Left Termination of the query pattern sum_in_3(g, a, g) w.r.t. the given Prolog program could successfully be proven:



Prolog
  ↳ PrologToPiTRSProof

Clauses:

sum([], [], []).
sum(.(X1, Y1), .(X2, Y2), .(X3, Y3)) :- ','(add(X1, X2, X3), sum(Y1, Y2, Y3)).
add(0, X, X).
add(s(X), Y, s(Z)) :- add(X, Y, Z).

Queries:

sum(g,a,g).

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

sum_in_gag([], [], []) → sum_out_gag([], [], [])
sum_in_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_gag(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))
U1_gag(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_out_gag(Y1, Y2, Y3)) → sum_out_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3))

The argument filtering Pi contains the following mapping:
sum_in_gag(x1, x2, x3)  =  sum_in_gag(x1, x3)
[]  =  []
sum_out_gag(x1, x2, x3)  =  sum_out_gag(x2)
.(x1, x2)  =  .(x1, x2)
U1_gag(x1, x2, x3, x4, x5, x6, x7)  =  U1_gag(x2, x6, x7)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U2_gag(x1, x2, x3, x4, x5, x6, x7)  =  U2_gag(x3, x7)

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:

sum_in_gag([], [], []) → sum_out_gag([], [], [])
sum_in_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_gag(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))
U1_gag(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_out_gag(Y1, Y2, Y3)) → sum_out_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3))

The argument filtering Pi contains the following mapping:
sum_in_gag(x1, x2, x3)  =  sum_in_gag(x1, x3)
[]  =  []
sum_out_gag(x1, x2, x3)  =  sum_out_gag(x2)
.(x1, x2)  =  .(x1, x2)
U1_gag(x1, x2, x3, x4, x5, x6, x7)  =  U1_gag(x2, x6, x7)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U2_gag(x1, x2, x3, x4, x5, x6, x7)  =  U2_gag(x3, x7)


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

SUM_IN_GAG(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
SUM_IN_GAG(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → ADD_IN_GAG(X1, X2, X3)
ADD_IN_GAG(s(X), Y, s(Z)) → U3_GAG(X, Y, Z, add_in_gag(X, Y, Z))
ADD_IN_GAG(s(X), Y, s(Z)) → ADD_IN_GAG(X, Y, Z)
U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_GAG(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → SUM_IN_GAG(Y1, Y2, Y3)

The TRS R consists of the following rules:

sum_in_gag([], [], []) → sum_out_gag([], [], [])
sum_in_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_gag(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))
U1_gag(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_out_gag(Y1, Y2, Y3)) → sum_out_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3))

The argument filtering Pi contains the following mapping:
sum_in_gag(x1, x2, x3)  =  sum_in_gag(x1, x3)
[]  =  []
sum_out_gag(x1, x2, x3)  =  sum_out_gag(x2)
.(x1, x2)  =  .(x1, x2)
U1_gag(x1, x2, x3, x4, x5, x6, x7)  =  U1_gag(x2, x6, x7)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U2_gag(x1, x2, x3, x4, x5, x6, x7)  =  U2_gag(x3, x7)
U1_GAG(x1, x2, x3, x4, x5, x6, x7)  =  U1_GAG(x2, x6, x7)
U3_GAG(x1, x2, x3, x4)  =  U3_GAG(x4)
SUM_IN_GAG(x1, x2, x3)  =  SUM_IN_GAG(x1, x3)
ADD_IN_GAG(x1, x2, x3)  =  ADD_IN_GAG(x1, x3)
U2_GAG(x1, x2, x3, x4, x5, x6, x7)  =  U2_GAG(x3, x7)

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:

SUM_IN_GAG(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
SUM_IN_GAG(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → ADD_IN_GAG(X1, X2, X3)
ADD_IN_GAG(s(X), Y, s(Z)) → U3_GAG(X, Y, Z, add_in_gag(X, Y, Z))
ADD_IN_GAG(s(X), Y, s(Z)) → ADD_IN_GAG(X, Y, Z)
U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_GAG(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → SUM_IN_GAG(Y1, Y2, Y3)

The TRS R consists of the following rules:

sum_in_gag([], [], []) → sum_out_gag([], [], [])
sum_in_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_gag(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))
U1_gag(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_out_gag(Y1, Y2, Y3)) → sum_out_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3))

The argument filtering Pi contains the following mapping:
sum_in_gag(x1, x2, x3)  =  sum_in_gag(x1, x3)
[]  =  []
sum_out_gag(x1, x2, x3)  =  sum_out_gag(x2)
.(x1, x2)  =  .(x1, x2)
U1_gag(x1, x2, x3, x4, x5, x6, x7)  =  U1_gag(x2, x6, x7)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U2_gag(x1, x2, x3, x4, x5, x6, x7)  =  U2_gag(x3, x7)
U1_GAG(x1, x2, x3, x4, x5, x6, x7)  =  U1_GAG(x2, x6, x7)
U3_GAG(x1, x2, x3, x4)  =  U3_GAG(x4)
SUM_IN_GAG(x1, x2, x3)  =  SUM_IN_GAG(x1, x3)
ADD_IN_GAG(x1, x2, x3)  =  ADD_IN_GAG(x1, x3)
U2_GAG(x1, x2, x3, x4, x5, x6, x7)  =  U2_GAG(x3, x7)

We have to consider all (P,R,Pi)-chains
The approximation of the Dependency Graph [30] contains 2 SCCs with 3 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_GAG(s(X), Y, s(Z)) → ADD_IN_GAG(X, Y, Z)

The TRS R consists of the following rules:

sum_in_gag([], [], []) → sum_out_gag([], [], [])
sum_in_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_gag(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))
U1_gag(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_out_gag(Y1, Y2, Y3)) → sum_out_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3))

The argument filtering Pi contains the following mapping:
sum_in_gag(x1, x2, x3)  =  sum_in_gag(x1, x3)
[]  =  []
sum_out_gag(x1, x2, x3)  =  sum_out_gag(x2)
.(x1, x2)  =  .(x1, x2)
U1_gag(x1, x2, x3, x4, x5, x6, x7)  =  U1_gag(x2, x6, x7)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U2_gag(x1, x2, x3, x4, x5, x6, x7)  =  U2_gag(x3, x7)
ADD_IN_GAG(x1, x2, x3)  =  ADD_IN_GAG(x1, x3)

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_GAG(s(X), Y, s(Z)) → ADD_IN_GAG(X, Y, Z)

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

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_GAG(s(X), s(Z)) → ADD_IN_GAG(X, Z)

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:

U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → SUM_IN_GAG(Y1, Y2, Y3)
SUM_IN_GAG(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))

The TRS R consists of the following rules:

sum_in_gag([], [], []) → sum_out_gag([], [], [])
sum_in_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_gag(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))
add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))
U1_gag(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_in_gag(Y1, Y2, Y3))
U2_gag(X1, Y1, X2, Y2, X3, Y3, sum_out_gag(Y1, Y2, Y3)) → sum_out_gag(.(X1, Y1), .(X2, Y2), .(X3, Y3))

The argument filtering Pi contains the following mapping:
sum_in_gag(x1, x2, x3)  =  sum_in_gag(x1, x3)
[]  =  []
sum_out_gag(x1, x2, x3)  =  sum_out_gag(x2)
.(x1, x2)  =  .(x1, x2)
U1_gag(x1, x2, x3, x4, x5, x6, x7)  =  U1_gag(x2, x6, x7)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U2_gag(x1, x2, x3, x4, x5, x6, x7)  =  U2_gag(x3, x7)
U1_GAG(x1, x2, x3, x4, x5, x6, x7)  =  U1_GAG(x2, x6, x7)
SUM_IN_GAG(x1, x2, x3)  =  SUM_IN_GAG(x1, x3)

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:

U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_out_gag(X1, X2, X3)) → SUM_IN_GAG(Y1, Y2, Y3)
SUM_IN_GAG(.(X1, Y1), .(X2, Y2), .(X3, Y3)) → U1_GAG(X1, Y1, X2, Y2, X3, Y3, add_in_gag(X1, X2, X3))

The TRS R consists of the following rules:

add_in_gag(0, X, X) → add_out_gag(0, X, X)
add_in_gag(s(X), Y, s(Z)) → U3_gag(X, Y, Z, add_in_gag(X, Y, Z))
U3_gag(X, Y, Z, add_out_gag(X, Y, Z)) → add_out_gag(s(X), Y, s(Z))

The argument filtering Pi contains the following mapping:
.(x1, x2)  =  .(x1, x2)
add_in_gag(x1, x2, x3)  =  add_in_gag(x1, x3)
0  =  0
add_out_gag(x1, x2, x3)  =  add_out_gag(x2)
s(x1)  =  s(x1)
U3_gag(x1, x2, x3, x4)  =  U3_gag(x4)
U1_GAG(x1, x2, x3, x4, x5, x6, x7)  =  U1_GAG(x2, x6, x7)
SUM_IN_GAG(x1, x2, x3)  =  SUM_IN_GAG(x1, x3)

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:

SUM_IN_GAG(.(X1, Y1), .(X3, Y3)) → U1_GAG(Y1, Y3, add_in_gag(X1, X3))
U1_GAG(Y1, Y3, add_out_gag(X2)) → SUM_IN_GAG(Y1, Y3)

The TRS R consists of the following rules:

add_in_gag(0, X) → add_out_gag(X)
add_in_gag(s(X), s(Z)) → U3_gag(add_in_gag(X, Z))
U3_gag(add_out_gag(Y)) → add_out_gag(Y)

The set Q consists of the following terms:

add_in_gag(x0, x1)
U3_gag(x0)

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: