Left Termination of the query pattern max_in_3(a, g, a) w.r.t. the given Prolog program could successfully be proven:



Prolog
  ↳ PrologToPiTRSProof

Clauses:

max(X, Y, X) :- less(Y, X).
max(X, Y, Y) :- less(X, s(Y)).
less(0, s(X)).
less(s(X), s(Y)) :- less(X, Y).

Queries:

max(a,g,a).

We use the technique of [30]. With regard to the inferred argument filtering the predicates were used in the following modes:
max_in: (f,b,f)
less_in: (b,f) (f,b)
Transforming Prolog into the following Term Rewriting System:
Pi-finite rewrite system:
The TRS R consists of the following rules:

max_in_aga(X, Y, X) → U1_aga(X, Y, less_in_ga(Y, X))
less_in_ga(0, s(X)) → less_out_ga(0, s(X))
less_in_ga(s(X), s(Y)) → U3_ga(X, Y, less_in_ga(X, Y))
U3_ga(X, Y, less_out_ga(X, Y)) → less_out_ga(s(X), s(Y))
U1_aga(X, Y, less_out_ga(Y, X)) → max_out_aga(X, Y, X)
max_in_aga(X, Y, Y) → U2_aga(X, Y, less_in_ag(X, s(Y)))
less_in_ag(0, s(X)) → less_out_ag(0, s(X))
less_in_ag(s(X), s(Y)) → U3_ag(X, Y, less_in_ag(X, Y))
U3_ag(X, Y, less_out_ag(X, Y)) → less_out_ag(s(X), s(Y))
U2_aga(X, Y, less_out_ag(X, s(Y))) → max_out_aga(X, Y, Y)

The argument filtering Pi contains the following mapping:
max_in_aga(x1, x2, x3)  =  max_in_aga(x2)
U1_aga(x1, x2, x3)  =  U1_aga(x3)
less_in_ga(x1, x2)  =  less_in_ga(x1)
0  =  0
less_out_ga(x1, x2)  =  less_out_ga
s(x1)  =  s(x1)
U3_ga(x1, x2, x3)  =  U3_ga(x3)
max_out_aga(x1, x2, x3)  =  max_out_aga
U2_aga(x1, x2, x3)  =  U2_aga(x3)
less_in_ag(x1, x2)  =  less_in_ag(x2)
less_out_ag(x1, x2)  =  less_out_ag(x1)
U3_ag(x1, x2, x3)  =  U3_ag(x3)

Infinitary Constructor Rewriting Termination of PiTRS implies Termination of Prolog



↳ Prolog
  ↳ PrologToPiTRSProof
PiTRS
      ↳ DependencyPairsProof

Pi-finite rewrite system:
The TRS R consists of the following rules:

max_in_aga(X, Y, X) → U1_aga(X, Y, less_in_ga(Y, X))
less_in_ga(0, s(X)) → less_out_ga(0, s(X))
less_in_ga(s(X), s(Y)) → U3_ga(X, Y, less_in_ga(X, Y))
U3_ga(X, Y, less_out_ga(X, Y)) → less_out_ga(s(X), s(Y))
U1_aga(X, Y, less_out_ga(Y, X)) → max_out_aga(X, Y, X)
max_in_aga(X, Y, Y) → U2_aga(X, Y, less_in_ag(X, s(Y)))
less_in_ag(0, s(X)) → less_out_ag(0, s(X))
less_in_ag(s(X), s(Y)) → U3_ag(X, Y, less_in_ag(X, Y))
U3_ag(X, Y, less_out_ag(X, Y)) → less_out_ag(s(X), s(Y))
U2_aga(X, Y, less_out_ag(X, s(Y))) → max_out_aga(X, Y, Y)

The argument filtering Pi contains the following mapping:
max_in_aga(x1, x2, x3)  =  max_in_aga(x2)
U1_aga(x1, x2, x3)  =  U1_aga(x3)
less_in_ga(x1, x2)  =  less_in_ga(x1)
0  =  0
less_out_ga(x1, x2)  =  less_out_ga
s(x1)  =  s(x1)
U3_ga(x1, x2, x3)  =  U3_ga(x3)
max_out_aga(x1, x2, x3)  =  max_out_aga
U2_aga(x1, x2, x3)  =  U2_aga(x3)
less_in_ag(x1, x2)  =  less_in_ag(x2)
less_out_ag(x1, x2)  =  less_out_ag(x1)
U3_ag(x1, x2, x3)  =  U3_ag(x3)


Using Dependency Pairs [1,30] we result in the following initial DP problem:
Pi DP problem:
The TRS P consists of the following rules:

MAX_IN_AGA(X, Y, X) → U1_AGA(X, Y, less_in_ga(Y, X))
MAX_IN_AGA(X, Y, X) → LESS_IN_GA(Y, X)
LESS_IN_GA(s(X), s(Y)) → U3_GA(X, Y, less_in_ga(X, Y))
LESS_IN_GA(s(X), s(Y)) → LESS_IN_GA(X, Y)
MAX_IN_AGA(X, Y, Y) → U2_AGA(X, Y, less_in_ag(X, s(Y)))
MAX_IN_AGA(X, Y, Y) → LESS_IN_AG(X, s(Y))
LESS_IN_AG(s(X), s(Y)) → U3_AG(X, Y, less_in_ag(X, Y))
LESS_IN_AG(s(X), s(Y)) → LESS_IN_AG(X, Y)

The TRS R consists of the following rules:

max_in_aga(X, Y, X) → U1_aga(X, Y, less_in_ga(Y, X))
less_in_ga(0, s(X)) → less_out_ga(0, s(X))
less_in_ga(s(X), s(Y)) → U3_ga(X, Y, less_in_ga(X, Y))
U3_ga(X, Y, less_out_ga(X, Y)) → less_out_ga(s(X), s(Y))
U1_aga(X, Y, less_out_ga(Y, X)) → max_out_aga(X, Y, X)
max_in_aga(X, Y, Y) → U2_aga(X, Y, less_in_ag(X, s(Y)))
less_in_ag(0, s(X)) → less_out_ag(0, s(X))
less_in_ag(s(X), s(Y)) → U3_ag(X, Y, less_in_ag(X, Y))
U3_ag(X, Y, less_out_ag(X, Y)) → less_out_ag(s(X), s(Y))
U2_aga(X, Y, less_out_ag(X, s(Y))) → max_out_aga(X, Y, Y)

The argument filtering Pi contains the following mapping:
max_in_aga(x1, x2, x3)  =  max_in_aga(x2)
U1_aga(x1, x2, x3)  =  U1_aga(x3)
less_in_ga(x1, x2)  =  less_in_ga(x1)
0  =  0
less_out_ga(x1, x2)  =  less_out_ga
s(x1)  =  s(x1)
U3_ga(x1, x2, x3)  =  U3_ga(x3)
max_out_aga(x1, x2, x3)  =  max_out_aga
U2_aga(x1, x2, x3)  =  U2_aga(x3)
less_in_ag(x1, x2)  =  less_in_ag(x2)
less_out_ag(x1, x2)  =  less_out_ag(x1)
U3_ag(x1, x2, x3)  =  U3_ag(x3)
U1_AGA(x1, x2, x3)  =  U1_AGA(x3)
U3_AG(x1, x2, x3)  =  U3_AG(x3)
U2_AGA(x1, x2, x3)  =  U2_AGA(x3)
U3_GA(x1, x2, x3)  =  U3_GA(x3)
MAX_IN_AGA(x1, x2, x3)  =  MAX_IN_AGA(x2)
LESS_IN_GA(x1, x2)  =  LESS_IN_GA(x1)
LESS_IN_AG(x1, x2)  =  LESS_IN_AG(x2)

We have to consider all (P,R,Pi)-chains

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
PiDP
          ↳ DependencyGraphProof

Pi DP problem:
The TRS P consists of the following rules:

MAX_IN_AGA(X, Y, X) → U1_AGA(X, Y, less_in_ga(Y, X))
MAX_IN_AGA(X, Y, X) → LESS_IN_GA(Y, X)
LESS_IN_GA(s(X), s(Y)) → U3_GA(X, Y, less_in_ga(X, Y))
LESS_IN_GA(s(X), s(Y)) → LESS_IN_GA(X, Y)
MAX_IN_AGA(X, Y, Y) → U2_AGA(X, Y, less_in_ag(X, s(Y)))
MAX_IN_AGA(X, Y, Y) → LESS_IN_AG(X, s(Y))
LESS_IN_AG(s(X), s(Y)) → U3_AG(X, Y, less_in_ag(X, Y))
LESS_IN_AG(s(X), s(Y)) → LESS_IN_AG(X, Y)

The TRS R consists of the following rules:

max_in_aga(X, Y, X) → U1_aga(X, Y, less_in_ga(Y, X))
less_in_ga(0, s(X)) → less_out_ga(0, s(X))
less_in_ga(s(X), s(Y)) → U3_ga(X, Y, less_in_ga(X, Y))
U3_ga(X, Y, less_out_ga(X, Y)) → less_out_ga(s(X), s(Y))
U1_aga(X, Y, less_out_ga(Y, X)) → max_out_aga(X, Y, X)
max_in_aga(X, Y, Y) → U2_aga(X, Y, less_in_ag(X, s(Y)))
less_in_ag(0, s(X)) → less_out_ag(0, s(X))
less_in_ag(s(X), s(Y)) → U3_ag(X, Y, less_in_ag(X, Y))
U3_ag(X, Y, less_out_ag(X, Y)) → less_out_ag(s(X), s(Y))
U2_aga(X, Y, less_out_ag(X, s(Y))) → max_out_aga(X, Y, Y)

The argument filtering Pi contains the following mapping:
max_in_aga(x1, x2, x3)  =  max_in_aga(x2)
U1_aga(x1, x2, x3)  =  U1_aga(x3)
less_in_ga(x1, x2)  =  less_in_ga(x1)
0  =  0
less_out_ga(x1, x2)  =  less_out_ga
s(x1)  =  s(x1)
U3_ga(x1, x2, x3)  =  U3_ga(x3)
max_out_aga(x1, x2, x3)  =  max_out_aga
U2_aga(x1, x2, x3)  =  U2_aga(x3)
less_in_ag(x1, x2)  =  less_in_ag(x2)
less_out_ag(x1, x2)  =  less_out_ag(x1)
U3_ag(x1, x2, x3)  =  U3_ag(x3)
U1_AGA(x1, x2, x3)  =  U1_AGA(x3)
U3_AG(x1, x2, x3)  =  U3_AG(x3)
U2_AGA(x1, x2, x3)  =  U2_AGA(x3)
U3_GA(x1, x2, x3)  =  U3_GA(x3)
MAX_IN_AGA(x1, x2, x3)  =  MAX_IN_AGA(x2)
LESS_IN_GA(x1, x2)  =  LESS_IN_GA(x1)
LESS_IN_AG(x1, x2)  =  LESS_IN_AG(x2)

We have to consider all (P,R,Pi)-chains
The approximation of the Dependency Graph [30] contains 2 SCCs with 6 less nodes.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
PiDP
                ↳ UsableRulesProof
              ↳ PiDP

Pi DP problem:
The TRS P consists of the following rules:

LESS_IN_AG(s(X), s(Y)) → LESS_IN_AG(X, Y)

The TRS R consists of the following rules:

max_in_aga(X, Y, X) → U1_aga(X, Y, less_in_ga(Y, X))
less_in_ga(0, s(X)) → less_out_ga(0, s(X))
less_in_ga(s(X), s(Y)) → U3_ga(X, Y, less_in_ga(X, Y))
U3_ga(X, Y, less_out_ga(X, Y)) → less_out_ga(s(X), s(Y))
U1_aga(X, Y, less_out_ga(Y, X)) → max_out_aga(X, Y, X)
max_in_aga(X, Y, Y) → U2_aga(X, Y, less_in_ag(X, s(Y)))
less_in_ag(0, s(X)) → less_out_ag(0, s(X))
less_in_ag(s(X), s(Y)) → U3_ag(X, Y, less_in_ag(X, Y))
U3_ag(X, Y, less_out_ag(X, Y)) → less_out_ag(s(X), s(Y))
U2_aga(X, Y, less_out_ag(X, s(Y))) → max_out_aga(X, Y, Y)

The argument filtering Pi contains the following mapping:
max_in_aga(x1, x2, x3)  =  max_in_aga(x2)
U1_aga(x1, x2, x3)  =  U1_aga(x3)
less_in_ga(x1, x2)  =  less_in_ga(x1)
0  =  0
less_out_ga(x1, x2)  =  less_out_ga
s(x1)  =  s(x1)
U3_ga(x1, x2, x3)  =  U3_ga(x3)
max_out_aga(x1, x2, x3)  =  max_out_aga
U2_aga(x1, x2, x3)  =  U2_aga(x3)
less_in_ag(x1, x2)  =  less_in_ag(x2)
less_out_ag(x1, x2)  =  less_out_ag(x1)
U3_ag(x1, x2, x3)  =  U3_ag(x3)
LESS_IN_AG(x1, x2)  =  LESS_IN_AG(x2)

We have to consider all (P,R,Pi)-chains
For (infinitary) constructor rewriting [30] we can delete all non-usable rules from R.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
                ↳ UsableRulesProof
PiDP
                    ↳ PiDPToQDPProof
              ↳ PiDP

Pi DP problem:
The TRS P consists of the following rules:

LESS_IN_AG(s(X), s(Y)) → LESS_IN_AG(X, Y)

R is empty.
The argument filtering Pi contains the following mapping:
s(x1)  =  s(x1)
LESS_IN_AG(x1, x2)  =  LESS_IN_AG(x2)

We have to consider all (P,R,Pi)-chains
Transforming (infinitary) constructor rewriting Pi-DP problem [30] into ordinary QDP problem [15] by application of Pi.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
                ↳ UsableRulesProof
                  ↳ PiDP
                    ↳ PiDPToQDPProof
QDP
                        ↳ QDPSizeChangeProof
              ↳ PiDP

Q DP problem:
The TRS P consists of the following rules:

LESS_IN_AG(s(Y)) → LESS_IN_AG(Y)

R is empty.
Q is empty.
We have to consider all (P,Q,R)-chains.
By using the subterm criterion [20] together with the size-change analysis [32] we have proven that there are no infinite chains for this DP problem.

From the DPs we obtained the following set of size-change graphs:



↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
PiDP
                ↳ UsableRulesProof

Pi DP problem:
The TRS P consists of the following rules:

LESS_IN_GA(s(X), s(Y)) → LESS_IN_GA(X, Y)

The TRS R consists of the following rules:

max_in_aga(X, Y, X) → U1_aga(X, Y, less_in_ga(Y, X))
less_in_ga(0, s(X)) → less_out_ga(0, s(X))
less_in_ga(s(X), s(Y)) → U3_ga(X, Y, less_in_ga(X, Y))
U3_ga(X, Y, less_out_ga(X, Y)) → less_out_ga(s(X), s(Y))
U1_aga(X, Y, less_out_ga(Y, X)) → max_out_aga(X, Y, X)
max_in_aga(X, Y, Y) → U2_aga(X, Y, less_in_ag(X, s(Y)))
less_in_ag(0, s(X)) → less_out_ag(0, s(X))
less_in_ag(s(X), s(Y)) → U3_ag(X, Y, less_in_ag(X, Y))
U3_ag(X, Y, less_out_ag(X, Y)) → less_out_ag(s(X), s(Y))
U2_aga(X, Y, less_out_ag(X, s(Y))) → max_out_aga(X, Y, Y)

The argument filtering Pi contains the following mapping:
max_in_aga(x1, x2, x3)  =  max_in_aga(x2)
U1_aga(x1, x2, x3)  =  U1_aga(x3)
less_in_ga(x1, x2)  =  less_in_ga(x1)
0  =  0
less_out_ga(x1, x2)  =  less_out_ga
s(x1)  =  s(x1)
U3_ga(x1, x2, x3)  =  U3_ga(x3)
max_out_aga(x1, x2, x3)  =  max_out_aga
U2_aga(x1, x2, x3)  =  U2_aga(x3)
less_in_ag(x1, x2)  =  less_in_ag(x2)
less_out_ag(x1, x2)  =  less_out_ag(x1)
U3_ag(x1, x2, x3)  =  U3_ag(x3)
LESS_IN_GA(x1, x2)  =  LESS_IN_GA(x1)

We have to consider all (P,R,Pi)-chains
For (infinitary) constructor rewriting [30] we can delete all non-usable rules from R.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
              ↳ PiDP
                ↳ UsableRulesProof
PiDP
                    ↳ PiDPToQDPProof

Pi DP problem:
The TRS P consists of the following rules:

LESS_IN_GA(s(X), s(Y)) → LESS_IN_GA(X, Y)

R is empty.
The argument filtering Pi contains the following mapping:
s(x1)  =  s(x1)
LESS_IN_GA(x1, x2)  =  LESS_IN_GA(x1)

We have to consider all (P,R,Pi)-chains
Transforming (infinitary) constructor rewriting Pi-DP problem [30] into ordinary QDP problem [15] by application of Pi.

↳ Prolog
  ↳ PrologToPiTRSProof
    ↳ PiTRS
      ↳ DependencyPairsProof
        ↳ PiDP
          ↳ DependencyGraphProof
            ↳ AND
              ↳ PiDP
              ↳ PiDP
                ↳ UsableRulesProof
                  ↳ PiDP
                    ↳ PiDPToQDPProof
QDP
                        ↳ QDPSizeChangeProof

Q DP problem:
The TRS P consists of the following rules:

LESS_IN_GA(s(X)) → LESS_IN_GA(X)

R is empty.
Q is empty.
We have to consider all (P,Q,R)-chains.
By using the subterm criterion [20] together with the size-change analysis [32] we have proven that there are no infinite chains for this DP problem.

From the DPs we obtained the following set of size-change graphs: