NO Prover = TRS(tech=GUIDED_UNF_TRIPLES, nb_unfoldings=unlimited, unfold_variables=false, max_nb_coefficients=12, max_nb_unfolded_rules=-1, strategy=LEFTMOST_NE) ** BEGIN proof argument ** The following rule was generated while unfolding the analyzed TRS: [iteration = 3] f(f(f(h(_0),_1),_2),_3) -> f(_3,f(f(_2,f(f(_1,f(_0,h(f(a,a)))),h(f(a,a)))),h(f(a,a)))) Let l be the left-hand side and r be the right-hand side of this rule. Let p = epsilon, theta1 = {_2->h(_4), _3->f(f(h(_5),_6),h(_7))} and theta2 = {_5->_4, _1->_6, _6->f(f(_1,f(_0,h(f(a,a)))),h(f(a,a))), _7->f(a,a), _4->_7, _0->_5}. We have r|p = f(_3,f(f(_2,f(f(_1,f(_0,h(f(a,a)))),h(f(a,a)))),h(f(a,a)))) and theta2(theta1(l)) = theta1(r|p). Hence, the term theta1(l) = f(f(f(h(_0),_1),h(_4)),f(f(h(_5),_6),h(_7))) loops w.r.t. the analyzed TRS. ** END proof argument ** ** BEGIN proof description ** ## Searching for a generalized rewrite rule (a rule whose right-hand side contains a variable that does not occur in the left-hand side)... No generalized rewrite rule found! ## Applying the DP framework... ## Round 1: ## DP problem: Dependency pairs = [f^#(h(_0),_1) -> f^#(_1,f(_0,h(f(a,a)))), f^#(h(_0),_1) -> f^#(_0,h(f(a,a)))] TRS = {f(h(_0),_1) -> h(f(_1,f(_0,h(f(a,a)))))} ## Trying with homeomorphic embeddings... Failed! ## Trying with polynomial interpretations... Failed! ## Trying with lexicographic path orders... Failed! ## Trying to prove nontermination by unfolding the dependency pairs with the rules of the TRS # max_depth=20, unfold_variables=false: # Iteration 0: nontermination not detected, 2 unfolded rules generated. # Iteration 1: nontermination not detected, 6 unfolded rules generated. # Iteration 2: nontermination not detected, 7 unfolded rules generated. # Iteration 3: nontermination detected, 6 unfolded rules generated. Here is the successful unfolding. Let IR be the TRS under analysis. L0 = f^#(h(_0),_1) -> f^#(_1,f(_0,h(f(a,a)))) [trans] is in U_IR^0. We build a unit triple from L0. ==> L1 = f^#(h(_0),_1) -> f^#(_1,f(_0,h(f(a,a)))) [unit] is in U_IR^1. Let p1 = [0]. We unfold the rule of L1 backwards at position p1 with the rule f(h(_0),_1) -> h(f(_1,f(_0,h(f(a,a))))). ==> L2 = f^#(f(h(_0),_1),_2) -> f^#(_2,f(f(_1,f(_0,h(f(a,a)))),h(f(a,a)))) [unit] is in U_IR^2. Let p2 = [0, 0]. We unfold the rule of L2 backwards at position p2 with the rule f(h(_0),_1) -> h(f(_1,f(_0,h(f(a,a))))). ==> L3 = f^#(f(f(h(_0),_1),_2),_3) -> f^#(_3,f(f(_2,f(f(_1,f(_0,h(f(a,a)))),h(f(a,a)))),h(f(a,a)))) [unit] is in U_IR^3. This DP problem is infinite. ** END proof description ** Proof stopped at iteration 3 Number of unfolded rules generated by this proof = 21 Number of unfolded rules generated by all the parallel proofs = 184