In fact the code doesn't even care about the tensor symmetry. This code also fails to terminate. #include <iostream> #include <ginac/ginac.h> using namespace std; using namespace GiNaC; int main() { symbol i_sym("i"), j_sym("j"), k_sym("k"), l_sym("l"), m_sym("m"), n_sym("n"); idx i(i_sym, 2), j(j_sym, 2), k(k_sym, 2), l(l_sym, 2), m(m_sym, 2), n(n_sym, 2); symbol alpha_sym("\\alpha"), beta_sym("\\beta"), gamma_sym("\\gamma"); idx Va(alpha_sym, 3), Vb(beta_sym, 3), Vg(gamma_sym, 3); symbol U1("U1"), U2("U2"), U3("U3"), U4("U4"), U5("U5"), U6("U6"), h("h"); exvector IJKLMNVec; idx IJKLMNIA[] ={i, j, k, l, m, n}; IJKLMNVec.assign (IJKLMNIA,IJKLMNIA+6); ex myEx1 = (indexed(h, IJKLMNVec)*indexed(U1, i, Va)*indexed(U5, m, Vg) *indexed(U3, k, Vb)*indexed(U2, j, Va)*indexed(U4, l, Vb)*indexed(U6, n, Vg)); ex myEx2 = (indexed(h, IJKLMNVec)*indexed(U1, i, Va)*indexed(U1, m, Vg) *indexed(U1, k, Vb)*indexed(U1, j, Va)*indexed(U1, l, Vb)*indexed(U1, n, Vg)); ex myEx3 = (indexed(h, IJKLMNVec)*indexed(U1, i, Va)*indexed(U2, m, Vg) *indexed(U1, k, Vb)*indexed(U2, j, Va)*indexed(U1, l, Vb)*indexed(U2, n, Vg)); // swap comments to see .simplify_indexed() fails in all cases cout << myEx2.simplify_indexed() << endl; //cout << myEx3.simplify_indexed() << endl; //cout << myEx1.simplify_indexed() << endl; return 0; } Could this be an error in simplify_indexed_product? ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program.