Karatsuba-Ofman multiplication algorithm.

[u/mdw/catacomb] / mpx.h

diff --git a/mpx.h b/mpx.h
index 96bb358..7d8a2cd 100644 (file)
--- a/mpx.h
+++ b/mpx.h
@@ -1,6 +1,6 @@
 /* -*-c-*-
  *
- * $Id: mpx.h,v 1.5 1999/11/20 22:23:27 mdw Exp $
+ * $Id: mpx.h,v 1.6 1999/12/10 23:23:51 mdw Exp $
  *
  * Low level multiprecision arithmetic
  *
@@ -30,6 +30,9 @@
 /*----- Revision history --------------------------------------------------* 
  *
  * $Log: mpx.h,v $
+ * Revision 1.6  1999/12/10 23:23:51  mdw
+ * Karatsuba-Ofman multiplication algorithm.
+ *
  * Revision 1.5  1999/11/20 22:23:27  mdw
  * Add function versions of some low-level macros with wider use.
  *
@@ -47,8 +50,8 @@
  *
  */
 
-#ifndef MPX_H
-#define MPX_H
+#ifndef CATACOMB_MPX_H
+#define CATACOMB_MPX_H
 
 #ifdef __cplusplus
   extern "C" {
@@ -71,7 +74,7 @@
 
 #include <string.h>
 
-#ifndef MPW_H
+#ifndef CATACOMB_MPW_H
 #  include "mpw.h"
 #endif
 
@@ -509,6 +512,32 @@ extern void mpx_umlan(mpw */*dv*/, mpw */*dvl*/,
 extern void mpx_usqr(mpw */*dv*/, mpw */*dvl*/,
                     const mpw */*av*/, const mpw */*avl*/);
 
+/* --- @mpx_kmul@ --- *
+ *
+ * Arguments:  @mpw *dv, *dvl@ = pointer to destination buffer
+ *             @const mpw *av, *avl@ = pointer to first argument
+ *             @const mpw *bv, *bvl@ = pointer to second argument
+ *             @mpw *sv, *svl@ = pointer to scratch workspace
+ *
+ * Returns:    ---
+ *
+ * Use:                Multiplies two multiprecision integers using Karatsuba's
+ *             algorithm.  This is rather faster than traditional long
+ *             multiplication (e.g., @mpx_umul@) on large numbers, although
+ *             more expensive on small ones.
+ *
+ *             The destination and scratch buffers must be twice as large as
+ *             the larger argument.
+ */
+
+#define KARATSUBA_CUTOFF 16
+#define KARATSUBA_SLOP 32
+
+extern void mpx_kmul(mpw */*dv*/, mpw */*dvl*/,
+                    const mpw */*av*/, const mpw */*avl*/,
+                    const mpw */*bv*/, const mpw */*bvl*/,
+                    mpw */*sv*/, mpw */*svl*/);
+
 /* --- @mpx_udiv@ --- *
  *
  * Arguments:  @mpw *qv, *qvl@ = quotient vector base and limit