN(&iv);
     }
-    INSTR(GFRI_LSL, (MPW_BITS + i - d)%MPW_BITS);
-    if ((MPW_BITS + i - d)%MPW_BITS)
+    INSTR(GFRI_LSL, (bb + i)%MPW_BITS);
+    if ((bb + i)%MPW_BITS)
       f |= f_lsr;
   }
   wl = DA_LEN(&iv);
@@ -338,7 +339,7 @@ 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);
@@ -410,7 +411,7 @@ 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);
@@ -450,13 +451,19 @@ 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);
 }