Left Termination of the query pattern mult_in_3(g, g, a) w.r.t. the given Prolog program could successfully be proven:



Prolog
  ↳ PrologToPiTRSProof

Clauses:

mult(0, Y, 0).
mult(s(X), Y, Z) :- ','(mult(X, Y, Z1), add(Z1, Y, Z)).
add(0, Y, Y).
add(s(X), Y, s(Z)) :- add(X, Y, Z).

Queries:

mult(g,g,a).

We use the technique of [30].Transforming Prolog into the following Term Rewriting System:
Pi-finite rewrite system:
The TRS R consists of the following rules:

mult_in(s(X), Y, Z) → U1(X, Y, Z, mult_in(X, Y, Z1))
mult_in(0, Y, 0) → mult_out(0, Y, 0)
U1(X, Y, Z, mult_out(X, Y, Z1)) → U2(X, Y, Z, add_in(Z1, Y, Z))
add_in(s(X), Y, s(Z)) → U3(X, Y, Z, add_in(X, Y, Z))
add_in(0, Y, Y) → add_out(0, Y, Y)
U3(X, Y, Z, add_out(X, Y, Z)) → add_out(s(X), Y, s(Z))
U2(X, Y, Z, add_out(Z1, Y, Z)) → mult_out(s(X), Y, Z)

The argument filtering Pi contains the following mapping:
mult_in(x1, x2, x3)  =  mult_in(x1, x2)
s(x1)  =  s(x1)
U1(x1, x2, x3, x4)  =  U1(x2, x4)
0  =  0
mult_out(x1, x2, x3)  =  mult_out(x3)
U2(x1, x2, x3, x4)  =  U2(x4)
add_in(x1, x2, x3)  =  add_in(x1, x2)
U3(x1, x2, x3, x4)  =  U3(x4)
add_out(x1, x2, x3)  =  add_out(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:

mult_in(s(X), Y, Z) → U1(X, Y, Z, mult_in(X, Y, Z1))
mult_in(0, Y, 0) → mult_out(0, Y, 0)
U1(X, Y, Z, mult_out(X, Y, Z1)) → U2(X, Y, Z, add_in(Z1, Y, Z))
add_in(s(X), Y, s(Z)) → U3(X, Y, Z, add_in(X, Y, Z))
add_in(0, Y, Y) → add_out(0, Y, Y)
U3(X, Y, Z, add_out(X, Y, Z)) → add_out(s(X), Y, s(Z))
U2(X, Y, Z, add_out(Z1, Y, Z)) → mult_out(s(X), Y, Z)

The argument filtering Pi contains the following mapping:
mult_in(x1, x2, x3)  =  mult_in(x1, x2)
s(x1)  =  s(x1)
U1(x1, x2, x3, x4)  =  U1(x2, x4)
0  =  0
mult_out(x1, x2, x3)  =  mult_out(x3)
U2(x1, x2, x3, x4)  =  U2(x4)
add_in(x1, x2, x3)  =  add_in(x1, x2)
U3(x1, x2, x3, x4)  =  U3(x4)
add_out(x1, x2, x3)  =  add_out(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:

MULT_IN(s(X), Y, Z) → U11(X, Y, Z, mult_in(X, Y, Z1))
MULT_IN(s(X), Y, Z) → MULT_IN(X, Y, Z1)
U11(X, Y, Z, mult_out(X, Y, Z1)) → U21(X, Y, Z, add_in(Z1, Y, Z))
U11(X, Y, Z, mult_out(X, Y, Z1)) → ADD_IN(Z1, Y, Z)
ADD_IN(s(X), Y, s(Z)) → U31(X, Y, Z, add_in(X, Y, Z))
ADD_IN(s(X), Y, s(Z)) → ADD_IN(X, Y, Z)

The TRS R consists of the following rules:

mult_in(s(X), Y, Z) → U1(X, Y, Z, mult_in(X, Y, Z1))
mult_in(0, Y, 0) → mult_out(0, Y, 0)
U1(X, Y, Z, mult_out(X, Y, Z1)) → U2(X, Y, Z, add_in(Z1, Y, Z))
add_in(s(X), Y, s(Z)) → U3(X, Y, Z, add_in(X, Y, Z))
add_in(0, Y, Y) → add_out(0, Y, Y)
U3(X, Y, Z, add_out(X, Y, Z)) → add_out(s(X), Y, s(Z))
U2(X, Y, Z, add_out(Z1, Y, Z)) → mult_out(s(X), Y, Z)

The argument filtering Pi contains the following mapping:
mult_in(x1, x2, x3)  =  mult_in(x1, x2)
s(x1)  =  s(x1)
U1(x1, x2, x3, x4)  =  U1(x2, x4)
0  =  0
mult_out(x1, x2, x3)  =  mult_out(x3)
U2(x1, x2, x3, x4)  =  U2(x4)
add_in(x1, x2, x3)  =  add_in(x1, x2)
U3(x1, x2, x3, x4)  =  U3(x4)
add_out(x1, x2, x3)  =  add_out(x3)
ADD_IN(x1, x2, x3)  =  ADD_IN(x1, x2)
U31(x1, x2, x3, x4)  =  U31(x4)
U21(x1, x2, x3, x4)  =  U21(x4)
MULT_IN(x1, x2, x3)  =  MULT_IN(x1, x2)
U11(x1, x2, x3, x4)  =  U11(x2, x4)

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:

MULT_IN(s(X), Y, Z) → U11(X, Y, Z, mult_in(X, Y, Z1))
MULT_IN(s(X), Y, Z) → MULT_IN(X, Y, Z1)
U11(X, Y, Z, mult_out(X, Y, Z1)) → U21(X, Y, Z, add_in(Z1, Y, Z))
U11(X, Y, Z, mult_out(X, Y, Z1)) → ADD_IN(Z1, Y, Z)
ADD_IN(s(X), Y, s(Z)) → U31(X, Y, Z, add_in(X, Y, Z))
ADD_IN(s(X), Y, s(Z)) → ADD_IN(X, Y, Z)

The TRS R consists of the following rules:

mult_in(s(X), Y, Z) → U1(X, Y, Z, mult_in(X, Y, Z1))
mult_in(0, Y, 0) → mult_out(0, Y, 0)
U1(X, Y, Z, mult_out(X, Y, Z1)) → U2(X, Y, Z, add_in(Z1, Y, Z))
add_in(s(X), Y, s(Z)) → U3(X, Y, Z, add_in(X, Y, Z))
add_in(0, Y, Y) → add_out(0, Y, Y)
U3(X, Y, Z, add_out(X, Y, Z)) → add_out(s(X), Y, s(Z))
U2(X, Y, Z, add_out(Z1, Y, Z)) → mult_out(s(X), Y, Z)

The argument filtering Pi contains the following mapping:
mult_in(x1, x2, x3)  =  mult_in(x1, x2)
s(x1)  =  s(x1)
U1(x1, x2, x3, x4)  =  U1(x2, x4)
0  =  0
mult_out(x1, x2, x3)  =  mult_out(x3)
U2(x1, x2, x3, x4)  =  U2(x4)
add_in(x1, x2, x3)  =  add_in(x1, x2)
U3(x1, x2, x3, x4)  =  U3(x4)
add_out(x1, x2, x3)  =  add_out(x3)
ADD_IN(x1, x2, x3)  =  ADD_IN(x1, x2)
U31(x1, x2, x3, x4)  =  U31(x4)
U21(x1, x2, x3, x4)  =  U21(x4)
MULT_IN(x1, x2, x3)  =  MULT_IN(x1, x2)
U11(x1, x2, x3, x4)  =  U11(x2, x4)

We have to consider all (P,R,Pi)-chains
The approximation of the Dependency Graph [30] contains 2 SCCs with 4 less nodes.

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

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

ADD_IN(s(X), Y, s(Z)) → ADD_IN(X, Y, Z)

The TRS R consists of the following rules:

mult_in(s(X), Y, Z) → U1(X, Y, Z, mult_in(X, Y, Z1))
mult_in(0, Y, 0) → mult_out(0, Y, 0)
U1(X, Y, Z, mult_out(X, Y, Z1)) → U2(X, Y, Z, add_in(Z1, Y, Z))
add_in(s(X), Y, s(Z)) → U3(X, Y, Z, add_in(X, Y, Z))
add_in(0, Y, Y) → add_out(0, Y, Y)
U3(X, Y, Z, add_out(X, Y, Z)) → add_out(s(X), Y, s(Z))
U2(X, Y, Z, add_out(Z1, Y, Z)) → mult_out(s(X), Y, Z)

The argument filtering Pi contains the following mapping:
mult_in(x1, x2, x3)  =  mult_in(x1, x2)
s(x1)  =  s(x1)
U1(x1, x2, x3, x4)  =  U1(x2, x4)
0  =  0
mult_out(x1, x2, x3)  =  mult_out(x3)
U2(x1, x2, x3, x4)  =  U2(x4)
add_in(x1, x2, x3)  =  add_in(x1, x2)
U3(x1, x2, x3, x4)  =  U3(x4)
add_out(x1, x2, x3)  =  add_out(x3)
ADD_IN(x1, x2, x3)  =  ADD_IN(x1, 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:

ADD_IN(s(X), Y, s(Z)) → ADD_IN(X, Y, Z)

R is empty.
The argument filtering Pi contains the following mapping:
s(x1)  =  s(x1)
ADD_IN(x1, x2, x3)  =  ADD_IN(x1, 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:

ADD_IN(s(X), Y) → ADD_IN(X, 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:

MULT_IN(s(X), Y, Z) → MULT_IN(X, Y, Z1)

The TRS R consists of the following rules:

mult_in(s(X), Y, Z) → U1(X, Y, Z, mult_in(X, Y, Z1))
mult_in(0, Y, 0) → mult_out(0, Y, 0)
U1(X, Y, Z, mult_out(X, Y, Z1)) → U2(X, Y, Z, add_in(Z1, Y, Z))
add_in(s(X), Y, s(Z)) → U3(X, Y, Z, add_in(X, Y, Z))
add_in(0, Y, Y) → add_out(0, Y, Y)
U3(X, Y, Z, add_out(X, Y, Z)) → add_out(s(X), Y, s(Z))
U2(X, Y, Z, add_out(Z1, Y, Z)) → mult_out(s(X), Y, Z)

The argument filtering Pi contains the following mapping:
mult_in(x1, x2, x3)  =  mult_in(x1, x2)
s(x1)  =  s(x1)
U1(x1, x2, x3, x4)  =  U1(x2, x4)
0  =  0
mult_out(x1, x2, x3)  =  mult_out(x3)
U2(x1, x2, x3, x4)  =  U2(x4)
add_in(x1, x2, x3)  =  add_in(x1, x2)
U3(x1, x2, x3, x4)  =  U3(x4)
add_out(x1, x2, x3)  =  add_out(x3)
MULT_IN(x1, x2, x3)  =  MULT_IN(x1, 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
              ↳ PiDP
                ↳ UsableRulesProof
PiDP
                    ↳ PiDPToQDPProof

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

MULT_IN(s(X), Y, Z) → MULT_IN(X, Y, Z1)

R is empty.
The argument filtering Pi contains the following mapping:
s(x1)  =  s(x1)
MULT_IN(x1, x2, x3)  =  MULT_IN(x1, 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
              ↳ PiDP
                ↳ UsableRulesProof
                  ↳ PiDP
                    ↳ PiDPToQDPProof
QDP
                        ↳ QDPSizeChangeProof

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

MULT_IN(s(X), Y) → MULT_IN(X, 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: