X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/423c89a3b19646bd914c2c0826b7ae05c41fb0a1..cc3ca08f22460b15423bb88632f3a12741b19003:/pgen-gcd.c

diff --git a/pgen-gcd.c b/pgen-gcd.c
index cd23c37..863b151 100644
--- a/pgen-gcd.c
+++ b/pgen-gcd.c
@@ -1,13 +1,13 @@
 /* -*-c-*-
  *
- * $Id: pgen-gcd.c,v 1.1 2000/06/17 11:51:53 mdw Exp $
+ * $Id: pgen-gcd.c,v 1.3 2004/04/08 01:36:15 mdw Exp $
  *
  * Prime search stepper ensuring a low GCD for %$(p - 1)/2$%
  *
  * (c) 2000 Straylight/Edgeware
  */
 
-/*----- Licensing notice --------------------------------------------------* 
+/*----- Licensing notice --------------------------------------------------*
  *
  * This file is part of Catacomb.
  *
@@ -15,27 +15,18 @@
  * it under the terms of the GNU Library General Public License as
  * published by the Free Software Foundation; either version 2 of the
  * License, or (at your option) any later version.
- * 
+ *
  * Catacomb is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU Library General Public License for more details.
- * 
+ *
  * You should have received a copy of the GNU Library General Public
  * License along with Catacomb; if not, write to the Free
  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  * MA 02111-1307, USA.
  */
 
-/*----- Revision history --------------------------------------------------* 
- *
- * $Log: pgen-gcd.c,v $
- * Revision 1.1  2000/06/17 11:51:53  mdw
- * Filter which imposes additional restrictions on GCD of %$(p - 1)/2$%
- * with a given integer.
- *
- */
-
 /*----- Header files ------------------------------------------------------*/
 
 #include "mp.h"
@@ -52,16 +43,24 @@ int pgen_gcdstep(int rq, pgen_event *ev, void *p)
 
     /* --- Set everything up --- *
      *
-     * Call things off if @q@ and @jq@ have common factors.
+     * Call things off if @p@ and @jp@ have common factors, or if @q@, @r@
+     * and @jq@ have common factors greater than @max@.
      */
 
     case PGEN_BEGIN: {
       mp *p = ev->m;
+      mp_gcd(&g->g, 0, 0, p, g->jp.m);
+      if (MP_CMP(g->g, >, MP_ONE))
+	return (PGEN_ABORT);
       g->q = mp_lsr(MP_NEW, p, 1);
       g->jq = mp_lsr(MP_NEW, g->jp.m, 1);
       mp_gcd(&g->g, 0, 0, g->q, g->jq);
-      if (MP_CMP(g->g, >, MP_ONE))
+      mp_gcd(&g->g, 0, 0, g->g, g->r);
+      if (MP_CMP(g->g, >, g->max)) {
+	mp_drop(g->q);
+	mp_drop(g->jq);
 	return (PGEN_ABORT);
+      }
       rc = pfilt_create(&g->p, p);
       mp_drop(p);
     } break;