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[ginac.git] / ginac / polynomial / pgcd.cpp

diff --git a/ginac/polynomial/pgcd.cpp b/ginac/polynomial/pgcd.cpp
index 6e5e6b2ebc4bbaadc6adc1bcc20401f672d5af9d..e8b7357f563905fbc1e5087ae86d4ebdb91698ab 100644 (file)
--- a/ginac/polynomial/pgcd.cpp
+++ b/ginac/polynomial/pgcd.cpp
@@ -3,7 +3,7 @@
  *  GCD for polynomials in prime field. */
 
 /*
- *  GiNaC Copyright (C) 1999-2009 Johannes Gutenberg University Mainz, Germany
+ *  GiNaC Copyright (C) 1999-2019 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
@@ -80,7 +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);
@@ -105,8 +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.
@@ -132,8 +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
@@ -145,8 +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);