X-Git-Url: https://www.ginac.de/ginac.git//ginac.git?p=ginac.git;a=blobdiff_plain;f=ginac%2Fpolynomial%2Fpgcd.cpp;h=a33b02d78a7dfc2fdb9fc20818b9c30271c52fb2;hp=ddc3b8cb109ef7154cbf36f0202d5663954abb34;hb=edf1ae46a926d0a718063c149b78c1b9a7ec2043;hpb=45b1e47372090352ac5af655b32473df2abab23b

diff --git a/ginac/polynomial/pgcd.cpp b/ginac/polynomial/pgcd.cpp
index ddc3b8cb..a33b02d7 100644
--- a/ginac/polynomial/pgcd.cpp
+++ b/ginac/polynomial/pgcd.cpp
@@ -1,3 +1,25 @@
+/** @file pgcd.cpp
+ *
+ *  GCD for polynomials in prime field. */
+
+/*
+ *  GiNaC Copyright (C) 1999-2010 Johannes Gutenberg University Mainz, Germany
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
 #include "pgcd.h"
 #include "collect_vargs.h"
 #include "smod_helpers.h"
@@ -6,8 +28,7 @@
 #include "newton_interpolate.h"
 #include "divide_in_z_p.h"
 
-namespace GiNaC
-{
+namespace GiNaC {
 
 extern void
 primpart_content(ex& pp, ex& c, ex e, const exvector& vars, const long p);
@@ -59,7 +80,8 @@ ex pgcd(const ex& A, const ex& B, const exvector& vars, const long p)
 	const ex lc_gcd = euclid_gcd(AL, BL, mainvar, p);
 
 	// The estimate of degree of the gcd of Ab and Bb
-	int gcd_deg = std::min(degree(Aprim, mainvar), degree(Bprim, mainvar));
+	exp_vector_t gcd_deg = std::min(degree_vector(Aprim, restvars),
+					degree_vector(Bprim, restvars));
 	eval_point_finder::value_type b;
 
 	eval_point_finder find_eval_point(p);
@@ -84,8 +106,11 @@ ex pgcd(const ex& A, const ex& B, const exvector& vars, const long p)
 		const cln::cl_I correct_lc = smod(lcb_gcd*recip(Cblc, p), p);
 		Cb = (Cb*numeric(correct_lc)).smod(pn);
 
+		const exp_vector_t img_gcd_deg = degree_vector(Cb, restvars);
+		// Test for relatively prime polynomials
+		if (zerop(img_gcd_deg))
+			return cont_gcd;
 		// Test for unlucky homomorphisms
-		const int img_gcd_deg = Cb.degree(restvars.back());
 		if (img_gcd_deg < gcd_deg) {
 			// The degree decreased, previous homomorphisms were
 			// bad, so we have to start it all over.
@@ -111,8 +136,6 @@ ex pgcd(const ex& A, const ex& B, const exvector& vars, const long p)
 		const ex H_lcoeff = lcoeff_wrt(H, restvars);
 
 		if (H_lcoeff.is_equal(lc_gcd)) {
-			if ((Hprev-H).expand().smod(pn).is_zero())
-				continue;
 			ex C /* primitive part of H */, contH /* dummy */;
 			primpart_content(C, contH, H, vars, p);
 			// Normalize GCD so that leading coefficient is 1
@@ -124,8 +147,6 @@ ex pgcd(const ex& A, const ex& B, const exvector& vars, const long p)
 			if (divide_in_z_p(Aprim, C, dummy1, vars, p) &&
 					divide_in_z_p(Bprim, C, dummy2, vars, p))
 				return (cont_gcd*C).expand().smod(pn);
-			else if (img_gcd_deg == 0)
-				return cont_gcd;
 			// else continue building the candidate
 		} 
 	} while(true);
@@ -133,4 +154,3 @@ ex pgcd(const ex& A, const ex& B, const exvector& vars, const long p)
 }
 
 } // namespace GiNaC
-