Add an option to disable Montgomery reduction, so that performance

[u/mdw/catacomb] / mpmont.c

diff --git a/mpmont.c b/mpmont.c
index 35bffc2..7522dba 100644 (file)
--- a/mpmont.c
+++ b/mpmont.c
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpmont.c,v 1.4 1999/11/21 12:27:06 mdw Exp $
+ * $Id: mpmont.c,v 1.5 1999/11/22 13:58:40 mdw Exp $
  *
  * Montgomery reduction
  *
@@ -30,6 +30,10 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpmont.c,v $
+ * Revision 1.5  1999/11/22 13:58:40  mdw
+ * Add an option to disable Montgomery reduction, so that performance
+ * comparisons can be done.
+ *
  * Revision 1.4  1999/11/21 12:27:06  mdw
  * Remove a division from the Montgomery setup by calculating
  * %$R^2 \bmod m$% first and then %$R \bmod m$% by Montgomery reduction of
@@ -53,6 +57,16 @@
 #include "mp.h"
 #include "mpmont.h"
 
+/*----- Tweakables --------------------------------------------------------*/
+
+/* --- @MPMONT_DISABLE@ --- *
+ *
+ * Replace all the clever Montgomery reduction with good old-fashioned long
+ * division.
+ */
+
+/* #define MPMONT_DISABLE */
+
 /*----- Main code ---------------------------------------------------------*/
 
 /* --- @mpmont_create@ --- *
@@ -65,6 +79,18 @@
  * Use:                Initializes a Montgomery reduction context ready for use.
  */
 
+#ifdef MPMONT_DISABLE
+
+void mpmont_create(mpmont *mm, mp *m)
+{
+  mp_shrink(m);
+  mm->m = MP_COPY(m);
+  mm->r = MP_ONE;
+  mm->r2 = MP_ONE;
+}
+
+#else
+
 void mpmont_create(mpmont *mm, mp *m)
 {
   /* --- Take a copy of the modulus --- */
@@ -109,6 +135,8 @@ void mpmont_create(mpmont *mm, mp *m)
   }
 }
 
+#endif
+
 /* --- @mpmont_destroy@ --- *
  *
  * Arguments:  @mpmont *mm@ = pointer to a Montgomery reduction context
@@ -135,6 +163,16 @@ void mpmont_destroy(mpmont *mm)
  * Returns:    Result, %$a R^{-1} \bmod m$%.
  */
 
+#ifdef MPMONT_DISABLE
+
+mp *mpmont_reduce(mpmont *mm, mp *d, const mp *a)
+{
+  mp_div(0, &d, a, mm->m);
+  return (d);
+}
+
+#else
+
 mp *mpmont_reduce(mpmont *mm, mp *d, const mp *a)
 {
   mpw *dv, *dvl;
@@ -175,6 +213,8 @@ mp *mpmont_reduce(mpmont *mm, mp *d, const mp *a)
   return (d);
 }
 
+#endif
+
 /* --- @mpmont_mul@ --- *
  *
  * Arguments:  @mpmont *mm@ = pointer to Montgomery reduction context
@@ -184,6 +224,17 @@ mp *mpmont_reduce(mpmont *mm, mp *d, const mp *a)
  * Returns:    Result, %$a b R^{-1} \bmod m$%.
  */
 
+#ifdef MPMONT_DISABLE
+
+mp *mpmont_mul(mpmont *mm, mp *d, const mp *a, const mp *b)
+{
+  d = mp_mul(d, a, b);
+  mp_div(0, &d, d, mm->m);
+  return (d);
+}
+
+#else
+
 mp *mpmont_mul(mpmont *mm, mp *d, const mp *a, const mp *b)
 {
   mpw *dv, *dvl;
@@ -240,6 +291,8 @@ mp *mpmont_mul(mpmont *mm, mp *d, const mp *a, const mp *b)
   return (d);
 }
 
+#endif
+
 /* --- @mpmont_expr@ --- *
  *
  * Arguments:  @mpmont *mm@ = pointer to Montgomery reduction context