Standard curves and curve checking.

[u/mdw/catacomb] / mpx-kmul.c

diff --git a/mpx-kmul.c b/mpx-kmul.c
index eaa0848..228cabd 100644 (file)
--- a/mpx-kmul.c
+++ b/mpx-kmul.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpx-kmul.c,v 1.6 2000/10/08 12:11:01 mdw Exp $
+ * $Id: mpx-kmul.c,v 1.9 2004/03/27 17:54:12 mdw Exp $
  *
  * Karatsuba's multiplication algorithm
  *
@@ -30,6 +30,15 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpx-kmul.c,v $
+ * Revision 1.9  2004/03/27 17:54:12  mdw
+ * Standard curves and curve checking.
+ *
+ * Revision 1.8  2002/10/09 00:36:03  mdw
+ * Fix bounds on workspace for Karatsuba operations.
+ *
+ * Revision 1.7  2000/10/08 15:48:35  mdw
+ * Rename Karatsuba constants now that we have @gfx_kmul@ too.
+ *
  * Revision 1.6  2000/10/08 12:11:01  mdw
  * Use @mpx_ueq@ instead of @MPX_UCMP@.
  *
@@ -57,13 +66,13 @@
 #include <stdio.h>
 
 #include "mpx.h"
-#include "mpx-kmac.h"
+#include "karatsuba.h"
 
 /*----- Tweakables --------------------------------------------------------*/
 
 #ifdef TEST_RIG
-#  undef KARATSUBA_CUTOFF
-#  define KARATSUBA_CUTOFF 2
+#  undef MPK_THRESH
+#  define MPK_THRESH 4                 /* Smallest possible correct value */
 #endif
 
 /*----- Main code ---------------------------------------------------------*/
@@ -82,9 +91,9 @@
  *             multiplication (e.g., @mpx_umul@) on large numbers, although
  *             more expensive on small ones.
  *
- *             The destination must be twice as large as the larger
- *             argument.  The scratch space must be twice as large as the
- *             larger argument, plus the magic number @KARATSUBA_SLOP@.
+ *             The destination must be three times as large as the larger
+ *             argument.  The scratch space must be five times as large as
+ *             the larger argument.
  */
 
 void mpx_kmul(mpw *dv, mpw *dvl,
@@ -106,7 +115,7 @@ void mpx_kmul(mpw *dv, mpw *dvl,
   MPX_SHRINK(av, avl);
   MPX_SHRINK(bv, bvl);
 
-  if (avl - av <= KARATSUBA_CUTOFF || bvl - bv <= KARATSUBA_CUTOFF) {
+  if (avl - av <= MPK_THRESH || bvl - bv <= MPK_THRESH) {
     mpx_umul(dv, dvl, av, avl, bv, bvl);
     return;
   }
@@ -126,7 +135,7 @@ void mpx_kmul(mpw *dv, mpw *dvl,
   /* --- First things --- *
    *
    * Sort out where to break the factors in half.  I'll choose the midpoint
-   * of the largest one, since this minimizes the amount of work I have to do
+   * of the larger one, since this minimizes the amount of work I have to do
    * most effectively.
    */
 
@@ -146,20 +155,17 @@ void mpx_kmul(mpw *dv, mpw *dvl,
       avm = avl;
   }
 
-  assert(((void)"Destination too small for Karatsuba multiply",
-         dvl - dv >= 4 * m));
-  assert(((void)"Not enough workspace for Karatsuba multiply",
-         svl - sv >= 4 * m));
-
   /* --- Sort out the middle term --- */
 
   {
     mpw *bsv = sv + m + 1, *ssv = bsv + m + 1;
     mpw *rdv = dv + m, *rdvl = rdv + 2 * (m + 2);
 
+    assert(rdvl <= dvl);
+    assert(ssv <= svl);
     UADD2(sv, bsv, av, avm, avm, avl);
     UADD2(bsv, ssv, bv, bvm, bvm, bvl);
-    if (m > KARATSUBA_CUTOFF)
+    if (m > MPK_THRESH)
       mpx_kmul(rdv, rdvl, sv, bsv, bsv, ssv, ssv, svl);
     else
       mpx_umul(rdv, rdvl, sv, bsv, bsv, ssv);
@@ -175,7 +181,7 @@ void mpx_kmul(mpw *dv, mpw *dvl,
     if (avl == avm || bvl == bvm)
       MPX_ZERO(rdv + m + 1, dvl);
     else {
-      if (m > KARATSUBA_CUTOFF)
+      if (m > MPK_THRESH)
        mpx_kmul(sv, ssv, avm, avl, bvm, bvl, ssv, svl);
       else
        mpx_umul(sv, ssv, avm, avl, bvm, bvl);
@@ -184,7 +190,7 @@ void mpx_kmul(mpw *dv, mpw *dvl,
       USUB(tdv, sv, svn);
     }
 
-    if (m > KARATSUBA_CUTOFF)
+    if (m > MPK_THRESH)
       mpx_kmul(sv, ssv, av, avm, bv, bvm, ssv, svl);
     else
       mpx_umul(sv, ssv, av, avm, bv, bvm);
@@ -243,8 +249,8 @@ static int umul(dstr *v)
   LOAD(b, bl, &v[1]);
   LOAD(c, cl, &v[2]);
   m = MAX(al - a, bl - b) + 1;
-  ALLOC(d, dl, 2 * m);
-  ALLOC(s, sl, 2 * m + 32);
+  ALLOC(d, dl, 3 * m);
+  ALLOC(s, sl, 5 * m);
 
   mpx_kmul(d, dl, a, al, b, bl, s, sl);
   if (!mpx_ueq(d, dl, c, cl)) {