YES

We show the termination of the TRS R:

  a(a(x)) -> b(b(x))
  b(b(a(x))) -> a(b(b(x)))

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: a#(a(x)) -> b#(b(x))
p2: a#(a(x)) -> b#(x)
p3: b#(b(a(x))) -> a#(b(b(x)))
p4: b#(b(a(x))) -> b#(b(x))
p5: b#(b(a(x))) -> b#(x)

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The estimated dependency graph contains the following SCCs:

  {p1, p2, p3, p4, p5}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: a#(a(x)) -> b#(b(x))
p2: b#(b(a(x))) -> b#(x)
p3: b#(b(a(x))) -> b#(b(x))
p4: b#(b(a(x))) -> a#(b(b(x)))
p5: a#(a(x)) -> b#(x)

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The set of usable rules consists of

  r1, r2

Take the monotone reduction pair:

  weighted path order
  
    base order:
  
      max/plus interpretations on natural numbers:
      
        a#_A(x1) = max{15, x1 + 10}
        a_A(x1) = max{10, x1 + 9}
        b#_A(x1) = x1 + 5
        b_A(x1) = max{3, x1 + 2}
  
    precedence:
    
      a# = a = b# = b
    
    partial status:
  
      pi(a#) = [1]
      pi(a) = [1]
      pi(b#) = [1]
      pi(b) = [1]

The next rules are strictly ordered:

  p1

We remove them from the problem.

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: b#(b(a(x))) -> b#(x)
p2: b#(b(a(x))) -> b#(b(x))
p3: b#(b(a(x))) -> a#(b(b(x)))
p4: a#(a(x)) -> b#(x)

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The estimated dependency graph contains the following SCCs:

  {p1, p2, p3, p4}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: b#(b(a(x))) -> b#(x)
p2: b#(b(a(x))) -> a#(b(b(x)))
p3: a#(a(x)) -> b#(x)
p4: b#(b(a(x))) -> b#(b(x))

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The set of usable rules consists of

  r1, r2

Take the reduction pair:

  weighted path order
  
    base order:
  
      max/plus interpretations on natural numbers:
      
        b#_A(x1) = max{7, x1 + 6}
        b_A(x1) = x1
        a_A(x1) = x1 + 4
        a#_A(x1) = x1 + 5
  
    precedence:
    
      b# = b = a = a#
    
    partial status:
  
      pi(b#) = []
      pi(b) = [1]
      pi(a) = [1]
      pi(a#) = [1]

The next rules are strictly ordered:

  p1

We remove them from the problem.

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: b#(b(a(x))) -> a#(b(b(x)))
p2: a#(a(x)) -> b#(x)
p3: b#(b(a(x))) -> b#(b(x))

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The estimated dependency graph contains the following SCCs:

  {p1, p2, p3}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: b#(b(a(x))) -> a#(b(b(x)))
p2: a#(a(x)) -> b#(x)
p3: b#(b(a(x))) -> b#(b(x))

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The set of usable rules consists of

  r1, r2

Take the reduction pair:

  weighted path order
  
    base order:
  
      max/plus interpretations on natural numbers:
      
        b#_A(x1) = x1 + 6
        b_A(x1) = x1
        a_A(x1) = x1 + 2
        a#_A(x1) = max{5, x1 + 4}
  
    precedence:
    
      b# = b = a = a#
    
    partial status:
  
      pi(b#) = []
      pi(b) = [1]
      pi(a) = [1]
      pi(a#) = []

The next rules are strictly ordered:

  p3

We remove them from the problem.

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: b#(b(a(x))) -> a#(b(b(x)))
p2: a#(a(x)) -> b#(x)

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The estimated dependency graph contains the following SCCs:

  {p1, p2}


-- Reduction pair.

Consider the dependency pair problem (P, R), where P consists of

p1: b#(b(a(x))) -> a#(b(b(x)))
p2: a#(a(x)) -> b#(x)

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The set of usable rules consists of

  r1, r2

Take the monotone reduction pair:

  weighted path order
  
    base order:
  
      max/plus interpretations on natural numbers:
      
        b#_A(x1) = x1 + 4
        b_A(x1) = x1
        a_A(x1) = x1 + 4
        a#_A(x1) = max{1, x1}
  
    precedence:
    
      b# = b = a = a#
    
    partial status:
  
      pi(b#) = [1]
      pi(b) = [1]
      pi(a) = [1]
      pi(a#) = [1]

The next rules are strictly ordered:

  p1

We remove them from the problem.

-- SCC decomposition.

Consider the dependency pair problem (P, R), where P consists of

p1: a#(a(x)) -> b#(x)

and R consists of:

r1: a(a(x)) -> b(b(x))
r2: b(b(a(x))) -> a(b(b(x)))

The estimated dependency graph contains the following SCCs:

  (no SCCs)