index 56fd0b6b4080ebaafa72845978bfea39d5198ae9..bc6aa838303f0a9d1df8af635b8fe1cc878e41d0 100644 (file)
@@ -668,29 +668,6 @@ try_again:
}
}

-                       // Contraction of symmetric with antisymmetric object is zero
-                       if (num_dummies > 1
-                        && ex_to<symmetry>(ex_to<indexed>(*it1).symtree).has_symmetry()
-                        && ex_to<symmetry>(ex_to<indexed>(*it2).symtree).has_symmetry()) {
-
-                               // Check all pairs of dummy indices
-                               for (unsigned idx1=0; idx1<num_dummies-1; idx1++) {
-                                       for (unsigned idx2=idx1+1; idx2<num_dummies; idx2++) {
-
-                                               // Try and swap the index pair and check whether the
-                                               // relative sign changed
-                                               lst subs_lst(dummy[idx1].op(0), dummy[idx2].op(0)), repl_lst(dummy[idx2].op(0), dummy[idx1].op(0));
-                                               ex swapped1 = it1->subs(subs_lst, repl_lst);
-                                               ex swapped2 = it2->subs(subs_lst, repl_lst);
-                                               if (it1->is_equal(swapped1) && it2->is_equal(-swapped2)
-                                                || it1->is_equal(-swapped1) && it2->is_equal(swapped2)) {
-                                                       free_indices.clear();
-                                                       return _ex0();
-                                               }
-                                       }
-                               }
-                       }
-
// Try to contract the first one with the second one
contracted = it1->op(0).bp->contract_with(it1, it2, v);
if (!contracted) {
@@ -749,6 +726,19 @@ contraction_done:
else
r = e;

+       // The result should be symmetric with respect to exchange of dummy
+       // indices, so if the symmetrization vanishes, the whole expression is
+       // zero. This detects things like eps.i.j.k * p.j * p.k = 0.
+       if (local_dummy_indices.size() >= 2) {
+               lst dummy_syms;
+               for (int i=0; i<local_dummy_indices.size(); i++)
+                       dummy_syms.append(local_dummy_indices[i].op(0));
+               if (r.symmetrize(dummy_syms).is_zero()) {
+                       free_indices.clear();
+                       return _ex0();
+               }
+       }
+
// Dummy index renaming
r = rename_dummy_indices(r, dummy_indices, local_dummy_indices);